1422 lines
38 KiB
C
1422 lines
38 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1995 Linus Torvalds
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* Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
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* Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
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*/
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#include <linux/sched.h> /* test_thread_flag(), ... */
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#include <linux/sched/task_stack.h> /* task_stack_*(), ... */
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#include <linux/kdebug.h> /* oops_begin/end, ... */
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#include <linux/extable.h> /* search_exception_tables */
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#include <linux/memblock.h> /* max_low_pfn */
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#include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
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#include <linux/mmiotrace.h> /* kmmio_handler, ... */
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#include <linux/perf_event.h> /* perf_sw_event */
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#include <linux/hugetlb.h> /* hstate_index_to_shift */
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#include <linux/prefetch.h> /* prefetchw */
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#include <linux/context_tracking.h> /* exception_enter(), ... */
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#include <linux/uaccess.h> /* faulthandler_disabled() */
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#include <linux/efi.h> /* efi_recover_from_page_fault()*/
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#include <linux/mm_types.h>
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#include <asm/cpufeature.h> /* boot_cpu_has, ... */
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#include <asm/traps.h> /* dotraplinkage, ... */
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#include <asm/fixmap.h> /* VSYSCALL_ADDR */
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#include <asm/vsyscall.h> /* emulate_vsyscall */
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#include <asm/vm86.h> /* struct vm86 */
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#include <asm/mmu_context.h> /* vma_pkey() */
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#include <asm/efi.h> /* efi_recover_from_page_fault()*/
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#include <asm/desc.h> /* store_idt(), ... */
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#include <asm/cpu_entry_area.h> /* exception stack */
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#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
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#include <asm/kvm_para.h> /* kvm_handle_async_pf */
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#define CREATE_TRACE_POINTS
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#include <asm/trace/exceptions.h>
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/*
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* Returns 0 if mmiotrace is disabled, or if the fault is not
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* handled by mmiotrace:
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*/
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static nokprobe_inline int
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kmmio_fault(struct pt_regs *regs, unsigned long addr)
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{
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if (unlikely(is_kmmio_active()))
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if (kmmio_handler(regs, addr) == 1)
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return -1;
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return 0;
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}
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/*
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* Prefetch quirks:
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*
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* 32-bit mode:
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*
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* Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
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* Check that here and ignore it.
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*
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* 64-bit mode:
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*
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* Sometimes the CPU reports invalid exceptions on prefetch.
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* Check that here and ignore it.
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*
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* Opcode checker based on code by Richard Brunner.
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*/
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static inline int
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check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
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unsigned char opcode, int *prefetch)
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{
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unsigned char instr_hi = opcode & 0xf0;
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unsigned char instr_lo = opcode & 0x0f;
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switch (instr_hi) {
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case 0x20:
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case 0x30:
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/*
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* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
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* In X86_64 long mode, the CPU will signal invalid
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* opcode if some of these prefixes are present so
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* X86_64 will never get here anyway
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*/
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return ((instr_lo & 7) == 0x6);
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#ifdef CONFIG_X86_64
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case 0x40:
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/*
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* In AMD64 long mode 0x40..0x4F are valid REX prefixes
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* Need to figure out under what instruction mode the
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* instruction was issued. Could check the LDT for lm,
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* but for now it's good enough to assume that long
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* mode only uses well known segments or kernel.
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*/
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return (!user_mode(regs) || user_64bit_mode(regs));
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#endif
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case 0x60:
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/* 0x64 thru 0x67 are valid prefixes in all modes. */
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return (instr_lo & 0xC) == 0x4;
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case 0xF0:
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/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
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return !instr_lo || (instr_lo>>1) == 1;
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case 0x00:
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/* Prefetch instruction is 0x0F0D or 0x0F18 */
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if (get_kernel_nofault(opcode, instr))
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return 0;
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*prefetch = (instr_lo == 0xF) &&
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(opcode == 0x0D || opcode == 0x18);
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return 0;
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default:
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return 0;
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}
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}
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static int
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is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
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{
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unsigned char *max_instr;
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unsigned char *instr;
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int prefetch = 0;
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/*
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* If it was a exec (instruction fetch) fault on NX page, then
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* do not ignore the fault:
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*/
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if (error_code & X86_PF_INSTR)
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return 0;
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instr = (void *)convert_ip_to_linear(current, regs);
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max_instr = instr + 15;
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if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
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return 0;
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while (instr < max_instr) {
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unsigned char opcode;
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if (get_kernel_nofault(opcode, instr))
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break;
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instr++;
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if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
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break;
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}
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return prefetch;
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}
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DEFINE_SPINLOCK(pgd_lock);
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LIST_HEAD(pgd_list);
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#ifdef CONFIG_X86_32
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static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
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{
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unsigned index = pgd_index(address);
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pgd_t *pgd_k;
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p4d_t *p4d, *p4d_k;
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pud_t *pud, *pud_k;
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pmd_t *pmd, *pmd_k;
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pgd += index;
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pgd_k = init_mm.pgd + index;
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if (!pgd_present(*pgd_k))
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return NULL;
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/*
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* set_pgd(pgd, *pgd_k); here would be useless on PAE
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* and redundant with the set_pmd() on non-PAE. As would
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* set_p4d/set_pud.
