| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Copyright (C) 1995 Linus Torvalds |
| * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. |
| * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar |
| */ |
| #include <linux/sched.h> /* test_thread_flag(), ... */ |
| #include <linux/sched/task_stack.h> /* task_stack_*(), ... */ |
| #include <linux/kdebug.h> /* oops_begin/end, ... */ |
| #include <linux/extable.h> /* search_exception_tables */ |
| #include <linux/memblock.h> /* max_low_pfn */ |
| #include <linux/kfence.h> /* kfence_handle_page_fault */ |
| #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ |
| #include <linux/mmiotrace.h> /* kmmio_handler, ... */ |
| #include <linux/perf_event.h> /* perf_sw_event */ |
| #include <linux/hugetlb.h> /* hstate_index_to_shift */ |
| #include <linux/prefetch.h> /* prefetchw */ |
| #include <linux/context_tracking.h> /* exception_enter(), ... */ |
| #include <linux/uaccess.h> /* faulthandler_disabled() */ |
| #include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/ |
| #include <linux/mm_types.h> |
| #include <linux/mm.h> /* find_and_lock_vma() */ |
| |
| #include <asm/cpufeature.h> /* boot_cpu_has, ... */ |
| #include <asm/traps.h> /* dotraplinkage, ... */ |
| #include <asm/fixmap.h> /* VSYSCALL_ADDR */ |
| #include <asm/vsyscall.h> /* emulate_vsyscall */ |
| #include <asm/vm86.h> /* struct vm86 */ |
| #include <asm/mmu_context.h> /* vma_pkey() */ |
| #include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/ |
| #include <asm/desc.h> /* store_idt(), ... */ |
| #include <asm/cpu_entry_area.h> /* exception stack */ |
| #include <asm/pgtable_areas.h> /* VMALLOC_START, ... */ |
| #include <asm/kvm_para.h> /* kvm_handle_async_pf */ |
| #include <asm/vdso.h> /* fixup_vdso_exception() */ |
| #include <asm/irq_stack.h> |
| |
| #define CREATE_TRACE_POINTS |
| #include <asm/trace/exceptions.h> |
| |
| /* |
| * Returns 0 if mmiotrace is disabled, or if the fault is not |
| * handled by mmiotrace: |
| */ |
| static nokprobe_inline int |
| kmmio_fault(struct pt_regs *regs, unsigned long addr) |
| { |
| if (unlikely(is_kmmio_active())) |
| if (kmmio_handler(regs, addr) == 1) |
| return -1; |
| return 0; |
| } |
| |
| /* |
| * Prefetch quirks: |
| * |
| * 32-bit mode: |
| * |
| * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. |
| * Check that here and ignore it. This is AMD erratum #91. |
| * |
| * 64-bit mode: |
| * |
| * Sometimes the CPU reports invalid exceptions on prefetch. |
| * Check that here and ignore it. |
| * |
| * Opcode checker based on code by Richard Brunner. |
| */ |
| static inline int |
| check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, |
| unsigned char opcode, int *prefetch) |
| { |
| unsigned char instr_hi = opcode & 0xf0; |
| unsigned char instr_lo = opcode & 0x0f; |
| |
| switch (instr_hi) { |
| case 0x20: |
| case 0x30: |
| /* |
| * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. |
| * In X86_64 long mode, the CPU will signal invalid |
| * opcode if some of these prefixes are present so |
| * X86_64 will never get here anyway |
| */ |
| return ((instr_lo & 7) == 0x6); |
| #ifdef CONFIG_X86_64 |
| case 0x40: |
| /* |
| * In 64-bit mode 0x40..0x4F are valid REX prefixes |
| */ |
| return (!user_mode(regs) || user_64bit_mode(regs)); |
| #endif |
| case 0x60: |
| /* 0x64 thru 0x67 are valid prefixes in all modes. */ |
| return (instr_lo & 0xC) == 0x4; |
| case 0xF0: |
| /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ |
| return !instr_lo || (instr_lo>>1) == 1; |
| case 0x00: |
| /* Prefetch instruction is 0x0F0D or 0x0F18 */ |
| if (get_kernel_nofault(opcode, instr)) |
| return 0; |
| |
| *prefetch = (instr_lo == 0xF) && |
| (opcode == 0x0D || opcode == 0x18); |
| return 0; |
| default: |
| return 0; |
| } |
| } |
| |
| static bool is_amd_k8_pre_npt(void) |
| { |
| struct cpuinfo_x86 *c = &boot_cpu_data; |
| |
| return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) && |
| c->x86_vendor == X86_VENDOR_AMD && |
| c->x86 == 0xf && c->x86_model < 0x40); |
