1141 lines
27 KiB
C
1141 lines
27 KiB
C
/*
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* Copyright (C) 1995 Linus Torvalds
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* Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
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* Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
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*/
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#include <linux/magic.h> /* STACK_END_MAGIC */
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#include <linux/sched.h> /* test_thread_flag(), ... */
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#include <linux/kdebug.h> /* oops_begin/end, ... */
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#include <linux/module.h> /* search_exception_table */
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#include <linux/bootmem.h> /* max_low_pfn */
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#include <linux/kprobes.h> /* __kprobes, ... */
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#include <linux/mmiotrace.h> /* kmmio_handler, ... */
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#include <linux/perf_event.h> /* perf_sw_event */
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#include <asm/traps.h> /* dotraplinkage, ... */
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#include <asm/pgalloc.h> /* pgd_*(), ... */
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#include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
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/*
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* Page fault error code bits:
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*
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* bit 0 == 0: no page found 1: protection fault
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* bit 1 == 0: read access 1: write access
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* bit 2 == 0: kernel-mode access 1: user-mode access
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* bit 3 == 1: use of reserved bit detected
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* bit 4 == 1: fault was an instruction fetch
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*/
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enum x86_pf_error_code {
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PF_PROT = 1 << 0,
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PF_WRITE = 1 << 1,
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PF_USER = 1 << 2,
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PF_RSVD = 1 << 3,
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PF_INSTR = 1 << 4,
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};
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/*
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* Returns 0 if mmiotrace is disabled, or if the fault is not
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* handled by mmiotrace:
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*/
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static inline int __kprobes
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kmmio_fault(struct pt_regs *regs, unsigned long addr)
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{
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if (unlikely(is_kmmio_active()))
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if (kmmio_handler(regs, addr) == 1)
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return -1;
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return 0;
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}
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static inline int __kprobes notify_page_fault(struct pt_regs *regs)
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{
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int ret = 0;
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/* kprobe_running() needs smp_processor_id() */
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if (kprobes_built_in() && !user_mode_vm(regs)) {
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preempt_disable();
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if (kprobe_running() && kprobe_fault_handler(regs, 14))
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ret = 1;
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preempt_enable();
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}
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return ret;
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}
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/*
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* Prefetch quirks:
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*
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* 32-bit mode:
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*
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* Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
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* Check that here and ignore it.
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*
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* 64-bit mode:
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*
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* Sometimes the CPU reports invalid exceptions on prefetch.
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* Check that here and ignore it.
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*
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* Opcode checker based on code by Richard Brunner.
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*/
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static inline int
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check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
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unsigned char opcode, int *prefetch)
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{
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unsigned char instr_hi = opcode & 0xf0;
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unsigned char instr_lo = opcode & 0x0f;
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switch (instr_hi) {
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case 0x20:
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case 0x30:
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/*
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* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
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* In X86_64 long mode, the CPU will signal invalid
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* opcode if some of these prefixes are present so
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* X86_64 will never get here anyway
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*/
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return ((instr_lo & 7) == 0x6);
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#ifdef CONFIG_X86_64
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case 0x40:
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/*
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* In AMD64 long mode 0x40..0x4F are valid REX prefixes
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* Need to figure out under what instruction mode the
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* instruction was issued. Could check the LDT for lm,
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* but for now it's good enough to assume that long
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* mode only uses well known segments or kernel.
