| /* |
| * Copyright (C) 1995 Linus Torvalds |
| * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. |
| * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar |
| */ |
| #include <linux/magic.h> /* STACK_END_MAGIC */ |
| #include <linux/sched.h> /* test_thread_flag(), ... */ |
| #include <linux/kdebug.h> /* oops_begin/end, ... */ |
| #include <linux/module.h> /* search_exception_table */ |
| #include <linux/bootmem.h> /* max_low_pfn */ |
| #include <linux/kprobes.h> /* __kprobes, ... */ |
| #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 <asm/traps.h> /* dotraplinkage, ... */ |
| #include <asm/pgalloc.h> /* pgd_*(), ... */ |
| #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ |
| #include <asm/fixmap.h> /* VSYSCALL_START */ |
| |
| /* |
| * Page fault error code bits: |
| * |
| * bit 0 == 0: no page found 1: protection fault |
| * bit 1 == 0: read access 1: write access |
| * bit 2 == 0: kernel-mode access 1: user-mode access |
| * bit 3 == 1: use of reserved bit detected |
| * bit 4 == 1: fault was an instruction fetch |
| */ |
| enum x86_pf_error_code { |
| |
| PF_PROT = 1 << 0, |
| PF_WRITE = 1 << 1, |
| PF_USER = 1 << 2, |
| PF_RSVD = 1 << 3, |
| PF_INSTR = 1 << 4, |
| }; |
| |
| /* |
| * Returns 0 if mmiotrace is disabled, or if the fault is not |
| * handled by mmiotrace: |
| */ |
| static inline int __kprobes |
| kmmio_fault(struct pt_regs *regs, unsigned long addr) |
| { |
| if (unlikely(is_kmmio_active())) |
| if (kmmio_handler(regs, addr) == 1) |
| return -1; |
| return 0; |
| } |
| |
| static inline int __kprobes notify_page_fault(struct pt_regs *regs) |
| { |
| int ret = 0; |
| |
| /* kprobe_running() needs smp_processor_id() */ |
| if (kprobes_built_in() && !user_mode_vm(regs)) { |
| preempt_disable(); |
| if (kprobe_running() && kprobe_fault_handler(regs, 14)) |
| ret = 1; |
| preempt_enable(); |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * Prefetch quirks: |
| * |
| * 32-bit mode: |
| * |
| * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. |
| * Check that here and ignore it. |
| * |
| * 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 AMD64 long mode 0x40..0x4F are valid REX prefixes |
| * Need to figure out under what instruction mode the |
| * instruction was issued. Could check the LDT for lm, |
| * but for now it's good enough to assume that long |
| * mode only uses well known segments or kernel. |
| */ |
| 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 (probe_kernel_address(instr, opcode)) |
| return 0; |
| |
| *prefetch = (instr_lo == 0xF) && |
| (opcode == 0x0D || opcode == 0x18); |
| return 0; |
| default: |
| return 0; |
| } |
| } |
| |
| 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; |
| |
| /* |
| * If it was a exec (instruction fetch) fault on NX page, then |
| * do not ignore the fault: |
| */ |
| if (error_code & PF_INSTR) |
| return 0; |
| |
| instr = (void *)convert_ip_to_linear(current, regs); |
| max_instr = instr + 15; |
| |
| if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE) |
| return 0; |
| |
| while (instr < max_instr) { |
| unsigned char opcode; |
| |
| if (probe_kernel_address(instr, opcode)) |
| break; |
| |
| instr++; |
| |
| if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) |
| break; |
| } |
| return prefetch; |
| } |
| |
| static void |
| force_sig_info_fault(int si_signo, int si_code, unsigned long address, |
| struct task_struct *tsk, int fault) |
| { |
| unsigned lsb = 0; |
| siginfo_t info; |
| |
| info.si_signo = si_signo; |
| info.si_errno = 0; |
| info.si_code = si_code; |
| info.si_addr = (void __user *)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; |
| info.si_addr_lsb = lsb; |
| |
| force_sig_info(si_signo, &info, tsk); |
| } |
| |
| 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; |
| 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_pud. |
| */ |
| pud = pud_offset(pgd, address); |
| pud_k = pud_offset(pgd_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_k)) |
| return NULL; |
| |
| if (!pmd_present(*pmd)) |
| set_pmd(pmd, *pmd_k); |
| else |
| BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); |
| |
| return pmd_k; |
| } |
| |
