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1535 lines
42 KiB
1535 lines
42 KiB
// 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/kfence.h> /* kfence_handle_page_fault */ |
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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_crash_gracefully_on_page_fault()*/ |
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#include <linux/mm_types.h> |
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|
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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_crash_gracefully_on_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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#include <asm/vdso.h> /* fixup_vdso_exception() */ |
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|
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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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/* |
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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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/* |
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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. This is AMD erratum #91. |
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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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|
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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 64-bit mode 0x40..0x4F are valid REX prefixes |
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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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|
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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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|
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static bool is_amd_k8_pre_npt(void) |
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{ |
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struct cpuinfo_x86 *c = &boot_cpu_data; |
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|
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return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) && |
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c->x86_vendor == X86_VENDOR_AMD && |
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c->x86 == 0xf && c->x86_model < 0x40); |
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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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/* Erratum #91 affects AMD K8, pre-NPT CPUs */ |
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if (!is_amd_k8_pre_npt()) |
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return 0; |
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|
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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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|
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instr = (void *)convert_ip_to_linear(current, regs); |
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max_instr = instr + 15; |
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|
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/* |
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* This code has historically always bailed out if IP points to a |
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* not-present page (e.g. due to a race). No one has ever |
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* complained about this. |
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*/ |
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pagefault_disable(); |
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|
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while (instr < max_instr) { |
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unsigned char opcode; |
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|
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if (user_mode(regs)) { |
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if (get_user(opcode, instr)) |
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break; |
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} else { |
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if (get_kernel_nofault(opcode, instr)) |
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break; |
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} |
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|
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instr++; |
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|
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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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|
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pagefault_enable(); |
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return prefetch; |
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} |
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|
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DEFINE_SPINLOCK(pgd_lock); |
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LIST_HEAD(pgd_list); |
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|
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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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|
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pgd += index; |
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pgd_k = init_mm.pgd + index; |
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|
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if (!pgd_present(*pgd_k)) |
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return NULL; |
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|
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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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|
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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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|
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pmd = pmd_offset(pud, address); |
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pmd_k = pmd_offset(pud_k, address); |
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|
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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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|