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*/
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return (!user_mode(regs)) || (regs->cs == __USER_CS);
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#endif
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case 0x60:
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/* 0x64 thru 0x67 are valid prefixes in all modes. */
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return (instr_lo & 0xC) == 0x4;
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case 0xF0:
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/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
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return !instr_lo || (instr_lo>>1) == 1;
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case 0x00:
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/* Prefetch instruction is 0x0F0D or 0x0F18 */
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if (probe_kernel_address(instr, opcode))
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return 0;
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*prefetch = (instr_lo == 0xF) &&
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(opcode == 0x0D || opcode == 0x18);
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return 0;
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default:
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return 0;
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}
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}
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static int
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is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
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{
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unsigned char *max_instr;
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unsigned char *instr;
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int prefetch = 0;
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/*
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* If it was a exec (instruction fetch) fault on NX page, then
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* do not ignore the fault:
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*/
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if (error_code & PF_INSTR)
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return 0;
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instr = (void *)convert_ip_to_linear(current, regs);
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max_instr = instr + 15;
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if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
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return 0;
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while (instr < max_instr) {
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unsigned char opcode;
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if (probe_kernel_address(instr, opcode))
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break;
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instr++;
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if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
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break;
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}
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return prefetch;
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}
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static void
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force_sig_info_fault(int si_signo, int si_code, unsigned long address,
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struct task_struct *tsk)
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{
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siginfo_t info;
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info.si_signo = si_signo;
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info.si_errno = 0;
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info.si_code = si_code;
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info.si_addr = (void __user *)address;
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info.si_addr_lsb = si_code == BUS_MCEERR_AR ? PAGE_SHIFT : 0;
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force_sig_info(si_signo, &info, tsk);
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}
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DEFINE_SPINLOCK(pgd_lock);
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LIST_HEAD(pgd_list);
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#ifdef CONFIG_X86_32
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static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
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{
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unsigned index = pgd_index(address);
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pgd_t *pgd_k;
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pud_t *pud, *pud_k;
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pmd_t *pmd, *pmd_k;
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pgd += index;
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pgd_k = init_mm.pgd + index;
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if (!pgd_present(*pgd_k))
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return NULL;
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/*
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* set_pgd(pgd, *pgd_k); here would be useless on PAE
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* and redundant with the set_pmd() on non-PAE. As would
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* set_pud.
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*/
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pud = pud_offset(pgd, address);
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pud_k = pud_offset(pgd_k, address);
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if (!pud_present(*pud_k))
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return NULL;
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pmd = pmd_offset(pud, address);
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pmd_k = pmd_offset(pud_k, address);
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if (!pmd_present(*pmd_k))
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return NULL;
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if (!pmd_present(*pmd))
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set_pmd(pmd, *pmd_k);
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else
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BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
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return pmd_k;
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}
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void vmalloc_sync_all(void)
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{
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unsigned long address;
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if (SHARED_KERNEL_PMD)
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return;
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for (address = VMALLOC_START & PMD_MASK;
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address >= TASK_SIZE && address < FIXADDR_TOP;
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address += PMD_SIZE) {
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unsigned long flags;
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struct page *page;
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spin_lock_irqsave(&pgd_lock, flags);
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list_for_each_entry(page, &pgd_list, lru) {
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if (!vmalloc_sync_one(page_address(page), address))
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break;
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}
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spin_unlock_irqrestore(&pgd_lock, flags);
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}
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}
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/*
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* 32-bit:
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*
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* Handle a fault on the vmalloc or module mapping area
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*/
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static noinline __kprobes int vmalloc_fault(unsigned long address)
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{
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unsigned long pgd_paddr;
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pmd_t *pmd_k;
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pte_t *pte_k;
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/* Make sure we are in vmalloc area: */
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if (!(address >= VMALLOC_START && address < VMALLOC_END))
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return -1;
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/*
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* Synchronize this task's top level page-table
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* with the 'reference' page table.
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*
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* Do _not_ use "current" here. We might be inside
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* an interrupt in the middle of a task switch..
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*/
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pgd_paddr = read_cr3();
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pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
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if (!pmd_k)
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return -1;
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pte_k = pte_offset_kernel(pmd_k, address);
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if (!pte_present(*pte_k))
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return -1;
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return 0;
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}
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/*
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* Did it hit the DOS screen memory VA from vm86 mode?