| void vmalloc_sync_all(void) |
| { |
| unsigned long address; |
| |
| if (SHARED_KERNEL_PMD) |
| return; |
| |
| for (address = VMALLOC_START & PMD_MASK; |
| address >= TASK_SIZE && address < FIXADDR_TOP; |
| address += PMD_SIZE) { |
| struct page *page; |
| |
| spin_lock(&pgd_lock); |
| list_for_each_entry(page, &pgd_list, lru) { |
| spinlock_t *pgt_lock; |
| pmd_t *ret; |
| |
| /* the pgt_lock only for Xen */ |
| pgt_lock = &pgd_page_get_mm(page)->page_table_lock; |
| |
| spin_lock(pgt_lock); |
| ret = vmalloc_sync_one(page_address(page), address); |
| spin_unlock(pgt_lock); |
| |
| if (!ret) |
| break; |
| } |
| spin_unlock(&pgd_lock); |
| } |
| } |
| |
| /* |
| * 32-bit: |
| * |
| * Handle a fault on the vmalloc or module mapping area |
| */ |
| static noinline __kprobes 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; |
| |
| WARN_ON_ONCE(in_nmi()); |
| |
| /* |
| * 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(); |
| pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); |
| if (!pmd_k) |
| return -1; |
| |
| pte_k = pte_offset_kernel(pmd_k, address); |
| if (!pte_present(*pte_k)) |
| return -1; |
| |
| return 0; |
| } |
| |
| /* |
| * Did it hit the DOS screen memory VA from vm86 mode? |
| */ |
| static inline void |
| check_v8086_mode(struct pt_regs *regs, unsigned long address, |
| struct task_struct *tsk) |
| { |
| unsigned long bit; |
| |
| if (!v8086_mode(regs)) |
| return; |
| |
| bit = (address - 0xA0000) >> PAGE_SHIFT; |
| if (bit < 32) |
| tsk->thread.screen_bitmap |= 1 << bit; |
| } |
| |
| 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()); |
| pgd_t *pgd = &base[pgd_index(address)]; |
| pmd_t *pmd; |
| pte_t *pte; |
| |
| #ifdef CONFIG_X86_PAE |
| printk("*pdpt = %016Lx ", pgd_val(*pgd)); |
| if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) |
| goto out; |
| #endif |
| pmd = pmd_offset(pud_offset(pgd, address), address); |
| printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); |
| |
| /* |
| * 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); |
| printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); |
| out: |
| printk("\n"); |
| } |
| |
| #else /* CONFIG_X86_64: */ |
| |
| void vmalloc_sync_all(void) |
| { |
| sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); |
| } |
| |
| /* |
| * 64-bit: |
| * |
| * Handle a fault on the vmalloc area |
| * |
| * This assumes no large pages in there. |
| */ |
| static noinline __kprobes int vmalloc_fault(unsigned long address) |
| { |
| pgd_t *pgd, *pgd_ref; |
| pud_t *pud, *pud_ref; |
| pmd_t *pmd, *pmd_ref; |
| pte_t *pte, *pte_ref; |
| |
| /* Make sure we are in vmalloc area: */ |
| if (!(address >= VMALLOC_START && address < VMALLOC_END)) |
| return -1; |
| |
| WARN_ON_ONCE(in_nmi()); |
| |
| /* |
| * Copy kernel mappings over when needed. This can also |
| * happen within a race in page table update. In the later |
| * case just flush: |
| */ |
| pgd = pgd_offset(current->active_mm, address); |
| pgd_ref = pgd_offset_k(address); |
| if (pgd_none(*pgd_ref)) |
| return -1; |
| |
| if (pgd_none(*pgd)) { |
| set_pgd(pgd, *pgd_ref); |
| arch_flush_lazy_mmu_mode(); |
| } else { |
| BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); |
| } |
| |
| /* |
| * Below here mismatches are bugs because these lower tables |
| * are shared: |
| */ |
| |
| pud = pud_offset(pgd, address); |
| pud_ref = pud_offset(pgd_ref, address); |
| if (pud_none(*pud_ref)) |
| return -1; |
| |
| if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) |
| BUG(); |
| |
| pmd = pmd_offset(pud, address); |
| pmd_ref = pmd_offset(pud_ref, address); |
| if (pmd_none(*pmd_ref)) |
| return -1; |
| |
| if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) |
| BUG(); |
| |
| pte_ref = pte_offset_kernel(pmd_ref, address); |
| if (!pte_present(*pte_ref)) |
| return -1; |
| |
| pte = pte_offset_kernel(pmd, address); |
| |
| /* |
| * Don't use pte_page here, because the mappings can point |
| * outside mem_map, and the NUMA hash lookup cannot handle |
| * that: |
| */ |
| if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) |
| BUG(); |
| |
| return 0; |
| } |
| |
| #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 |
