| /* |
| * linux/arch/i386/mm/fault.c |
| * |
| * Copyright (C) 1995 Linus Torvalds |
| */ |
| |
| #include <linux/signal.h> |
| #include <linux/sched.h> |
| #include <linux/kernel.h> |
| #include <linux/errno.h> |
| #include <linux/string.h> |
| #include <linux/types.h> |
| #include <linux/ptrace.h> |
| #include <linux/mman.h> |
| #include <linux/mm.h> |
| #include <linux/smp.h> |
| #include <linux/interrupt.h> |
| #include <linux/init.h> |
| #include <linux/tty.h> |
| #include <linux/vt_kern.h> /* For unblank_screen() */ |
| #include <linux/highmem.h> |
| #include <linux/bootmem.h> /* for max_low_pfn */ |
| #include <linux/vmalloc.h> |
| #include <linux/module.h> |
| #include <linux/kprobes.h> |
| #include <linux/uaccess.h> |
| #include <linux/kdebug.h> |
| |
| #include <asm/system.h> |
| #include <asm/desc.h> |
| #include <asm/segment.h> |
| |
| extern void die(const char *,struct pt_regs *,long); |
| |
| static ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); |
| |
| int register_page_fault_notifier(struct notifier_block *nb) |
| { |
| vmalloc_sync_all(); |
| return atomic_notifier_chain_register(¬ify_page_fault_chain, nb); |
| } |
| EXPORT_SYMBOL_GPL(register_page_fault_notifier); |
| |
| int unregister_page_fault_notifier(struct notifier_block *nb) |
| { |
| return atomic_notifier_chain_unregister(¬ify_page_fault_chain, nb); |
| } |
| EXPORT_SYMBOL_GPL(unregister_page_fault_notifier); |
| |
| static inline int notify_page_fault(struct pt_regs *regs, long err) |
| { |
| struct die_args args = { |
| .regs = regs, |
| .str = "page fault", |
| .err = err, |
| .trapnr = 14, |
| .signr = SIGSEGV |
| }; |
| return atomic_notifier_call_chain(¬ify_page_fault_chain, |
| DIE_PAGE_FAULT, &args); |
| } |
| |
| /* |
| * Return EIP plus the CS segment base. The segment limit is also |
| * adjusted, clamped to the kernel/user address space (whichever is |
| * appropriate), and returned in *eip_limit. |
| * |
| * The segment is checked, because it might have been changed by another |
| * task between the original faulting instruction and here. |
| * |
| * If CS is no longer a valid code segment, or if EIP is beyond the |
| * limit, or if it is a kernel address when CS is not a kernel segment, |
| * then the returned value will be greater than *eip_limit. |
| * |
| * This is slow, but is very rarely executed. |
| */ |
| static inline unsigned long get_segment_eip(struct pt_regs *regs, |
| unsigned long *eip_limit) |
| { |
| unsigned long eip = regs->eip; |
| unsigned seg = regs->xcs & 0xffff; |
| u32 seg_ar, seg_limit, base, *desc; |
| |
| /* Unlikely, but must come before segment checks. */ |
| if (unlikely(regs->eflags & VM_MASK)) { |
| base = seg << 4; |
| *eip_limit = base + 0xffff; |
| return base + (eip & 0xffff); |
| } |
| |
| /* The standard kernel/user address space limit. */ |
| *eip_limit = user_mode(regs) ? USER_DS.seg : KERNEL_DS.seg; |
| |
| /* By far the most common cases. */ |
| if (likely(SEGMENT_IS_FLAT_CODE(seg))) |
| return eip; |
| |
| /* Check the segment exists, is within the current LDT/GDT size, |
| that kernel/user (ring 0..3) has the appropriate privilege, |
| that it's a code segment, and get the limit. */ |
| __asm__ ("larl %3,%0; lsll %3,%1" |
| : "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg)); |
| if ((~seg_ar & 0x9800) || eip > seg_limit) { |
| *eip_limit = 0; |
| return 1; /* So that returned eip > *eip_limit. */ |
| } |
| |
| /* Get the GDT/LDT descriptor base. |
| When you look for races in this code remember that |
| LDT and other horrors are only used in user space. */ |
| if (seg & (1<<2)) { |
| /* Must lock the LDT while reading it. */ |
| down(¤t->mm->context.sem); |
| desc = current->mm->context.ldt; |
| desc = (void *)desc + (seg & ~7); |
| } else { |
| /* Must disable preemption while reading the GDT. */ |
| desc = (u32 *)get_cpu_gdt_table(get_cpu()); |
| desc = (void *)desc + (seg & ~7); |
| } |
| |
| /* Decode the code segment base from the descriptor */ |
