/*P:100 * This is the Launcher code, a simple program which lays out the "physical" * memory for the new Guest by mapping the kernel image and the virtual * devices, then opens /dev/lguest to tell the kernel about the Guest and * control it. :*/ #define _LARGEFILE64_SOURCE #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifndef VIRTIO_F_ANY_LAYOUT #define VIRTIO_F_ANY_LAYOUT 27 #endif /*L:110 * We can ignore the 43 include files we need for this program, but I do want * to draw attention to the use of kernel-style types. * * As Linus said, "C is a Spartan language, and so should your naming be." I * like these abbreviations, so we define them here. Note that u64 is always * unsigned long long, which works on all Linux systems: this means that we can * use %llu in printf for any u64. */ typedef unsigned long long u64; typedef uint32_t u32; typedef uint16_t u16; typedef uint8_t u8; /*:*/ #define VIRTIO_CONFIG_NO_LEGACY #define VIRTIO_PCI_NO_LEGACY #define VIRTIO_BLK_NO_LEGACY /* Use in-kernel ones, which defines VIRTIO_F_VERSION_1 */ #include "../../include/uapi/linux/virtio_config.h" #include "../../include/uapi/linux/virtio_net.h" #include "../../include/uapi/linux/virtio_blk.h" #include "../../include/uapi/linux/virtio_console.h" #include "../../include/uapi/linux/virtio_rng.h" #include #include "../../include/uapi/linux/virtio_pci.h" #include #include "../../include/linux/lguest_launcher.h" #define BRIDGE_PFX "bridge:" #ifndef SIOCBRADDIF #define SIOCBRADDIF 0x89a2 /* add interface to bridge */ #endif /* We can have up to 256 pages for devices. */ #define DEVICE_PAGES 256 /* This will occupy 3 pages: it must be a power of 2. */ #define VIRTQUEUE_NUM 256 /*L:120 * verbose is both a global flag and a macro. The C preprocessor allows * this, and although I wouldn't recommend it, it works quite nicely here. */ static bool verbose; #define verbose(args...) \ do { if (verbose) printf(args); } while(0) /*:*/ /* The pointer to the start of guest memory. */ static void *guest_base; /* The maximum guest physical address allowed, and maximum possible. */ static unsigned long guest_limit, guest_max, guest_mmio; /* The /dev/lguest file descriptor. */ static int lguest_fd; /* a per-cpu variable indicating whose vcpu is currently running */ static unsigned int __thread cpu_id; /* 5 bit device number in the PCI_CONFIG_ADDR => 32 only */ #define MAX_PCI_DEVICES 32 /* This is our list of devices. */ struct device_list { /* Counter to assign interrupt numbers. */ unsigned int next_irq; /* Counter to print out convenient device numbers. */ unsigned int device_num; /* PCI devices. */ struct device *pci[MAX_PCI_DEVICES]; }; /* The list of Guest devices, based on command line arguments. */ static struct device_list devices; struct virtio_pci_cfg_cap { struct virtio_pci_cap cap; u32 pci_cfg_data; /* Data for BAR access. */ }; struct virtio_pci_mmio { struct virtio_pci_common_cfg cfg; u16 notify; u8 isr; u8 padding; /* Device-specific configuration follows this. */ }; /* This is the layout (little-endian) of the PCI config space. */ struct pci_config { u16 vendor_id, device_id; u16 command, status; u8 revid, prog_if, subclass, class; u8 cacheline_size, lat_timer, header_type, bist; u32 bar[6]; u32 cardbus_cis_ptr; u16 subsystem_vendor_id, subsystem_device_id; u32 expansion_rom_addr; u8 capabilities, reserved1[3]; u32 reserved2; u8 irq_line, irq_pin, min_grant, max_latency; /* Now, this is the linked capability list. */ struct virtio_pci_cap common; struct virtio_pci_notify_cap notify; struct virtio_pci_cap isr; struct virtio_pci_cap device; struct virtio_pci_cfg_cap cfg_access; }; /* The device structure describes a single device. */ struct device { /* The name of this device, for --verbose. */ const char *name; /* Any queues attached to this device */ struct virtqueue *vq; /* Is it operational */ bool running; /* PCI configuration */ union { struct pci_config config; u32 config_words[sizeof(struct pci_config) / sizeof(u32)]; }; /* Features we offer, and those accepted. */ u64 features, features_accepted; /* Device-specific config hangs off the end of this. */ struct virtio_pci_mmio *mmio; /* PCI MMIO resources (all in BAR0) */ size_t mmio_size; u32 mmio_addr; /* Device-specific data. */ void *priv; }; /* The virtqueue structure describes a queue attached to a device. */ struct virtqueue { struct virtqueue *next; /* Which device owns me. */ struct device *dev; /* The actual ring of buffers. */ struct vring vring; /* The information about this virtqueue (we only use queue_size on) */ struct virtio_pci_common_cfg pci_config; /* Last available index we saw. */ u16 last_avail_idx; /* How many are used since we sent last irq? */ unsigned int pending_used; /* Eventfd where Guest notifications arrive. */ int eventfd; /* Function for the thread which is servicing this virtqueue. */ void (*service)(struct virtqueue *vq); pid_t thread; }; /* Remember the arguments to the program so we can "reboot" */ static char **main_args; /* The original tty settings to restore on exit. */ static struct termios orig_term; /* * We have to be careful with barriers: our devices are all run in separate * threads and so we need to make sure that changes visible to the Guest happen * in precise order. */ #define wmb() __asm__ __volatile__("" : : : "memory") #define rmb() __asm__ __volatile__("lock; addl $0,0(%%esp)" : : : "memory") #define mb() __asm__ __volatile__("lock; addl $0,0(%%esp)" : : : "memory") /* Wrapper for the last available index. Makes it easier to change. */ #define lg_last_avail(vq) ((vq)->last_avail_idx) /* * The virtio configuration space is defined to be little-endian. x86 is * little-endian too, but it's nice to be explicit so we have these helpers. */ #define cpu_to_le16(v16) (v16) #define cpu_to_le32(v32) (v32) #define cpu_to_le64(v64) (v64) #define le16_to_cpu(v16) (v16) #define le32_to_cpu(v32) (v32) #define le64_to_cpu(v64) (v64) /* Is this iovec empty? */ static bool iov_empty(const struct iovec iov[], unsigned int num_iov) { unsigned int i; for (i = 0; i < num_iov; i++) if (iov[i].iov_len) return false; return true; } /* Take len bytes from the front of this iovec. */ static void iov_consume(struct iovec iov[], unsigned num_iov, void *dest, unsigned len) { unsigned int i; for (i = 0; i < num_iov; i++) { unsigned int used; used = iov[i].iov_len < len ? iov[i].iov_len : len; if (dest) { memcpy(dest, iov[i].iov_base, used); dest += used; } iov[i].iov_base += used; iov[i].iov_len -= used; len -= used; } if (len != 0) errx(1, "iovec too short!"); } /*L:100 * The Launcher code itself takes us out into userspace, that scary place where * pointers run wild and free! Unfortunately, like most userspace programs, * it's quite boring (which is why everyone likes to hack on the kernel!). * Perhaps if you make up an Lguest Drinking Game at this point, it will get * you through this section. Or, maybe not. * * The Launcher sets up a big chunk of memory to be the Guest's "physical" * memory and stores it in "guest_base". In other words, Guest physical == * Launcher virtual with an offset. * * This can be tough to get your head around, but usually it just means that we * use these trivial conversion functions when the Guest gives us its * "physical" addresses: */ static void *from_guest_phys(unsigned long addr) { return guest_base + addr; } static unsigned long to_guest_phys(const void *addr) { return (addr - guest_base); } /*L:130 * Loading the Kernel. * * We start with couple of simple helper routines. open_or_die() avoids * error-checking code cluttering the callers: */ static int open_or_die(const char *name, int flags) { int fd = open(name, flags); if (fd < 0) err(1, "Failed to open %s", name); return fd; } /* map_zeroed_pages() takes a number of pages. */ static void *map_zeroed_pages(unsigned int num) { int fd = open_or_die("/dev/zero", O_RDONLY); void *addr; /* * We use a private mapping (ie. if we write to the page, it will be * copied). We allocate an extra two pages PROT_NONE to act as guard * pages against read/write attempts that exceed allocated space. */ addr = mmap(NULL, getpagesize() * (num+2), PROT_NONE, MAP_PRIVATE, fd, 0); if (addr == MAP_FAILED) err(1, "Mmapping %u pages of /dev/zero", num); if (mprotect(addr + getpagesize(), getpagesize() * num, PROT_READ|PROT_WRITE) == -1) err(1, "mprotect rw %u pages failed", num); /* * One neat mmap feature is that you can close the fd, and it * stays mapped. */ close(fd); /* Return address after PROT_NONE page */ return addr + getpagesize(); } /* Get some bytes which won't be mapped into the guest. */ static unsigned long get_mmio_region(size_t size) { unsigned long addr = guest_mmio; size_t i; if (!size) return addr; /* Size has to be a power of 2 (and multiple of 16) */ for (i = 1; i < size; i <<= 1); guest_mmio += i; return addr; } /* * This routine is used to load the kernel or initrd. It tries mmap, but if * that fails (Plan 9's kernel file isn't nicely aligned on page boundaries), * it falls back to reading the memory in. */ static void map_at(int fd, void *addr, unsigned long offset, unsigned long len) { ssize_t r; /* * We map writable even though for some segments are marked read-only. * The kernel really wants to be writable: it patches its own * instructions. * * MAP_PRIVATE means that the page won't be copied until a write is * done to it. This allows us to share untouched memory between * Guests. */ if (mmap(addr, len, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED) return; /* pread does a seek and a read in one shot: saves a few lines. */ r = pread(fd, addr, len, offset); if (r != len) err(1, "Reading offset %lu len %lu gave %zi", offset, len, r); } /* * This routine takes an open vmlinux image, which is in ELF, and maps it into * the Guest memory. ELF = Embedded Linking Format, which is the format used * by all modern binaries on Linux including the kernel. * * The ELF headers give *two* addresses: a physical address, and a virtual * address. We use the physical address; the Guest will map itself to the * virtual address. * * We return the starting address. */ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr) { Elf32_Phdr phdr[ehdr->e_phnum]; unsigned int i; /* * Sanity checks on the main ELF header: an