diff options
| -rw-r--r-- | drivers/lguest/page_tables.c | 170 |
1 files changed, 101 insertions, 69 deletions
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index f074f34acb8..009c717fda9 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -291,6 +291,88 @@ static bool check_gpmd(struct lg_cpu *cpu, pmd_t gpmd) } #endif +/*H:331 + * This is the core routine to walk the shadow page tables and find the page + * table entry for a specific address. + * + * If allocate is set, then we allocate any missing levels, setting the flags + * on the new page directory and mid-level directories using the arguments + * (which are copied from the Guest's page table entries). + */ +static pte_t *find_spte(struct lg_cpu *cpu, unsigned long vaddr, bool allocate, + int pgd_flags, int pmd_flags) +{ + pgd_t *spgd; + /* Mid level for PAE. */ +#ifdef CONFIG_X86_PAE + pmd_t *spmd; +#endif + + /* Get top level entry. */ + spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); + if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { + /* No shadow entry: allocate a new shadow PTE page. */ + unsigned long ptepage; + + /* If they didn't want us to allocate anything, stop. */ + if (!allocate) + return NULL; + + ptepage = get_zeroed_page(GFP_KERNEL); + /* + * This is not really the Guest's fault, but killing it is + * simple for this corner case. + */ + if (!ptepage) { + kill_guest(cpu, "out of memory allocating pte page"); + return NULL; + } + /* + * And we copy the flags to the shadow PGD entry. The page + * number in the shadow PGD is the page we just allocated. + */ + set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags)); + } + + /* + * Intel's Physical Address Extension actually uses three levels of + * page tables, so we need to look in the mid-level. + */ +#ifdef CONFIG_X86_PAE + /* Now look at the mid-level shadow entry. */ + spmd = spmd_addr(cpu, *spgd, vaddr); + + if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) { + /* No shadow entry: allocate a new shadow PTE page. */ + unsigned long ptepage; + + /* If they didn't want us to allocate anything, stop. */ + if (!allocate) + return NULL; + + ptepage = get_zeroed_page(GFP_KERNEL); + + /* + * This is not really the Guest's fault, but killing it is + * simple for this corner case. + */ + if (!ptepage) { + kill_guest(cpu, "out of memory allocating pmd page"); + return NULL; + } + + /* + * And we copy the flags to the shadow PMD entry. The page + * number in the shadow PMD is the page we just allocated. + */ + set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags)); + } +#endif + + /* Get the pointer to the shadow PTE entry we're going to set. */ + return spte_addr(cpu, *spgd, vaddr); +} + /*H:330 * (i) Looking up a page table entry when the Guest faults. * @@ -304,17 +386,11 @@ static bool check_gpmd(struct lg_cpu *cpu, pmd_t gpmd) */ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) { - pgd_t gpgd; - pgd_t *spgd; unsigned long gpte_ptr; pte_t gpte; pte_t *spte; - - /* Mid level for PAE. */ -#ifdef CONFIG_X86_PAE - pmd_t *spmd; pmd_t gpmd; -#endif + pgd_t gpgd; /* We never demand page the Switcher, so trying is a mistake. */ if (vaddr >= switcher_addr) @@ -329,67 +405,31 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* 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); - if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { - /* No shadow entry: allocate a new shadow PTE page. */ - unsigned long ptepage = get_zeroed_page(GFP_KERNEL); - /* - * This is not really the Guest's fault, but killing it is - * simple for this corner case. + /* + * This kills the Guest if it has weird flags or tries to + * refer to a "physical" address outside the bounds. */ - if (!ptepage) { - kill_guest(cpu, "out of memory allocating pte page"); - return false; - } - /* We check that the Guest pgd is OK. */ if (!check_gpgd(cpu, gpgd)) return false; - /* - * And we copy the flags to the shadow PGD entry. The page - * number in the shadow PGD is the page we just allocated. - */ - set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd))); } + /* This "mid-level" entry is only used for non-linear, PAE mode. */ + gpmd = __pmd(_PAGE_TABLE); + #ifdef CONFIG_X86_PAE - if (unlikely(cpu->linear_pages)) { - /* Faking up a linear mapping. */ - gpmd = __pmd(_PAGE_TABLE); - } else { + if (likely(!cpu->linear_pages)) { 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); - - if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) { - /* No shadow entry: allocate a new shadow PTE page. */ - unsigned long ptepage = get_zeroed_page(GFP_KERNEL); - /* - * This is not really the Guest's fault, but killing it is - * simple for this corner case. + /* + * This kills the Guest if it has weird flags or tries to + * refer to a "physical" address outside the bounds. */ - if (!ptepage) { - kill_guest(cpu, "out of memory allocating pte page"); - return false; - } - - /* We check that the Guest pmd is OK. */ if (!check_gpmd(cpu, gpmd)) return false; - - /* - * And we copy the flags to the shadow PMD entry. The page - * number in the shadow PMD is the page we just allocated. - */ - set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd))); } /* @@ -441,7 +481,9 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) gpte = pte_mkdirty(gpte); /* Get the pointer to the shadow PTE entry we're going to set. */ - spte = spte_addr(cpu, *spgd, vaddr); + spte = find_spte(cpu, vaddr, true, pgd_flags(gpgd), pmd_flags(gpmd)); + if (!spte) + return false; /* * If there was a valid shadow PTE entry here before, we release it. @@ -493,33 +535,23 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) */ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr) { - pgd_t *spgd; + pte_t *spte; unsigned long flags; -#ifdef CONFIG_X86_PAE - pmd_t *spmd; -#endif /* You can't put your stack in the Switcher! */ if (vaddr >= switcher_addr) return false; - /* Look at the current top level entry: is it present? */ - spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); - if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) + /* If there's no shadow PTE, it's not writable. */ + spte = find_spte(cpu, vaddr, false, 0, 0); + if (!spte) return false; -#ifdef CONFIG_X86_PAE - spmd = spmd_addr(cpu, *spgd, vaddr); - if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) - return false; -#endif - /* * Check the flags on the pte entry itself: it must be present and * writable. */ - flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr))); - + flags = pte_flags(*spte); return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); } |