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*/
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p4d = p4d_offset(pgd, address);
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p4d_k = p4d_offset(pgd_k, address);
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if (!p4d_present(*p4d_k))
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return NULL;
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pud = pud_offset(p4d, address);
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pud_k = pud_offset(p4d_k, address);
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if (!pud_present(*pud_k))
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return NULL;
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pmd = pmd_offset(pud, address);
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pmd_k = pmd_offset(pud_k, address);
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if (pmd_present(*pmd) != pmd_present(*pmd_k))
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set_pmd(pmd, *pmd_k);
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if (!pmd_present(*pmd_k))
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return NULL;
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else
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BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
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return pmd_k;
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}
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void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
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{
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unsigned long addr;
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for (addr = start & PMD_MASK;
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addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
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addr += PMD_SIZE) {
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struct page *page;
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spin_lock(&pgd_lock);
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list_for_each_entry(page, &pgd_list, lru) {
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spinlock_t *pgt_lock;
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/* the pgt_lock only for Xen */
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pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
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spin_lock(pgt_lock);
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vmalloc_sync_one(page_address(page), addr);
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spin_unlock(pgt_lock);
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}
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spin_unlock(&pgd_lock);
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}
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}
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/*
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* Did it hit the DOS screen memory VA from vm86 mode?
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*/
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static inline void
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check_v8086_mode(struct pt_regs *regs, unsigned long address,
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struct task_struct *tsk)
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{
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#ifdef CONFIG_VM86
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unsigned long bit;
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if (!v8086_mode(regs) || !tsk->thread.vm86)
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return;
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bit = (address - 0xA0000) >> PAGE_SHIFT;
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if (bit < 32)
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tsk->thread.vm86->screen_bitmap |= 1 << bit;
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#endif
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}
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static bool low_pfn(unsigned long pfn)
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{
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return pfn < max_low_pfn;
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}
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static void dump_pagetable(unsigned long address)
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{
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pgd_t *base = __va(read_cr3_pa());
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pgd_t *pgd = &base[pgd_index(address)];
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p4d_t *p4d;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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#ifdef CONFIG_X86_PAE
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pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
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if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
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goto out;
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#define pr_pde pr_cont
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#else
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#define pr_pde pr_info
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#endif
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p4d = p4d_offset(pgd, address);
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pud = pud_offset(p4d, address);
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pmd = pmd_offset(pud, address);
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pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
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#undef pr_pde
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/*
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* We must not directly access the pte in the highpte
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* case if the page table is located in highmem.
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* And let's rather not kmap-atomic the pte, just in case
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* it's allocated already:
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*/
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if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
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goto out;
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pte = pte_offset_kernel(pmd, address);
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pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
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out:
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pr_cont("\n");
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}
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#else /* CONFIG_X86_64: */
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#ifdef CONFIG_CPU_SUP_AMD
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static const char errata93_warning[] =
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KERN_ERR
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"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
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"******* Working around it, but it may cause SEGVs or burn power.\n"
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"******* Please consider a BIOS update.\n"
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"******* Disabling USB legacy in the BIOS may also help.\n";
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#endif
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/*
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* No vm86 mode in 64-bit mode:
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*/
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static inline void
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check_v8086_mode(struct pt_regs *regs, unsigned long address,
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struct task_struct *tsk)
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{
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}
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static int bad_address(void *p)
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{
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unsigned long dummy;
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return get_kernel_nofault(dummy, (unsigned long *)p);
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}
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static void dump_pagetable(unsigned long address)
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{
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pgd_t *base = __va(read_cr3_pa());
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pgd_t *pgd = base + pgd_index(address);
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p4d_t *p4d;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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if (bad_address(pgd))
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goto bad;
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pr_info("PGD %lx ", pgd_val(*pgd));
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if (!pgd_present(*pgd))
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goto out;
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p4d = p4d_offset(pgd, address);
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if (bad_address(p4d))
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goto bad;
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pr_cont("P4D %lx ", p4d_val(*p4d));
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if (!p4d_present(*p4d) || p4d_large(*p4d))
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goto out;
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pud = pud_offset(p4d, address);
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if (bad_address(pud))
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goto bad;
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pr_cont("PUD %lx ", pud_val(*pud));
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if (!pud_present(*pud) || pud_large(*pud))
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goto out;
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pmd = pmd_offset(pud, address);
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if (bad_address(pmd))
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goto bad;
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pr_cont("PMD %lx ", pmd_val(*pmd));
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if (!pmd_present(*pmd) || pmd_large(*pmd))
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goto out;
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pte = pte_offset_kernel(pmd, address);
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if (bad_address(pte))
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goto bad;
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pr_cont("PTE %lx", pte_val(*pte));
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out:
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pr_cont("\n");
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return;
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bad:
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pr_info("BAD\n");
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}
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#endif /* CONFIG_X86_64 */
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/*
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* Workaround for K8 erratum #93 & buggy BIOS.
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*
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* BIOS SMM functions are required to use a specific workaround
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* to avoid corruption of the 64bit RIP register on C stepping K8.
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*
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* A lot of BIOS that didn't get tested properly miss this.
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*
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* The OS sees this as a page fault with the upper 32bits of RIP cleared.
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* Try to work around it here.
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*
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* Note we only handle faults in kernel here.
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* Does nothing on 32-bit.
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*/
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static int is_errata93(struct pt_regs *regs, unsigned long address)
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{
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#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
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if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
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|| boot_cpu_data.x86 != 0xf)
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return 0;
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if (address != regs->ip)
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return 0;
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if ((address >> 32) != 0)
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return 0;
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address |= 0xffffffffUL << 32;
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if ((address >= (u64)_stext && address <= (u64)_etext) ||
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(address >= MODULES_VADDR && address <= MODULES_END)) {
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printk_once(errata93_warning);
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regs->ip = address;
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return 1;
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}
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#endif
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return 0;
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}
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/*
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* Work around K8 erratum #100 K8 in compat mode occasionally jumps
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* to illegal addresses >4GB.
