diff options
Diffstat (limited to 'arch/x86/mm/fault_64.c')
| -rw-r--r-- | arch/x86/mm/fault_64.c | 636 |
1 files changed, 636 insertions, 0 deletions
diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c new file mode 100644 index 000000000000..54816adb8e93 --- /dev/null +++ b/arch/x86/mm/fault_64.c @@ -0,0 +1,636 @@ +/* + * linux/arch/x86-64/mm/fault.c + * + * Copyright (C) 1995 Linus Torvalds + * Copyright (C) 2001,2002 Andi Kleen, SuSE Labs. + */ + +#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/compiler.h> +#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/pgalloc.h> +#include <asm/smp.h> +#include <asm/tlbflush.h> +#include <asm/proto.h> +#include <asm-generic/sections.h> + +/* Page fault error code bits */ +#define PF_PROT (1<<0) /* or no page found */ +#define PF_WRITE (1<<1) +#define PF_USER (1<<2) +#define PF_RSVD (1<<3) +#define PF_INSTR (1<<4) + +static ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); + +/* Hook to register for page fault notifications */ +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); +} + +/* Sometimes the CPU reports invalid exceptions on prefetch. + Check that here and ignore. + Opcode checker based on code by Richard Brunner */ +static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr, + unsigned long error_code) +{ + unsigned char *instr; + int scan_more = 1; + int prefetch = 0; + unsigned char *max_instr; + + /* If it was a exec fault ignore */ + if (error_code & PF_INSTR) + return 0; + + instr = (unsigned char __user *)convert_rip_to_linear(current, regs); + max_instr = instr + 15; + + if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE) + return 0; + + while (scan_more && instr < max_instr) { + unsigned char opcode; + unsigned char instr_hi; + unsigned char instr_lo; + + 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. In long mode, the CPU will signal + invalid opcode if some of these prefixes are + present so we will never get here anyway */ + scan_more = ((instr_lo & 7) == 0x6); + break; + + case 0x40: + /* In AMD64 long mode, 0x40 to 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. */ + scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS); + 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 in all modes. */ + scan_more = !instr_lo || (instr_lo>>1) == 1; + break; + case 0x00: + /* Prefetch instruction is 0x0F0D or 0x0F18 */ + scan_more = 0; + if (probe_kernel_address(instr, opcode)) + break; + prefetch = (instr_lo == 0xF) && + (opcode == 0x0D || opcode == 0x18); + break; + default: + scan_more = 0; + break; + } + } + return prefetch; +} + +static int bad_address(void *p) +{ + unsigned long dummy; + return probe_kernel_address((unsigned long *)p, dummy); +} + +void dump_pagetable(unsigned long address) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + + pgd = (pgd_t *)read_cr3(); + + pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK); + pgd += pgd_index(address); + if (bad_address(pgd)) goto bad; + printk("PGD %lx ", pgd_val(*pgd)); + if (!pgd_present(*pgd)) goto ret; + + pud = pud_offset(pgd, address); + if (bad_address(pud)) goto bad; + printk("PUD %lx ", pud_val(*pud)); + if (!pud_present(*pud)) goto ret; + + pmd = pmd_offset(pud, address); + if (bad_address(pmd)) goto bad; + printk("PMD %lx ", pmd_val(*pmd)); + if (!pmd_present(*pmd)) goto ret; + + pte = pte_offset_kernel(pmd, address); + if (bad_address(pte)) goto bad; + printk("PTE %lx", pte_val(*pte)); +ret: + printk("\n"); + return; +bad: + printk("BAD\n"); +} + +static const char errata93_warning[] = +KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n" +KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n" +KERN_ERR "******* Please consider a BIOS update.\n" +KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n"; + +/* 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. */ + +static int is_errata93(struct pt_regs *regs, unsigned long address) +{ + static int warned; + if (address != regs->rip) + return 0; + if ((address >> 32) != 0) + return 0; + address |= 0xffffffffUL << 32; + if ((address >= (u64)_stext && address <= (u64)_etext) || + (address >= MODULES_VADDR && address <= MODULES_END)) { + if (!warned) { + printk(errata93_warning); + warned = 1; + } + regs->rip = address; + return 1; + } + return 0; +} + +static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs, + unsigned long error_code) +{ + unsigned long flags = oops_begin(); + struct task_struct *tsk; + + printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", + current->comm, address); + dump_pagetable(address); + tsk = current; + tsk->thread.cr2 = address; + tsk->thread.trap_no = 14; + tsk->thread.error_code = error_code; + __die("Bad pagetable", regs, error_code); + oops_end(flags); + do_exit(SIGKILL); +} + +/* + * Handle a fault on the vmalloc area + * + * This assumes no large pages in there. + */ +static 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; + + /* 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->mm ?: &init_mm, address); + pgd_ref = pgd_offset_k(address); + if (pgd_none(*pgd_ref)) + return -1; + if (pgd_none(*pgd)) + set_pgd(pgd, *pgd_ref); + 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; +} + +static int page_fault_trace; +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. + */ +asmlinkage 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; + const struct exception_table_entry *fixup; + int write, fault; + unsigned long flags; + siginfo_t info; + + tsk = current; + mm = tsk->mm; + prefetchw(&mm->mmap_sem); + + /* get the address */ + address = read_cr2(); + + info.