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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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|
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return pmd_k; |
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} |
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|
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/* |
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* Handle a fault on the vmalloc or module mapping area |
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* |
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* This is needed because there is a race condition between the time |
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* when the vmalloc mapping code updates the PMD to the point in time |
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* where it synchronizes this update with the other page-tables in the |
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* system. |
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* |
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* In this race window another thread/CPU can map an area on the same |
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* PMD, finds it already present and does not synchronize it with the |
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* rest of the system yet. As a result v[mz]alloc might return areas |
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* which are not mapped in every page-table in the system, causing an |
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* unhandled page-fault when they are accessed. |
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*/ |
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static noinline int vmalloc_fault(unsigned long address) |
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{ |
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unsigned long pgd_paddr; |
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pmd_t *pmd_k; |
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pte_t *pte_k; |
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|
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/* Make sure we are in vmalloc area: */ |
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if (!(address >= VMALLOC_START && address < VMALLOC_END)) |
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return -1; |
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|
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/* |
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* Synchronize this task's top level page-table |
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* with the 'reference' page table. |
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* |
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* Do _not_ use "current" here. We might be inside |
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* an interrupt in the middle of a task switch.. |
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*/ |
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pgd_paddr = read_cr3_pa(); |
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pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); |
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if (!pmd_k) |
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return -1; |
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|
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if (pmd_large(*pmd_k)) |
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return 0; |
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|
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pte_k = pte_offset_kernel(pmd_k, address); |
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if (!pte_present(*pte_k)) |
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return -1; |
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|
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return 0; |
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} |
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NOKPROBE_SYMBOL(vmalloc_fault); |
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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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|
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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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|
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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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|
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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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|
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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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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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|
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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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|
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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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/* |
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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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|
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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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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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static void dump_pagetable(unsigned long address) |
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{ |
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pgd_t *base = __va(read_cr3_pa()); |
|
pgd_t *pgd = base + pgd_index(address); |
|
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); |
|
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)) |
|
goto bad; |
|
|
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pr_cont("PUD %lx ", pud_val(*pud)); |
|
if (!pud_present(*pud) || pud_large(*pud)) |
|
goto out; |
|
|
|
pmd = pmd_offset(pud, address); |
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if (bad_address(pmd)) |
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goto bad; |
|
|
|
pr_cont("PMD %lx ", pmd_val(*pmd)); |
|
if (!pmd_present(*pmd) || pmd_large(*pmd)) |
|
goto out; |
|
|
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pte = pte_offset_kernel(pmd, address); |
|
if (bad_address(pte)) |
|
goto bad; |
|
|
|