x86 executable with a * reasonable number of correctly-sized program headers. */ if (ehdr->e_type != ET_EXEC || ehdr->e_machine != EM_386 || ehdr->e_phentsize != sizeof(Elf32_Phdr) || ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr)) errx(1, "Malformed elf header"); /* * An ELF executable contains an ELF header and a number of "program" * headers which indicate which parts ("segments") of the program to * load where. */ /* We read in all the program headers at once: */ if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0) err(1, "Seeking to program headers"); if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr)) err(1, "Reading program headers"); /* * Try all the headers: there are usually only three. A read-only one, * a read-write one, and a "note" section which we don't load. */ for (i = 0; i < ehdr->e_phnum; i++) { /* If this isn't a loadable segment, we ignore it */ if (phdr[i].p_type != PT_LOAD) continue; verbose("Section %i: size %i addr %p\n", i, phdr[i].p_memsz, (void *)phdr[i].p_paddr); /* We map this section of the file at its physical address. */ map_at(elf_fd, from_guest_phys(phdr[i].p_paddr), phdr[i].p_offset, phdr[i].p_filesz); } /* The entry point is given in the ELF header. */ return ehdr->e_entry; } /*L:150 * A bzImage, unlike an ELF file, is not meant to be loaded. You're supposed * to jump into it and it will unpack itself. We used to have to perform some * hairy magic because the unpacking code scared me. * * Fortunately, Jeremy Fitzhardinge convinced me it wasn't that hard and wrote * a small patch to jump over the tricky bits in the Guest, so now we just read * the funky header so we know where in the file to load, and away we go! */ static unsigned long load_bzimage(int fd) { struct boot_params boot; int r; /* Modern bzImages get loaded at 1M. */ void *p = from_guest_phys(0x100000); /* * Go back to the start of the file and read the header. It should be * a Linux boot header (see Documentation/x86/boot.txt) */ lseek(fd, 0, SEEK_SET); read(fd, &boot, sizeof(boot)); /* Inside the setup_hdr, we expect the magic "HdrS" */ if (memcmp(&boot.hdr.header, "HdrS", 4) != 0) errx(1, "This doesn't look like a bzImage to me"); /* Skip over the extra sectors of the header. */ lseek(fd, (boot.hdr.setup_sects+1) * 512, SEEK_SET); /* Now read everything into memory. in nice big chunks. */ while ((r = read(fd, p, 65536)) > 0) p += r; /* Finally, code32_start tells us where to enter the kernel. */ return boot.hdr.code32_start; } /*L:140 * Loading the kernel is easy when it's a "vmlinux", but most kernels * come wrapped up in the self-decompressing "bzImage" format. With a little * work, we can load those, too. */ static unsigned long load_kernel(int fd) { Elf32_Ehdr hdr; /* Read in the first few bytes. */ if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) err(1, "Reading kernel"); /* If it's an ELF file, it starts with "\177ELF" */ if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0) return map_elf(fd, &hdr); /* Otherwise we assume it's a bzImage, and try to load it. */ return load_bzimage(fd); } /* * This is a trivial little helper to align pages. Andi Kleen hated it because * it calls getpagesize() twice: "it's dumb code." * * Kernel guys get really het up about optimization, even when it's not * necessary. I leave this code as a reaction against that. */ static inline unsigned long page_align(unsigned long addr) { /* Add upwards and truncate downwards. */ return ((addr + getpagesize()-1) & ~(getpagesize()-1)); } /*L:180 * An "initial ram disk" is a disk image loaded into memory along with the * kernel which the kernel can use to boot from without needing any drivers. * Most distributions now use this as standard: the initrd contains the code to * load the appropriate driver modules for the current machine. * * Importantly, James Morris works for RedHat, and Fedora uses initrds for its * kernels. He sent me this (and tells me when I break it). */ static unsigned long load_initrd(const char *name, unsigned long mem) { int ifd; struct stat st; unsigned long len; ifd = open_or_die(name, O_RDONLY); /* fstat() is needed to get the file size. */ if (fstat(ifd, &st) < 0) err(1, "fstat() on initrd '%s'", name); /* * We map the initrd at the top of memory, but mmap wants it to be * page-aligned, so we round the size up for that. */ len = page_align(st.st_size); map_at(ifd, from_guest_phys(mem - len), 0, st.st_size); /* * Once a file is mapped, you can close the file descriptor. It's a * little odd, but quite useful. */ close(ifd); verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len); /* We return the initrd size. */ return len; } /*:*/ /* * Simple routine to roll all the commandline arguments together with spaces * between them. */ static void concat(char *dst, char *args[]) { unsigned int i, len = 0; for (i = 0; args[i]; i++) { if (i) { strcat(dst+len, " "); len++; } strcpy(dst+len, args[i]); len += strlen(args[i]); } /* In case it's empty. */ dst[len] = '\0'; } /*L:185 * This is where we actually tell the kernel to initialize the Guest. We * saw the arguments it expects when we looked at initialize() in lguest_user.c: * the base of Guest "physical" memory, the top physical page to allow and the * entry point for the Guest. */ static void tell_kernel(unsigned long start) { unsigned long args[] = { LHREQ_INITIALIZE, (unsigned long)guest_base, guest_limit / getpagesize(), start, (guest_mmio+getpagesize()-1) / getpagesize() }; verbose("Guest: %p - %p (%#lx, MMIO %#lx)\n", guest_base, guest_base + guest_limit, guest_limit, guest_mmio); lguest_fd = open_or_die("/dev/lguest", O_RDWR); if (write(lguest_fd, args, sizeof(args)) < 0) err(1, "Writing to /dev/lguest"); } /*:*/ /*L:200 * Device Handling. * * When the Guest gives us a buffer, it sends an array of addresses and sizes. * We need to make sure it's not trying to reach into the Launcher itself, so * we have a convenient routine which checks it and exits with an error message * if something funny is going on: */ static void *_check_pointer(unsigned long addr, unsigned int size, unsigned int line) { /* * Check if the requested address and size exceeds the allocated memory, * or addr + size wraps around. */ if ((addr + size) > guest_limit || (addr + size) < addr) errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr); /* * We return a pointer for the caller's convenience, now we know it's * safe to use. */ return from_guest_phys(addr); } /* A macro which transparently hands the line number to the real function. */ #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__) /* * Each buffer in the virtqueues is actually a chain of descriptors. This * function returns the next descriptor in the chain, or vq->vring.num if we're * at the end. */ static unsigned next_desc(struct vring_desc *desc, unsigned int i, unsigned int max) { unsigned int next; /* If this descriptor says it doesn't chain, we're done. */ if (!(desc[i].flags & VRING_DESC_F_NEXT)) return max; /* Check they're not leading us off end of descriptors. */ next = desc[i].next; /* Make sure compiler knows to grab that: we don't want it changing! */ wmb(); if (next >= max) errx(1, "Desc next is %u", next); return next; } /* * This actually sends the interrupt for this virtqueue, if we've used a * buffer. */ static void trigger_irq(struct virtqueue *vq) { unsigned long buf[] = { LHREQ_IRQ, vq->dev->config.irq_line }; /* Don't inform them if nothing used. */ if (!vq->pending_used) return; vq->pending_used = 0; /* If they don't want an interrupt, don't send one... */ if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) { return; } /* * 4.1.4.5.1: * * If MSI-X capability is disabled, the device MUST set the Queue * Interrupt bit in ISR status before sending a virtqueue notification * to the driver. */ vq->dev->mmio->isr = 0x1; /* Send the Guest an interrupt tell them we used something up. */ if (write(lguest_fd, buf, sizeof(buf)) != 0) err(1, "Triggering irq %i", vq->dev->config.irq_line); } /* * This looks in the virtqueue for the first available buffer, and converts * it to an iovec for convenient access. Since descriptors consist of some * number of output then some number of input descriptors, it's actually two * iovecs, but we pack them into one and note how many of each there were. * * This function waits if necessary, and returns the descriptor number found. */ static unsigned wait_for_vq_desc(struct virtqueue *vq, struct iovec iov[], unsigned int *out_num, unsigned int *in_num) { unsigned int i, head, max; struct vring_desc *desc; u16 last_avail = lg_last_avail(vq); /* There's nothing available? */ while (last_avail == vq->vring.avail->idx) { u64 event; /* * Since we're about to sleep, now is a good time to tell the * Guest about what we've used up to now. */ trigger_irq(vq); /* OK, now we need to know about added descriptors. */ vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY; /* * They could have slipped one in as we were doing that: make * sure it's written, then check again. */ mb(); if (last_avail != vq->vring.avail->idx) { vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY; break; } /* Nothing new? Wait for eventfd to tell us they refilled. */ if (read(vq->eventfd, &event, sizeof(event)) != sizeof(event)) errx(1, "Event read failed?"); /* We don't need to be notified again. */ vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY; } /* Check it isn't doing very strange things with descriptor numbers. */ if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num) errx(1, "Guest moved used index from %u to %u", last_avail, vq->vring.avail->idx); /* * Make sure we read the descriptor number *after* we read the ring * update; don't let the cpu or compiler change the order. */ rmb(); /* * Grab the next descriptor number they're advertising, and increment * the index we've seen. */ head = vq->vring.avail->ring[last_avail % vq->vring.num]; lg_last_avail(vq)++; /* If their number is silly, that's a fatal mistake. */ if (head >= vq->vring.num) errx(1, "Guest says index %u is available", head); /* When we start there are none of either input nor output. */ *out_num = *in_num = 0; max = vq->vring.num; desc = vq->vring.desc; i = head; /* * We have to read the descriptor after we read the descriptor