| } |
| |
| static int |
| is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) |
| { |
| unsigned char *max_instr; |
| unsigned char *instr; |
| int prefetch = 0; |
| |
| /* Erratum #91 affects AMD K8, pre-NPT CPUs */ |
| if (!is_amd_k8_pre_npt()) |
| return 0; |
| |
| /* |
| * If it was a exec (instruction fetch) fault on NX page, then |
| * do not ignore the fault: |
| */ |
| if (error_code & X86_PF_INSTR) |
| return 0; |
| |
| instr = (void *)convert_ip_to_linear(current, regs); |
| max_instr = instr + 15; |
| |
| /* |
| * This code has historically always bailed out if IP points to a |
| * not-present page (e.g. due to a race). No one has ever |
| * complained about this. |
| */ |
| pagefault_disable(); |
| |
| while (instr < max_instr) { |
| unsigned char opcode; |
| |
| if (user_mode(regs)) { |
| if (get_user(opcode, (unsigned char __user *) instr)) |
| break; |
| } else { |
| if (get_kernel_nofault(opcode, instr)) |
| break; |
| } |
| |
| instr++; |
| |
| if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) |
| break; |
| } |
| |
| pagefault_enable(); |
| return prefetch; |
| } |
| |
| DEFINE_SPINLOCK(pgd_lock); |
| LIST_HEAD(pgd_list); |
| |
| #ifdef CONFIG_X86_32 |
| static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) |
| { |
| unsigned index = pgd_index(address); |
| pgd_t *pgd_k; |
| p4d_t *p4d, *p4d_k; |
| pud_t *pud, *pud_k; |
| pmd_t *pmd, *pmd_k; |
| |
| pgd += index; |
| pgd_k = init_mm.pgd + index; |
| |
| if (!pgd_present(*pgd_k)) |
| return NULL; |
| |
| /* |
| * set_pgd(pgd, *pgd_k); here would be useless on PAE |
| * and redundant with the set_pmd() on non-PAE. As would |
| * set_p4d/set_pud. |
| */ |
| p4d = p4d_offset(pgd, address); |
| p4d_k = p4d_offset(pgd_k, address); |
| if (!p4d_present(*p4d_k)) |
| return NULL; |
| |
| pud = pud_offset(p4d, address); |
| pud_k = pud_offset(p4d_k, address); |
| if (!pud_present(*pud_k)) |
| return NULL; |
| |
| pmd = pmd_offset(pud, address); |
| pmd_k = pmd_offset(pud_k, address); |
| |
| if (pmd_present(*pmd) != pmd_present(*pmd_k)) |
| set_pmd(pmd, *pmd_k); |
| |
| if (!pmd_present(*pmd_k)) |
| return NULL; |
| else |
| BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k)); |
| |
| return pmd_k; |
| } |
| |
| /* |
| * Handle a fault on the vmalloc or module mapping area |
| * |
| * This is needed because there is a race condition between the time |
| * when the vmalloc mapping code updates the PMD to the point in time |
| * where it synchronizes this update with the other page-tables in the |
| * system. |
| * |
| * In this race window another thread/CPU can map an area on the same |
| * PMD, finds it already present and does not synchronize it with the |
| * rest of the system yet. As a result v[mz]alloc might return areas |
| * which are not mapped in every page-table in the system, causing an |
| * unhandled page-fault when they are accessed. |
| */ |
| static noinline int vmalloc_fault(unsigned long address) |
| { |
| unsigned long pgd_paddr; |
| pmd_t *pmd_k; |
| pte_t *pte_k; |
| |
| /* Make sure we are in vmalloc area: */ |
| if (!(address >= VMALLOC_START && address < VMALLOC_END)) |
| return -1; |
| |
| /* |
| * Synchronize this task's top level page-table |
| * with the 'reference' page table. |
| * |
| * Do _not_ use "current" here. We might be inside |
| * an interrupt in the middle of a task switch.. |
| */ |
| pgd_paddr = read_cr3_pa(); |
| pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); |
| if (!pmd_k) |
| return -1; |
| |
| if (pmd_large(*pmd_k)) |
| return 0; |
| |
| pte_k = pte_offset_kernel(pmd_k, address); |
| if (!pte_present(*pte_k)) |
| return -1; |
| |
| return 0; |
| } |
| NOKPROBE_SYMBOL(vmalloc_fault); |
| |
| static void __arch_sync_kernel_mappings(unsigned long start, unsigned long end) |
| { |
| unsigned long addr; |
| |
| for (addr = start & PMD_MASK; |
| addr >= TASK_SIZE_MAX && addr < VMALLOC_END; |
| addr += PMD_SIZE) { |
| struct page *page; |
| |
| spin_lock(&pgd_lock); |
| list_for_each_entry(page, &pgd_list, lru) { |