pr_cont("PTE %lx", pte_val(*pte)); |
|
out: |
|
pr_cont("\n"); |
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return; |
|
bad: |
|
pr_info("BAD\n"); |
|
} |
|
|
|
#endif /* CONFIG_X86_64 */ |
|
|
|
/* |
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* Workaround for K8 erratum #93 & buggy BIOS. |
|
* |
|
* BIOS SMM functions are required to use a specific workaround |
|
* to avoid corruption of the 64bit RIP register on C stepping K8. |
|
* |
|
* A lot of BIOS that didn't get tested properly miss this. |
|
* |
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* The OS sees this as a page fault with the upper 32bits of RIP cleared. |
|
* Try to work around it here. |
|
* |
|
* Note we only handle faults in kernel here. |
|
* Does nothing on 32-bit. |
|
*/ |
|
static int is_errata93(struct pt_regs *regs, unsigned long address) |
|
{ |
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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) |
|
return 0; |
|
|
|
if (user_mode(regs)) |
|
return 0; |
|
|
|
if (address != regs->ip) |
|
return 0; |
|
|
|
if ((address >> 32) != 0) |
|
return 0; |
|
|
|
address |= 0xffffffffUL << 32; |
|
if ((address >= (u64)_stext && address <= (u64)_etext) || |
|
(address >= MODULES_VADDR && address <= MODULES_END)) { |
|
printk_once(errata93_warning); |
|
regs->ip = address; |
|
return 1; |
|
} |
|
#endif |
|
return 0; |
|
} |
|
|
|
/* |
|
* Work around K8 erratum #100 K8 in compat mode occasionally jumps |
|
* to illegal addresses >4GB. |
|
* |
|
* We catch this in the page fault handler because these addresses |
|
* are not reachable. Just detect this case and return. Any code |
|
* segment in LDT is compatibility mode. |
|
*/ |
|
static int is_errata100(struct pt_regs *regs, unsigned long address) |
|
{ |
|
#ifdef CONFIG_X86_64 |
|
if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) |
|
return 1; |
|
#endif |
|
return 0; |
|
} |
|
|
|
/* Pentium F0 0F C7 C8 bug workaround: */ |
|
static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code, |
|
unsigned long address) |
|
{ |
|
#ifdef CONFIG_X86_F00F_BUG |
|
if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) && |
|
idt_is_f00f_address(address)) { |
|
handle_invalid_op(regs); |
|
return 1; |
|
} |
|
#endif |
|
return 0; |
|
} |
|
|
|
static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) |
|
{ |
|
u32 offset = (index >> 3) * sizeof(struct desc_struct); |
|
unsigned long addr; |
|
struct ldttss_desc desc; |
|
|
|
if (index == 0) { |
|
pr_alert("%s: NULL\n", name); |
|
return; |
|
} |
|
|
|
if (offset + sizeof(struct ldttss_desc) >= gdt->size) { |
|
pr_alert("%s: 0x%hx -- out of bounds\n", name, index); |
|
return; |
|
} |
|
|
|
if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset), |
|
sizeof(struct ldttss_desc))) { |
|
pr_alert("%s: 0x%hx -- GDT entry is not readable\n", |
|
name, index); |
|
return; |
|
} |
|
|
|
addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); |
|
#ifdef CONFIG_X86_64 |
|
addr |= ((u64)desc.base3 << 32); |
|
#endif |
|
pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", |
|
name, index, addr, (desc.limit0 | (desc.limit1 << 16))); |
|
} |
|
|
|
static void |
|
show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) |
|
{ |
|
if (!oops_may_print()) |
|
return; |
|
|
|
if (error_code & X86_PF_INSTR) { |
|
unsigned int level; |
|
pgd_t *pgd; |
|
pte_t *pte; |
|
|
|
pgd = __va(read_cr3_pa()); |
|
pgd += pgd_index(address); |
|
|
|
pte = lookup_address_in_pgd(pgd, address, &level); |
|
|
|
if (pte && pte_present(*pte) && !pte_exec(*pte)) |
|
pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", |
|
from_kuid(&init_user_ns, current_uid())); |
|
if (pte && pte_present(*pte) && pte_exec(*pte) && |
|
(pgd_flags(*pgd) & _PAGE_USER) && |
|
(__read_cr4() & X86_CR4_SMEP)) |
|
pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", |
|
from_kuid(&init_user_ns, current_uid())); |
|
} |
|
|
|
if (address < PAGE_SIZE && !user_mode(regs)) |
|
pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", |
|
(void *)address); |
|
else |
|
pr_alert("BUG: unable to handle page fault for address: %px\n", |
|
(void *)address); |
|
|
|
pr_alert("#PF: %s %s in %s mode\n", |
|
(error_code & X86_PF_USER) ? "user" : "supervisor", |
|
(error_code & X86_PF_INSTR) ? "instruction fetch" : |
|
(error_code & X86_PF_WRITE) ? "write access" : |
|
"read access", |
|
user_mode(regs) ? "user" : "kernel"); |
|
pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, |
|
!(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 sanitize_error_code(unsigned long address, |
|
unsigned long *error_code) |
|
{ |
|
/* |
|
* 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; |
|
} |
|
|
|
static void set_signal_archinfo(unsigned long address, |
|
unsigned long error_code) |
|
{ |
|
struct task_struct *tsk = current; |
|
|
|
tsk->thread.trap_nr = X86_TRAP_PF; |
|
tsk->thread.error_code = error_code | X86_PF_USER; |
|
tsk->thread.cr2 = address; |
|
} |
|
|
|
static noinline void |
|
page_fault_oops(struct pt_regs *regs, unsigned long error_code, |
|
unsigned long address) |
|
{ |
|
unsigned long flags; |
|
int sig; |
|
|
|
if (user_mode(regs)) { |
|
/* |
|
* Implicit kernel access from user mode? Skip the stack |
|
* overflow and EFI special cases. |
|
*/ |
|
goto oops; |
|
} |
|
|
|
#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)current->stack - 1 - address < PAGE_SIZE) || |
|
address - ((unsigned long)current->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 |
|
|
|
/* |
|
* Buggy firmware could access regions which might page fault. If |
|
* this happens, EFI has a special OOPS path that will try to |
|
* avoid hanging the system. |
|
*/ |
|
if (IS_ENABLED(CONFIG_EFI)) |
|
efi_crash_gracefully_on_page_fault(address); |
|
|
|
/* Only not-present faults should be handled by KFENCE. */ |
|
if (!(error_code & X86_PF_PROT) && |
|
kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs)) |
|
return; |
|
|
|
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(current)) |
|
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); |
|
} |
|
|
|
static noinline void |
|
kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, |
|
unsigned long address, int signal, int si_code) |
|
{ |
|
WARN_ON_ONCE(user_mode(regs)); |
|
|
|
/* 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) { |
|
sanitize_error_code(address, &error_code); |
|
|
|
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; |
|
} |
|
|
|
/* |
|
* AMD erratum #91 manifests as a spurious page fault on a PREFETCH |
|
* instruction. |
|
*/ |
|
if (is_prefetch(regs, error_code, address)) |
|
return; |
|
|
|
page_fault_oops(regs, error_code, address); |
|
} |
|
|
|
/* |
|
* 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; |
|
|
