101f12af16
Registering a callback handler through register_die_notifier() is obviously primarily intended for use by modules. However, the way these currently get called it is basically impossible for them to actually be used by modules, as there is, on non-PAE configurationes, a good chance (the larger the module, the better) for the system to crash as a result. This is because the callback gets invoked (a) in the page fault path before the top level page table propagation gets carried out (hence a fault to propagate the top level page table entry/entries mapping to module's code/data would nest infinitly) and (b) in the NMI path, where nested faults must absolutely not happen, since otherwise the IRET from the nested fault re-enables NMIs, potentially resulting in nested NMI occurences. Besides the modular aspect, similar problems would even arise for in- kernel consumers of the API if they touched ioremap()ed or vmalloc()ed memory inside their handlers. Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
619 lines
16 KiB
C
619 lines
16 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/smp_lock.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/module.h>
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#include <linux/kprobes.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include <asm/desc.h>
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#include <asm/kdebug.h>
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extern void die(const char *,struct pt_regs *,long);
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/*
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* Unlock any spinlocks which will prevent us from getting the
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* message out
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*/
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void bust_spinlocks(int yes)
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{
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int loglevel_save = console_loglevel;
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if (yes) {
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oops_in_progress = 1;
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return;
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}
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#ifdef CONFIG_VT
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unblank_screen();
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#endif
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oops_in_progress = 0;
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/*
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* OK, the message is on the console. Now we call printk()
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* without oops_in_progress set so that printk will give klogd
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* a poke. Hold onto your hats...
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*/
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console_loglevel = 15; /* NMI oopser may have shut the console up */
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printk(" ");
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console_loglevel = loglevel_save;
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}
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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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/* The standard kernel/user address space limit. */
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*eip_limit = (seg & 3) ? USER_DS.seg : KERNEL_DS.seg;
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/* Unlikely, but must come before segment checks. */
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if (unlikely((regs->eflags & VM_MASK) != 0))
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return eip + (seg << 4);
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/* By far the most common cases. */
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if (likely(seg == __USER_CS || seg == __KERNEL_CS))
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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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down(¤t->mm->context.sem);
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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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up(¤t->mm->context.sem);
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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 long instr = 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 > limit)
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break;
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if (__get_user(opcode, (unsigned char __user *) instr))
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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 > limit)
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break;
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if (__get_user(opcode, (unsigned char __user *) instr))
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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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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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/*
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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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unsigned long page;
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int write, si_code;
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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_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
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SIGSEGV) == NOTIFY_STOP)
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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_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
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SIGSEGV) == NOTIFY_STOP)
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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. Unfortunatly, in the case of an
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* erroneous fault occuring 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 possibilty 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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|
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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 "+ 32" is there due to some instructions (like
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* pusha) doing post-decrement on the stack and that
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* doesn't show up until later..
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*/
|
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if (address + 32 < 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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* 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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#ifdef TEST_VERIFY_AREA
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if (regs->cs == KERNEL_CS)
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printk("WP fault at %08lx\n", regs->eip);
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|
#endif
|
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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;
|
|
case 1: /* read, present */
|
|
goto bad_area;
|
|
case 0: /* read, not present */
|
|
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
|
|
goto bad_area;
|
|
}
|
|
|
|
survive:
|
|
/*
|
|
* If for any reason at all we couldn't handle the fault,
|
|
* make sure we exit gracefully rather than endlessly redo
|
|
* the fault.
|
|
*/
|
|
switch (handle_mm_fault(mm, vma, address, write)) {
|
|
case VM_FAULT_MINOR:
|
|
tsk->min_flt++;
|
|
break;
|
|
case VM_FAULT_MAJOR:
|
|
tsk->maj_flt++;
|
|
break;
|
|
case VM_FAULT_SIGBUS:
|
|
goto do_sigbus;
|
|
case VM_FAULT_OOM:
|
|
goto out_of_memory;
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
/*
|
|
* Did it hit the DOS screen memory VA from vm86 mode?
|
|
*/
|
|
if (regs->eflags & VM_MASK) {
|
|
unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT;
|
|
if (bit < 32)
|
|
tsk->thread.screen_bitmap |= 1 << bit;
|
|
}
|
|
up_read(&mm->mmap_sem);
|
|
return;
|
|
|
|
/*
|
|
* Something tried to access memory that isn't in our memory map..
