diff options
Diffstat (limited to 'arch/um/os-Linux/skas')
| -rw-r--r-- | arch/um/os-Linux/skas/process.c | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c index 03b3c4cc7735..819d68656673 100644 --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -108,7 +108,7 @@ static void get_skas_faultinfo(int pid, struct faultinfo *fi) wait_stub_done(pid); /* - * faultinfo is prepared by the stub-segv-handler at start of + * faultinfo is prepared by the stub_segv_handler at start of * the stub stack page. We just have to copy it. */ memcpy(fi, (void *)current_stub_stack(), sizeof(*fi)); @@ -175,6 +175,21 @@ static void handle_trap(int pid, struct uml_pt_regs *regs, extern char __syscall_stub_start[]; +/** + * userspace_tramp() - userspace trampoline + * @stack: pointer to the new userspace stack page, can be NULL, if? FIXME: + * + * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed. + * This function will run on a temporary stack page. + * It ptrace()'es itself, then + * Two pages are mapped into the userspace address space: + * - STUB_CODE (with EXEC), which contains the skas stub code + * - STUB_DATA (with R/W), which contains a data page that is used to transfer certain data between the UML userspace process and the UML kernel. + * Also for the userspace process a SIGSEGV handler is installed to catch pagefaults in the userspace process. + * And last the process stops itself to give control to the UML kernel for this userspace process. + * + * Return: Always zero, otherwise the current userspace process is ended with non null exit() call + */ static int userspace_tramp(void *stack) { void *addr; @@ -236,12 +251,24 @@ static int userspace_tramp(void *stack) int userspace_pid[NR_CPUS]; +/** + * start_userspace() - prepare a new userspace process + * @stub_stack: pointer to the stub stack. Can be NULL, if? FIXME: + * + * Setups a new temporary stack page that is used while userspace_tramp() runs + * Clones the kernel process into a new userspace process, with FDs only. + * + * Return: When positive: the process id of the new userspace process, + * when negative: an error number. + * FIXME: can PIDs become negative?! + */ int start_userspace(unsigned long stub_stack) { void *stack; unsigned long sp; int pid, status, n, flags, err; + /* setup a temporary stack page */ stack = mmap(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); @@ -252,10 +279,12 @@ int start_userspace(unsigned long stub_stack) return err; } + /* set stack pointer to the end of the stack page, so it can grow downwards */ sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *); flags = CLONE_FILES | SIGCHLD; + /* clone into new userspace process */ pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack); if (pid < 0) { err = -errno; @@ -323,11 +352,17 @@ void userspace(struct uml_pt_regs *regs) * fail. In this case, there is nothing to do but * just kill the process. */ - if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) + if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) { + printk(UM_KERN_ERR "userspace - ptrace set regs " + "failed, errno = %d\n", errno); fatal_sigsegv(); + } - if (put_fp_registers(pid, regs->fp)) + if (put_fp_registers(pid, regs->fp)) { + printk(UM_KERN_ERR "userspace - ptrace set fp regs " + "failed, errno = %d\n", errno); fatal_sigsegv(); + } /* Now we set local_using_sysemu to be used for one loop */ local_using_sysemu = get_using_sysemu(); |