| |
| /* |
| * No vm86 mode in 64-bit mode: |
| */ |
| static inline void |
| check_v8086_mode(struct pt_regs *regs, unsigned long address, |
| struct task_struct *tsk) |
| { |
| } |
| |
| static int bad_address(void *p) |
| { |
| unsigned long dummy; |
| |
| return probe_kernel_address((unsigned long *)p, dummy); |
| } |
| |
| static void dump_pagetable(unsigned long address) |
| { |
| pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK); |
| pgd_t *pgd = base + pgd_index(address); |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| |
| if (bad_address(pgd)) |
| goto bad; |
| |
| printk("PGD %lx ", pgd_val(*pgd)); |
| |
| if (!pgd_present(*pgd)) |
| goto out; |
| |
| pud = pud_offset(pgd, address); |
| if (bad_address(pud)) |
| goto bad; |
| |
| printk("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; |
| |
| printk("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; |
| |
| printk("PTE %lx", pte_val(*pte)); |
| out: |
| printk("\n"); |
| return; |
| bad: |
| printk("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 (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; |
| } |
| |
| static int is_f00f_bug(struct pt_regs *regs, unsigned long address) |
| { |
| #ifdef CONFIG_X86_F00F_BUG |
| unsigned long nr; |
| |
| /* |
| * Pentium F0 0F C7 C8 bug workaround: |
| */ |
| if (boot_cpu_has_bug(X86_BUG_F00F)) { |
| nr = (address - idt_descr.address) >> 3; |
| |
| if (nr == 6) { |
| do_invalid_op(regs, 0); |
| return 1; |
| } |
| } |
| #endif |
| return 0; |
| } |
| |
| static const char nx_warning[] = KERN_CRIT |
| "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; |
| |
| static void |
| show_fault_oops(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address) |
| { |
| if (!oops_may_print()) |
| return; |
| |
| if (error_code & PF_INSTR) { |
| unsigned int level; |
| |
| pte_t *pte = lookup_address(address, &level); |
| |
| if (pte && pte_present(*pte) && !pte_exec(*pte)) |
| printk(nx_warning, from_kuid(&init_user_ns, current_uid())); |
| } |
| |
| printk(KERN_ALERT "BUG: unable to handle kernel "); |
| if (address < PAGE_SIZE) |
| printk(KERN_CONT "NULL pointer dereference"); |
| else |
| printk(KERN_CONT "paging request"); |
| |
| printk(KERN_CONT " at %p\n", (void *) address); |
| printk(KERN_ALERT "IP:"); |
| printk_address(regs->ip, 1); |
| |
| 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); |
| |
| tsk->thread.cr2 = address; |
| tsk->thread.trap_nr = X86_TRAP_PF; |
| tsk->thread.error_code = error_code; |
| |
| if (__die("Bad pagetable", regs, error_code)) |
| sig = 0; |
| |
| oops_end(flags, regs, sig); |
| } |
| |
| static noinline void |
| no_context(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address, int signal, int si_code) |
| { |
| struct task_struct *tsk = current; |
| unsigned long *stackend; |
| unsigned long flags; |
| int sig; |
| |
| /* Are we prepared to handle this kernel fault? */ |
| if (fixup_exception(regs)) { |
| if (current_thread_info()->sig_on_uaccess_error && signal) { |
| tsk->thread.trap_nr = X86_TRAP_PF; |
| tsk->thread.error_code = error_code | PF_USER; |
| tsk->thread.cr2 = address; |
| |
| /* XXX: hwpoison faults will set the wrong code. */ |
| force_sig_info_fault(signal, si_code, address, tsk, 0); |
| } |
| return; |
| } |
| |
| /* |
| * 32-bit: |
| * |
| * Valid to do another page fault here, because if this fault |
| * had been triggered by is_prefetch fixup_exception would have |
| * handled it. |
| * |
| * 64-bit: |
| * |
| * Hall of shame of CPU/BIOS bugs. |
| */ |
| if (is_prefetch(regs, error_code, address)) |
| return; |
| |
| if (is_errata93(regs, address)) |
| return; |
| |
| /* |
| * 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); |
| |
| stackend = end_of_stack(tsk); |
| if (tsk != &init_task && *stackend != STACK_END_MAGIC) |
| printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); |
| |
| tsk->thread.cr2 = address; |
| tsk->thread.trap_nr = X86_TRAP_PF; |
| tsk->thread.error_code = error_code; |
| |
| sig = SIGKILL; |
| if (__die("Oops", regs, error_code)) |
| sig = 0; |
| |
| /* Executive summary in case the body of the oops scrolled away */ |
| printk(KERN_DEFAULT "CR2: %016lx\n", address); |
