diff options
Diffstat (limited to 'arch/x86/mm/fault_32.c')
| -rw-r--r-- | arch/x86/mm/fault_32.c | 657 |
1 files changed, 657 insertions, 0 deletions
diff --git a/arch/x86/mm/fault_32.c b/arch/x86/mm/fault_32.c new file mode 100644 index 000000000000..fcb38e7f3543 --- /dev/null +++ b/arch/x86/mm/fault_32.c @@ -0,0 +1,657 @@ +/* + * 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); + arch_flush_lazy_mmu_mode(); + } 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; +} + +int show_unhandled_signals = 1; + +/* + * 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; + + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && + printk_ratelimit()) { + printk("%s%s[%d]: segfault at %08lx eip %08lx " + "esp %08lx error %lx\n", + tsk->pid > 1 ? KERN_INFO : KERN_EMERG, + tsk->comm, tsk->pid, address, regs->eip, + regs->esp, error_code); + } + 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; + } +} |