| base = get_desc_base((unsigned long *)desc); |
| |
| if (seg & (1<<2)) { |
| up(¤t->mm->context.sem); |
| } else |
| put_cpu(); |
| |
| /* Adjust EIP and segment limit, and clamp at the kernel limit. |
| It's legitimate for segments to wrap at 0xffffffff. */ |
| seg_limit += base; |
| if (seg_limit < *eip_limit && seg_limit >= base) |
| *eip_limit = seg_limit; |
| return eip + base; |
| } |
| |
| /* |
| * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. |
| * Check that here and ignore it. |
| */ |
| static int __is_prefetch(struct pt_regs *regs, unsigned long addr) |
| { |
| unsigned long limit; |
| unsigned char *instr = (unsigned char *)get_segment_eip (regs, &limit); |
| int scan_more = 1; |
| int prefetch = 0; |
| int i; |
| |
| for (i = 0; scan_more && i < 15; i++) { |
| unsigned char opcode; |
| unsigned char instr_hi; |
| unsigned char instr_lo; |
| |
| if (instr > (unsigned char *)limit) |
| break; |
| if (probe_kernel_address(instr, opcode)) |
| break; |
| |
| instr_hi = opcode & 0xf0; |
| instr_lo = opcode & 0x0f; |
| instr++; |
| |
| switch (instr_hi) { |
| case 0x20: |
| case 0x30: |
| /* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */ |
| scan_more = ((instr_lo & 7) == 0x6); |
| break; |
| |
| case 0x60: |
| /* 0x64 thru 0x67 are valid prefixes in all modes. */ |
| scan_more = (instr_lo & 0xC) == 0x4; |
| break; |
| case 0xF0: |
| /* 0xF0, 0xF2, and 0xF3 are valid prefixes */ |
| scan_more = !instr_lo || (instr_lo>>1) == 1; |
| break; |
| case 0x00: |
| /* Prefetch instruction is 0x0F0D or 0x0F18 */ |
| scan_more = 0; |
| if (instr > (unsigned char *)limit) |
| break; |
| if (probe_kernel_address(instr, opcode)) |
| break; |
| prefetch = (instr_lo == 0xF) && |
| (opcode == 0x0D || opcode == 0x18); |
| break; |
| default: |
| scan_more = 0; |
| break; |
| } |
| } |
| return prefetch; |
| } |
| |
| static inline int is_prefetch(struct pt_regs *regs, unsigned long addr, |
| unsigned long error_code) |
| { |
| if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD && |
| boot_cpu_data.x86 >= 6)) { |
| /* Catch an obscure case of prefetch inside an NX page. */ |
| if (nx_enabled && (error_code & 16)) |
| return 0; |
| return __is_prefetch(regs, addr); |
| } |
| return 0; |
| } |
| |
| static noinline void force_sig_info_fault(int si_signo, int si_code, |
| unsigned long address, struct task_struct *tsk) |
| { |
| siginfo_t info; |
| |
| info.si_signo = si_signo; |
| info.si_errno = 0; |
| info.si_code = si_code; |
| info.si_addr = (void __user *)address; |
| force_sig_info(si_signo, &info, tsk); |
| } |
| |
| fastcall void do_invalid_op(struct pt_regs *, unsigned long); |
| |
| 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; |
| } |
| |
| /* |
| * Handle a fault on the vmalloc or module mapping area |
| * |
| * This assumes no large pages in there. |
| */ |
| static inline int vmalloc_fault(unsigned long address) |
| { |
| unsigned long pgd_paddr; |
| pmd_t *pmd_k; |
| pte_t *pte_k; |
| /* |
| * 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; |
| } |
| |
| /* |
| * This routine handles page faults. It determines the address, |
| * and the problem, and then passes it off to one of the appropriate |
| * routines. |
| * |
| * error_code: |
| * bit 0 == 0 means no page found, 1 means protection fault |
| * bit 1 == 0 means read, 1 means write |
| * bit 2 == 0 means kernel, 1 means user-mode |
| * bit 3 == 1 means use of reserved bit detected |
| * bit 4 == 1 means fault was an instruction fetch |
| */ |
| fastcall void __kprobes do_page_fault(struct pt_regs *regs, |
| unsigned long error_code) |
| { |
| struct task_struct *tsk; |
| struct mm_struct *mm; |
| struct vm_area_struct * vma; |
| unsigned long address; |
| int write, si_code; |
| int fault; |
| |
| /* get the address */ |
| address = read_cr2(); |
| |
| tsk = current; |
| |
| si_code = SEGV_MAPERR; |
| |
| /* |
| * 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(address >= TASK_SIZE)) { |