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*
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* We catch this in the page fault handler because these addresses
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* are not reachable. Just detect this case and return. Any code
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* segment in LDT is compatibility mode.
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*/
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static int is_errata100(struct pt_regs *regs, unsigned long address)
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{
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#ifdef CONFIG_X86_64
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if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
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return 1;
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#endif
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return 0;
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}
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/* Pentium F0 0F C7 C8 bug workaround: */
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static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
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{
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#ifdef CONFIG_X86_F00F_BUG
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if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) {
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handle_invalid_op(regs);
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return 1;
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}
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#endif
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return 0;
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}
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static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
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{
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u32 offset = (index >> 3) * sizeof(struct desc_struct);
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unsigned long addr;
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struct ldttss_desc desc;
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if (index == 0) {
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pr_alert("%s: NULL\n", name);
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return;
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}
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if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
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pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
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return;
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}
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if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
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sizeof(struct ldttss_desc))) {
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pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
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name, index);
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return;
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}
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|
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addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
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#ifdef CONFIG_X86_64
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addr |= ((u64)desc.base3 << 32);
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#endif
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pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
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name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
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}
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|
|
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static void
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show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
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{
|
|
if (!oops_may_print())
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return;
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|
|
|
if (error_code & X86_PF_INSTR) {
|
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unsigned int level;
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pgd_t *pgd;
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pte_t *pte;
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|
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pgd = __va(read_cr3_pa());
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pgd += pgd_index(address);
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pte = lookup_address_in_pgd(pgd, address, &level);
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if (pte && pte_present(*pte) && !pte_exec(*pte))
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pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
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from_kuid(&init_user_ns, current_uid()));
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if (pte && pte_present(*pte) && pte_exec(*pte) &&
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(pgd_flags(*pgd) & _PAGE_USER) &&
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(__read_cr4() & X86_CR4_SMEP))
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pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
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from_kuid(&init_user_ns, current_uid()));
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}
|
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|
|
if (address < PAGE_SIZE && !user_mode(regs))
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|
pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
|
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(void *)address);
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|
else
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pr_alert("BUG: unable to handle page fault for address: %px\n",
|
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(void *)address);
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|
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pr_alert("#PF: %s %s in %s mode\n",
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(error_code & X86_PF_USER) ? "user" : "supervisor",
|
|
(error_code & X86_PF_INSTR) ? "instruction fetch" :
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(error_code & X86_PF_WRITE) ? "write access" :
|
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"read access",
|
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user_mode(regs) ? "user" : "kernel");
|
|
pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
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|
!(error_code & X86_PF_PROT) ? "not-present page" :
|
|
(error_code & X86_PF_RSVD) ? "reserved bit violation" :
|
|
(error_code & X86_PF_PK) ? "protection keys violation" :
|
|
"permissions violation");
|
|
|
|
if (!(error_code & X86_PF_USER) && user_mode(regs)) {
|
|
struct desc_ptr idt, gdt;
|
|
u16 ldtr, tr;
|
|
|
|
/*
|
|
* This can happen for quite a few reasons. The more obvious
|
|
* ones are faults accessing the GDT, or LDT. Perhaps
|
|
* surprisingly, if the CPU tries to deliver a benign or
|
|
* contributory exception from user code and gets a page fault
|
|
* during delivery, the page fault can be delivered as though
|
|
* it originated directly from user code. This could happen
|
|
* due to wrong permissions on the IDT, GDT, LDT, TSS, or
|
|
* kernel or IST stack.
|
|
*/
|
|
store_idt(&idt);
|
|
|
|
/* Usable even on Xen PV -- it's just slow. */
|
|
native_store_gdt(&gdt);
|
|
|
|
pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
|
|
idt.address, idt.size, gdt.address, gdt.size);
|
|
|
|
store_ldt(ldtr);
|
|
show_ldttss(&gdt, "LDTR", ldtr);
|
|
|
|
store_tr(tr);
|
|
show_ldttss(&gdt, "TR", tr);
|
|
}
|
|
|
|
dump_pagetable(address);
|
|
}
|
|
|
|
static noinline void
|
|
pgtable_bad(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address)
|
|
{
|
|
struct task_struct *tsk;
|
|
unsigned long flags;
|
|
int sig;
|
|
|
|
flags = oops_begin();
|
|
tsk = current;
|
|
sig = SIGKILL;
|
|
|
|
printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
|
|
tsk->comm, address);
|
|
dump_pagetable(address);
|
|
|
|
if (__die("Bad pagetable", regs, error_code))
|
|
sig = 0;
|
|
|
|
oops_end(flags, regs, sig);
|
|
}
|
|
|
|
static void set_signal_archinfo(unsigned long address,
|
|
unsigned long error_code)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
|
|
/*
|
|
* To avoid leaking information about the kernel page
|
|
* table layout, pretend that user-mode accesses to
|
|
* kernel addresses are always protection faults.
|
|
*
|
|
* NB: This means that failed vsyscalls with vsyscall=none
|
|
* will have the PROT bit. This doesn't leak any
|
|
* information and does not appear to cause any problems.
|
|
*/
|
|
if (address >= TASK_SIZE_MAX)
|
|
error_code |= X86_PF_PROT;
|
|
|
|
tsk->thread.trap_nr = X86_TRAP_PF;
|
|
tsk->thread.error_code = error_code | X86_PF_USER;
|
|
tsk->thread.cr2 = address;
|
|
}
|
|
|
|
static noinline void
|
|
no_context(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, int signal, int si_code)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
unsigned long flags;
|
|
int sig;
|
|
|
|
if (user_mode(regs)) {
|
|
/*
|
|
* This is an implicit supervisor-mode access from user
|
|
* mode. Bypass all the kernel-mode recovery code and just
|
|
* OOPS.
