660 lines
17 KiB
C
660 lines
17 KiB
C
/*
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* linux/arch/i386/mm/fault.c
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*
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* Copyright (C) 1995 Linus Torvalds
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*/
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#include <linux/signal.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/interrupt.h>
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#include <linux/init.h>
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#include <linux/tty.h>
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#include <linux/vt_kern.h> /* For unblank_screen() */
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#include <linux/highmem.h>
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#include <linux/bootmem.h> /* for max_low_pfn */
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#include <linux/vmalloc.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#include <linux/uaccess.h>
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#include <linux/kdebug.h>
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#include <linux/kprobes.h>
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#include <asm/system.h>
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#include <asm/desc.h>
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#include <asm/segment.h>
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extern void die(const char *,struct pt_regs *,long);
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#ifdef CONFIG_KPROBES
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static inline int 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 (!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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#else
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static inline int notify_page_fault(struct pt_regs *regs)
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{
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return 0;
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}
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#endif
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/*
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* Return EIP plus the CS segment base. The segment limit is also
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* adjusted, clamped to the kernel/user address space (whichever is
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* appropriate), and returned in *eip_limit.
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*
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* The segment is checked, because it might have been changed by another
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* task between the original faulting instruction and here.
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*
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* If CS is no longer a valid code segment, or if EIP is beyond the
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* limit, or if it is a kernel address when CS is not a kernel segment,
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* then the returned value will be greater than *eip_limit.
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*
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* This is slow, but is very rarely executed.
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*/
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static inline unsigned long get_segment_eip(struct pt_regs *regs,
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unsigned long *eip_limit)
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{
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unsigned long eip = regs->eip;
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unsigned seg = regs->xcs & 0xffff;
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u32 seg_ar, seg_limit, base, *desc;
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/* Unlikely, but must come before segment checks. */
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if (unlikely(regs->eflags & VM_MASK)) {
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base = seg << 4;
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*eip_limit = base + 0xffff;
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return base + (eip & 0xffff);
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}
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/* The standard kernel/user address space limit. */
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*eip_limit = user_mode(regs) ? USER_DS.seg : KERNEL_DS.seg;
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/* By far the most common cases. */
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if (likely(SEGMENT_IS_FLAT_CODE(seg)))
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return eip;
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/* Check the segment exists, is within the current LDT/GDT size,
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that kernel/user (ring 0..3) has the appropriate privilege,
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that it's a code segment, and get the limit. */
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__asm__ ("larl %3,%0; lsll %3,%1"
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: "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg));
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if ((~seg_ar & 0x9800) || eip > seg_limit) {
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*eip_limit = 0;
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return 1; /* So that returned eip > *eip_limit. */
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}
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/* Get the GDT/LDT descriptor base.
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When you look for races in this code remember that
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LDT and other horrors are only used in user space. */
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if (seg & (1<<2)) {
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/* Must lock the LDT while reading it. */
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mutex_lock(¤t->mm->context.lock);
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desc = current->mm->context.ldt;
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desc = (void *)desc + (seg & ~7);
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} else {
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/* Must disable preemption while reading the GDT. */
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desc = (u32 *)get_cpu_gdt_table(get_cpu());
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desc = (void *)desc + (seg & ~7);
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}
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/* Decode the code segment base from the descriptor */
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base = get_desc_base((unsigned long *)desc);
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if (seg & (1<<2)) {
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mutex_unlock(¤t->mm->context.lock);
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} else
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put_cpu();
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/* Adjust EIP and segment limit, and clamp at the kernel limit.
