diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/lg.h | 2 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 278 |
2 files changed, 86 insertions, 194 deletions
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index 9136411fadd5..295df06e6590 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -59,6 +59,8 @@ struct lg_cpu { struct lguest_pages *last_pages; + /* Initialization mode: linear map everything. */ + bool linear_pages; int cpu_pgd; /* Which pgd this cpu is currently using */ /* If a hypercall was asked for, this points to the arguments. */ diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index d21578ee95de..00026222bde8 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -17,7 +17,6 @@ #include <linux/percpu.h> #include <asm/tlbflush.h> #include <asm/uaccess.h> -#include <asm/bootparam.h> #include "lg.h" /*M:008 @@ -325,10 +324,15 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) #endif /* First step: get the top-level Guest page table entry. */ - gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); - /* Toplevel not present? We can't map it in. */ - if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) - return false; + if (unlikely(cpu->linear_pages)) { + /* Faking up a linear mapping. */ + gpgd = __pgd(CHECK_GPGD_MASK); + } else { + gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); + /* Toplevel not present? We can't map it in. */ + if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) + return false; + } /* Now look at the matching shadow entry. */ spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); @@ -353,10 +357,15 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) } #ifdef CONFIG_X86_PAE - gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); - /* Middle level not present? We can't map it in. */ - if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) - return false; + if (unlikely(cpu->linear_pages)) { + /* Faking up a linear mapping. */ + gpmd = __pmd(_PAGE_TABLE); + } else { + gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); + /* Middle level not present? We can't map it in. */ + if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) + return false; + } /* Now look at the matching shadow entry. */ spmd = spmd_addr(cpu, *spgd, vaddr); @@ -397,8 +406,13 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) gpte_ptr = gpte_addr(cpu, gpgd, vaddr); #endif - /* Read the actual PTE value. */ - gpte = lgread(cpu, gpte_ptr, pte_t); + if (unlikely(cpu->linear_pages)) { + /* Linear? Make up a PTE which points to same page. */ + gpte = __pte((vaddr & PAGE_MASK) | _PAGE_RW | _PAGE_PRESENT); + } else { + /* Read the actual PTE value. */ + gpte = lgread(cpu, gpte_ptr, pte_t); + } /* If this page isn't in the Guest page tables, we can't page it in. */ if (!(pte_flags(gpte) & _PAGE_PRESENT)) @@ -454,7 +468,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) * Finally, we write the Guest PTE entry back: we've set the * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */ - lgwrite(cpu, gpte_ptr, pte_t, gpte); + if (likely(!cpu->linear_pages)) + lgwrite(cpu, gpte_ptr, pte_t, gpte); /* * The fault is fixed, the page table is populated, the mapping @@ -612,6 +627,11 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) #ifdef CONFIG_X86_PAE pmd_t gpmd; #endif + + /* Still not set up? Just map 1:1. */ + if (unlikely(cpu->linear_pages)) + return vaddr; + /* First step: get the top-level Guest page table entry. */ gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ @@ -708,32 +728,6 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, return next; } -/*H:430 - * (iv) Switching page tables - * - * Now we've seen all the page table setting and manipulation, let's see - * what happens when the Guest changes page tables (ie. changes the top-level - * pgdir). This occurs on almost every context switch. - */ -void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) -{ - int newpgdir, repin = 0; - - /* Look to see if we have this one already. */ - newpgdir = find_pgdir(cpu->lg, pgtable); - /* - * If not, we allocate or mug an existing one: if it's a fresh one, - * repin gets set to 1. - */ - if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs)) - newpgdir = new_pgdir(cpu, pgtable, &repin); - /* Change the current pgd index to the new one. */ - cpu->cpu_pgd = newpgdir; - /* If it was completely blank, we map in the Guest kernel stack */ - if (repin) - pin_stack_pages(cpu); -} - /*H:470 * Finally, a routine which throws away everything: all PGD entries in all * the shadow page tables, including the Guest's kernel mappings. This is used @@ -780,6 +774,44 @@ void guest_pagetable_clear_all(struct lg_cpu *cpu) /* We need the Guest kernel stack mapped again. */ pin_stack_pages(cpu); } + +/*H:430 + * (iv) Switching page tables + * + * Now we've seen all the page table setting and manipulation, let's see + * what happens when the Guest changes page tables (ie. changes the top-level + * pgdir). This occurs on almost every context switch. + */ +void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) +{ + int newpgdir, repin = 0; + + /* + * The very first time they call this, we're actually running without + * any page tables; we've been making it up. Throw them away now. + */ + if (unlikely(cpu->linear_pages)) { + release_all_pagetables(cpu->lg); + cpu->linear_pages = false; + /* Force allocation of a new pgdir. */ + newpgdir = ARRAY_SIZE(cpu->lg->pgdirs); + } else { + /* Look to see if we have this one already. */ + newpgdir = find_pgdir(cpu->lg, pgtable); + } + + /* + * If not, we allocate or mug an existing one: if it's a fresh one, + * repin gets set to 1. + */ + if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs)) + newpgdir = new_pgdir(cpu, pgtable, &repin); + /* Change the current pgd index to the new one. */ + cpu->cpu_pgd = newpgdir; + /* If it was completely blank, we map in the Guest kernel stack */ + if (repin) + pin_stack_pages(cpu); +} /*:*/ /*M:009 @@ -919,168 +951,26 @@ void guest_set_pmd(struct lguest *lg, unsigned long pmdp, u32 idx) } #endif -/*H:505 - * To get through boot, we construct simple identity page mappings (which - * set virtual == physical) and linear mappings which will get the Guest far - * enough into the boot to create its own. The linear mapping means we - * simplify the Guest boot, but it makes assumptions about their PAGE_OFFSET, - * as you'll see. - * - * We lay them out of the way, just below the initrd (which is why we need to - * know its size here). - */ -static unsigned long setup_pagetables(struct lguest *lg, - unsigned long mem, - unsigned long initrd_size) -{ - pgd_t __user *pgdir; - pte_t __user *linear; - unsigned long mem_base = (unsigned long)lg->mem_base; - unsigned int mapped_pages, i, linear_pages; -#ifdef CONFIG_X86_PAE - pmd_t __user *pmds; - unsigned int j; - pgd_t pgd; - pmd_t pmd; -#else - unsigned int phys_linear; -#endif - - /* - * We have mapped_pages frames to map, so we need linear_pages page - * tables to map them. - */ - mapped_pages = mem / PAGE_SIZE; - linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE; - - /* We put the toplevel page directory page at the top of memory. */ - pgdir = (pgd_t *)(mem + mem_base - initrd_size - PAGE_SIZE); - - /* Now we use the next linear_pages pages as pte pages */ - linear = (void *)pgdir - linear_pages * PAGE_SIZE; - -#ifdef CONFIG_X86_PAE - /* - * And the single mid page goes below that. We only use one, but - * that's enough to map 1G, which definitely gets us through boot. - */ - pmds = (void *)linear - PAGE_SIZE; -#endif - /* - * Linear mapping is easy: put every page's address into the - * mapping in order. - */ - for (i = 0; i < mapped_pages; i++) { - pte_t pte; - pte = pfn_pte(i, __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_USER)); - if (copy_to_user(&linear[i], &pte, sizeof(pte)) != 0) - return -EFAULT; - } - -#ifdef CONFIG_X86_PAE - /* - * Make the Guest PMD entries point to the corresponding place in the - * linear mapping (up to one page worth of PMD). - */ - for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD; - i += PTRS_PER_PTE, j++) { - pmd = pfn_pmd(((unsigned long)&linear[i] - mem_base)/PAGE_SIZE, - __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_USER)); - - if (copy_to_user(&pmds[j], &pmd, sizeof(pmd)) != 0) - return -EFAULT; - } - - /* One PGD entry, pointing to that PMD page. */ - pgd = __pgd(((unsigned long)pmds - mem_base) | _PAGE_PRESENT); - /* Copy it in as the first PGD entry (ie. addresses 0-1G). */ - if (copy_to_user(&pgdir[0], &pgd, sizeof(pgd)) != 0) - return -EFAULT; - /* - * And the other PGD entry to make the linear mapping at PAGE_OFFSET - */ - if (copy_to_user(&pgdir[KERNEL_PGD_BOUNDARY], &pgd, sizeof(pgd))) - return -EFAULT; -#else - /* - * The top level points to the linear page table pages above. - * We setup the identity and linear mappings here. - */ - phys_linear = (unsigned long)linear - mem_base; - for (i = 0; i < mapped_pages; i += PTRS_PER_PTE) { - pgd_t pgd; - /* - * Create a PGD entry which points to the right part of the - * linear PTE pages. - */ - pgd = __pgd((phys_linear + i * sizeof(pte_t)) | - (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER)); - - /* - * Copy it into the PGD page at 0 and PAGE_OFFSET. - */ - if (copy_to_user(&pgdir[i / PTRS_PER_PTE], &pgd, sizeof(pgd)) - || copy_to_user(&pgdir[pgd_index(PAGE_OFFSET) - + i / PTRS_PER_PTE], - &pgd, sizeof(pgd))) - return -EFAULT; - } -#endif - - /* - * We return the top level (guest-physical) address: we remember where - * this is to write it into lguest_data when the Guest initializes. - */ - return (unsigned long)pgdir - mem_base; -} - /*H:500 * (vii) Setting up the page tables initially. * - * When a Guest is first created, the Launcher tells us where the toplevel of - * its first page table is. We set some things up here: + * When a Guest is first created, set initialize a shadow page table which + * we will populate on future faults. The Guest doesn't have any actual + * pagetables yet, so we set linear_pages to tell demand_page() to fake it + * for the moment. */ int init_guest_pagetable(struct lguest *lg) { - u64 mem; - u32 initrd_size; - struct boot_params __user *boot = (struct boot_params *)lg->mem_base; -#ifdef CONFIG_X86_PAE - pgd_t *pgd; - pmd_t *pmd_table; -#endif - /* - * Get the Guest memory size and the ramdisk size from the boot header - * located at lg->mem_base (Guest address 0). - */ - if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem)) - || get_user(initrd_size, &boot->hdr.ramdisk_size)) - return -EFAULT; + struct lg_cpu *cpu = &lg->cpus[0]; + int allocated = 0; - /* - * We start on the first shadow page table, and give it a blank PGD - * page. - */ - lg->pgdirs[0].gpgdir = setup_pagetables(lg, mem, initrd_size); - if (IS_ERR_VALUE(lg->pgdirs[0].gpgdir)) - return lg->pgdirs[0].gpgdir; - lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL); - if (!lg->pgdirs[0].pgdir) + /* lg (and lg->cpus[]) starts zeroed: this allocates a new pgdir */ + cpu->cpu_pgd = new_pgdir(cpu, 0, &allocated); + if (!allocated) return -ENOMEM; -#ifdef CONFIG_X86_PAE - /* For PAE, we also create the initial mid-level. */ - pgd = lg->pgdirs[0].pgdir; - pmd_table = (pmd_t *) get_zeroed_page(GFP_KERNEL); - if (!pmd_table) - return -ENOMEM; - - set_pgd(pgd + SWITCHER_PGD_INDEX, - __pgd(__pa(pmd_table) | _PAGE_PRESENT)); -#endif - - /* This is the current page table. */ - lg->cpus[0].cpu_pgd = 0; + /* We start with a linear mapping until the initialize. */ + cpu->linear_pages = true; return 0; } @@ -1095,10 +985,10 @@ void page_table_guest_data_init(struct lg_cpu *cpu) * of virtual addresses used by the Switcher. */ || put_user(RESERVE_MEM * 1024 * 1024, - &cpu->lg->lguest_data->reserve_mem) - || put_user(cpu->lg->pgdirs[0].gpgdir, - &cpu->lg->lguest_data->pgdir)) + &cpu->lg->lguest_data->reserve_mem)) { kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); + return; + } /* * In flush_user_mappings() we loop from 0 to |