|
|
*/
|
|
goto oops;
|
|
}
|
|
|
|
/* Are we prepared to handle this kernel fault? */
|
|
if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
|
|
/*
|
|
* Any interrupt that takes a fault gets the fixup. This makes
|
|
* the below recursive fault logic only apply to a faults from
|
|
* task context.
|
|
*/
|
|
if (in_interrupt())
|
|
return;
|
|
|
|
/*
|
|
* Per the above we're !in_interrupt(), aka. task context.
|
|
*
|
|
* In this case we need to make sure we're not recursively
|
|
* faulting through the emulate_vsyscall() logic.
|
|
*/
|
|
if (current->thread.sig_on_uaccess_err && signal) {
|
|
set_signal_archinfo(address, error_code);
|
|
|
|
/* XXX: hwpoison faults will set the wrong code. */
|
|
force_sig_fault(signal, si_code, (void __user *)address);
|
|
}
|
|
|
|
/*
|
|
* Barring that, we can do the fixup and be happy.
|
|
*/
|
|
return;
|
|
}
|
|
|
|
#ifdef CONFIG_VMAP_STACK
|
|
/*
|
|
* Stack overflow? During boot, we can fault near the initial
|
|
* stack in the direct map, but that's not an overflow -- check
|
|
* that we're in vmalloc space to avoid this.
|
|
*/
|
|
if (is_vmalloc_addr((void *)address) &&
|
|
(((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
|
|
address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
|
|
unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
|
|
/*
|
|
* We're likely to be running with very little stack space
|
|
* left. It's plausible that we'd hit this condition but
|
|
* double-fault even before we get this far, in which case
|
|
* we're fine: the double-fault handler will deal with it.
|
|
*
|
|
* We don't want to make it all the way into the oops code
|
|
* and then double-fault, though, because we're likely to
|
|
* break the console driver and lose most of the stack dump.
|
|
*/
|
|
asm volatile ("movq %[stack], %%rsp\n\t"
|
|
"call handle_stack_overflow\n\t"
|
|
"1: jmp 1b"
|
|
: ASM_CALL_CONSTRAINT
|
|
: "D" ("kernel stack overflow (page fault)"),
|
|
"S" (regs), "d" (address),
|
|
[stack] "rm" (stack));
|
|
unreachable();
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* 32-bit:
|
|
*
|
|
* Valid to do another page fault here, because if this fault
|
|
* had been triggered by is_prefetch fixup_exception would have
|
|
* handled it.
|
|
*
|
|
* 64-bit:
|
|
*
|
|
* Hall of shame of CPU/BIOS bugs.
|
|
*/
|
|
if (is_prefetch(regs, error_code, address))
|
|
return;
|
|
|
|
if (is_errata93(regs, address))
|
|
return;
|
|
|
|
/*
|
|
* Buggy firmware could access regions which might page fault, try to
|
|
* recover from such faults.
|
|
*/
|
|
if (IS_ENABLED(CONFIG_EFI))
|
|
efi_recover_from_page_fault(address);
|
|
|
|
oops:
|
|
/*
|
|
* Oops. The kernel tried to access some bad page. We'll have to
|
|
* terminate things with extreme prejudice:
|
|
*/
|
|
flags = oops_begin();
|
|
|
|
show_fault_oops(regs, error_code, address);
|
|
|
|
if (task_stack_end_corrupted(tsk))
|
|
printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
|
|
|
|
sig = SIGKILL;
|
|
if (__die("Oops", regs, error_code))
|
|
sig = 0;
|
|
|
|
/* Executive summary in case the body of the oops scrolled away */
|
|
printk(KERN_DEFAULT "CR2: %016lx\n", address);
|
|
|
|
oops_end(flags, regs, sig);
|
|
}
|
|
|
|
/*
|
|
* Print out info about fatal segfaults, if the show_unhandled_signals
|
|
* sysctl is set:
|
|
*/
|
|
static inline void
|
|
show_signal_msg(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, struct task_struct *tsk)
|
|
{
|
|
const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
|
|
|
|
if (!unhandled_signal(tsk, SIGSEGV))
|
|
return;
|
|
|
|
if (!printk_ratelimit())
|
|
return;
|
|
|
|
printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
|
|
loglvl, tsk->comm, task_pid_nr(tsk), address,
|
|
(void *)regs->ip, (void *)regs->sp, error_code);
|
|
|
|
print_vma_addr(KERN_CONT " in ", regs->ip);
|
|
|
|
printk(KERN_CONT "\n");
|
|
|
|
show_opcodes(regs, loglvl);
|
|
}
|
|
|
|
/*
|
|
* The (legacy) vsyscall page is the long page in the kernel portion
|
|
* of the address space that has user-accessible permissions.
|
|
*/
|
|
static bool is_vsyscall_vaddr(unsigned long vaddr)
|
|
{
|
|
return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
|
|
}
|
|
|
|
static void
|
|
__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, u32 pkey, int si_code)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
|
|
/* User mode accesses just cause a SIGSEGV */
|
|
if (user_mode(regs) && (error_code & X86_PF_USER)) {
|
|
/*
|
|
* It's possible to have interrupts off here:
|
|
*/
|
|
local_irq_enable();
|
|
|
|
/*
|
|
* Valid to do another page fault here because this one came
|
|
* from user space:
|
|
*/
|
|
if (is_prefetch(regs, error_code, address))
|
|
return;
|
|
|
|
if (is_errata100(regs, address))
|
|
return;
|
|
|
|
/*
|
|
* To avoid leaking information about the kernel page table
|
|
* layout, pretend that user-mode accesses to kernel addresses
|
|
* are always protection faults.