|
if (!user_mode(regs)) { |
|
kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code); |
|
return; |
|
} |
|
|
|
if (!(error_code & X86_PF_USER)) { |
|
/* Implicit user access to kernel memory -- just oops */ |
|
page_fault_oops(regs, error_code, address); |
|
return; |
|
} |
|
|
|
/* |
|
* User mode accesses just cause a SIGSEGV. |
|
* 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; |
|
|
|
sanitize_error_code(address, &error_code); |
|
|
|
if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) |
|
return; |
|
|
|
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(); |
|
} |
|
|
|
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 (!user_mode(regs)) { |
|
kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR); |
|
return; |
|
} |
|
|
|
/* User-space => ok to do another page fault: */ |
|
if (is_prefetch(regs, error_code, address)) |
|
return; |
|
|
|
sanitize_error_code(address, &error_code); |
|
|
|
if (fixup_vdso_exception(regs, X86_TRAP_PF, 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 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; |
|
|
|
/* |
|
* SGX hardware blocked the access. This usually happens |
|
* when the enclave memory contents have been destroyed, like |
|
* after a suspend/resume cycle. In any case, the kernel can't |
|
* fix the cause of the fault. Handle the fault as an access |
|
* error even in cases where no actual access violation |
|
* occurred. This allows userspace to rebuild the enclave in |
|
* response to the signal. |
|
*/ |
|
if (unlikely(error_code & X86_PF_SGX)) |
|
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; |
|
} |
|
|
|
bool 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); |
|
|
|
#ifdef CONFIG_X86_32 |
|
/* |
|
* We can fault-in kernel-space virtual memory on-demand. The |
|
* 'reference' page table is init_mm.pgd. |
|
* |
|
* NOTE! We MUST NOT take any locks for this case. We may |
|
* be in an interrupt or a critical region, and should |
|
* only copy the information from the master page table, |
|
* nothing more. |
|
* |
|
* Before doing this on-demand faulting, ensure that the |
|
* fault is not any of the following: |
|
* 1. A fault on a PTE with a reserved bit set. |
|
* 2. A fault caused by a user-mode access. (Do not demand- |
|
* fault kernel memory due to user-mode accesses). |
|
* 3. A fault caused by a page-level protection violation. |
|
* (A demand fault would be on a non-present page which |
|
* would have X86_PF_PROT==0). |
|
* |
|
* This is only needed to close a race condition on x86-32 in |
|
* the vmalloc mapping/unmapping code. See the comment above |
|
* vmalloc_fault() for details. On x86-64 the race does not |
|
* exist as the vmalloc mappings don't need to be synchronized |
|
* there. |
|
*/ |
|
if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { |
|
if (vmalloc_fault(address) >= 0) |
|
return; |
|
} |
|
#endif |
|
|
|
if (is_f00f_bug(regs, hw_error_code, address)) |
|
return; |
|
|
|
/* 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. Nothing in here |
|
* should check X86_PF_USER without a specific justification: for almost |
|
* all purposes, we should treat a normal kernel access to user memory |
|
* (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction. |
|
* The one exception is AC flag handling, which is, per the x86 |
|
* architecture, special for WRUSS. |
|
*/ |
|
static inline |
|
void do_user_addr_fault(struct pt_regs *regs, |
|
unsigned long error_code, |
|
unsigned long address) |
|
{ |
|
struct vm_area_struct *vma; |
|
struct task_struct *tsk; |
|
struct mm_struct *mm; |
|
vm_fault_t fault; |
|
unsigned int flags = FAULT_FLAG_DEFAULT; |
|
|
|
tsk = current; |
|
mm = tsk->mm; |
|
|
|
if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) { |
|
/* |
|
* Whoops, this is kernel mode code trying to execute from |
|
* user memory. Unless this is AMD erratum #93, which |
|
* corrupts RIP such that it looks like a user address, |
|
* this is unrecoverable. Don't even try to look up the |
|
* VMA or look for extable entries. |
|
*/ |
|
if (is_errata93(regs, address)) |
|
return; |
|
|
|
page_fault_oops(regs, error_code, address); |
|
return; |
|
} |
|
|
|
/* 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(error_code & X86_PF_RSVD)) |
|
pgtable_bad(regs, 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) && |
|
!(error_code & X86_PF_USER) && |
|
!(regs->flags & X86_EFLAGS_AC))) { |
|
/* |
|
* No extable entry here. This was a kernel access to an |
|
* invalid pointer. get_kernel_nofault() will not get here. |
|
*/ |
|
page_fault_oops(regs, 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, 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 (error_code & X86_PF_WRITE) |
|
flags |= FAULT_FLAG_WRITE; |
|
if (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(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, 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, error_code, address); |
|
return; |
|
} |
|
if (likely(vma->vm_start <= address)) |
|
goto good_area; |
|
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { |
|
bad_area(regs, error_code, address); |
|
return; |
|
} |
|
if (unlikely(expand_stack(vma, address))) { |
|
bad_area(regs, 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(error_code, vma))) { |
|
bad_area_access_error(regs, 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, regs); |
|
|
|
if (fault_signal_pending(fault, regs)) { |
|
/* |
|
* Quick path to respond to signals. The core mm code |
|
* has unlocked the mm for us if we get here. |
|
*/ |
|
if (!user_mode(regs)) |
|
kernelmode_fixup_or_oops(regs, 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 (likely(!(fault & VM_FAULT_ERROR))) |
|
return; |
|
|
|
if (fatal_signal_pending(current) && !user_mode(regs)) { |
|
kernelmode_fixup_or_oops(regs, error_code, address, 0, 0); |
|
return; |
|
} |
|
|
|
if (fault & VM_FAULT_OOM) { |
|
/* Kernel mode? Handle exceptions or die: */ |
|
if (!user_mode(regs)) { |
|
kernelmode_fixup_or_oops(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(); |
|
} |
|
} |
|
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 uses #PF vector to deliver 'page not present' events to guests |
|
* (asynchronous page fault mechanism). The event happens when a |
|
* userspace task is trying to access some valid (from guest's point of |
|
* view) memory which is not currently mapped by the host (e.g. the |
|
* memory is swapped out). Note, the corresponding "page ready" event |
|
* which is injected when the memory becomes available, is delived via |
|
* an interrupt mechanism and not a #PF exception |
|
* (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()). |
|
* |
|
* 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); |
|
}
|
|
|