number, * but there's a data dependency there so the CPU shouldn't reorder * that: no rmb() required. */ do { /* * If this is an indirect entry, then this buffer contains a * descriptor table which we handle as if it's any normal * descriptor chain. */ if (desc[i].flags & VRING_DESC_F_INDIRECT) { if (desc[i].len % sizeof(struct vring_desc)) errx(1, "Invalid size for indirect buffer table"); max = desc[i].len / sizeof(struct vring_desc); desc = check_pointer(desc[i].addr, desc[i].len); i = 0; } /* Grab the first descriptor, and check it's OK. */ iov[*out_num + *in_num].iov_len = desc[i].len; iov[*out_num + *in_num].iov_base = check_pointer(desc[i].addr, desc[i].len); /* If this is an input descriptor, increment that count. */ if (desc[i].flags & VRING_DESC_F_WRITE) (*in_num)++; else { /* * If it's an output descriptor, they're all supposed * to come before any input descriptors. */ if (*in_num) errx(1, "Descriptor has out after in"); (*out_num)++; } /* If we've got too many, that implies a descriptor loop. */ if (*out_num + *in_num > max) errx(1, "Looped descriptor"); } while ((i = next_desc(desc, i, max)) != max); return head; } /* * After we've used one of their buffers, we tell the Guest about it. Sometime * later we'll want to send them an interrupt using trigger_irq(); note that * wait_for_vq_desc() does that for us if it has to wait. */ static void add_used(struct virtqueue *vq, unsigned int head, int len) { struct vring_used_elem *used; /* * The virtqueue contains a ring of used buffers. Get a pointer to the * next entry in that used ring. */ used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num]; used->id = head; used->len = len; /* Make sure buffer is written before we update index. */ wmb(); vq->vring.used->idx++; vq->pending_used++; } /* And here's the combo meal deal. Supersize me! */ static void add_used_and_trigger(struct virtqueue *vq, unsigned head, int len) { add_used(vq, head, len); trigger_irq(vq); } /* * The Console * * We associate some data with the console for our exit hack. */ struct console_abort { /* How many times have they hit ^C? */ int count; /* When did they start? */ struct timeval start; }; /* This is the routine which handles console input (ie. stdin). */ static void console_input(struct virtqueue *vq) { int len; unsigned int head, in_num, out_num; struct console_abort *abort = vq->dev->priv; struct iovec iov[vq->vring.num]; /* Make sure there's a descriptor available. */ head = wait_for_vq_desc(vq, iov, &out_num, &in_num); if (out_num) errx(1, "Output buffers in console in queue?"); /* Read into it. This is where we usually wait. */ len = readv(STDIN_FILENO, iov, in_num); if (len <= 0) { /* Ran out of input? */ warnx("Failed to get console input, ignoring console."); /* * For simplicity, dying threads kill the whole Launcher. So * just nap here. */ for (;;) pause(); } /* Tell the Guest we used a buffer. */ add_used_and_trigger(vq, head, len); /* * Three ^C within one second? Exit. * * This is such a hack, but works surprisingly well. Each ^C has to * be in a buffer by itself, so they can't be too fast. But we check * that we get three within about a second, so they can't be too * slow. */ if (len != 1 || ((char *)iov[0].iov_base)[0] != 3) { abort->count = 0; return; } abort->count++; if (abort->count == 1) gettimeofday(&abort->start, NULL); else if (abort->count == 3) { struct timeval now; gettimeofday(&now, NULL); /* Kill all Launcher processes with SIGINT, like normal ^C */ if (now.tv_sec <= abort->start.tv_sec+1) kill(0, SIGINT); abort->count = 0; } } /* This is the routine which handles console output (ie. stdout). */ static void console_output(struct virtqueue *vq) { unsigned int head, out, in; struct iovec iov[vq->vring.num]; /* We usually wait in here, for the Guest to give us something. */ head = wait_for_vq_desc(vq, iov, &out, &in); if (in) errx(1, "Input buffers in console output queue?"); /* writev can return a partial write, so we loop here. */ while (!iov_empty(iov, out)) { int len = writev(STDOUT_FILENO, iov, out); if (len <= 0) { warn("Write to stdout gave %i (%d)", len, errno); break; } iov_consume(iov, out, NULL, len); } /* * We're finished with that buffer: if we're going to sleep, * wait_for_vq_desc() will prod the Guest with an interrupt. */ add_used(vq, head, 0); } /* * The Network * * Handling output for network is also simple: we get all the output buffers * and write them to /dev/net/tun. */ struct net_info { int tunfd; }; static void net_output(struct virtqueue *vq) { struct net_info *net_info = vq->dev->priv; unsigned int head, out, in; struct iovec iov[vq->vring.num]; /* We usually wait in here for the Guest to give us a packet. */ head = wait_for_vq_desc(vq, iov, &out, &in); if (in) errx(1, "Input buffers in net output queue?"); /* * Send the whole thing through to /dev/net/tun. It expects the exact * same format: what a coincidence! */ if (writev(net_info->tunfd, iov, out) < 0) warnx("Write to tun failed (%d)?", errno); /* * Done with that one; wait_for_vq_desc() will send the interrupt if * all packets are processed. */ add_used(vq, head, 0); } /* * Handling network input is a bit trickier, because I've tried to optimize it. * * First we have a helper routine which tells is if from this file descriptor * (ie. the /dev/net/tun device) will block: */ static bool will_block(int fd) { fd_set fdset; struct timeval zero = { 0, 0 }; FD_ZERO(&fdset); FD_SET(fd, &fdset); return select(fd+1, &fdset, NULL, NULL, &zero) != 1; } /* * This handles packets coming in from the tun device to our Guest. Like all * service routines, it gets called again as soon as it returns, so you don't * see a while(1) loop here. */ static void net_input(struct virtqueue *vq) { int len; unsigned int head, out, in; struct iovec iov[vq->vring.num]; struct net_info *net_info = vq->dev->priv; /* * Get a descriptor to write an incoming packet into. This will also * send an interrupt if they're out of descriptors. */ head = wait_for_vq_desc(vq, iov, &out, &in); if (out) errx(1, "Output buffers in net input queue?"); /* * If it looks like we'll block reading from the tun device, send them * an interrupt. */ if (vq->pending_used && will_block(net_info->tunfd)) trigger_irq(vq); /* * Read in the packet. This is where we normally wait (when there's no * incoming network traffic). */ len = readv(net_info->tunfd, iov, in); if (len <= 0) warn("Failed to read from tun (%d).", errno); /* * Mark that packet buffer as used, but don't interrupt here. We want * to wait until we've done as much work as we can. */ add_used(vq, head, len); } /*:*/ /* This is the helper to create threads: run the service routine in a loop. */ static int do_thread(void *_vq) { struct virtqueue *vq = _vq; for (;;) vq->service(vq); return 0; } /* * When a child dies, we kill our entire process group with SIGTERM. This * also has the side effect that the shell restores the console for us! */ static void kill_launcher(int signal) { kill(0, SIGTERM); } static void reset_vq_pci_config(struct virtqueue *vq) { vq->pci_config.queue_size = VIRTQUEUE_NUM; vq->pci_config.queue_enable = 0; } static void reset_device(struct device *dev) { struct virtqueue *vq; verbose("Resetting device %s\n", dev->name); /* Clear any features they've acked. */ dev->features_accepted = 0; /* We're going to be explicitly killing threads, so ignore them. */ signal(SIGCHLD, SIG_IGN); /* * 4.1.4.3.1: * * The device MUST present a 0 in queue_enable on reset. * * This means we set it here, and reset the saved ones in every vq. */ dev->mmio->cfg.queue_enable = 0; /* Get rid of the virtqueue threads */ for (vq = dev->vq; vq; vq = vq->next) { vq->last_avail_idx = 0; reset_vq_pci_config(vq); if (vq->thread != (pid_t)-1) { kill(vq->thread, SIGTERM); waitpid(vq->thread, NULL, 0); vq->thread = (pid_t)-1; } } dev->running = false; /* Now we care if threads die. */ signal(SIGCHLD, (void *)kill_launcher); } static void cleanup_devices(void) { unsigned int i; for (i = 1; i < MAX_PCI_DEVICES; i++) { struct device *d = devices.pci[i]; if (!d) continue; reset_device(d); } /* If we saved off the original terminal settings, restore them now. */ if (orig_term.c_lflag & (ISIG|ICANON|ECHO)) tcsetattr(STDIN_FILENO, TCSANOW, &orig_term); } /*L:217 * We do PCI. This is mainly done to let us test the kernel virtio PCI * code. */ /* Linux expects a PCI host bridge: ours is a dummy, and first on the bus. */ static struct device pci_host_bridge; static void init_pci_host_bridge(void) { pci_host_bridge.name = "PCI Host Bridge"; pci_host_bridge.config.class = 0x06; /* bridge */ pci_host_bridge.config.subclass = 0; /* host bridge */ devices.pci[0] = &pci_host_bridge; } /* The IO ports used to read the PCI config space. */ #define PCI_CONFIG_ADDR 0xCF8 #define PCI_CONFIG_DATA 0xCFC /* * Not really portable, but does help readability: this is what the Guest * writes to the PCI_CONFIG_ADDR IO port. */ union pci_config_addr { struct { unsigned mbz: 2; unsigned offset: 6; unsigned funcnum: 3; unsigned devnum: 5; unsigned busnum: 8; unsigned reserved: 7; unsigned enabled : 1; } bits; u32 val; }; /* * We cache what they wrote to the address port, so we know what they're * talking about when they access the data port. */ static union pci_config_addr pci_config_addr; static struct device *find_pci_device(unsigned int index) { return devices.pci[index]; } /* PCI can do 1, 2 and 4 byte reads; we handle that here. */ static void ioread(u16 off, u32 v, u32 mask, u32 *val) { assert(off < 4); assert(mask == 0xFF || mask == 0xFFFF || mask == 0xFFFFFFFF); *val = (v >> (off * 8)) & mask; } /* PCI can do 1, 2 and 4 byte writes; we handle that here. */ static void iowrite(u16 off, u32 v, u32 mask, u32 *dst) { assert(off < 4); assert(mask == 0xFF || mask == 0xFFFF || mask == 0xFFFFFFFF); *dst &= ~(mask << (off * 8)); *dst |= (v & mask) << (off * 8); } /* * Where PCI_CONFIG_DATA accesses depends on the previous write to * PCI_CONFIG_ADDR. */ static struct device *dev_and_reg(u32 *reg) { if (!pci_config_addr.bits.enabled) return NULL; if (pci_config_addr.bits.funcnum != 0) return NULL; if (pci_config_addr.bits.busnum != 0) return NULL; if (pci_config_addr.bits.offset * 4 >= sizeof(struct pci_config)) return NULL; *reg = pci_config_addr.bits.offset; return