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*/
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static inline void
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check_v8086_mode(struct pt_regs *regs, unsigned long address,
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struct task_struct *tsk)
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{
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unsigned long bit;
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if (!v8086_mode(regs))
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return;
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bit = (address - 0xA0000) >> PAGE_SHIFT;
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if (bit < 32)
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tsk->thread.screen_bitmap |= 1 << bit;
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}
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static bool low_pfn(unsigned long pfn)
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{
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return pfn < max_low_pfn;
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}
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static void dump_pagetable(unsigned long address)
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{
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pgd_t *base = __va(read_cr3());
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pgd_t *pgd = &base[pgd_index(address)];
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pmd_t *pmd;
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pte_t *pte;
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#ifdef CONFIG_X86_PAE
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printk("*pdpt = %016Lx ", pgd_val(*pgd));
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if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
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goto out;
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#endif
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pmd = pmd_offset(pud_offset(pgd, address), address);
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printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
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/*
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* We must not directly access the pte in the highpte
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* case if the page table is located in highmem.
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* And let's rather not kmap-atomic the pte, just in case
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* it's allocated already:
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*/
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if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
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goto out;
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pte = pte_offset_kernel(pmd, address);
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printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
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out:
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printk("\n");
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}
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#else /* CONFIG_X86_64: */
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void vmalloc_sync_all(void)
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{
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unsigned long address;
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for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
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address += PGDIR_SIZE) {
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const pgd_t *pgd_ref = pgd_offset_k(address);
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unsigned long flags;
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struct page *page;
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if (pgd_none(*pgd_ref))
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continue;
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spin_lock_irqsave(&pgd_lock, flags);
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list_for_each_entry(page, &pgd_list, lru) {
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pgd_t *pgd;
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pgd = (pgd_t *)page_address(page) + pgd_index(address);
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if (pgd_none(*pgd))
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set_pgd(pgd, *pgd_ref);
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else
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BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
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}
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spin_unlock_irqrestore(&pgd_lock, flags);
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}
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}
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/*
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* 64-bit:
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*
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* Handle a fault on the vmalloc area
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*
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* This assumes no large pages in there.
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*/
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static noinline __kprobes int vmalloc_fault(unsigned long address)
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{
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pgd_t *pgd, *pgd_ref;
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pud_t *pud, *pud_ref;
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pmd_t *pmd, *pmd_ref;
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pte_t *pte, *pte_ref;
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/* Make sure we are in vmalloc area: */
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if (!(address >= VMALLOC_START && address < VMALLOC_END))
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return -1;
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/*
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* Copy kernel mappings over when needed. This can also
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* happen within a race in page table update. In the later
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* case just flush:
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*/
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pgd = pgd_offset(current->active_mm, address);
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pgd_ref = pgd_offset_k(address);
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if (pgd_none(*pgd_ref))
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return -1;
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if (pgd_none(*pgd))
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set_pgd(pgd, *pgd_ref);
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else
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BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
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/*
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* Below here mismatches are bugs because these lower tables
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* are shared:
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*/
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pud = pud_offset(pgd, address);
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pud_ref = pud_offset(pgd_ref, address);
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if (pud_none(*pud_ref))
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return -1;
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if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
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BUG();
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pmd = pmd_offset(pud, address);
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pmd_ref = pmd_offset(pud_ref, address);
