#include <asm/cpufeature.h>
#include <asm/hypervisor.h>
+#include <asm/vsyscall.h>
#include <asm/cmdline.h>
#include <asm/pti.h>
#include <asm/pgtable.h>
#undef pr_fmt
#define pr_fmt(fmt) "Kernel/User page tables isolation: " fmt
+/* Backporting helper */
+#ifndef __GFP_NOTRACK
+#define __GFP_NOTRACK 0
+#endif
+
static void __init pti_print_if_insecure(const char *reason)
{
- if (boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
+ if (boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
pr_info("%s\n", reason);
}
static void __init pti_print_if_secure(const char *reason)
{
- if (!boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
+ if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
pr_info("%s\n", reason);
}
}
autosel:
- if (!boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
+ if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
return;
enable:
setup_force_cpu_cap(X86_FEATURE_PTI);
return pgd;
}
+/*
+ * Walk the user copy of the page tables (optionally) trying to allocate
+ * page table pages on the way down.
+ *
+ * Returns a pointer to a P4D on success, or NULL on failure.
+ */
+static __init p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
+{
+ pgd_t *pgd = kernel_to_user_pgdp(pgd_offset_k(address));
+ gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
+
+ if (address < PAGE_OFFSET) {
+ WARN_ONCE(1, "attempt to walk user address\n");
+ return NULL;
+ }
+
+ if (pgd_none(*pgd)) {
+ unsigned long new_p4d_page = __get_free_page(gfp);
+ if (!new_p4d_page)
+ return NULL;
+
+ set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
+ }
+ BUILD_BUG_ON(pgd_large(*pgd) != 0);
+
+ return p4d_offset(pgd, address);
+}
+
+/*
+ * Walk the user copy of the page tables (optionally) trying to allocate
+ * page table pages on the way down.
+ *
+ * Returns a pointer to a PMD on success, or NULL on failure.
+ */
+static __init pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
+{
+ gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
+ p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
+ pud_t *pud;
+
+ BUILD_BUG_ON(p4d_large(*p4d) != 0);
+ if (p4d_none(*p4d)) {
+ unsigned long new_pud_page = __get_free_page(gfp);
+ if (!new_pud_page)
+ return NULL;
+
+ set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
+ }
+
+ pud = pud_offset(p4d, address);
+ /* The user page tables do not use large mappings: */
+ if (pud_large(*pud)) {
+ WARN_ON(1);
+ return NULL;
+ }
+ if (pud_none(*pud)) {
+ unsigned long new_pmd_page = __get_free_page(gfp);
+ if (!new_pmd_page)
+ return NULL;
+
+ set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
+ }
+
+ return pmd_offset(pud, address);
+}
+
+#ifdef CONFIG_X86_VSYSCALL_EMULATION
+/*
+ * Walk the shadow copy of the page tables (optionally) trying to allocate
+ * page table pages on the way down. Does not support large pages.
+ *
+ * Note: this is only used when mapping *new* kernel data into the
+ * user/shadow page tables. It is never used for userspace data.
+ *
+ * Returns a pointer to a PTE on success, or NULL on failure.
+ */
+static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address)
+{
+ gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
+ pmd_t *pmd = pti_user_pagetable_walk_pmd(address);
+ pte_t *pte;
+
+ /* We can't do anything sensible if we hit a large mapping. */
+ if (pmd_large(*pmd)) {
+ WARN_ON(1);
+ return NULL;
+ }
+
+ if (pmd_none(*pmd)) {
+ unsigned long new_pte_page = __get_free_page(gfp);
+ if (!new_pte_page)
+ return NULL;
+
+ set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
+ }
+
+ pte = pte_offset_kernel(pmd, address);
+ if (pte_flags(*pte) & _PAGE_USER) {
+ WARN_ONCE(1, "attempt to walk to user pte\n");
+ return NULL;
+ }
+ return pte;
+}
+
+static void __init pti_setup_vsyscall(void)
+{
+ pte_t *pte, *target_pte;
+ unsigned int level;
+
+ pte = lookup_address(VSYSCALL_ADDR, &level);
+ if (!pte || WARN_ON(level != PG_LEVEL_4K) || pte_none(*pte))
+ return;
+
+ target_pte = pti_user_pagetable_walk_pte(VSYSCALL_ADDR);
+ if (WARN_ON(!target_pte))
+ return;
+
+ *target_pte = *pte;
+ set_vsyscall_pgtable_user_bits(kernel_to_user_pgdp(swapper_pg_dir));
+}
+#else
+static void __init pti_setup_vsyscall(void) { }
+#endif
+
+static void __init
+pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear)
+{
+ unsigned long addr;
+
+ /*
+ * Clone the populated PMDs which cover start to end. These PMD areas
+ * can have holes.
+ */
+ for (addr = start; addr < end; addr += PMD_SIZE) {
+ pmd_t *pmd, *target_pmd;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+
+ pgd = pgd_offset_k(addr);
+ if (WARN_ON(pgd_none(*pgd)))
+ return;
+ p4d = p4d_offset(pgd, addr);
+ if (WARN_ON(p4d_none(*p4d)))
+ return;
+ pud = pud_offset(p4d, addr);
+ if (pud_none(*pud))
+ continue;
+ pmd = pmd_offset(pud, addr);
+ if (pmd_none(*pmd))
+ continue;
+
+ target_pmd = pti_user_pagetable_walk_pmd(addr);
+ if (WARN_ON(!target_pmd))
+ return;
+
+ /*
+ * Copy the PMD. That is, the kernelmode and usermode
+ * tables will share the last-level page tables of this
+ * address range
+ */
+ *target_pmd = pmd_clear_flags(*pmd, clear);
+ }
+}
+
+/*
+ * Clone a single p4d (i.e. a top-level entry on 4-level systems and a
+ * next-level entry on 5-level systems.
+ */
+static void __init pti_clone_p4d(unsigned long addr)
+{
+ p4d_t *kernel_p4d, *user_p4d;
+ pgd_t *kernel_pgd;
+
+ user_p4d = pti_user_pagetable_walk_p4d(addr);
+ kernel_pgd = pgd_offset_k(addr);
+ kernel_p4d = p4d_offset(kernel_pgd, addr);
+ *user_p4d = *kernel_p4d;
+}
+
+/*
+ * Clone the CPU_ENTRY_AREA into the user space visible page table.
+ */
+static void __init pti_clone_user_shared(void)
+{
+ pti_clone_p4d(CPU_ENTRY_AREA_BASE);
+}
+
+/*
+ * Clone the ESPFIX P4D into the user space visinble page table
+ */
+static void __init pti_setup_espfix64(void)
+{
+#ifdef CONFIG_X86_ESPFIX64
+ pti_clone_p4d(ESPFIX_BASE_ADDR);
+#endif
+}
+
+/*
+ * Clone the populated PMDs of the entry and irqentry text and force it RO.
+ */
+static void __init pti_clone_entry_text(void)
+{
+ pti_clone_pmds((unsigned long) __entry_text_start,
+ (unsigned long) __irqentry_text_end,
+ _PAGE_RW | _PAGE_GLOBAL);
+}
+
/*
* Initialize kernel page table isolation
*/
return;
pr_info("enabled\n");
+
+ pti_clone_user_shared();
+ pti_clone_entry_text();
+ pti_setup_espfix64();
+ pti_setup_vsyscall();
}
projects / linux-2.6-block.git / blobdiff