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_SIZE64)) { + /* + * Don't check for the module range here: its PML4 + * is always initialized because it's shared with the main + * kernel text. Only vmalloc may need PML4 syncups. + */ + if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) && + ((address >= VMALLOC_START && address < VMALLOC_END))) { + if (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; + + if (likely(regs->eflags & X86_EFLAGS_IF)) + local_irq_enable(); + + if (unlikely(page_fault_trace)) + printk("pagefault rip:%lx rsp:%lx cs:%lu ss:%lu address %lx error %lx\n", + regs->rip,regs->rsp,regs->cs,regs->ss,address,error_code); + + if (unlikely(error_code & PF_RSVD)) + pgtable_bad(address, regs, error_code); + + /* + * If we're in an interrupt or have no user + * context, we must not take the fault.. + */ + if (unlikely(in_atomic() || !mm)) + goto bad_area_nosemaphore; + + /* + * User-mode registers count as a user access even for any + * potential system fault or CPU buglet. + */ + if (user_mode_vm(regs)) + error_code |= PF_USER; + + again: + /* 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 & PF_USER) == 0 && + !search_exception_tables(regs->rip)) + goto bad_area_nosemaphore; + down_read(&mm->mmap_sem); + } + + vma = find_vma(mm, address); + if (!vma) + goto bad_area; + if (likely(vma->vm_start <= address)) + goto good_area; + if (!(vma->vm_flags & VM_GROWSDOWN)) + goto bad_area; + if (error_code & 4) { + /* Allow userspace just enough access below the stack pointer + * to let the 'enter' instruction work. + */ + if (address + 65536 + 32 * sizeof(unsigned long) < regs->rsp) + 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: + info.si_code = SEGV_ACCERR; + write = 0; + switch (error_code & (PF_PROT|PF_WRITE)) { + default: /* 3: write, present */ + /* fall through */ + case PF_WRITE: /* write, not present */ + if (!(vma->vm_flags & VM_WRITE)) + goto bad_area; + write++; + break; + case PF_PROT: /* read, present */ + goto bad_area; + case 0: /* read, not present */ + if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) + goto bad_area; + } + + /* + * 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++; + 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 & PF_USER) { + + /* + * It's possible to have interrupts off here. + */ + local_irq_enable(); + + if (is_prefetch(regs, address, error_code)) + return; + + /* Work around K8 erratum #100 K8 in compat mode + occasionally jumps to illegal addresses >4GB. We + catch this here 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. */ + if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && + (address >> 32)) + return; + + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && + printk_ratelimit()) { + printk( + "%s%s[%d]: segfault at %016lx rip %016lx rsp %016lx error %lx\n", + tsk->pid > 1 ? KERN_INFO : KERN_EMERG, + tsk->comm, tsk->pid, address, regs->rip, + regs->rsp, 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; + info.si_signo = SIGSEGV; + info.si_errno = 0; + /* info.si_code has been set above */ + info.si_addr = (void __user *)address; + force_sig_info(SIGSEGV, &info, tsk); + return; + } + +no_context: + + /* Are we prepared to handle this kernel fault? */ + fixup = search_exception_tables(regs->rip); + if (fixup) { + regs->rip = fixup->fixup; + return; + } + + /* + * Hall of shame of CPU/BIOS bugs. + */ + + if (is_prefetch(regs, address, error_code)) + 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(); + + if (address < PAGE_SIZE) + printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference"); + else + printk(KERN_ALERT "Unable to handle kernel paging request"); + printk(" at %016lx RIP: \n" KERN_ALERT,address); + printk_address(regs->rip); + dump_pagetable(address); + tsk->thread.cr2 = address; + tsk->thread.trap_no = 14; + tsk->thread.error_code = error_code; + __die("Oops", regs, error_code); + /* Executive summary in case the body of the oops scrolled away */ + printk(KERN_EMERG "CR2: %016lx\n", address); + oops_end(flags); + 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(current)) { + yield(); + goto again; + } + printk("VM: killing process %s\n", tsk->comm); + if (error_code & 4) + do_group_exit(SIGKILL); + goto no_context; + +do_sigbus: + up_read(&mm->mmap_sem); + + /* Kernel mode? Handle exceptions or die */ + if (!(error_code & PF_USER)) + goto no_context; + + tsk->thread.cr2 = address; + tsk->thread.error_code = error_code; + tsk->thread.trap_no = 14; + info.si_signo = SIGBUS; + info.si_errno = 0; + info.si_code = BUS_ADRERR; + info.si_addr = (void __user *)address; + force_sig_info(SIGBUS, &info, tsk); + return; +} + +DEFINE_SPINLOCK(pgd_lock); +LIST_HEAD(pgd_list); + +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 = VMALLOC_START & PGDIR_MASK; + unsigned long address; + + for (address = start; address <= VMALLOC_END; address += PGDIR_SIZE) { + if (!test_bit(pgd_index(address), insync)) { + const pgd_t *pgd_ref = pgd_offset_k(address); + struct page *page; + + if (pgd_none(*pgd_ref)) + continue; + spin_lock(&pgd_lock); + list_for_each_entry(page, &pgd_list, lru) { + pgd_t *pgd; + pgd = (pgd_t *)page_address(page) + pgd_index(address); + if (pgd_none(*pgd)) + set_pgd(pgd, *pgd_ref); + else + BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); + } + spin_unlock(&pgd_lock); + set_bit(pgd_index(address), insync); + } + if (address == start) + start = address + PGDIR_SIZE; + } + /* Check that there is no need to do the same for the modules area. */ + BUILD_BUG_ON(!(MODULES_VADDR > __START_KERNEL)); + BUILD_BUG_ON(!(((MODULES_END - 1) & PGDIR_MASK) == + (__START_KERNEL & PGDIR_MASK))); +} + +static int __init enable_pagefaulttrace(char *str) +{ + page_fault_trace = 1; + return 1; +} +__setup("pagefaulttrace", enable_pagefaulttrace); |