|
|
* Fix it, but check if it's kernel or user first..
|
|
*/
|
|
bad_area:
|
|
up_read(&mm->mmap_sem);
|
|
|
|
bad_area_nosemaphore:
|
|
/* User mode accesses just cause a SIGSEGV */
|
|
if (error_code & 4) {
|
|
/*
|
|
* Valid to do another page fault here because this one came
|
|
* from user space.
|
|
*/
|
|
if (is_prefetch(regs, address, error_code))
|
|
return;
|
|
|
|
tsk->thread.cr2 = address;
|
|
/* Kernel addresses are always protection faults */
|
|
tsk->thread.error_code = error_code | (address >= TASK_SIZE);
|
|
tsk->thread.trap_no = 14;
|
|
force_sig_info_fault(SIGSEGV, si_code, address, tsk);
|
|
return;
|
|
}
|
|
|
|
#ifdef CONFIG_X86_F00F_BUG
|
|
/*
|
|
* Pentium F0 0F C7 C8 bug workaround.
|
|
*/
|
|
if (boot_cpu_data.f00f_bug) {
|
|
unsigned long nr;
|
|
|
|
nr = (address - idt_descr.address) >> 3;
|
|
|
|
if (nr == 6) {
|
|
do_invalid_op(regs, 0);
|
|
return;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
no_context:
|
|
/* Are we prepared to handle this kernel fault? */
|
|
if (fixup_exception(regs))
|
|
return;
|
|
|
|
/*
|
|
* Valid to do another page fault here, because if this fault
|
|
* had been triggered by is_prefetch fixup_exception would have
|
|
* handled it.
|
|
*/
|
|
if (is_prefetch(regs, address, error_code))
|
|
return;
|
|
|
|
/*
|
|
* Oops. The kernel tried to access some bad page. We'll have to
|
|
* terminate things with extreme prejudice.
|
|
*/
|
|
|
|
bust_spinlocks(1);
|
|
|
|
#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 "Unable to handle kernel NULL pointer dereference");
|
|
else
|
|
printk(KERN_ALERT "Unable to handle kernel paging request");
|
|
printk(" at virtual address %08lx\n",address);
|
|
printk(KERN_ALERT " printing eip:\n");
|
|
printk("%08lx\n", regs->eip);
|
|
page = read_cr3();
|
|
page = ((unsigned long *) __va(page))[address >> 22];
|
|
printk(KERN_ALERT "*pde = %08lx\n", page);
|
|
/*
|
|
* We must not directly access the pte in the highpte
|
|
* case, the page table might be allocated in highmem.
|
|
* And lets rather not kmap-atomic the pte, just in case
|
|
* it's allocated already.
|
|
*/
|
|
#ifndef CONFIG_HIGHPTE
|
|
if (page & 1) {
|
|
page &= PAGE_MASK;
|
|
address &= 0x003ff000;
|
|
page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
|
|
printk(KERN_ALERT "*pte = %08lx\n", page);
|
|
}
|
|
#endif
|
|
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 (tsk->pid == 1) {
|
|
yield();
|
|
down_read(&mm->mmap_sem);
|
|
goto survive;
|
|
}
|
|
printk("VM: killing process %s\n", tsk->comm);
|
|
if (error_code & 4)
|
|
do_exit(SIGKILL);
|
|
goto no_context;
|
|
|
|
do_sigbus:
|
|
up_read(&mm->mmap_sem);
|
|
|
|
/* Kernel mode? Handle exceptions or die */
|
|
if (!(error_code & 4))
|
|
goto no_context;
|
|
|
|
/* User space => ok to do another page fault */
|
|
if (is_prefetch(regs, address, error_code))
|
|
return;
|
|
|
|
tsk->thread.cr2 = address;
|
|
tsk->thread.error_code = error_code;
|
|
tsk->thread.trap_no = 14;
|
|
force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
|
|
}
|
|
|
|
#ifndef CONFIG_X86_PAE
|
|
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;
|
|
|
|
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;
|
|
}
|
|
}
|
|
#endif
|