|
|
*/
|
|
if (address >= TASK_SIZE_MAX)
|
|
error_code |= X86_PF_PROT;
|
|
|
|
if (likely(show_unhandled_signals))
|
|
show_signal_msg(regs, error_code, address, tsk);
|
|
|
|
set_signal_archinfo(address, error_code);
|
|
|
|
if (si_code == SEGV_PKUERR)
|
|
force_sig_pkuerr((void __user *)address, pkey);
|
|
|
|
force_sig_fault(SIGSEGV, si_code, (void __user *)address);
|
|
|
|
local_irq_disable();
|
|
|
|
return;
|
|
}
|
|
|
|
if (is_f00f_bug(regs, address))
|
|
return;
|
|
|
|
no_context(regs, error_code, address, SIGSEGV, si_code);
|
|
}
|
|
|
|
static noinline void
|
|
bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address)
|
|
{
|
|
__bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
|
|
}
|
|
|
|
static void
|
|
__bad_area(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, u32 pkey, int si_code)
|
|
{
|
|
struct mm_struct *mm = current->mm;
|
|
/*
|
|
* Something tried to access memory that isn't in our memory map..
|
|
* Fix it, but check if it's kernel or user first..
|
|
*/
|
|
mmap_read_unlock(mm);
|
|
|
|
__bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
|
|
}
|
|
|
|
static noinline void
|
|
bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
|
|
{
|
|
__bad_area(regs, error_code, address, 0, SEGV_MAPERR);
|
|
}
|
|
|
|
static inline bool bad_area_access_from_pkeys(unsigned long error_code,
|
|
struct vm_area_struct *vma)
|
|
{
|
|
/* This code is always called on the current mm */
|
|
bool foreign = false;
|
|
|
|
if (!boot_cpu_has(X86_FEATURE_OSPKE))
|
|
return false;
|
|
if (error_code & X86_PF_PK)
|
|
return true;
|
|
/* this checks permission keys on the VMA: */
|
|
if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
|
|
(error_code & X86_PF_INSTR), foreign))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
static noinline void
|
|
bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, struct vm_area_struct *vma)
|
|
{
|
|
/*
|
|
* This OSPKE check is not strictly necessary at runtime.
|
|
* But, doing it this way allows compiler optimizations
|
|
* if pkeys are compiled out.
|
|
*/
|
|
if (bad_area_access_from_pkeys(error_code, vma)) {
|
|
/*
|
|
* A protection key fault means that the PKRU value did not allow
|
|
* access to some PTE. Userspace can figure out what PKRU was
|
|
* from the XSAVE state. This function captures the pkey from
|
|
* the vma and passes it to userspace so userspace can discover
|
|
* which protection key was set on the PTE.
|
|
*
|
|
* If we get here, we know that the hardware signaled a X86_PF_PK
|
|
* fault and that there was a VMA once we got in the fault
|
|
* handler. It does *not* guarantee that the VMA we find here
|
|
* was the one that we faulted on.
|
|
*
|
|
* 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
|
|
* 2. T1 : set PKRU to deny access to pkey=4, touches page
|
|
* 3. T1 : faults...
|
|
* 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
|
|
* 5. T1 : enters fault handler, takes mmap_lock, etc...
|
|
* 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
|
|
* faulted on a pte with its pkey=4.
|
|
*/
|
|
u32 pkey = vma_pkey(vma);
|
|
|
|
__bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
|
|
} else {
|
|
__bad_area(regs, error_code, address, 0, SEGV_ACCERR);
|
|
}
|
|
}
|
|
|
|
static void
|
|
do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
|
|
vm_fault_t fault)
|
|
{
|
|
/* Kernel mode? Handle exceptions or die: */
|
|
if (!(error_code & X86_PF_USER)) {
|
|
no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
|
|
return;
|
|
}
|
|
|
|
/* User-space => ok to do another page fault: */
|
|
if (is_prefetch(regs, error_code, address))
|
|
return;
|
|
|
|
set_signal_archinfo(address, error_code);
|
|
|
|
#ifdef CONFIG_MEMORY_FAILURE
|
|
if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
|
|
struct task_struct *tsk = current;
|
|
unsigned lsb = 0;
|
|
|
|
pr_err(
|
|
"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
|
|
tsk->comm, tsk->pid, address);
|
|
if (fault & VM_FAULT_HWPOISON_LARGE)
|
|
lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
|
|
if (fault & VM_FAULT_HWPOISON)
|
|
lsb = PAGE_SHIFT;
|
|
force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
|
|
return;
|
|
}
|
|
#endif
|
|
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
|
|
}
|
|
|
|
static noinline void
|
|
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, vm_fault_t fault)
|
|
{
|
|
if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
|
|
no_context(regs, error_code, address, 0, 0);
|
|
return;
|
|
}
|
|
|
|
if (fault & VM_FAULT_OOM) {
|
|
/* Kernel mode? Handle exceptions or die: */
|
|
if (!(error_code & X86_PF_USER)) {
|
|
no_context(regs, error_code, address,
|
|
SIGSEGV, SEGV_MAPERR);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* We ran out of memory, call the OOM killer, and return the
|
|
* userspace (which will retry the fault, or kill us if we got
|
|
* oom-killed):
|
|
*/
|
|
pagefault_out_of_memory();
|
|
} else {
|
|
if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
|
|
VM_FAULT_HWPOISON_LARGE))
|
|
do_sigbus(regs, error_code, address, fault);
|
|
else if (fault & VM_FAULT_SIGSEGV)
|
|
bad_area_nosemaphore(regs, error_code, address);
|
|
else
|
|
BUG();
|
|
}
|
|
}
|
|
|
|
static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
|
|
{
|
|
if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
|
|
return 0;
|
|
|
|
if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Handle a spurious fault caused by a stale TLB entry.