| spinlock_t *pgt_lock; |
| |
| /* the pgt_lock only for Xen */ |
| pgt_lock = &pgd_page_get_mm(page)->page_table_lock; |
| |
| spin_lock(pgt_lock); |
| vmalloc_sync_one(page_address(page), addr); |
| spin_unlock(pgt_lock); |
| } |
| spin_unlock(&pgd_lock); |
| } |
| } |
| |
| void arch_sync_kernel_mappings(unsigned long start, unsigned long end) |
| { |
| __arch_sync_kernel_mappings(start, end); |
| #ifdef CONFIG_KMSAN |
| /* |
| * KMSAN maintains two additional metadata page mappings for the |
| * [VMALLOC_START, VMALLOC_END) range. These mappings start at |
| * KMSAN_VMALLOC_SHADOW_START and KMSAN_VMALLOC_ORIGIN_START and |
| * have to be synced together with the vmalloc memory mapping. |
| */ |
| if (start >= VMALLOC_START && end < VMALLOC_END) { |
| __arch_sync_kernel_mappings( |
| start - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START, |
| end - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START); |
| __arch_sync_kernel_mappings( |
| start - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START, |
| end - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START); |
| } |
| #endif |
| } |
| |
| static bool low_pfn(unsigned long pfn) |
| { |
| return pfn < max_low_pfn; |
| } |
| |
| static void dump_pagetable(unsigned long address) |
| { |
| pgd_t *base = __va(read_cr3_pa()); |
| pgd_t *pgd = &base[pgd_index(address)]; |
| p4d_t *p4d; |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| |
| #ifdef CONFIG_X86_PAE |
| pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); |
| if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) |
| goto out; |
| #define pr_pde pr_cont |
| #else |
| #define pr_pde pr_info |
| #endif |
| p4d = p4d_offset(pgd, address); |
| pud = pud_offset(p4d, address); |
| pmd = pmd_offset(pud, address); |
| pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); |
| #undef pr_pde |
| |
| /* |
| * We must not directly access the pte in the highpte |
| * case if the page table is located in highmem. |
| * And let's rather not kmap-atomic the pte, just in case |
| * it's allocated already: |
| */ |
| if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) |
| goto out; |
| |
| pte = pte_offset_kernel(pmd, address); |
| pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); |
| out: |
| pr_cont("\n"); |
| } |
| |
| #else /* CONFIG_X86_64: */ |
| |
| #ifdef CONFIG_CPU_SUP_AMD |
| static const char errata93_warning[] = |
| KERN_ERR |
| "******* Your BIOS seems to not contain a fix for K8 errata #93\n" |
| "******* Working around it, but it may cause SEGVs or burn power.\n" |
| "******* Please consider a BIOS update.\n" |
| "******* Disabling USB legacy in the BIOS may also help.\n"; |
| #endif |
| |
| static int bad_address(void *p) |
| { |
| unsigned long dummy; |
| |
| return get_kernel_nofault(dummy, (unsigned long *)p); |
| } |
| |
| static void dump_pagetable(unsigned long address) |
| { |
| pgd_t *base = __va(read_cr3_pa()); |
| pgd_t *pgd = base + pgd_index(address); |
| p4d_t *p4d; |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| |
| if (bad_address(pgd)) |
| goto bad; |
| |
| pr_info("PGD %lx ", pgd_val(*pgd)); |
| |
| if (!pgd_present(*pgd)) |
| goto out; |
| |
| p4d = p4d_offset(pgd, address); |
| if (bad_address(p4d)) |
| goto bad; |
| |
| pr_cont("P4D %lx ", p4d_val(*p4d)); |
| if (!p4d_present(*p4d) || p4d_large(*p4d)) |
| goto out; |
| |
| pud = pud_offset(p4d, address); |
| if (bad_address(pud)) |
| goto bad; |
| |
| pr_cont("PUD %lx ", pud_val(*pud)); |
| if (!pud_present(*pud) || pud_large(*pud)) |
| goto out; |
| |
| pmd = pmd_offset(pud, address); |
| if (bad_address(pmd)) |
| goto bad; |
| |
| pr_cont("PMD %lx ", pmd_val(*pmd)); |
| if (!pmd_present(*pmd) || pmd_large(*pmd)) |
| goto out; |
| |
| pte = pte_offset_kernel(pmd, address); |
| if (bad_address(pte)) |
| goto bad; |
| |
| pr_cont("PTE %lx", pte_val(*pte)); |
| out: |
| pr_cont("\n"); |
| return; |
| bad: |
| pr_info("BAD\n"); |
| } |
| |
| #endif /* CONFIG_X86_64 */ |
| |
| /* |
| * 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. |