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It's legitimate for segments to wrap at 0xffffffff. */
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seg_limit += base;
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if (seg_limit < *eip_limit && seg_limit >= base)
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*eip_limit = seg_limit;
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return eip + base;
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}
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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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static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
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{
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unsigned long limit;
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unsigned char *instr = (unsigned char *)get_segment_eip (regs, &limit);
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int scan_more = 1;
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int prefetch = 0;
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int i;
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for (i = 0; scan_more && i < 15; i++) {
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unsigned char opcode;
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unsigned char instr_hi;
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unsigned char instr_lo;
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if (instr > (unsigned char *)limit)
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break;
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if (probe_kernel_address(instr, opcode))
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break;
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instr_hi = opcode & 0xf0;
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instr_lo = opcode & 0x0f;
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instr++;
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switch (instr_hi) {
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case 0x20:
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case 0x30:
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/* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
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scan_more = ((instr_lo & 7) == 0x6);
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break;
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case 0x60:
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/* 0x64 thru 0x67 are valid prefixes in all modes. */
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scan_more = (instr_lo & 0xC) == 0x4;
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break;
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case 0xF0:
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/* 0xF0, 0xF2, and 0xF3 are valid prefixes */
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scan_more = !instr_lo || (instr_lo>>1) == 1;
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break;
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case 0x00:
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/* Prefetch instruction is 0x0F0D or 0x0F18 */
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scan_more = 0;
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if (instr > (unsigned char *)limit)
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break;
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if (probe_kernel_address(instr, opcode))
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break;
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prefetch = (instr_lo == 0xF) &&
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(opcode == 0x0D || opcode == 0x18);
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break;
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default:
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scan_more = 0;
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break;
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}
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}
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return prefetch;
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}
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static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
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unsigned long error_code)
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{
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if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
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boot_cpu_data.x86 >= 6)) {
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/* Catch an obscure case of prefetch inside an NX page. */
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if (nx_enabled && (error_code & 16))
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return 0;
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return __is_prefetch(regs, addr);
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}
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return 0;
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}
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static noinline void force_sig_info_fault(int si_signo, int si_code,
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unsigned long address, 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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force_sig_info(si_signo, &info, tsk);
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}
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fastcall void do_invalid_op(struct pt_regs *, unsigned long);
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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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arch_flush_lazy_mmu_mode();
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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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/*
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* Handle a fault on the vmalloc or module mapping 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 inline 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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/*
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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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int show_unhandled_signals = 1;
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/*
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* This routine handles page faults. It determines the address,
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* and the problem, and then passes it off to one of the appropriate
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* routines.
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*
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* error_code:
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* bit 0 == 0 means no page found, 1 means protection fault
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* bit 1 == 0 means read, 1 means write
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* bit 2 == 0 means kernel, 1 means user-mode
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* bit 3 == 1 means use of reserved bit detected
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* bit 4 == 1 means fault was an instruction fetch
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*/
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fastcall void __kprobes do_page_fault(struct pt_regs *regs,
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unsigned long error_code)
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{
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struct task_struct *tsk;
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struct mm_struct *mm;
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struct vm_area_struct * vma;
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unsigned long address;
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int write, si_code;
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int fault;
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/*
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* We can fault from pretty much anywhere, with unknown IRQ state.
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*/
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trace_hardirqs_fixup();
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/* get the address */
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address = read_cr2();
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tsk = current;
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si_code = SEGV_MAPERR;
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/*
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* We fault-in kernel-space virtual memory on-demand. The
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* 'reference' page table is init_mm.pgd.
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*
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* NOTE! We MUST NOT take any locks for this case. We may
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* be in an interrupt or a critical region, and should
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* only copy the information from the master page table,
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* nothing more.
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*
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* This verifies that the fault happens in kernel space
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* (error_code & 4) == 0, and that the fault was not a
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* protection error (error_code & 9) == 0.
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*/
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if (unlikely(address >= TASK_SIZE)) {
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if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
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return;
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if (notify_page_fault(regs))
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return;
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/*
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* Don't take the mm semaphore here. If we fixup a prefetch
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* fault we could otherwise deadlock.
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*/
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goto bad_area_nosemaphore;
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}
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if (notify_page_fault(regs))
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return;
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/* It's safe to allow irq's after cr2 has been saved and the vmalloc
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fault has been handled. */
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if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
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local_irq_enable();
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mm = tsk->mm;
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/*
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* If we're in an interrupt, have no user context or are running in an
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* atomic region then we must not take the fault..
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*/
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if (in_atomic() || !mm)
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goto bad_area_nosemaphore;
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/* When running in the kernel we expect faults to occur only to
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* addresses in user space. All other faults represent errors in the
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* kernel and should generate an OOPS. Unfortunately, in the case of an
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* erroneous fault occurring in a code path which already holds mmap_sem
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* we will deadlock attempting to validate the fault against the
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* address space. Luckily the kernel only validly references user
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* space from well defined areas of code, which are listed in the
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* exceptions table.
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*
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* As the vast majority of faults will be valid we will only perform
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* the source reference check when there is a possibility of a deadlock.
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* Attempt to lock the address space, if we cannot we then validate the
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* source. If this is invalid we can skip the address space check,
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* thus avoiding the deadlock.