find_pci_device(pci_config_addr.bits.devnum); } /* * We can get invalid combinations of values while they're writing, so we * only fault if they try to write with some invalid bar/offset/length. */ static bool valid_bar_access(struct device *d, struct virtio_pci_cfg_cap *cfg_access) { /* We only have 1 bar (BAR0) */ if (cfg_access->cap.bar != 0) return false; /* Check it's within BAR0. */ if (cfg_access->cap.offset >= d->mmio_size || cfg_access->cap.offset + cfg_access->cap.length > d->mmio_size) return false; /* Check length is 1, 2 or 4. */ if (cfg_access->cap.length != 1 && cfg_access->cap.length != 2 && cfg_access->cap.length != 4) return false; /* * 4.1.4.7.2: * * The driver MUST NOT write a cap.offset which is not a multiple of * cap.length (ie. all accesses MUST be aligned). */ if (cfg_access->cap.offset % cfg_access->cap.length != 0) return false; /* Return pointer into word in BAR0. */ return true; } /* Is this accessing the PCI config address port?. */ static bool is_pci_addr_port(u16 port) { return port >= PCI_CONFIG_ADDR && port < PCI_CONFIG_ADDR + 4; } static bool pci_addr_iowrite(u16 port, u32 mask, u32 val) { iowrite(port - PCI_CONFIG_ADDR, val, mask, &pci_config_addr.val); verbose("PCI%s: %#x/%x: bus %u dev %u func %u reg %u\n", pci_config_addr.bits.enabled ? "" : " DISABLED", val, mask, pci_config_addr.bits.busnum, pci_config_addr.bits.devnum, pci_config_addr.bits.funcnum, pci_config_addr.bits.offset); return true; } static void pci_addr_ioread(u16 port, u32 mask, u32 *val) { ioread(port - PCI_CONFIG_ADDR, pci_config_addr.val, mask, val); } /* Is this accessing the PCI config data port?. */ static bool is_pci_data_port(u16 port) { return port >= PCI_CONFIG_DATA && port < PCI_CONFIG_DATA + 4; } static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask); static bool pci_data_iowrite(u16 port, u32 mask, u32 val) { u32 reg, portoff; struct device *d = dev_and_reg(®); /* Complain if they don't belong to a device. */ if (!d) return false; /* They can do 1 byte writes, etc. */ portoff = port - PCI_CONFIG_DATA; /* * PCI uses a weird way to determine the BAR size: the OS * writes all 1's, and sees which ones stick. */ if (&d->config_words[reg] == &d->config.bar[0]) { int i; iowrite(portoff, val, mask, &d->config.bar[0]); for (i = 0; (1 << i) < d->mmio_size; i++) d->config.bar[0] &= ~(1 << i); return true; } else if ((&d->config_words[reg] > &d->config.bar[0] && &d->config_words[reg] <= &d->config.bar[6]) || &d->config_words[reg] == &d->config.expansion_rom_addr) { /* Allow writing to any other BAR, or expansion ROM */ iowrite(portoff, val, mask, &d->config_words[reg]); return true; /* We let them overide latency timer and cacheline size */ } else if (&d->config_words[reg] == (void *)&d->config.cacheline_size) { /* Only let them change the first two fields. */ if (mask == 0xFFFFFFFF) mask = 0xFFFF; iowrite(portoff, val, mask, &d->config_words[reg]); return true; } else if (&d->config_words[reg] == (void *)&d->config.command && mask == 0xFFFF) { /* Ignore command writes. */ return true; } else if (&d->config_words[reg] == (void *)&d->config.cfg_access.cap.bar || &d->config_words[reg] == &d->config.cfg_access.cap.length || &d->config_words[reg] == &d->config.cfg_access.cap.offset) { /* * The VIRTIO_PCI_CAP_PCI_CFG capability * provides a backdoor to access the MMIO * regions without mapping them. Weird, but * useful. */ iowrite(portoff, val, mask, &d->config_words[reg]); return true; } else if (&d->config_words[reg] == &d->config.cfg_access.pci_cfg_data) { u32 write_mask; /* * 4.1.4.7.1: * * Upon detecting driver write access to pci_cfg_data, the * device MUST execute a write access at offset cap.offset at * BAR selected by cap.bar using the first cap.length bytes * from pci_cfg_data. */ /* Must be bar 0 */ if (!valid_bar_access(d, &d->config.cfg_access)) return false; iowrite(portoff, val, mask, &d->config.cfg_access.pci_cfg_data); /* * Now emulate a write. The mask we use is set by * len, *not* this write! */ write_mask = (1ULL<<(8*d->config.cfg_access.cap.length)) - 1; verbose("Window writing %#x/%#x to bar %u, offset %u len %u\n", d->config.cfg_access.pci_cfg_data, write_mask, d->config.cfg_access.cap.bar, d->config.cfg_access.cap.offset, d->config.cfg_access.cap.length); emulate_mmio_write(d, d->config.cfg_access.cap.offset, d->config.cfg_access.pci_cfg_data, write_mask); return true; } /* * 4.1.4.1: * * The driver MUST NOT write into any field of the capability * structure, with the exception of those with cap_type * VIRTIO_PCI_CAP_PCI_CFG... */ return false; } static u32 emulate_mmio_read(struct device *d, u32 off, u32 mask); static void pci_data_ioread(u16 port, u32 mask, u32 *val) { u32 reg; struct device *d = dev_and_reg(®); if (!d) return; /* Read through the PCI MMIO access window is special */ if (&d->config_words[reg] == &d->config.cfg_access.pci_cfg_data) { u32 read_mask; /* * 4.1.4.7.1: * * Upon detecting driver read access to pci_cfg_data, the * device MUST execute a read access of length cap.length at * offset cap.offset at BAR selected by cap.bar and store the * first cap.length bytes in pci_cfg_data. */ /* Must be bar 0 */ if (!valid_bar_access(d, &d->config.cfg_access)) errx(1, "Invalid cfg_access to bar%u, offset %u len %u", d->config.cfg_access.cap.bar, d->config.cfg_access.cap.offset, d->config.cfg_access.cap.length); /* * Read into the window. The mask we use is set by * len, *not* this read! */ read_mask = (1ULL<<(8*d->config.cfg_access.cap.length))-1; d->config.cfg_access.pci_cfg_data = emulate_mmio_read(d, d->config.cfg_access.cap.offset, read_mask); verbose("Window read %#x/%#x from bar %u, offset %u len %u\n", d->config.cfg_access.pci_cfg_data, read_mask, d->config.cfg_access.cap.bar, d->config.cfg_access.cap.offset, d->config.cfg_access.cap.length); } ioread(port - PCI_CONFIG_DATA, d->config_words[reg], mask, val); } /*L:216 * This is where we emulate a handful of Guest instructions. It's ugly * and we used to do it in the kernel but it grew over time. */ /* * We use the ptrace syscall's pt_regs struct to talk about registers * to lguest: these macros convert the names to the offsets. */ #define getreg(name) getreg_off(offsetof(struct user_regs_struct, name)) #define setreg(name, val) \ setreg_off(offsetof(struct user_regs_struct, name), (val)) static u32 getreg_off(size_t offset) { u32 r; unsigned long args[] = { LHREQ_GETREG, offset }; if (pwrite(lguest_fd, args, sizeof(args), cpu_id) < 0) err(1, "Getting register %u", offset); if (pread(lguest_fd, &r, sizeof(r), cpu_id) != sizeof(r)) err(1, "Reading register %u", offset); return r; } static void setreg_off(size_t offset, u32 val) { unsigned long args[] = { LHREQ_SETREG, offset, val }; if (pwrite(lguest_fd, args, sizeof(args), cpu_id) < 0) err(1, "Setting register %u", offset); } /* Get register by instruction encoding */ static u32 getreg_num(unsigned regnum, u32 mask) { /* 8 bit ops use regnums 4-7 for high parts of word */ if (mask == 0xFF && (regnum & 0x4)) return getreg_num(regnum & 0x3, 0xFFFF) >> 8; switch (regnum) { case 0: return getreg(eax) & mask; case 1: return getreg(ecx) & mask; case 2: return getreg(edx) & mask; case 3: return getreg(ebx) & mask; case 4: return getreg(esp) & mask; case 5: return getreg(ebp) & mask; case 6: return getreg(esi) & mask; case 7: return getreg(edi) & mask; } abort(); } /* Set register by instruction encoding */ static void setreg_num(unsigned regnum, u32 val, u32 mask) { /* Don't try to set bits out of range */ assert(~(val & ~mask)); /* 8 bit ops use regnums 4-7 for high parts of word */ if (mask == 0xFF && (regnum & 0x4)) { /* Construct the 16 bits we want. */ val = (val << 8) | getreg_num(regnum & 0x3, 0xFF); setreg_num(regnum & 0x3, val, 0xFFFF); return; } switch (regnum) { case 0: setreg(eax, val | (getreg(eax) & ~mask)); return; case 1: setreg(ecx, val | (getreg(ecx) & ~mask)); return; case 2: setreg(edx, val | (getreg(edx) & ~mask)); return; case 3: setreg(ebx, val | (getreg(ebx) & ~mask)); return; case 4: setreg(esp, val | (getreg(esp) & ~mask)); return; case 5: setreg(ebp, val | (getreg(ebp) & ~mask)); return; case 6: setreg(esi, val | (getreg(esi) & ~mask)); return; case 7: setreg(edi, val | (getreg(edi) & ~mask)); return; } abort(); } /* Get bytes of displacement appended to instruction, from r/m encoding */ static u32 insn_displacement_len(u8 mod_reg_rm) { /* Switch on the mod bits */ switch (mod_reg_rm >> 6) { case 0: /* If mod == 0, and r/m == 101, 16-bit displacement follows */ if ((mod_reg_rm & 0x7) == 0x5) return 2; /* Normally, mod == 0 means no literal displacement */ return 0; case 1: /* One byte displacement */ return 1; case 2: /* Four byte displacement */ return 4; case 3: /* Register mode */ return 0; } abort(); } static void emulate_insn(const u8 insn[]) { unsigned long args[] = { LHREQ_TRAP, 13 }; unsigned int insnlen = 0, in = 0, small_operand = 0, byte_access; unsigned int eax, port, mask; /* * Default is to return all-ones on IO port reads, which traditionally * means "there's nothing there". */ u32 val = 0xFFFFFFFF; /* * This must be the Guest kernel trying to do something, not userspace! * The bottom two bits of the CS segment register are the privilege * level. */ if ((getreg(xcs) & 3) != 0x1) goto no_emulate; /* Decoding x86 instructions is icky. */ /* * Around 2.6.33, the kernel started using an emulation for the * cmpxchg8b instruction in early boot on many configurations. This * code isn't paravirtualized, and it tries to disable interrupts. * Ignore it, which will Mostly Work. */ if (insn[insnlen] == 0xfa) { /* "cli", or Clear Interrupt Enable instruction. Skip it. */ insnlen = 1; goto skip_insn; } /* * 0x66 is an "operand prefix". It means a 16, not 32 bit in/out. */ if (insn[insnlen] == 0x66) { small_operand = 1; /* The instruction is 1 byte so far, read the next byte. */ insnlen = 1; } /* If the lower bit isn't set, it's a single byte access */ byte_access = !