| if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0) |
| return; |
| if (notify_page_fault(regs, error_code) == NOTIFY_STOP) |
| return; |
| /* |
| * Don't take the mm semaphore here. If we fixup a prefetch |
| * fault we could otherwise deadlock. |
| */ |
| goto bad_area_nosemaphore; |
| } |
| |
| if (notify_page_fault(regs, error_code) == NOTIFY_STOP) |
| return; |
| |
| /* It's safe to allow irq's after cr2 has been saved and the vmalloc |
| fault has been handled. */ |
| if (regs->eflags & (X86_EFLAGS_IF|VM_MASK)) |
| local_irq_enable(); |
| |
| mm = tsk->mm; |
| |
| /* |
| * 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 (in_atomic() || !mm) |
| goto bad_area_nosemaphore; |
| |
| /* 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. Unfortunatly, 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 possibilty 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 (!down_read_trylock(&mm->mmap_sem)) { |
| if ((error_code & 4) == 0 && |
| !search_exception_tables(regs->eip)) |
| goto bad_area_nosemaphore; |
| down_read(&mm->mmap_sem); |
| } |
| |
| vma = find_vma(mm, address); |
| if (!vma) |
| goto bad_area; |
| if (vma->vm_start <= address) |
| goto good_area; |
| if (!(vma->vm_flags & VM_GROWSDOWN)) |
| goto bad_area; |
| if (error_code & 4) { |
| /* |
| * Accessing the stack below %esp is always a bug. |
| * The large cushion allows instructions like enter |
| * and pusha to work. ("enter $65535,$31" pushes |
| * 32 pointers and then decrements %esp by 65535.) |
| */ |
| if (address + 65536 + 32 * sizeof(unsigned long) < regs->esp) |
| goto bad_area; |
| } |
| if (expand_stack(vma, address)) |
| goto bad_area; |
| /* |
| * Ok, we have a good vm_area for this memory access, so |
| * we can handle it.. |
| */ |
| good_area: |
| si_code = SEGV_ACCERR; |
| write = 0; |
| switch (error_code & 3) { |
| default: /* 3: write, present */ |
| /* fall through */ |
| case 2: /* write, not present */ |
| if (!(vma->vm_flags & VM_WRITE)) |
| goto bad_area; |
| write++; |
| break; |
| case 1: /* read, present */ |
| goto bad_area; |
| case 0: /* read, not present */ |
| if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) |
| goto bad_area; |
| } |
| |
| survive: |
| /* |
| * 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, write); |
| if (unlikely(fault & VM_FAULT_ERROR)) { |
| if (fault & VM_FAULT_OOM) |
| goto out_of_memory; |
| else if (fault & VM_FAULT_SIGBUS) |
| goto do_sigbus; |
| BUG(); |
| } |
| if (fault & VM_FAULT_MAJOR) |
| tsk->maj_flt++; |
| else |
| tsk->min_flt++; |
| |
| /* |
| * Did it hit the DOS screen memory VA from vm86 mode? |
| */ |
| if (regs->eflags & VM_MASK) { |
| unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT; |
| if (bit < 32) |
| tsk->thread.screen_bitmap |= 1 << bit; |
| } |
| up_read(&mm->mmap_sem); |
| return; |
| |
| /* |
| * Something tried to access memory that isn't in our memory map.. |
| * Fix it, but check if it's kernel or user first.. |
| */ |
| bad_area: |
| up_read(&mm->mmap_sem); |
| |
| bad_area_nosemaphore: |
| /* User mode accesses just cause a SIGSEGV */ |
| if (error_code & 4) { |
| /* |
| * 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, address, error_code)) |
| return; |
| |
| tsk->thread.cr2 = address; |
| /* Kernel addresses are always protection faults */ |
| tsk->thread.error_code = error_code | (address >= TASK_SIZE); |
| tsk->thread.trap_no = 14; |
| force_sig_info_fault(SIGSEGV, si_code, address, tsk); |
| return; |
| } |
| |
| #ifdef CONFIG_X86_F00F_BUG |
| /* |
| * Pentium F0 0F C7 C8 bug workaround. |
| */ |
| if (boot_cpu_data.f00f_bug) { |
| unsigned long nr; |
| |
| nr = (address - idt_descr.address) >> 3; |
| |
| if (nr == 6) { |
| do_invalid_op(regs, 0); |
| return; |
| } |
| } |
| #endif |
| |
| no_context: |
| /* Are we prepared to handle this kernel fault? */ |
| if (fixup_exception(regs)) |
| return; |
| |
| /* |
| * Valid to do another page fault here, because if this fault |