|
|
*
|
|
* This allows us to lazily refresh the TLB when increasing the
|
|
* permissions of a kernel page (RO -> RW or NX -> X). Doing it
|
|
* eagerly is very expensive since that implies doing a full
|
|
* cross-processor TLB flush, even if no stale TLB entries exist
|
|
* on other processors.
|
|
*
|
|
* Spurious faults may only occur if the TLB contains an entry with
|
|
* fewer permission than the page table entry. Non-present (P = 0)
|
|
* and reserved bit (R = 1) faults are never spurious.
|
|
*
|
|
* There are no security implications to leaving a stale TLB when
|
|
* increasing the permissions on a page.
|
|
*
|
|
* Returns non-zero if a spurious fault was handled, zero otherwise.
|
|
*
|
|
* See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
|
|
* (Optional Invalidation).
|
|
*/
|
|
static noinline int
|
|
spurious_kernel_fault(unsigned long error_code, unsigned long address)
|
|
{
|
|
pgd_t *pgd;
|
|
p4d_t *p4d;
|
|
pud_t *pud;
|
|
pmd_t *pmd;
|
|
pte_t *pte;
|
|
int ret;
|
|
|
|
/*
|
|
* Only writes to RO or instruction fetches from NX may cause
|
|
* spurious faults.
|
|
*
|
|
* These could be from user or supervisor accesses but the TLB
|
|
* is only lazily flushed after a kernel mapping protection
|
|
* change, so user accesses are not expected to cause spurious
|
|
* faults.
|
|
*/
|
|
if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
|
|
error_code != (X86_PF_INSTR | X86_PF_PROT))
|
|
return 0;
|
|
|
|
pgd = init_mm.pgd + pgd_index(address);
|
|
if (!pgd_present(*pgd))
|
|
return 0;
|
|
|
|
p4d = p4d_offset(pgd, address);
|
|
if (!p4d_present(*p4d))
|
|
return 0;
|
|
|
|
if (p4d_large(*p4d))
|
|
return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
|
|
|
|
pud = pud_offset(p4d, address);
|
|
if (!pud_present(*pud))
|
|
return 0;
|
|
|
|
if (pud_large(*pud))
|
|
return spurious_kernel_fault_check(error_code, (pte_t *) pud);
|
|
|
|
pmd = pmd_offset(pud, address);
|
|
if (!pmd_present(*pmd))
|
|
return 0;
|
|
|
|
if (pmd_large(*pmd))
|
|
return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
|
|
|
|
pte = pte_offset_kernel(pmd, address);
|
|
if (!pte_present(*pte))
|
|
return 0;
|
|
|
|
ret = spurious_kernel_fault_check(error_code, pte);
|
|
if (!ret)
|
|
return 0;
|
|
|
|
/*
|
|
* Make sure we have permissions in PMD.
|
|
* If not, then there's a bug in the page tables:
|
|
*/
|
|
ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
|
|
WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
|
|
|
|
return ret;
|
|
}
|
|
NOKPROBE_SYMBOL(spurious_kernel_fault);
|
|
|
|
int show_unhandled_signals = 1;
|
|
|
|
static inline int
|
|
access_error(unsigned long error_code, struct vm_area_struct *vma)
|
|
{
|
|
/* This is only called for the current mm, so: */
|
|
bool foreign = false;
|
|
|
|
/*
|
|
* Read or write was blocked by protection keys. This is
|
|
* always an unconditional error and can never result in
|
|
* a follow-up action to resolve the fault, like a COW.
|
|
*/
|
|
if (error_code & X86_PF_PK)
|
|
return 1;
|
|
|
|
/*
|
|
* Make sure to check the VMA so that we do not perform
|
|
* faults just to hit a X86_PF_PK as soon as we fill in a
|
|
* page.
|
|
*/
|
|
if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
|
|
(error_code & X86_PF_INSTR), foreign))
|
|
return 1;
|
|
|
|
if (error_code & X86_PF_WRITE) {
|
|
/* write, present and write, not present: */
|
|
if (unlikely(!(vma->vm_flags & VM_WRITE)))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/* read, present: */
|
|
if (unlikely(error_code & X86_PF_PROT))
|
|
return 1;
|
|
|
|
/* read, not present: */
|
|
if (unlikely(!vma_is_accessible(vma)))
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int fault_in_kernel_space(unsigned long address)
|
|
{
|
|
/*
|
|
* On 64-bit systems, the vsyscall page is at an address above
|
|
* TASK_SIZE_MAX, but is not considered part of the kernel
|
|
* address space.
|
|
*/
|
|
if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
|
|
return false;
|
|
|
|
return address >= TASK_SIZE_MAX;
|
|
}
|
|
|
|
/*
|
|
* Called for all faults where 'address' is part of the kernel address
|
|
* space. Might get called for faults that originate from *code* that
|
|
* ran in userspace or the kernel.
|
|
*/
|
|
static void
|
|
do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
|
|
unsigned long address)
|
|
{
|
|
/*
|
|
* Protection keys exceptions only happen on user pages. We
|
|
* have no user pages in the kernel portion of the address
|
|
* space, so do not expect them here.
