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555 lines
14 KiB
555 lines
14 KiB
/*
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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 <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 *)&per_cpu(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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fastcall void do_invalid_op(struct pt_regs *, unsigned long);
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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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*/
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fastcall void do_page_fault(struct pt_regs *regs, 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;
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siginfo_t info;
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/* get the address */
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__asm__("movl %%cr2,%0":"=r" (address));
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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 */
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if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
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local_irq_enable();
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tsk = current;
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info.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 & 1) == 0.
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*/
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if (unlikely(address >= TASK_SIZE)) {
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if (!(error_code & 5))
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goto vmalloc_fault;
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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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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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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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/*
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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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info.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;
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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)))
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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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switch (handle_mm_fault(mm, vma, address, write)) {
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case VM_FAULT_MINOR:
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tsk->min_flt++;
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break;
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case VM_FAULT_MAJOR:
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tsk->maj_flt++;
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break;
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case VM_FAULT_SIGBUS:
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goto do_sigbus;
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case VM_FAULT_OOM:
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goto out_of_memory;
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default:
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BUG();
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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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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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* 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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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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info.si_signo = SIGSEGV;
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info.si_errno = 0;
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/* info.si_code has been set above */
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info.si_addr = (void __user *)address;
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force_sig_info(SIGSEGV, &info, 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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/*
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* Oops. The kernel tried to access some bad page. We'll have to
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* terminate things with extreme prejudice.
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*/
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bust_spinlocks(1);
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#ifdef CONFIG_X86_PAE
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if (error_code & 16) {
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pte_t *pte = lookup_address(address);
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if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
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printk(KERN_CRIT "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", current->uid);
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}
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#endif
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if (address < PAGE_SIZE)
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printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
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else
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printk(KERN_ALERT "Unable to handle kernel paging request");
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printk(" at virtual address %08lx\n",address);
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printk(KERN_ALERT " printing eip:\n");
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printk("%08lx\n", regs->eip);
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asm("movl %%cr3,%0":"=r" (page));
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page = ((unsigned long *) __va(page))[address >> 22];
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printk(KERN_ALERT "*pde = %08lx\n", page);
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/*
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* We must not directly access the pte in the highpte
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* case, the page table might be allocated in highmem.
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* And lets 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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#ifndef CONFIG_HIGHPTE
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if (page & 1) {
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page &= PAGE_MASK;
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address &= 0x003ff000;
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page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
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printk(KERN_ALERT "*pte = %08lx\n", page);
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}
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#endif
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tsk->thread.cr2 = address;
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tsk->thread.trap_no = 14;
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tsk->thread.error_code = error_code;
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die("Oops", regs, error_code);
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bust_spinlocks(0);
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do_exit(SIGKILL);
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/*
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* We ran out of memory, or some other thing happened to us that made
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* us unable to handle the page fault gracefully.
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*/
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out_of_memory:
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up_read(&mm->mmap_sem);
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if (tsk->pid == 1) {
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yield();
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down_read(&mm->mmap_sem);
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goto survive;
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}
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printk("VM: killing process %s\n", tsk->comm);
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if (error_code & 4)
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do_exit(SIGKILL);
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goto no_context;
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do_sigbus:
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up_read(&mm->mmap_sem);
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/* Kernel mode? Handle exceptions or die */
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if (!(error_code & 4))
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goto no_context;
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/* User space => ok to do another page fault */
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if (is_prefetch(regs, address, error_code))
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return;
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tsk->thread.cr2 = address;
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tsk->thread.error_code = error_code;
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tsk->thread.trap_no = 14;
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info.si_signo = SIGBUS;
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info.si_errno = 0;
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info.si_code = BUS_ADRERR;
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info.si_addr = (void __user *)address;
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force_sig_info(SIGBUS, &info, tsk);
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return;
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vmalloc_fault:
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{
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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 "tsk" here. We might be inside
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* an interrupt in the middle of a task switch..
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*/
|
|
int index = pgd_index(address);
|
|
unsigned long pgd_paddr;
|
|
pgd_t *pgd, *pgd_k;
|
|
pud_t *pud, *pud_k;
|
|
pmd_t *pmd, *pmd_k;
|
|
pte_t *pte_k;
|
|
|
|
asm("movl %%cr3,%0":"=r" (pgd_paddr));
|
|
pgd = index + (pgd_t *)__va(pgd_paddr);
|
|
pgd_k = init_mm.pgd + index;
|
|
|
|
if (!pgd_present(*pgd_k))
|
|
goto no_context;
|
|
|
|
/*
|
|
* set_pgd(pgd, *pgd_k); here would be useless on PAE
|
|
* and redundant with the set_pmd() on non-PAE. As would
|
|
* set_pud.
|
|
*/
|
|
|
|
pud = pud_offset(pgd, address);
|
|
pud_k = pud_offset(pgd_k, address);
|
|
if (!pud_present(*pud_k))
|
|
goto no_context;
|
|
|
|
pmd = pmd_offset(pud, address);
|
|
pmd_k = pmd_offset(pud_k, address);
|
|
if (!pmd_present(*pmd_k))
|
|
goto no_context;
|
|
set_pmd(pmd, *pmd_k);
|
|
|
|
pte_k = pte_offset_kernel(pmd_k, address);
|
|
if (!pte_present(*pte_k))
|
|
goto no_context;
|
|
return;
|
|
}
|
|
}
|
|
|