| |
| oops_end(flags, regs, sig); |
| } |
| |
| /* |
| * Print out info about fatal segfaults, if the show_unhandled_signals |
| * sysctl is set: |
| */ |
| static inline void |
| show_signal_msg(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address, struct task_struct *tsk) |
| { |
| if (!unhandled_signal(tsk, SIGSEGV)) |
| return; |
| |
| if (!printk_ratelimit()) |
| return; |
| |
| printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", |
| task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, |
| 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"); |
| } |
| |
| static void |
| __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address, int si_code) |
| { |
| struct task_struct *tsk = current; |
| |
| /* User mode accesses just cause a SIGSEGV */ |
| if (error_code & PF_USER) { |
| /* |
| * It's possible to have interrupts off here: |
| */ |
| local_irq_enable(); |
| |
| /* |
| * Valid to do another page fault here because this one came |
| * from user space: |
| */ |
| if (is_prefetch(regs, error_code, address)) |
| return; |
| |
| if (is_errata100(regs, address)) |
| return; |
| |
| #ifdef CONFIG_X86_64 |
| /* |
| * Instruction fetch faults in the vsyscall page might need |
| * emulation. |
| */ |
| if (unlikely((error_code & PF_INSTR) && |
| ((address & ~0xfff) == VSYSCALL_START))) { |
| if (emulate_vsyscall(regs, address)) |
| return; |
| } |
| #endif |
| /* Kernel addresses are always protection faults: */ |
| if (address >= TASK_SIZE) |
| error_code |= PF_PROT; |
| |
| if (likely(show_unhandled_signals)) |
| show_signal_msg(regs, error_code, address, tsk); |
| |
| tsk->thread.cr2 = address; |
| tsk->thread.error_code = error_code; |
| tsk->thread.trap_nr = X86_TRAP_PF; |
| |
| force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0); |
| |
| return; |
| } |
| |
| if (is_f00f_bug(regs, address)) |
| return; |
| |
| no_context(regs, error_code, address, SIGSEGV, si_code); |
| } |
| |
| static noinline void |
| bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address) |
| { |
| __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR); |
| } |
| |
| static void |
| __bad_area(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address, 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.. |
| */ |
| up_read(&mm->mmap_sem); |
| |
| __bad_area_nosemaphore(regs, error_code, address, si_code); |
| } |
| |
| static noinline void |
| bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) |
| { |
| __bad_area(regs, error_code, address, SEGV_MAPERR); |
| } |
| |
| static noinline void |
| bad_area_access_error(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address) |
| { |
| __bad_area(regs, error_code, address, SEGV_ACCERR); |
| } |
| |
| static void |
| do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, |
| unsigned int fault) |
| { |
| struct task_struct *tsk = current; |
| struct mm_struct *mm = tsk->mm; |
| int code = BUS_ADRERR; |
| |
| up_read(&mm->mmap_sem); |
| |
| /* Kernel mode? Handle exceptions or die: */ |
| if (!(error_code & PF_USER)) { |
| no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); |
| return; |
| } |
| |
| /* User-space => ok to do another page fault: */ |
| if (is_prefetch(regs, error_code, address)) |
| return; |
| |
| tsk->thread.cr2 = address; |
| tsk->thread.error_code = error_code; |
| tsk->thread.trap_nr = X86_TRAP_PF; |
| |
| #ifdef CONFIG_MEMORY_FAILURE |
| if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { |
| printk(KERN_ERR |
| "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", |
| tsk->comm, tsk->pid, address); |
| code = BUS_MCEERR_AR; |
| } |
| #endif |
| force_sig_info_fault(SIGBUS, code, address, tsk, fault); |
| } |
| |
| static noinline int |
| mm_fault_error(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address, unsigned int fault) |
| { |
| /* |
| * Pagefault was interrupted by SIGKILL. We have no reason to |
| * continue pagefault. |
| */ |
| if (fatal_signal_pending(current)) { |
| if (!(fault & VM_FAULT_RETRY)) |
| up_read(¤t->mm->mmap_sem); |
| if (!(error_code & PF_USER)) |
| no_context(regs, error_code, address, 0, 0); |
| return 1; |
| } |