|
|
*/
|
|
WARN_ON_ONCE(hw_error_code & X86_PF_PK);
|
|
|
|
/* Was the fault spurious, caused by lazy TLB invalidation? */
|
|
if (spurious_kernel_fault(hw_error_code, address))
|
|
return;
|
|
|
|
/* kprobes don't want to hook the spurious faults: */
|
|
if (kprobe_page_fault(regs, X86_TRAP_PF))
|
|
return;
|
|
|
|
/*
|
|
* Note, despite being a "bad area", there are quite a few
|
|
* acceptable reasons to get here, such as erratum fixups
|
|
* and handling kernel code that can fault, like get_user().
|
|
*
|
|
* Don't take the mm semaphore here. If we fixup a prefetch
|
|
* fault we could otherwise deadlock:
|
|
*/
|
|
bad_area_nosemaphore(regs, hw_error_code, address);
|
|
}
|
|
NOKPROBE_SYMBOL(do_kern_addr_fault);
|
|
|
|
/* Handle faults in the user portion of the address space */
|
|
static inline
|
|
void do_user_addr_fault(struct pt_regs *regs,
|
|
unsigned long hw_error_code,
|
|
unsigned long address)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
struct task_struct *tsk;
|
|
struct mm_struct *mm;
|
|
vm_fault_t fault, major = 0;
|
|
unsigned int flags = FAULT_FLAG_DEFAULT;
|
|
|
|
tsk = current;
|
|
mm = tsk->mm;
|
|
|
|
/* kprobes don't want to hook the spurious faults: */
|
|
if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
|
|
return;
|
|
|
|
/*
|
|
* Reserved bits are never expected to be set on
|
|
* entries in the user portion of the page tables.
|
|
*/
|
|
if (unlikely(hw_error_code & X86_PF_RSVD))
|
|
pgtable_bad(regs, hw_error_code, address);
|
|
|
|
/*
|
|
* If SMAP is on, check for invalid kernel (supervisor) access to user
|
|
* pages in the user address space. The odd case here is WRUSS,
|
|
* which, according to the preliminary documentation, does not respect
|
|
* SMAP and will have the USER bit set so, in all cases, SMAP
|
|
* enforcement appears to be consistent with the USER bit.
|
|
*/
|
|
if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
|
|
!(hw_error_code & X86_PF_USER) &&
|
|
!(regs->flags & X86_EFLAGS_AC)))
|
|
{
|
|
bad_area_nosemaphore(regs, hw_error_code, address);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If we're in an interrupt, have no user context or are running
|
|
* in a region with pagefaults disabled then we must not take the fault
|
|
*/
|
|
if (unlikely(faulthandler_disabled() || !mm)) {
|
|
bad_area_nosemaphore(regs, hw_error_code, address);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* It's safe to allow irq's after cr2 has been saved and the
|
|
* vmalloc fault has been handled.
|
|
*
|
|
* User-mode registers count as a user access even for any
|
|
* potential system fault or CPU buglet:
|
|
*/
|
|
if (user_mode(regs)) {
|
|
local_irq_enable();
|
|
flags |= FAULT_FLAG_USER;
|
|
} else {
|
|
if (regs->flags & X86_EFLAGS_IF)
|
|
local_irq_enable();
|
|
}
|
|
|
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
|
|
|
|
if (hw_error_code & X86_PF_WRITE)
|
|
flags |= FAULT_FLAG_WRITE;
|
|
if (hw_error_code & X86_PF_INSTR)
|
|
flags |= FAULT_FLAG_INSTRUCTION;
|
|
|
|
#ifdef CONFIG_X86_64
|
|
/*
|
|
* Faults in the vsyscall page might need emulation. The
|
|
* vsyscall page is at a high address (>PAGE_OFFSET), but is
|
|
* considered to be part of the user address space.
|
|
*
|
|
* The vsyscall page does not have a "real" VMA, so do this
|
|
* emulation before we go searching for VMAs.
|
|
*
|
|
* PKRU never rejects instruction fetches, so we don't need
|
|
* to consider the PF_PK bit.
|
|
*/
|
|
if (is_vsyscall_vaddr(address)) {
|
|
if (emulate_vsyscall(hw_error_code, regs, address))
|
|
return;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Kernel-mode access to the user address space should only occur
|
|
* on well-defined single instructions listed in the exception
|
|
* tables. But, an erroneous kernel fault occurring outside one of
|
|
* those areas which also holds mmap_lock might deadlock attempting
|
|
* to validate the fault against the address space.
|
|
*
|
|
* Only do the expensive exception table search when we might be at
|
|
* risk of a deadlock. This happens if we
|
|
* 1. Failed to acquire mmap_lock, and
|
|
* 2. The access did not originate in userspace.
|
|
*/
|
|
if (unlikely(!mmap_read_trylock(mm))) {
|
|
if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
|
|
/*
|
|
* Fault from code in kernel from
|
|
* which we do not expect faults.
|
|
*/
|
|
bad_area_nosemaphore(regs, hw_error_code, address);
|
|
return;
|
|
}
|
|
retry:
|
|
mmap_read_lock(mm);
|
|
} else {
|
|
/*
|
|
* The above down_read_trylock() might have succeeded in
|
|
* which case we'll have missed the might_sleep() from
|
|
* down_read():
|
|
*/
|
|
might_sleep();
|
|
}
|
|
|
|
vma = find_vma(mm, address);
|
|
if (unlikely(!vma)) {
|
|
bad_area(regs, hw_error_code, address);
|
|
return;
|
|
}
|
|
if (likely(vma->vm_start <= address))
|
|
goto good_area;
|
|
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
|
|
bad_area(regs, hw_error_code, address);
|
|
return;
|
|
}
|
|
if (unlikely(expand_stack(vma, address))) {
|
|
bad_area(regs, hw_error_code, address);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Ok, we have a good vm_area for this memory access, so
|
|
* we can handle it..