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*/
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if (!down_read_trylock(&mm->mmap_sem)) {
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if ((error_code & 4) == 0 &&
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!search_exception_tables(regs->eip))
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goto bad_area_nosemaphore;
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down_read(&mm->mmap_sem);
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}
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vma = find_vma(mm, address);
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if (!vma)
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goto bad_area;
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if (vma->vm_start <= address)
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goto good_area;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto bad_area;
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if (error_code & 4) {
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/*
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* Accessing the stack below %esp is always a bug.
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* The large cushion allows instructions like enter
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* and pusha to work. ("enter $65535,$31" pushes
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* 32 pointers and then decrements %esp by 65535.)
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*/
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if (address + 65536 + 32 * sizeof(unsigned long) < regs->esp)
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goto bad_area;
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}
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if (expand_stack(vma, address))
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goto bad_area;
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/*
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* Ok, we have a good vm_area for this memory access, so
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* we can handle it..
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*/
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good_area:
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si_code = SEGV_ACCERR;
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write = 0;
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switch (error_code & 3) {
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default: /* 3: write, present */
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/* fall through */
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case 2: /* write, not present */
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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write++;
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break;
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case 1: /* read, present */
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goto bad_area;
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case 0: /* read, not present */
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if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
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goto bad_area;
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}
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survive:
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/*
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* If for any reason at all we couldn't handle the fault,
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* make sure we exit gracefully rather than endlessly redo
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* the fault.
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*/
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fault = handle_mm_fault(mm, vma, address, write);
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if (unlikely(fault & VM_FAULT_ERROR)) {
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if (fault & VM_FAULT_OOM)
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goto out_of_memory;
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else if (fault & VM_FAULT_SIGBUS)
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goto do_sigbus;
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BUG();
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}
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if (fault & VM_FAULT_MAJOR)
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tsk->maj_flt++;
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else
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tsk->min_flt++;
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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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if (regs->eflags & VM_MASK) {
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unsigned long 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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up_read(&mm->mmap_sem);
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return;
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/*
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* Something tried to access memory that isn't in our memory map..
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* Fix it, but check if it's kernel or user first..
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*/
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bad_area:
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up_read(&mm->mmap_sem);
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bad_area_nosemaphore:
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/* User mode accesses just cause a SIGSEGV */
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if (error_code & 4) {
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/*
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* It's possible to have interrupts off here.
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*/
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local_irq_enable();
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/*
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* Valid to do another page fault here because this one came
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* from user space.
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*/
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if (is_prefetch(regs, address, error_code))
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return;
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if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
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printk_ratelimit()) {
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printk("%s%s[%d]: segfault at %08lx eip %08lx "
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"esp %08lx error %lx\n",
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task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
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tsk->comm, task_pid_nr(tsk), address, regs->eip,
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regs->esp, error_code);
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}
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tsk->thread.cr2 = address;
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/* Kernel addresses are always protection faults */
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tsk->thread.error_code = error_code | (address >= TASK_SIZE);
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tsk->thread.trap_no = 14;
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force_sig_info_fault(SIGSEGV, si_code, address, tsk);
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return;
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}
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#ifdef CONFIG_X86_F00F_BUG
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/*
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* Pentium F0 0F C7 C8 bug workaround.
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*/
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if (boot_cpu_data.f00f_bug) {
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unsigned long nr;
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nr = (address - idt_descr.address) >> 3;
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if (nr == 6) {
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do_invalid_op(regs, 0);
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return;
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}
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}
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#endif
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no_context:
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/* Are we prepared to handle this kernel fault? */
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if (fixup_exception(regs))
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return;
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/*
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* Valid to do another page fault here, because if this fault
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* had been triggered by is_prefetch fixup_exception would have
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* handled it.
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*/
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if (is_prefetch(regs, address, error_code))
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return;
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/*
|
|
* 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: %08lx ", regs->eip);
|
|
|
|
page = read_cr3();
|
|
page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
|
|
#ifdef CONFIG_X86_PAE
|
|
printk("*pdpt = %016Lx ", 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_CONT "*pde = %016Lx ", page);
|
|
page &= ~_PAGE_NX;
|
|
}
|
|
#else
|
|
printk("*pde = %08lx ", 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_PSE)) {
|
|
page &= PAGE_MASK;
|
|
page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
|
|
& (PTRS_PER_PTE - 1)];
|
|
printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
|
|
}
|
|
|
|
printk("\n");
|
|
}
|
|
|
|
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_global_init(tsk)) {
|
|
yield();
|
|
down_read(&mm->mmap_sem);
|
|
goto survive;
|
|
}
|
|
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 & 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;
|
|
}
|
|
}
|