| if (!(fault & VM_FAULT_ERROR)) |
| return 0; |
| |
| if (fault & VM_FAULT_OOM) { |
| /* Kernel mode? Handle exceptions or die: */ |
| if (!(error_code & PF_USER)) { |
| up_read(¤t->mm->mmap_sem); |
| no_context(regs, error_code, address, |
| SIGSEGV, SEGV_MAPERR); |
| return 1; |
| } |
| |
| up_read(¤t->mm->mmap_sem); |
| |
| /* |
| * 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 |
| BUG(); |
| } |
| return 1; |
| } |
| |
| static int spurious_fault_check(unsigned long error_code, pte_t *pte) |
| { |
| if ((error_code & PF_WRITE) && !pte_write(*pte)) |
| return 0; |
| |
| if ((error_code & 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. |
| * |
| * There are no security implications to leaving a stale TLB when |
| * increasing the permissions on a page. |
| */ |
| static noinline __kprobes int |
| spurious_fault(unsigned long error_code, unsigned long address) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| int ret; |
| |
| /* Reserved-bit violation or user access to kernel space? */ |
| if (error_code & (PF_USER | PF_RSVD)) |
| return 0; |
| |
| pgd = init_mm.pgd + pgd_index(address); |
| if (!pgd_present(*pgd)) |
| return 0; |
| |
| pud = pud_offset(pgd, address); |
| if (!pud_present(*pud)) |
| return 0; |
| |
| if (pud_large(*pud)) |
| return spurious_fault_check(error_code, (pte_t *) pud); |
| |
| pmd = pmd_offset(pud, address); |
| if (!pmd_present(*pmd)) |
| return 0; |
| |
| if (pmd_large(*pmd)) |
| return spurious_fault_check(error_code, (pte_t *) pmd); |
| |
| pte = pte_offset_kernel(pmd, address); |
| if (!pte_present(*pte)) |
| return 0; |
| |
| ret = spurious_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_fault_check(error_code, (pte_t *) pmd); |
| WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); |
| |
| return ret; |
| } |
| |
| int show_unhandled_signals = 1; |
| |
| static inline int |
| access_error(unsigned long error_code, struct vm_area_struct *vma) |
| { |
| if (error_code & 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 & PF_PROT)) |
| return 1; |
| |
| /* read, not present: */ |
| if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) |
| return 1; |
| |
| return 0; |
| } |
| |
| static int fault_in_kernel_space(unsigned long address) |
| { |
| return address >= TASK_SIZE_MAX; |
| } |
| |
| static inline bool smap_violation(int error_code, struct pt_regs *regs) |
| { |
| if (!IS_ENABLED(CONFIG_X86_SMAP)) |
| return false; |
| |
| if (!static_cpu_has(X86_FEATURE_SMAP)) |
| return false; |
| |
| if (error_code & PF_USER) |
| return false; |
| |
| if (!user_mode_vm(regs) && (regs->flags & X86_EFLAGS_AC)) |
| return false; |
| |
| return true; |
| } |
| |
| /* |
| * This routine handles page faults. It determines the address, |
| * and the problem, and then passes it off to one of the appropriate |
| * routines. |
| */ |
| static void __kprobes |
| __do_page_fault(struct pt_regs *regs, unsigned long error_code) |
| { |
| struct vm_area_struct *vma; |
| struct task_struct *tsk; |
| unsigned long address; |
| struct mm_struct *mm; |
| int fault; |
| unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
| |
| tsk = current; |
| mm = tsk->mm; |
| |
| /* Get the faulting address: */ |
| address = read_cr2(); |
| |
| /* |
| * Detect and handle instructions that would cause a page fault for |
| * both a tracked kernel page and a userspace page. |
| */ |
| if (kmemcheck_active(regs)) |
| kmemcheck_hide(regs); |
| prefetchw(&mm->mmap_sem); |
| |
| if (unlikely(kmmio_fault(regs, address))) |
| return; |
| |
| /* |
| * We 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. |
| * |
| * This verifies that the fault happens in kernel space |
| * (error_code & 4) == 0, and that the fault was not a |
| * protection error (error_code & 9) == 0. |
| */ |
| if (unlikely(fault_in_kernel_space(address))) { |
| if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { |
| if (vmalloc_fault(address) >= 0) |
| return; |
| |
| if (kmemcheck_fault(regs, address, error_code)) |
| return; |
| } |
| |
| /* Can handle a stale RO->RW TLB: */ |
| if (spurious_fault(error_code, address)) |
| return; |
| |
| /* kprobes don't want to hook the spurious faults: */ |