| * had been triggered by is_prefetch fixup_exception would have |
| * handled it. |
| */ |
| if (is_prefetch(regs, address, error_code)) |
| return; |
| |
| /* |
| * Oops. The kernel tried to access some bad page. We'll have to |
| * terminate things with extreme prejudice. |
| */ |
| |
| bust_spinlocks(1); |
| |
| if (oops_may_print()) { |
| __typeof__(pte_val(__pte(0))) page; |
| |
| #ifdef CONFIG_X86_PAE |
| if (error_code & 16) { |
| pte_t *pte = lookup_address(address); |
| |
| if (pte && pte_present(*pte) && !pte_exec_kernel(*pte)) |
| printk(KERN_CRIT "kernel tried to execute " |
| "NX-protected page - exploit attempt? " |
| "(uid: %d)\n", current->uid); |
| } |
| #endif |
| if (address < PAGE_SIZE) |
| printk(KERN_ALERT "BUG: unable to handle kernel NULL " |
| "pointer dereference"); |
| else |
| printk(KERN_ALERT "BUG: unable to handle kernel paging" |
| " request"); |
| printk(" at virtual address %08lx\n",address); |
| printk(KERN_ALERT " printing eip:\n"); |
| printk("%08lx\n", regs->eip); |
| |
| page = read_cr3(); |
| page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT]; |
| #ifdef CONFIG_X86_PAE |
| printk(KERN_ALERT "*pdpt = %016Lx\n", page); |
| if ((page >> PAGE_SHIFT) < max_low_pfn |
| && page & _PAGE_PRESENT) { |
| page &= PAGE_MASK; |
| page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT) |
| & (PTRS_PER_PMD - 1)]; |
| printk(KERN_ALERT "*pde = %016Lx\n", page); |
| page &= ~_PAGE_NX; |
| } |
| #else |
| printk(KERN_ALERT "*pde = %08lx\n", page); |
| #endif |
| |
| /* |
| * 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 ((page >> PAGE_SHIFT) < max_low_pfn |
| && (page & _PAGE_PRESENT)) { |
| page &= PAGE_MASK; |
| page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT) |
| & (PTRS_PER_PTE - 1)]; |
| printk(KERN_ALERT "*pte = %0*Lx\n", sizeof(page)*2, (u64)page); |
| } |
| } |
| |
| tsk->thread.cr2 = address; |
| tsk->thread.trap_no = 14; |
| tsk->thread.error_code = error_code; |
| die("Oops", regs, error_code); |
| bust_spinlocks(0); |
| do_exit(SIGKILL); |
| |
| /* |
| * We ran out of memory, or some other thing happened to us that made |
| * us unable to handle the page fault gracefully. |
| */ |
| out_of_memory: |
| up_read(&mm->mmap_sem); |
| if (is_init(tsk)) { |
| yield(); |
| down_read(&mm->mmap_sem); |
| goto survive; |
| } |
| printk("VM: killing process %s\n", tsk->comm); |
| if (error_code & 4) |
| do_exit(SIGKILL); |
| goto no_context; |
| |
| do_sigbus: |
| up_read(&mm->mmap_sem); |
| |
| /* Kernel mode? Handle exceptions or die */ |
| if (!(error_code & 4)) |
| goto no_context; |
| |
| /* User space => ok to do another page fault */ |
| if (is_prefetch(regs, address, error_code)) |
| return; |
| |
| tsk->thread.cr2 = address; |
| tsk->thread.error_code = error_code; |
| tsk->thread.trap_no = 14; |
| force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk); |
| } |
| |
| void vmalloc_sync_all(void) |
| { |
| /* |
| * Note that races in the updates of insync and start aren't |
| * problematic: insync can only get set bits added, and updates to |
| * start are only improving performance (without affecting correctness |
| * if undone). |
| */ |
| static DECLARE_BITMAP(insync, PTRS_PER_PGD); |
| static unsigned long start = TASK_SIZE; |
| unsigned long address; |
| |
| if (SHARED_KERNEL_PMD) |
| return; |
| |
| BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK); |
| for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) { |
| if (!test_bit(pgd_index(address), insync)) { |
| unsigned long flags; |
| struct page *page; |
| |
| spin_lock_irqsave(&pgd_lock, flags); |
| for (page = pgd_list; page; page = |
| (struct page *)page->index) |
| if (!vmalloc_sync_one(page_address(page), |
| address)) { |
| BUG_ON(page != pgd_list); |
| break; |
| } |
| spin_unlock_irqrestore(&pgd_lock, flags); |
| if (!page) |
| set_bit(pgd_index(address), insync); |
| } |
| if (address == start && test_bit(pgd_index(address), insync)) |
| start = address + PGDIR_SIZE; |
| } |
| } |