(insn[insnlen] & 1); /* * Now we can ignore the lower bit and decode the 4 opcodes * we need to emulate. */ switch (insn[insnlen] & 0xFE) { case 0xE4: /* in ,%al */ port = insn[insnlen+1]; insnlen += 2; in = 1; break; case 0xEC: /* in (%dx),%al */ port = getreg(edx) & 0xFFFF; insnlen += 1; in = 1; break; case 0xE6: /* out %al, */ port = insn[insnlen+1]; insnlen += 2; break; case 0xEE: /* out %al,(%dx) */ port = getreg(edx) & 0xFFFF; insnlen += 1; break; default: /* OK, we don't know what this is, can't emulate. */ goto no_emulate; } /* Set a mask of the 1, 2 or 4 bytes, depending on size of IO */ if (byte_access) mask = 0xFF; else if (small_operand) mask = 0xFFFF; else mask = 0xFFFFFFFF; /* * If it was an "IN" instruction, they expect the result to be read * into %eax, so we change %eax. */ eax = getreg(eax); if (in) { /* This is the PS/2 keyboard status; 1 means ready for output */ if (port == 0x64) val = 1; else if (is_pci_addr_port(port)) pci_addr_ioread(port, mask, &val); else if (is_pci_data_port(port)) pci_data_ioread(port, mask, &val); /* Clear the bits we're about to read */ eax &= ~mask; /* Copy bits in from val. */ eax |= val & mask; /* Now update the register. */ setreg(eax, eax); } else { if (is_pci_addr_port(port)) { if (!pci_addr_iowrite(port, mask, eax)) goto bad_io; } else if (is_pci_data_port(port)) { if (!pci_data_iowrite(port, mask, eax)) goto bad_io; } /* There are many other ports, eg. CMOS clock, serial * and parallel ports, so we ignore them all. */ } verbose("IO %s of %x to %u: %#08x\n", in ? "IN" : "OUT", mask, port, eax); skip_insn: /* Finally, we've "done" the instruction, so move past it. */ setreg(eip, getreg(eip) + insnlen); return; bad_io: warnx("Attempt to %s port %u (%#x mask)", in ? "read from" : "write to", port, mask); no_emulate: /* Inject trap into Guest. */ if (write(lguest_fd, args, sizeof(args)) < 0) err(1, "Reinjecting trap 13 for fault at %#x", getreg(eip)); } static struct device *find_mmio_region(unsigned long paddr, u32 *off) { unsigned int i; for (i = 1; i < MAX_PCI_DEVICES; i++) { struct device *d = devices.pci[i]; if (!d) continue; if (paddr < d->mmio_addr) continue; if (paddr >= d->mmio_addr + d->mmio_size) continue; *off = paddr - d->mmio_addr; return d; } return NULL; } /* FIXME: Use vq array. */ static struct virtqueue *vq_by_num(struct device *d, u32 num) { struct virtqueue *vq = d->vq; while (num-- && vq) vq = vq->next; return vq; } static void save_vq_config(const struct virtio_pci_common_cfg *cfg, struct virtqueue *vq) { vq->pci_config = *cfg; } static void restore_vq_config(struct virtio_pci_common_cfg *cfg, struct virtqueue *vq) { /* Only restore the per-vq part */ size_t off = offsetof(struct virtio_pci_common_cfg, queue_size); memcpy((void *)cfg + off, (void *)&vq->pci_config + off, sizeof(*cfg) - off); } /* * When they enable the virtqueue, we check that their setup is valid. */ static void enable_virtqueue(struct device *d, struct virtqueue *vq) { /* * Create stack for thread. Since the stack grows upwards, we point * the stack pointer to the end of this region. */ char *stack = malloc(32768); /* Because lguest is 32 bit, all the descriptor high bits must be 0 */ if (vq->pci_config.queue_desc_hi || vq->pci_config.queue_avail_hi || vq->pci_config.queue_used_hi) errx(1, "%s: invalid 64-bit queue address", d->name); /* Initialize the virtqueue and check they're all in range. */ vq->vring.num = vq->pci_config.queue_size; vq->vring.desc = check_pointer(vq->pci_config.queue_desc_lo, sizeof(*vq->vring.desc) * vq->vring.num); vq->vring.avail = check_pointer(vq->pci_config.queue_avail_lo, sizeof(*vq->vring.avail) + (sizeof(vq->vring.avail->ring[0]) * vq->vring.num)); vq->vring.used = check_pointer(vq->pci_config.queue_used_lo, sizeof(*vq->vring.used) + (sizeof(vq->vring.used->ring[0]) * vq->vring.num)); /* Create a zero-initialized eventfd. */ vq->eventfd = eventfd(0, 0); if (vq->eventfd < 0) err(1, "Creating eventfd"); /* * CLONE_VM: because it has to access the Guest memory, and SIGCHLD so * we get a signal if it dies. */ vq->thread = clone(do_thread, stack + 32768, CLONE_VM | SIGCHLD, vq); if (vq->thread == (pid_t)-1) err(1, "Creating clone"); } static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask) { struct virtqueue *vq; switch (off) { case offsetof(struct virtio_pci_mmio, cfg.device_feature_select): /* * 4.1.4.3.1: * * The device MUST present the feature bits it is offering in * device_feature, starting at bit device_feature_select ∗ 32 * for any device_feature_select written by the driver */ if (val == 0) d->mmio->cfg.device_feature = d->features; else if (val == 1) d->mmio->cfg.device_feature = (d->features >> 32); else d->mmio->cfg.device_feature = 0; goto write_through32; case offsetof(struct virtio_pci_mmio, cfg.guest_feature_select): if (val > 1) errx(1, "%s: Unexpected driver select %u", d->name, val); goto write_through32; case offsetof(struct virtio_pci_mmio, cfg.guest_feature): if (d->mmio->cfg.guest_feature_select == 0) { d->features_accepted &= ~((u64)0xFFFFFFFF); d->features_accepted |= val; } else { assert(d->mmio->cfg.guest_feature_select == 1); d->features_accepted &= 0xFFFFFFFF; d->features_accepted |= ((u64)val) << 32; } if (d->features_accepted & ~d->features) errx(1, "%s: over-accepted features %#llx of %#llx", d->name, d->features_accepted, d->features); goto write_through32; case offsetof(struct virtio_pci_mmio, cfg.device_status): verbose("%s: device status -> %#x\n", d->name, val); /* * 4.1.4.3.1: * * The device MUST reset when 0 is written to device_status, * and present a 0 in device_status once that is done. */ if (val == 0) reset_device(d); goto write_through8; case offsetof(struct virtio_pci_mmio, cfg.queue_select): vq = vq_by_num(d, val); /* * 4.1.4.3.1: * * The device MUST present a 0 in queue_size if the virtqueue * corresponding to the current queue_select is unavailable. */ if (!vq) { d->mmio->cfg.queue_size = 0; goto write_through16; } /* Save registers for old vq, if it was a valid vq */ if (d->mmio->cfg.queue_size) save_vq_config(&d->mmio->cfg, vq_by_num(d, d->mmio->cfg.queue_select)); /* Restore the registers for the queue they asked for */ restore_vq_config(&d->mmio->cfg, vq); goto write_through16; case offsetof(struct virtio_pci_mmio, cfg.queue_size): /* * 4.1.4.3.2: * * The driver MUST NOT write a value which is not a power of 2 * to queue_size. */ if (val & (val-1)) errx(1, "%s: invalid queue size %u\n", d->name, val); if (d->mmio->cfg.queue_enable) errx(1, "%s: changing queue size on live device", d->name); goto write_through16; case offsetof(struct virtio_pci_mmio, cfg.queue_msix_vector): errx(1, "%s: attempt to set MSIX vector to %u", d->name, val); case offsetof(struct virtio_pci_mmio, cfg.queue_enable): /* * 4.1.4.3.2: * * The driver MUST NOT write a 0 to queue_enable. */ if (val != 1) errx(1, "%s: setting queue_enable to %u", d->name, val); d->mmio->cfg.queue_enable = val; save_vq_config(&d->mmio->cfg, vq_by_num(d, d->mmio->cfg.queue_select)); /* * 4.1.4.3.2: * * The driver MUST configure the other virtqueue fields before * enabling the virtqueue with queue_enable. */ enable_virtqueue(d, vq_by_num(d, d->mmio->cfg.queue_select)); goto write_through16; case offsetof(struct virtio_pci_mmio, cfg.queue_notify_off): errx(1, "%s: attempt to write to queue_notify_off", d->name); case offsetof(struct virtio_pci_mmio, cfg.queue_desc_lo): case offsetof(struct virtio_pci_mmio, cfg.queue_desc_hi): case offsetof(struct virtio_pci_mmio, cfg.queue_avail_lo): case offsetof(struct virtio_pci_mmio, cfg.queue_avail_hi): case offsetof(struct virtio_pci_mmio, cfg.queue_used_lo): case offsetof(struct virtio_pci_mmio, cfg.queue_used_hi): /* * 4.1.4.3.2: * * The driver MUST configure the other virtqueue fields before * enabling the virtqueue with queue_enable. */ if (d->mmio->cfg.queue_enable) errx(1, "%s: changing queue on live device", d->name); goto write_through32; case offsetof(struct virtio_pci_mmio, notify): vq = vq_by_num(d, val); if (!vq) errx(1, "Invalid vq notification on %u", val); /* Notify the process handling this vq by adding 1 to eventfd */ write(vq->eventfd, "\1\0\0\0\0\0\0\0", 8); goto write_through16; case offsetof(struct virtio_pci_mmio, isr): errx(1, "%s: Unexpected write to isr", d->name); /* Weird corner case: write to emerg_wr of console */ case sizeof(struct virtio_pci_mmio) + offsetof(struct virtio_console_config, emerg_wr): if (strcmp(d->name, "console") == 0) { char c = val; write(STDOUT_FILENO, &c, 1); goto write_through32; } /* Fall through... */ default: /* * 4.1.4.3.2: * * The driver MUST NOT write to device_feature, num_queues, * config_generation or queue_notify_off. */ errx(1, "%s: Unexpected write to offset %u", d->name, off); } /* * 4.1.3.1: * * The driver MUST access each field using the “natural” access * method, i.e. 32-bit accesses for 32-bit fields, 16-bit accesses for * 16-bit fields and 8-bit accesses for 8-bit fields. */ write_through32: if (mask != 0xFFFFFFFF) { errx(1, "%s: non-32-bit write to offset %u (%#x)", d->name, off, getreg(eip)); return; } memcpy((char *)d->mmio + off, &val, 4); return; write_through16: if (mask != 0xFFFF) errx(1, "%s: non-16-bit (%#x) write to offset %u (%#x)", d->name, mask, off, getreg(eip)); memcpy((char *)d->mmio + off, &val, 2); return; write_through8: if (mask != 0xFF) errx(1, "%s: non-8-bit write to offset %u (%#x)", d->name, off, getreg(eip)); memcpy((char *)d->mmio + off, &val, 1); return; } static u32 emulate_mmio_read(struct device *d, u32 off, u32 mask) { u8 isr; u32 val = 0; switch (off) { case offsetof(struct virtio_pci_mmio, cfg.device_feature_select): case offsetof(struct virtio_pci_mmio, cfg.device_feature): case offsetof(struct virtio_pci_mmio, cfg.guest_feature_select): case offsetof(struct virtio_pci_mmio, cfg.guest_feature): goto read_through32; case offsetof(struct virtio_pci_mmio, cfg.msix_config): errx(1, "%s: read of msix_config", d->name); case offsetof(struct virtio_pci_mmio, cfg.num_queues): goto read_through16; case offsetof(struct virtio_pci_mmio, cfg.device_status): case offsetof(struct virtio_pci_mmio, cfg.config_generation): /* * 4.1.4.3.1: * * The device MUST present a changed config_generation after * the driver has read a device-specific configuration value * which has changed since any part of the device-specific * configuration was last read. * * This is simple: none of our devices change config, so this * is always 0. */ goto read_through8; case offsetof(struct virtio_pci_mmio, notify): goto read_through16; case offsetof(struct virtio_pci_mmio, isr): if (mask != 0xFF) errx(1, "%s: non-8-bit read from offset %u (%#x)", d->name, off, getreg(eip)); isr = d->mmio->isr; /* * 4.1.4.5.1: * * The device MUST reset ISR status to 0 on driver read. */ d->mmio->isr = 0; return isr; case offsetof(struct virtio_pci_mmio, padding): errx(1, "%s: read from padding (%#x)", d->name, getreg(eip)); default: /* Read from device config space, beware unaligned overflow */ if (off > d->mmio_size - 4) errx(1, "%s: read past end (%#x)", d->name, getreg(eip)); if (mask == 0xFFFFFFFF) goto read_through32; else if (mask == 0xFFFF) goto read_through16; else goto read_through8; } /* * 4.1.3.1: * * The driver MUST access each field using the “natural” access * method, i.e. 32-bit accesses for 32-bit fields, 16-bit accesses for * 16-bit fields and 8-bit accesses for 8-bit fields. */ read_through32: if (mask != 0xFFFFFFFF) errx(1, "%s: non-32-bit read to offset %u (%#x)", d->name, off, getreg(eip)); memcpy(&val, (char *)d->mmio + off, 4); return val; read_through16: if (mask != 0xFFFF) errx(1, "%s: non-16-bit read to offset %u (%#x)", d->name, off, getreg(eip)); memcpy(&val, (char *)d->mmio + off, 2); return val; read_through8: if (mask != 0xFF) errx(1, "%s: non-8-bit read to offset %u (%#x)", d->name, off, getreg(eip)); memcpy(&val, (char *)d->mmio + off, 1); return val; } static void emulate_mmio(unsigned long paddr, const u8 *insn) { u32 val, off, mask = 0xFFFFFFFF, insnlen = 0; struct device *d = find_mmio_region(paddr, &off); unsigned long args[] = { LHREQ_TRAP, 14 }; if (!d) { warnx("MMIO touching %#08lx (not a device)", paddr); goto reinject; } /* Prefix makes it a 16 bit op */ if (insn[0] == 0x66) { mask = 0xFFFF; insnlen++; } /* iowrite */ if (insn[insnlen] == 0x89) { /* Next byte is r/m byte: bits 3-5 are register. */ val = getreg_num((insn[insnlen+1] >> 3) & 0x7, mask); emulate_mmio_write(d, off, val, mask); insnlen += 2 + insn_displacement_len(insn[insnlen+1]); } else if (insn[insnlen] == 0x8b) { /* ioread */ /* Next byte is r/m byte: bits 3-5 are register. */ val = emulate_mmio_read(d, off, mask); setreg_num((insn[insnlen+1] >> 3) & 0x7, val, mask); insnlen += 2 + insn_displacement_len(insn[insnlen+1]); } else if (insn[0] == 0x88) { /* 8-bit iowrite */ mask = 0xff; /* Next byte is r/m byte: bits 3-5 are register. */ val = getreg_num((insn[1] >> 3) & 0x7, mask); emulate_mmio_write(d, off, val, mask); insnlen = 2 + insn_displacement_len(insn[1]); } else if (insn[0] == 0x8a) { /* 8-bit ioread */ mask = 0xff; val = emulate_mmio_read(d, off, mask); setreg_num((insn[1] >> 3) & 0x7, val, mask); insnlen = 2 + insn_displacement_len(insn[1]); } else { warnx("Unknown MMIO instruction touching %#08lx:" " %02x %02x %02x %02x at %u", paddr, insn[0], insn[1], insn[2], insn[3], getreg(eip)); reinject: /* Inject trap into Guest. */ if (write(lguest_fd, args, sizeof(args)) < 0) err(1, "Reinjecting trap 14 for fault at %#x", getreg(eip)); return; } /* Finally, we've "done" the instruction, so move past it. */ setreg(eip, getreg(eip) + insnlen); } /*L:190 * Device Setup * * All devices need a descriptor so the Guest knows it exists, and a "struct * device" so the Launcher can keep track of it. We have common helper * routines to allocate and manage them. */ static void add_pci_virtqueue(struct device *dev, void (*service)(struct virtqueue *)) { struct virtqueue **i, *vq = malloc(sizeof(*vq)); /* Initialize the virtqueue */ vq->next = NULL; vq->last_avail_idx = 0; vq->dev = dev; /* * This is the routine the service thread will run, and its Process ID * once it's running. */ vq->service = service; vq->thread = (pid_t)-1; /* Initialize the configuration. */ reset_vq_pci_config(vq); vq->pci_config.queue_notify_off = 0; /* Add one to the number of queues */ vq->dev->mmio->cfg.num_queues++; /* * Add to tail of list, so dev->vq is first vq, dev->vq->next is * second. */ for (i = &dev->vq; *i; i = &(*i)->next); *i = vq; } /* The Guest accesses the feature bits via the PCI common config MMIO region */ static void add_pci_feature(struct device *dev, unsigned bit) { dev->features |= (1ULL << bit); } /* For devices with no config. */ static void no_device_config(struct device *dev) { dev->mmio_addr = get_mmio_region(dev->mmio_size); dev->config.bar[0] = dev->mmio_addr; /* Bottom 4 bits must be zero */ assert(~(dev->config.bar[0] & 0xF)); } /* This puts the device config into BAR0 */ static void set_device_config(struct device *dev, const void *conf, size_t len) { /* Set up BAR 0 */ dev->mmio_size += len; dev->mmio = realloc(dev->mmio, dev->mmio_size); memcpy(dev->mmio + 1, conf, len); /* * 4.1.4.6: * * The device MUST present at least one VIRTIO_PCI_CAP_DEVICE_CFG * capability for any device type which has a device-specific * configuration. */ /* Hook up device cfg */ dev->config.cfg_access.cap.cap_next = offsetof(struct pci_config, device); /* * 4.1.4.6.1: * * The offset for the device-specific configuration MUST be 4-byte * aligned. */ assert(dev->config.cfg_access.cap.cap_next % 4 == 0); /* Fix up device cfg field length. */ dev->config.device.length = len; /* The rest is the same as the no-config case */ no_device_config(dev); } static void init_cap(struct virtio_pci_cap *cap, size_t caplen, int type, size_t bar_offset, size_t bar_bytes, u8 next) { cap->cap_vndr = PCI_CAP_ID_VNDR; cap->cap_next = next; cap->cap_len = caplen; cap->cfg_type = type; cap->bar = 0; memset(cap->padding, 0, sizeof(cap->padding)); cap->offset = bar_offset; cap->length = bar_bytes; } /* * This sets up the pci_config structure, as defined in the virtio 1.0 * standard (and PCI standard). */ static void init_pci_config(struct pci_config *pci, u16 type, u8 class, u8 subclass) { size_t bar_offset, bar_len; /* * 4.1.4.4.1: * * The device MUST either present notify_off_multiplier as an even * power of 2, or present notify_off_multiplier as 0. */ memset(pci, 0, sizeof(*pci)); /* 4.1.2.1: Devices MUST have the PCI Vendor ID 0x1AF4 */ pci->vendor_id = 0x1AF4; /* 4.1.2.1: ... PCI Device ID calculated by adding 0x1040 ... */ pci->device_id = 0x1040 + type; /* * PCI have specific codes for different types of devices. * Linux doesn't care, but it's a good clue for people looking * at the device. */ pci->class = class; pci->subclass = subclass; /* * 4.1.2.1: * * Non-transitional devices SHOULD have a PCI Revision ID of 1 or * higher */ pci->revid = 1; /* * 4.1.2.1: * * Non-transitional devices SHOULD have a PCI Subsystem Device ID of * 0x40 or higher. */ pci->subsystem_device_id = 0x40; /* We use our dummy interrupt controller, and irq_line is the irq */ pci->irq_line = devices.next_irq++; pci->irq_pin = 0; /* Support for extended capabilities. */ pci->status = (1 << 4); /* Link them in. */ /* * 4.1.4.3.1: * * The device MUST present at least one common configuration * capability. */ pci->capabilities = offsetof(struct pci_config, common); /* 4.1.4.3.1 ... offset MUST be 4-byte aligned. */ assert(pci->capabilities % 4 == 0); bar_offset = offsetof(struct virtio_pci_mmio, cfg); bar_len = sizeof(((struct virtio_pci_mmio *)0)->cfg); init_cap(&pci->common, sizeof(pci->common), VIRTIO_PCI_CAP_COMMON_CFG, bar_offset, bar_len, offsetof(struct pci_config, notify)); /* * 4.1.4.4.1: * * The device MUST present at least one notification capability. */ bar_offset += bar_len; bar_len = sizeof(((struct virtio_pci_mmio *)0)->notify); /* * 4.1.4.4.1: * * The cap.offset MUST be 2-byte aligned. */ assert(pci->common.cap_next % 2 == 0); /* FIXME: Use a non-zero notify_off, for per-queue notification? */ /* * 4.1.4.4.1: * * The value cap.length presented by the device MUST be at least 2 and * MUST be large enough to support queue notification offsets for all * supported queues in all possible configurations. */ assert(bar_len >= 2); init_cap(&pci->notify.cap, sizeof(pci->notify), VIRTIO_PCI_CAP_NOTIFY_CFG, bar_offset, bar_len, offsetof(struct pci_config, isr)); bar_offset += bar_len; bar_len = sizeof(((struct virtio_pci_mmio *)0)->isr); /* * 4.1.4.5.1: * * The device MUST present at least one VIRTIO_PCI_CAP_ISR_CFG * capability. */ init_cap(&pci->isr, sizeof(pci->isr), VIRTIO_PCI_CAP_ISR_CFG, bar_offset, bar_len, offsetof(struct pci_config, cfg_access)); /* * 4.1.4.7.1: * * The device MUST present at least one VIRTIO_PCI_CAP_PCI_CFG * capability. */ /* This doesn't have any presence in the BAR */ init_cap(&pci->cfg_access.cap, sizeof(pci->cfg_access), VIRTIO_PCI_CAP_PCI_CFG, 0, 0, 0); bar_offset += bar_len + sizeof(((struct virtio_pci_mmio *)0)->padding); assert(bar_offset == sizeof(struct virtio_pci_mmio)); /* * This gets sewn in and length set in set_device_config(). * Some devices don't have a device configuration interface, so * we never expose this if we don't call set_device_config(). */ init_cap(&pci->device, sizeof(pci->device), VIRTIO_PCI_CAP_DEVICE_CFG, bar_offset, 0, 0); } /* * This routine does all the creation and setup of a new device, but we don't * actually place the MMIO region until we know the size (if any) of the * device-specific config. And we don't actually start the service threads * until later. * * See what I mean about userspace being boring? */ static struct device *new_pci_device(const char *name, u16 type, u8 class, u8 subclass) { struct device *dev = malloc(sizeof(*dev)); /* Now we populate the fields one at a time. */ dev->name = name; dev->vq = NULL; dev->running = false; dev->mmio_size = sizeof(struct virtio_pci_mmio); dev->mmio = calloc(1, dev->mmio_size); dev->features = (u64)1 << VIRTIO_F_VERSION_1; dev->features_accepted = 0; if (devices.device_num + 1 >= MAX_PCI_DEVICES) errx(1, "Can only handle 31 PCI devices"); init_pci_config(&dev->config, type, class, subclass); assert(!devices.pci[devices.device_num+1]); devices.pci[++devices.device_num] = dev; return dev; } /* * Our first setup routine is the console. It's a fairly simple device, but * UNIX tty handling makes it uglier than it could be. */ static void setup_console(void) { struct device *dev; struct virtio_console_config conf; /* If we can save the initial standard input settings... */ if (tcgetattr(STDIN_FILENO, &orig_term) == 0) { struct termios term = orig_term; /* * Then we turn off echo, line buffering and ^C etc: We want a * raw input stream to the Guest. */ term.c_lflag &= ~(ISIG|ICANON|ECHO); tcsetattr(STDIN_FILENO, TCSANOW, &term); } dev = new_pci_device("console", VIRTIO_ID_CONSOLE, 0x07, 0x00); /* We store the console state in dev->priv, and initialize it. */ dev->priv = malloc(sizeof(struct console_abort)); ((struct console_abort *)dev->priv)->count = 0; /* * The console needs two virtqueues: the input then the output. When * they put something the input queue, we make sure we're listening to * stdin. When they put something in the output queue, we write it to * stdout. */ add_pci_virtqueue(dev, console_input); add_pci_virtqueue(dev, console_output); /* We need a configuration area for the emerg_wr early writes. */ add_pci_feature(dev, VIRTIO_CONSOLE_F_EMERG_WRITE); set_device_config(dev, &conf, sizeof(conf)); verbose("device %u: console\n", devices.device_num); } /*:*/ /*M:010 * Inter-guest networking is an interesting area. Simplest is to have a * --sharenet= option which opens or creates a named pipe. This can be * used to send packets to another guest in a 1:1 manner. * * More sophisticated is to use one of the tools developed for project like UML * to do networking. * * Faster is to do virtio bonding in kernel. Doing this 1:1 would be * completely generic ("here's my vring, attach to your vring") and would work * for any traffic. Of course, namespace and permissions issues need to be * dealt with. A more sophisticated "multi-channel" virtio_net.c could hide * multiple inter-guest channels behind one interface, although it would * require some manner of hotplugging new virtio channels. * * Finally, we could use a virtio network switch in the kernel, ie. vhost. :*/ static u32 str2ip(const char *ipaddr) { unsigned int b[4]; if (sscanf(ipaddr, "%u.%u.%u.%u", &b[0], &b[1], &b[2], &b[3]) != 4) errx(1, "Failed to parse IP address '%s'", ipaddr); return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3]; } static void str2mac(const char *macaddr, unsigned char mac[6]) { unsigned int m[6]; if (sscanf(macaddr, "%02x:%02x:%02x:%02x:%02x:%02x", &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]) != 6) errx(1, "Failed to parse mac address '%s'", macaddr); mac[0] = m[0]; mac[1] = m[1]; mac[2] = m[2]; mac[3] = m[3]; mac[4] = m[4]; mac[5] = m[5]; } /* * This code is "adapted" from libbridge: it attaches the Host end of the * network device to the bridge device specified by the command line. * * This is yet another James Morris contribution (I'm an IP-level guy, so I * dislike bridging), and I just try not to break it. */ static void add_to_bridge(int fd, const char *if_name, const char *br_name) { int ifidx; struct ifreq ifr; if (!*br_name) errx(1, "must specify bridge name"); ifidx = if_nametoindex(if_name); if (!ifidx) errx(1, "interface %s does not exist!", if_name); strncpy(ifr.ifr_name, br_name, IFNAMSIZ); ifr.ifr_name[IFNAMSIZ-1] = '\0'; ifr.ifr_ifindex = ifidx; if (ioctl(fd, SIOCBRADDIF, &ifr) < 0) err(1, "can't add %s to bridge %s", if_name, br_name); } /* * This sets up the Host end of the network device with an IP address, brings * it up so packets will flow, the copies the MAC address into the hwaddr * pointer. */ static void configure_device(int fd, const char *tapif, u32 ipaddr) { struct ifreq ifr; struct sockaddr_in sin; memset(&ifr, 0, sizeof(ifr)); strcpy(ifr.ifr_name, tapif); /* Don't read these incantations. Just cut & paste them like I did! */ sin.sin_family = AF_INET; sin.sin_addr.s_addr = htonl(ipaddr); memcpy(&ifr.ifr_addr, &sin, sizeof(sin)); if (ioctl(fd, SIOCSIFADDR, &ifr) != 0) err(1, "Setting %s interface address", tapif); ifr.ifr_flags = IFF_UP; if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0) err(1, "Bringing interface %s up", tapif); } static int get_tun_device(char tapif[IFNAMSIZ]) { struct ifreq ifr; int vnet_hdr_sz; int netfd; /* Start with this zeroed. Messy but sure. */ memset(&ifr, 0, sizeof(ifr)); /* * We open the /dev/net/tun device and tell it we want a tap device. A * tap device is like a tun device, only somehow different. To tell * the truth, I completely blundered my way through this code, but it * works now! */ netfd = open_or_die("/dev/net/tun", O_RDWR); ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR; strcpy(ifr.ifr_name, "tap%d"); if (ioctl(netfd, TUNSETIFF, &ifr) != 0) err(1, "configuring /dev/net/tun"); if (ioctl(netfd, TUNSETOFFLOAD, TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0) err(1, "Could not set features for tun device"); /* * We don't need checksums calculated for packets coming in this * device: trust us! */ ioctl(netfd, TUNSETNOCSUM, 1); /* * In virtio before 1.0 (aka legacy virtio), we added a 16-bit * field at the end of the network header iff * VIRTIO_NET_F_MRG_RXBUF was negotiated. For virtio 1.0, * that became the norm, but we need to tell the tun device * about our expanded header (which is called * virtio_net_hdr_mrg_rxbuf in the legacy system). */ vnet_hdr_sz = sizeof(struct virtio_net_hdr_mrg_rxbuf); if (ioctl(netfd, TUNSETVNETHDRSZ, &vnet_hdr_sz) != 0) err(1, "Setting tun header size to %u", vnet_hdr_sz); memcpy(tapif, ifr.ifr_name, IFNAMSIZ); return netfd; } /*L:195 * Our network is a Host<->Guest network. This can either use bridging or * routing, but the principle is the same: it uses the "tun" device to inject * packets into the Host as if they came in from a normal network card. We * just shunt packets between the Guest and the tun device. */ static void setup_tun_net(char *arg) { struct device *dev; struct net_info *net_info = malloc(sizeof(*net_info)); int ipfd; u32 ip = INADDR_ANY; bool bridging = false; char tapif[IFNAMSIZ], *p; struct virtio_net_config conf; net_info->tunfd = get_tun_device(tapif); /* First we create a new network device. */ dev = new_pci_device("net", VIRTIO_ID_NET, 0x02, 0x00); dev->priv = net_info; /* Network devices need a recv and a send queue, just like console. */ add_pci_virtqueue(dev, net_input); add_pci_virtqueue(dev, net_output); /* * We need a socket to perform the magic network ioctls to bring up the * tap interface, connect to the bridge etc. Any socket will do! */ ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP); if (ipfd < 0) err(1, "opening IP socket"); /* If the command line was --tunnet=bridge: do bridging. */ if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) { arg += strlen(BRIDGE_PFX); bridging = true; } /* A mac address may follow the bridge name or IP address */ p = strchr(arg, ':'); if (p) { str2mac(p+1, conf.mac); add_pci_feature(dev, VIRTIO_NET_F_MAC); *p = '\0'; } /* arg is now either an IP address or a bridge name */ if (bridging) add_to_bridge(ipfd, tapif, arg); else ip = str2ip(arg); /* Set up the tun device. */ configure_device(ipfd, tapif, ip); /* Expect Guest to handle everything except UFO */ add_pci_feature(dev, VIRTIO_NET_F_CSUM); add_pci_feature(dev, VIRTIO_NET_F_GUEST_CSUM); add_pci_feature(dev, VIRTIO_NET_F_GUEST_TSO4); add_pci_feature(dev, VIRTIO_NET_F_GUEST_TSO6); add_pci_feature(dev, VIRTIO_NET_F_GUEST_ECN); add_pci_feature(dev, VIRTIO_NET_F_HOST_TSO4); add_pci_feature(dev, VIRTIO_NET_F_HOST_TSO6); add_pci_feature(dev, VIRTIO_NET_F_HOST_ECN); /* We handle indirect ring entries */ add_pci_feature(dev, VIRTIO_RING_F_INDIRECT_DESC); set_device_config(dev, &conf, sizeof(conf)); /* We don't need the socket any more; setup is done. */ close(ipfd); if (bridging) verbose("device %u: tun %s attached to bridge: %s\n", devices.device_num, tapif, arg); else verbose("device %u: tun %s: %s\n", devices.device_num, tapif, arg); } /*:*/ /* This hangs off device->priv. */ struct vblk_info { /* The size of the file. */ off64_t len; /* The file descriptor for the file. */ int fd; }; /*L:210 * The Disk * * The disk only has one virtqueue, so it only has one thread. It is really * simple: the Guest asks for a block number and we read or write that position * in the file. * * Before we serviced each virtqueue in a separate thread, that was unacceptably * slow: the Guest waits until the read is finished before running anything * else, even if it could have been doing useful work. * * We could have used async I/O, except it's reputed to suck so hard that * characters actually go missing from your code when you try to use it. */ static void blk_request(struct virtqueue *vq) { struct vblk_info *vblk = vq->dev->priv; unsigned int head, out_num, in_num, wlen; int ret, i; u8 *in; struct virtio_blk_outhdr out; struct iovec iov[vq->vring.num]; off64_t off; /* * Get the next request, where we normally wait. It triggers the * interrupt to acknowledge previously serviced requests (if any). */ head = wait_for_vq_desc(vq, iov, &out_num, &in_num); /* Copy the output header from the front of the iov (adjusts iov) */ iov_consume(iov, out_num, &out, sizeof(out)); /* Find and trim end of iov input array, for our status byte. */ in = NULL; for (i = out_num + in_num - 1; i >= out_num; i--) { if (iov[i].iov_len > 0) { in = iov[i].iov_base + iov[i].iov_len - 1; iov[i].iov_len--; break; } } if (!in) errx(1, "Bad virtblk cmd with no room for status"); /* * For historical reasons, block operations are expressed in 512 byte * "sectors". */ off = out.sector * 512; if (out.type & VIRTIO_BLK_T_OUT) { /* * Write * * Move to the right location in the block file. This can fail * if they try to write past end. */ if (lseek64(vblk->fd, off, SEEK_SET) != off) err(1, "Bad seek to sector %llu", out.sector); ret = writev(vblk->fd, iov, out_num); verbose("WRITE to sector %llu: %i\n", out.sector, ret); /* * Grr... Now we know how long the descriptor they sent was, we * make sure they didn't try to write over the end of the block * file (possibly extending it). */ if (ret > 0 && off + ret > vblk->len) { /* Trim it back to the correct length */ ftruncate64(vblk->fd, vblk->len); /* Die, bad Guest, die. */ errx(1, "Write past end %llu+%u", off, ret); } wlen = sizeof(*in); *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); } else if (out.type & VIRTIO_BLK_T_FLUSH) { /* Flush */ ret = fdatasync(vblk->fd); verbose("FLUSH fdatasync: %i\n", ret); wlen = sizeof(*in); *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); } else { /* * Read * * Move to the right location in the block file. This can fail * if they try to read past end. */ if (lseek64(vblk->fd, off, SEEK_SET) != off) err(1, "Bad seek to sector %llu", out.sector); ret = readv(vblk->fd, iov + out_num, in_num); if (ret >= 0) { wlen = sizeof(*in) + ret; *in = VIRTIO_BLK_S_OK; } else { wlen = sizeof(*in); *in = VIRTIO_BLK_S_IOERR; } } /* Finished that request. */ add_used(vq, head, wlen); } /*L:198 This actually sets up a virtual block device. */ static void setup_block_file(const char *filename) { struct device *dev; struct vblk_info *vblk; struct virtio_blk_config conf; /* Create the device. */ dev = new_pci_device("block", VIRTIO_ID_BLOCK, 0x01, 0x80); /* The device has one virtqueue, where the Guest places requests. */ add_pci_virtqueue(dev, blk_request); /* Allocate the room for our own bookkeeping */ vblk = dev->priv = malloc(sizeof(*vblk)); /* First we open the file and store the length. */ vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE); vblk->len = lseek64(vblk->fd, 0, SEEK_END); /* Tell Guest how many sectors this device has. */ conf.capacity = cpu_to_le64(vblk->len / 512); /* * Tell Guest not to put in too many descriptors at once: two are used * for the in and out elements. */ add_pci_feature(dev, VIRTIO_BLK_F_SEG_MAX); conf.seg_max = cpu_to_le32(VIRTQUEUE_NUM - 2); set_device_config(dev, &conf, sizeof(struct virtio_blk_config)); verbose("device %u: virtblock %llu sectors\n", devices.device_num, le64_to_cpu(conf.capacity)); } /*L:211 * Our random number generator device reads from /dev/urandom into the Guest's * input buffers. The usual case is that the Guest doesn't want random numbers * and so has no buffers although /dev/urandom is still readable, whereas * console is the reverse. * * The same logic applies, however. */ struct rng_info { int rfd; }; static void rng_input(struct virtqueue *vq) { int len; unsigned int head, in_num, out_num, totlen = 0; struct rng_info *rng_info = vq->dev->priv; struct iovec iov[vq->vring.num]; /* First we need a buffer from the Guests's virtqueue. */ head = wait_for_vq_desc(vq, iov, &out_num, &in_num); if (out_num) errx(1, "Output buffers in rng?"); /* * Just like the console write, we loop to cover the whole iovec. * In this case, short reads actually happen quite a bit. */ while (!iov_empty(iov, in_num)) { len = readv(rng_info->rfd, iov, in_num); if (len <= 0) err(1, "Read from /dev/urandom gave %i", len); iov_consume(iov, in_num, NULL, len); totlen += len; } /* Tell the Guest about the new input. */ add_used(vq, head, totlen); } /*L:199 * This creates a "hardware" random number device for the Guest. */ static void setup_rng(void) { struct device *dev; struct rng_info *rng_info = malloc(sizeof(*rng_info)); /* Our device's private info simply contains the /dev/urandom fd. */ rng_info->rfd = open_or_die("/dev/urandom", O_RDONLY); /* Create the new device. */ dev = new_pci_device("rng", VIRTIO_ID_RNG, 0xff, 0); dev->priv = rng_info; /* The device has one virtqueue, where the Guest places inbufs. */ add_pci_virtqueue(dev, rng_input); /* We don't have any configuration space */ no_device_config(dev); verbose("device %u: rng\n", devices.device_num); } /* That's the end of device setup. */ /*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */ static void __attribute__((noreturn)) restart_guest(void) { unsigned int i; /* * Since we don't track all open fds, we simply close everything beyond * stderr. */ for (i = 3; i < FD_SETSIZE; i++) close(i); /* Reset all the devices (kills all threads). */ cleanup_devices(); execv(main_args[0], main_args); err(1, "Could not exec %s", main_args[0]); } /*L:220 * Finally we reach the core of the Launcher which runs the Guest, serves * its input and output, and finally, lays it to rest. */ static void __attribute__((noreturn)) run_guest(void) { for (;;) { struct lguest_pending notify; int readval; /* We read from the /dev/lguest device to run the Guest. */ readval = pread(lguest_fd, ¬ify, sizeof(notify), cpu_id); if (readval == sizeof(notify)) { if (notify.trap == 13) { verbose("Emulating instruction at %#x\n", getreg(eip)); emulate_insn(notify.insn); } else if (notify.trap == 14) { verbose("Emulating MMIO at %#x\n", getreg(eip)); emulate_mmio(notify.addr, notify.insn); } else errx(1, "Unknown trap %i addr %#08x\n", notify.trap, notify.addr); /* ENOENT means the Guest died. Reading tells us why. */ } else if (errno == ENOENT) { char reason[1024] = { 0 }; pread(lguest_fd, reason, sizeof(reason)-1, cpu_id); errx(1, "%s", reason); /* ERESTART means that we need to reboot the guest */ } else if (errno == ERESTART) { restart_guest(); /* Anything else means a bug or incompatible change. */ } else err(1, "Running guest failed"); } } /*L:240 * This is the end of the Launcher. The good news: we are over halfway * through! The bad news: the most fiendish part of the code still lies ahead * of us. * * Are you ready? Take a deep breath and join me in the core of the Host, in * "make Host". :*/ static struct option opts[] = { { "verbose", 0, NULL, 'v' }, { "tunnet", 1, NULL, 't' }, { "block", 1, NULL, 'b' }, { "rng", 0, NULL, 'r' }, { "initrd", 1, NULL, 'i' }, { "username", 1, NULL, 'u' }, { "chroot", 1, NULL, 'c' }, { NULL }, }; static void usage(void) { errx(1, "Usage: lguest [--verbose] " "[--tunnet=(:|bridge::)\n" "|--block=|--initrd=]...\n" " vmlinux [args...]"); } /*L:105 The main routine is where the real work begins: */ int main(int argc, char *argv[]) { /* Memory, code startpoint and size of the (optional) initrd. */ unsigned long mem = 0, start, initrd_size = 0; /* Two temporaries. */ int i, c; /* The boot information for the Guest. */ struct boot_params *boot; /* If they specify an initrd file to load. */ const char *initrd_name = NULL; /* Password structure for initgroups/setres[gu]id */ struct passwd *user_details = NULL; /* Directory to chroot to */ char *chroot_path = NULL; /* Save the args: we "reboot" by execing ourselves again. */ main_args = argv; /* * First we initialize the device list. We remember next interrupt * number to use for devices (1: remember that 0 is used by the timer). */ devices.next_irq = 1; /* We're CPU 0. In fact, that's the only CPU possible right now. */ cpu_id = 0; /* * We need to know how much memory so we can set up the device * descriptor and memory pages for the devices as we parse the command * line. So we quickly look through the arguments to find the amount * of memory now. */ for (i = 1; i < argc; i++) { if (argv[i][0] != '-') { mem = atoi(argv[i]) * 1024 * 1024; /* * We start by mapping anonymous pages over all of * guest-physical memory range. This fills it with 0, * and ensures that the Guest won't be killed when it * tries to access it. */ guest_base = map_zeroed_pages(mem / getpagesize() + DEVICE_PAGES); guest_limit = mem; guest_max = guest_mmio = mem + DEVICE_PAGES*getpagesize(); break; } } /* We always have a console device, and it's always device 1. */ setup_console(); /* The options are fairly straight-forward */ while ((c = getopt_long(argc, argv, "v", opts, NULL)) != EOF) { switch (c) { case 'v': verbose = true; break; case 't': setup_tun_net(optarg); break; case 'b': setup_block_file(optarg); break; case 'r': setup_rng(); break; case 'i': initrd_name = optarg; break; case 'u': user_details = getpwnam(optarg); if (!user_details) err(1, "getpwnam failed, incorrect username?"); break; case 'c': chroot_path = optarg; break; default: warnx("Unknown argument %s", argv[optind]); usage(); } } /* * After the other arguments we expect memory and kernel image name, * followed by command line arguments for the kernel. */ if (optind + 2 > argc) usage(); verbose("Guest base is at %p\n", guest_base); /* Initialize the (fake) PCI host bridge device. */ init_pci_host_bridge(); /* Now we load the kernel */ start = load_kernel(open_or_die(argv[optind+1], O_RDONLY)); /* Boot information is stashed at physical address 0 */ boot = from_guest_phys(0); /* Map the initrd image if requested (at top of physical memory) */ if (initrd_name) { initrd_size = load_initrd(initrd_name, mem); /* * These are the location in the Linux boot header where the * start and size of the initrd are expected to be found. */ boot->hdr.ramdisk_image = mem - initrd_size; boot->hdr.ramdisk_size = initrd_size; /* The bootloader type 0xFF means "unknown"; that's OK. */ boot->hdr.type_of_loader = 0xFF; } /* * The Linux boot header contains an "E820" memory map: ours is a * simple, single region. */ boot->e820_entries = 1; boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM }); /* * The boot header contains a command line pointer: we put the command * line after the boot header. */ boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1); /* We use a simple helper to copy the arguments separated by spaces. */ concat((char *)(boot + 1), argv+optind+2); /* Set kernel alignment to 16M (CONFIG_PHYSICAL_ALIGN) */ boot->hdr.kernel_alignment = 0x1000000; /* Boot protocol version: 2.07 supports the fields for lguest. */ boot->hdr.version = 0x207; /* The hardware_subarch value of "1" tells the Guest it's an lguest. */ boot->hdr.hardware_subarch = 1; /* Tell the entry path not to try to reload segment registers. */ boot->hdr.loadflags |= KEEP_SEGMENTS; /* We tell the kernel to initialize the Guest. */ tell_kernel(start); /* Ensure that we terminate if a device-servicing child dies. */ signal(SIGCHLD, kill_launcher); /* If we exit via err(), this kills all the threads, restores tty. */ atexit(cleanup_devices); /* If requested, chroot to a directory */ if (chroot_path) { if (chroot(chroot_path) != 0) err(1, "chroot(\"%s\") failed", chroot_path); if (chdir("/") != 0) err(1, "chdir(\"/\") failed"); verbose("chroot done\n"); } /* If requested, drop privileges */ if (user_details) { uid_t u; gid_t g; u = user_details->pw_uid; g = user_details->pw_gid; if (initgroups(user_details->pw_name, g) != 0) err(1, "initgroups failed"); if (setresgid(g, g, g) != 0) err(1, "setresgid failed"); if (setresuid(u, u, u) != 0) err(1, "setresuid failed"); verbose("Dropping privileges completed\n"); } /* Finally, run the Guest. This doesn't return. */ run_guest(); } /*:*/ /*M:999 * Mastery is done: you now know everything I do. * * But surely you have seen code, features and bugs in your wanderings which * you now yearn to attack? That is the real game, and I look forward to you * patching and forking lguest into the Your-Name-Here-visor. * * Farewell, and good coding! * Rusty Russell. */