| * |
| * 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) |
| { |
| #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) |
| if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD |
| || 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) |
| { |
| #ifdef CONFIG_VMAP_STACK |
| struct stack_info info; |
| #endif |
| 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) && |
| get_stack_guard_info((void *)address, &info)) { |
| /* |
| * 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. |
| */ |
| call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*), |
| handle_stack_overflow, |
| ASM_CALL_ARG3, |
| , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info)); |
| |
| 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, |
| u32 pkey) |
| { |
| 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); |
| |
| if (si_code == SEGV_PKUERR) { |
| force_sig_pkuerr((void __user *)address, pkey); |
| } else { |
| /* 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; |
| /* This is a racy snapshot, but it's better than nothing. */ |
| int cpu = raw_smp_processor_id(); |
| |
| 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); |
| |
| /* |
| * Dump the likely CPU where the fatal segfault happened. |
| * This can help identify faulty hardware. |
| */ |
| printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu, |
| topology_core_id(cpu), topology_physical_package_id(cpu)); |
| |
| |
| 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, |
| SIGSEGV, si_code, pkey); |
| 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); |
| else |
| 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 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 (!cpu_feature_enabled(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, ARCH_DEFAULT_PKEY); |
| 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 (WARN_ON_ONCE(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 (WARN_ON_ONCE(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 |
| |
| if (!(flags & FAULT_FLAG_USER)) |
| goto lock_mmap; |
| |
| vma = lock_vma_under_rcu(mm, address); |
| if (!vma) |
| goto lock_mmap; |
| |
| if (unlikely(access_error(error_code, vma))) { |
| vma_end_read(vma); |
| goto lock_mmap; |
| } |
| fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); |
| if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) |
| vma_end_read(vma); |
| |
| if (!(fault & VM_FAULT_RETRY)) { |
| count_vm_vma_lock_event(VMA_LOCK_SUCCESS); |
| goto done; |
| } |
| count_vm_vma_lock_event(VMA_LOCK_RETRY); |
| if (fault & VM_FAULT_MAJOR) |
| flags |= FAULT_FLAG_TRIED; |
| |
| /* Quick path to respond to signals */ |
| if (fault_signal_pending(fault, regs)) { |
| if (!user_mode(regs)) |
| kernelmode_fixup_or_oops(regs, error_code, address, |
| SIGBUS, BUS_ADRERR, |
| ARCH_DEFAULT_PKEY); |
| return; |
| } |
| lock_mmap: |
| |
| retry: |
| vma = lock_mm_and_find_vma(mm, address, regs); |
| if (unlikely(!vma)) { |
| bad_area_nosemaphore(regs, error_code, address); |
| return; |
| } |
| |
| /* |
| * Ok, we have a good vm_area for this memory access, so |
| * we can handle it.. |
| */ |
| 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, |
| ARCH_DEFAULT_PKEY); |
| return; |
| } |
| |
| /* The fault is fully completed (including releasing mmap lock) */ |
| if (fault & VM_FAULT_COMPLETED) |
| 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_TRIED; |
| goto retry; |
| } |
| |
| mmap_read_unlock(mm); |
| done: |
| 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, ARCH_DEFAULT_PKEY); |
| 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, |
| ARCH_DEFAULT_PKEY); |
| 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 delivered 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 ct_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 |
| * debuggability. |
| */ |
| state = irqentry_enter(regs); |
| |
| instrumentation_begin(); |
| handle_page_fault(regs, error_code, address); |
| instrumentation_end(); |
| |
| irqentry_exit(regs, state); |
| } |