diff options
Diffstat (limited to 'arch/x86/kernel/ldt.c')
| -rw-r--r-- | arch/x86/kernel/ldt.c | 137 |
1 files changed, 112 insertions, 25 deletions
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index c9b14020f4dd..733e6ace0fa4 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -100,6 +100,102 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) return new_ldt; } +#ifdef CONFIG_PAGE_TABLE_ISOLATION + +static void do_sanity_check(struct mm_struct *mm, + bool had_kernel_mapping, + bool had_user_mapping) +{ + if (mm->context.ldt) { + /* + * We already had an LDT. The top-level entry should already + * have been allocated and synchronized with the usermode + * tables. + */ + WARN_ON(!had_kernel_mapping); + if (static_cpu_has(X86_FEATURE_PTI)) + WARN_ON(!had_user_mapping); + } else { + /* + * This is the first time we're mapping an LDT for this process. + * Sync the pgd to the usermode tables. + */ + WARN_ON(had_kernel_mapping); + if (static_cpu_has(X86_FEATURE_PTI)) + WARN_ON(had_user_mapping); + } +} + +#ifdef CONFIG_X86_PAE + +static pmd_t *pgd_to_pmd_walk(pgd_t *pgd, unsigned long va) +{ + p4d_t *p4d; + pud_t *pud; + + if (pgd->pgd == 0) + return NULL; + + p4d = p4d_offset(pgd, va); + if (p4d_none(*p4d)) + return NULL; + + pud = pud_offset(p4d, va); + if (pud_none(*pud)) + return NULL; + + return pmd_offset(pud, va); +} + +static void map_ldt_struct_to_user(struct mm_struct *mm) +{ + pgd_t *k_pgd = pgd_offset(mm, LDT_BASE_ADDR); + pgd_t *u_pgd = kernel_to_user_pgdp(k_pgd); + pmd_t *k_pmd, *u_pmd; + + k_pmd = pgd_to_pmd_walk(k_pgd, LDT_BASE_ADDR); + u_pmd = pgd_to_pmd_walk(u_pgd, LDT_BASE_ADDR); + + if (static_cpu_has(X86_FEATURE_PTI) && !mm->context.ldt) + set_pmd(u_pmd, *k_pmd); +} + +static void sanity_check_ldt_mapping(struct mm_struct *mm) +{ + pgd_t *k_pgd = pgd_offset(mm, LDT_BASE_ADDR); + pgd_t *u_pgd = kernel_to_user_pgdp(k_pgd); + bool had_kernel, had_user; + pmd_t *k_pmd, *u_pmd; + + k_pmd = pgd_to_pmd_walk(k_pgd, LDT_BASE_ADDR); + u_pmd = pgd_to_pmd_walk(u_pgd, LDT_BASE_ADDR); + had_kernel = (k_pmd->pmd != 0); + had_user = (u_pmd->pmd != 0); + + do_sanity_check(mm, had_kernel, had_user); +} + +#else /* !CONFIG_X86_PAE */ + +static void map_ldt_struct_to_user(struct mm_struct *mm) +{ + pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR); + + if (static_cpu_has(X86_FEATURE_PTI) && !mm->context.ldt) + set_pgd(kernel_to_user_pgdp(pgd), *pgd); +} + +static void sanity_check_ldt_mapping(struct mm_struct *mm) +{ + pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR); + bool had_kernel = (pgd->pgd != 0); + bool had_user = (kernel_to_user_pgdp(pgd)->pgd != 0); + + do_sanity_check(mm, had_kernel, had_user); +} + +#endif /* CONFIG_X86_PAE */ + /* * If PTI is enabled, this maps the LDT into the kernelmode and * usermode tables for the given mm. @@ -115,9 +211,8 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) static int map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) { -#ifdef CONFIG_PAGE_TABLE_ISOLATION - bool is_vmalloc, had_top_level_entry; unsigned long va; + bool is_vmalloc; spinlock_t *ptl; pgd_t *pgd; int i; @@ -131,13 +226,15 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) */ WARN_ON(ldt->slot != -1); + /* Check if the current mappings are sane */ + sanity_check_ldt_mapping(mm); + /* * Did we already have the top level entry allocated? We can't * use pgd_none() for this because it doens't do anything on * 4-level page table kernels. */ pgd = pgd_offset(mm, LDT_BASE_ADDR); - had_top_level_entry = (pgd->pgd != 0); is_vmalloc = is_vmalloc_addr(ldt->entries); @@ -172,41 +269,31 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) pte_unmap_unlock(ptep, ptl); } - if (mm->context.ldt) { - /* - * We already had an LDT. The top-level entry should already - * have been allocated and synchronized with the usermode - * tables. - */ - WARN_ON(!had_top_level_entry); - if (static_cpu_has(X86_FEATURE_PTI)) - WARN_ON(!kernel_to_user_pgdp(pgd)->pgd); - } else { - /* - * This is the first time we're mapping an LDT for this process. - * Sync the pgd to the usermode tables. - */ - WARN_ON(had_top_level_entry); - if (static_cpu_has(X86_FEATURE_PTI)) { - WARN_ON(kernel_to_user_pgdp(pgd)->pgd); - set_pgd(kernel_to_user_pgdp(pgd), *pgd); - } - } + /* Propagate LDT mapping to the user page-table */ + map_ldt_struct_to_user(mm); va = (unsigned long)ldt_slot_va(slot); flush_tlb_mm_range(mm, va, va + LDT_SLOT_STRIDE, 0); ldt->slot = slot; -#endif return 0; } +#else /* !CONFIG_PAGE_TABLE_ISOLATION */ + +static int +map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) +{ + return 0; +} +#endif /* CONFIG_PAGE_TABLE_ISOLATION */ + static void free_ldt_pgtables(struct mm_struct *mm) { #ifdef CONFIG_PAGE_TABLE_ISOLATION struct mmu_gather tlb; unsigned long start = LDT_BASE_ADDR; - unsigned long end = start + (1UL << PGDIR_SHIFT); + unsigned long end = LDT_END_ADDR; if (!static_cpu_has(X86_FEATURE_PTI)) return; |