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if (pmd_none(*pmd_ref))
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return -1;
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if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
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BUG();
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pte_ref = pte_offset_kernel(pmd_ref, address);
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if (!pte_present(*pte_ref))
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return -1;
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pte = pte_offset_kernel(pmd, address);
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|
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/*
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* Don't use pte_page here, because the mappings can point
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* outside mem_map, and the NUMA hash lookup cannot handle
|
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* that:
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*/
|
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if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
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BUG();
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return 0;
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}
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|
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static const char errata93_warning[] =
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KERN_ERR
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"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
|
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"******* Working around it, but it may cause SEGVs or burn power.\n"
|
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"******* Please consider a BIOS update.\n"
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"******* Disabling USB legacy in the BIOS may also help.\n";
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|
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/*
|
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* No vm86 mode in 64-bit mode:
|
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*/
|
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static inline void
|
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check_v8086_mode(struct pt_regs *regs, unsigned long address,
|
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struct task_struct *tsk)
|
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{
|
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}
|
|
|
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static int bad_address(void *p)
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{
|
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unsigned long dummy;
|
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return probe_kernel_address((unsigned long *)p, dummy);
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}
|
|
|
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static void dump_pagetable(unsigned long address)
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{
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pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
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pgd_t *pgd = base + pgd_index(address);
|
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pud_t *pud;
|
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pmd_t *pmd;
|
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pte_t *pte;
|
|
|
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if (bad_address(pgd))
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goto bad;
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|
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printk("PGD %lx ", pgd_val(*pgd));
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|
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if (!pgd_present(*pgd))
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goto out;
|
|
|
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pud = pud_offset(pgd, address);
|
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if (bad_address(pud))
|
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goto bad;
|
|
|
|
printk("PUD %lx ", pud_val(*pud));
|
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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;
|
|
|
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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)
|
|
{
|
|
#ifdef CONFIG_X86_64
|
|
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_data.f00f_bug) {
|
|
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, 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_no = 14;
|
|
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)
|
|
{
|
|
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))
|
|
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 (*stackend != STACK_END_MAGIC)
|
|
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
|
|
|
|
tsk->thread.cr2 = address;
|
|
tsk->thread.trap_no = 14;
|
|
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_EMERG "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;
|
|
|
|
if (unlikely(show_unhandled_signals))
|
|
show_signal_msg(regs, error_code, address, tsk);
|
|
|
|
/* Kernel addresses are always protection faults: */
|
|
tsk->thread.cr2 = address;
|
|
tsk->thread.error_code = error_code | (address >= TASK_SIZE);
|
|
tsk->thread.trap_no = 14;
|
|
|
|
force_sig_info_fault(SIGSEGV, si_code, address, tsk);
|
|
|
|
return;
|
|
}
|
|
|
|
if (is_f00f_bug(regs, address))
|
|
return;
|
|
|
|
no_context(regs, error_code, address);
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
|
|
static void
|
|
out_of_memory(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address)
|
|
{
|
|
/*
|
|
* 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):
|
|
*/
|
|
up_read(¤t->mm->mmap_sem);
|
|
|
|
pagefault_out_of_memory();
|
|
}
|
|
|
|
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);
|
|
|
|
/* 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_no = 14;
|
|
|
|
#ifdef CONFIG_MEMORY_FAILURE
|
|
if (fault & VM_FAULT_HWPOISON) {
|
|
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);
|
|
}
|
|
|
|
static noinline void
|
|
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
|
|
unsigned long address, unsigned int fault)
|
|
{
|
|
if (fault & VM_FAULT_OOM) {
|
|
out_of_memory(regs, error_code, address);
|
|
} else {
|
|
if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON))
|
|
do_sigbus(regs, error_code, address, fault);
|
|
else
|
|
BUG();
|
|
}
|
|
}
|
|
|
|
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, int write, struct vm_area_struct *vma)
|
|
{
|
|
if (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;
|
|
}
|
|
|
|
/*
|
|
* This routine handles page faults. It determines the address,
|
|
* and the problem, and then passes it off to one of the appropriate
|
|
* routines.
|
|
*/
|
|
dotraplinkage 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 write;
|
|
int fault;
|
|
|
|
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;
|
|
} else {
|
|
if (regs->flags & X86_EFLAGS_IF)
|
|
local_irq_enable();
|
|
}
|
|
|
|
if (unlikely(error_code & PF_RSVD))
|
|
pgtable_bad(regs, error_code, address);
|
|
|
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, 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;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
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:
|
|
write = error_code & PF_WRITE;
|
|
|
|
if (unlikely(access_error(error_code, write, 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, write ? FAULT_FLAG_WRITE : 0);
|
|
|
|
if (unlikely(fault & VM_FAULT_ERROR)) {
|
|
mm_fault_error(regs, error_code, address, fault);
|
|
return;
|
|
}
|
|
|
|
if (fault & VM_FAULT_MAJOR) {
|
|
tsk->maj_flt++;
|
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
|
|
regs, address);
|
|
} else {
|
|
tsk->min_flt++;
|
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
|
|
regs, address);
|
|
}
|
|
|
|
check_v8086_mode(regs, address, tsk);
|
|
|
|
up_read(&mm->mmap_sem);
|
|
}
|