| if (notify_page_fault(regs)) |
| return; |
| /* |
| * Don't take the mm semaphore here. If we fixup a prefetch |
| * fault we could otherwise deadlock: |
| */ |
| bad_area_nosemaphore(regs, error_code, address); |
| |
| return; |
| } |
| |
| /* kprobes don't want to hook the spurious faults: */ |
| if (unlikely(notify_page_fault(regs))) |
| 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_vm(regs)) { |
| local_irq_enable(); |
| error_code |= PF_USER; |
| flags |= FAULT_FLAG_USER; |
| } else { |
| if (regs->flags & X86_EFLAGS_IF) |
| local_irq_enable(); |
| } |
| |
| if (unlikely(error_code & PF_RSVD)) |
| pgtable_bad(regs, error_code, address); |
| |
| if (unlikely(smap_violation(error_code, regs))) { |
| bad_area_nosemaphore(regs, error_code, address); |
| return; |
| } |
| |
| perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); |
| |
| /* |
| * If we're in an interrupt, have no user context or are running |
| * in an atomic region then we must not take the fault: |
| */ |
| if (unlikely(in_atomic() || !mm)) { |
| bad_area_nosemaphore(regs, error_code, address); |
| return; |
| } |
| |
| if (error_code & PF_WRITE) |
| flags |= FAULT_FLAG_WRITE; |
| |
| /* |
| * When running in the kernel we expect faults to occur only to |
| * addresses in user space. All other faults represent errors in |
| * the kernel and should generate an OOPS. Unfortunately, in the |
| * case of an erroneous fault occurring in a code path which already |
| * holds mmap_sem we will deadlock attempting to validate the fault |
| * against the address space. Luckily the kernel only validly |
| * references user space from well defined areas of code, which are |
| * listed in the exceptions table. |
| * |
| * As the vast majority of faults will be valid we will only perform |
| * the source reference check when there is a possibility of a |
| * deadlock. Attempt to lock the address space, if we cannot we then |
| * validate the source. If this is invalid we can skip the address |
| * space check, thus avoiding the deadlock: |
| */ |
| if (unlikely(!down_read_trylock(&mm->mmap_sem))) { |
| if ((error_code & PF_USER) == 0 && |
| !search_exception_tables(regs->ip)) { |
| bad_area_nosemaphore(regs, error_code, address); |
| return; |
| } |
| retry: |
| down_read(&mm->mmap_sem); |
| } 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 (error_code & PF_USER) { |
| /* |
| * Accessing the stack below %sp is always a bug. |
| * The large cushion allows instructions like enter |
| * and pusha to work. ("enter $65535, $31" pushes |
| * 32 pointers and then decrements %sp by 65535.) |
| */ |
| if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { |
| 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); |
| return; |
| } |
| |
| /* |
| * If for any reason at all we couldn't handle the fault, |
| * make sure we exit gracefully rather than endlessly redo |
| * the fault: |
| */ |
| fault = handle_mm_fault(mm, vma, address, flags); |
| |
| if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) { |
| if (mm_fault_error(regs, error_code, address, fault)) |
| return; |
| } |
| |
| /* |
| * Major/minor page fault accounting is only done on the |
| * initial attempt. If we go through a retry, it is extremely |
| * likely that the page will be found in page cache at that point. |
| */ |
| if (flags & FAULT_FLAG_ALLOW_RETRY) { |
| if (fault & VM_FAULT_MAJOR) { |
| tsk->maj_flt++; |
| perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, |
| regs, address); |
| } else { |
| tsk->min_flt++; |
| perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, |
| regs, address); |
| } |
| if (fault & VM_FAULT_RETRY) { |
| /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk |
| * of starvation. */ |
| flags &= ~FAULT_FLAG_ALLOW_RETRY; |
| flags |= FAULT_FLAG_TRIED; |
| goto retry; |
| } |
| } |
| |
| check_v8086_mode(regs, address, tsk); |
| |
| up_read(&mm->mmap_sem); |
| } |
| |
| dotraplinkage void __kprobes |
| do_page_fault(struct pt_regs *regs, unsigned long error_code) |
| { |
| enum ctx_state prev_state; |
| |
| prev_state = exception_enter(); |
| __do_page_fault(regs, error_code); |
| exception_exit(prev_state); |
| } |