|
|
*/
|
|
good_area:
|
|
if (unlikely(access_error(hw_error_code, vma))) {
|
|
bad_area_access_error(regs, hw_error_code, address, vma);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If for any reason at all we couldn't handle the fault,
|
|
* make sure we exit gracefully rather than endlessly redo
|
|
* the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
|
|
* we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
|
|
*
|
|
* Note that handle_userfault() may also release and reacquire mmap_lock
|
|
* (and not return with VM_FAULT_RETRY), when returning to userland to
|
|
* repeat the page fault later with a VM_FAULT_NOPAGE retval
|
|
* (potentially after handling any pending signal during the return to
|
|
* userland). The return to userland is identified whenever
|
|
* FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
|
|
*/
|
|
fault = handle_mm_fault(vma, address, flags, NULL);
|
|
major |= fault & VM_FAULT_MAJOR;
|
|
|
|
/* Quick path to respond to signals */
|
|
if (fault_signal_pending(fault, regs)) {
|
|
if (!user_mode(regs))
|
|
no_context(regs, hw_error_code, address, SIGBUS,
|
|
BUS_ADRERR);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If we need to retry the mmap_lock has already been released,
|
|
* and if there is a fatal signal pending there is no guarantee
|
|
* that we made any progress. Handle this case first.
|
|
*/
|
|
if (unlikely((fault & VM_FAULT_RETRY) &&
|
|
(flags & FAULT_FLAG_ALLOW_RETRY))) {
|
|
flags |= FAULT_FLAG_TRIED;
|
|
goto retry;
|
|
}
|
|
|
|
mmap_read_unlock(mm);
|
|
if (unlikely(fault & VM_FAULT_ERROR)) {
|
|
mm_fault_error(regs, hw_error_code, address, fault);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Major/minor page fault accounting. If any of the events
|
|
* returned VM_FAULT_MAJOR, we account it as a major fault.
|
|
*/
|
|
if (major) {
|
|
tsk->maj_flt++;
|
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
|
|
} else {
|
|
tsk->min_flt++;
|
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
|
|
}
|
|
|
|
check_v8086_mode(regs, address, tsk);
|
|
}
|
|
NOKPROBE_SYMBOL(do_user_addr_fault);
|
|
|
|
static __always_inline void
|
|
trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address)
|
|
{
|
|
if (!trace_pagefault_enabled())
|
|
return;
|
|
|
|
if (user_mode(regs))
|
|
trace_page_fault_user(address, regs, error_code);
|
|
else
|
|
trace_page_fault_kernel(address, regs, error_code);
|
|
}
|
|
|
|
static __always_inline void
|
|
handle_page_fault(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address)
|
|
{
|
|
trace_page_fault_entries(regs, error_code, address);
|
|
|
|
if (unlikely(kmmio_fault(regs, address)))
|
|
return;
|
|
|
|
/* Was the fault on kernel-controlled part of the address space? */
|
|
if (unlikely(fault_in_kernel_space(address))) {
|
|
do_kern_addr_fault(regs, error_code, address);
|
|
} else {
|
|
do_user_addr_fault(regs, error_code, address);
|
|
/*
|
|
* User address page fault handling might have reenabled
|
|
* interrupts. Fixing up all potential exit points of
|
|
* do_user_addr_fault() and its leaf functions is just not
|
|
* doable w/o creating an unholy mess or turning the code
|
|
* upside down.
|
|
*/
|
|
local_irq_disable();
|
|
}
|
|
}
|
|
|
|
DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
|
|
{
|
|
unsigned long address = read_cr2();
|
|
irqentry_state_t state;
|
|
|
|
prefetchw(¤t->mm->mmap_lock);
|
|
|
|
/*
|
|
* KVM has two types of events that are, logically, interrupts, but
|
|
* are unfortunately delivered using the #PF vector. These events are
|
|
* "you just accessed valid memory, but the host doesn't have it right
|
|
* now, so I'll put you to sleep if you continue" and "that memory
|
|
* you tried to access earlier is available now."
|
|
*
|
|
* We are relying on the interrupted context being sane (valid RSP,
|
|
* relevant locks not held, etc.), which is fine as long as the
|
|
* interrupted context had IF=1. We are also relying on the KVM
|
|
* async pf type field and CR2 being read consistently instead of
|
|
* getting values from real and async page faults mixed up.
|
|
*
|
|
* Fingers crossed.
|
|
*
|
|
* The async #PF handling code takes care of idtentry handling
|
|
* itself.
|
|
*/
|
|
if (kvm_handle_async_pf(regs, (u32)address))
|
|
return;
|
|
|
|
/*
|
|
* Entry handling for valid #PF from kernel mode is slightly
|
|
* different: RCU is already watching and rcu_irq_enter() must not
|
|
* be invoked because a kernel fault on a user space address might
|
|
* sleep.
|
|
*
|
|
* In case the fault hit a RCU idle region the conditional entry
|
|
* code reenabled RCU to avoid subsequent wreckage which helps
|
|
* debugability.
|
|
*/
|
|
state = irqentry_enter(regs);
|
|
|
|
instrumentation_begin();
|
|
handle_page_fault(regs, error_code, address);
|
|
instrumentation_end();
|
|
|
|
irqentry_exit(regs, state);
|
|
}
|