4f339ecb30
If we are faulting in kernel it is quite possible this will lead to a panic. Save trap number, cr2 (in case of page fault) and error_code in the current thread (these fields already exist for signal delivery but are not used here). This helps later kdump crash analyzing from user-space (a script has been submitted to dig this info out in gdb). Signed-off-by: Alexander Nyberg <alexn@telia.com> Cc: <fastboot@lists.osdl.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
555 lines
14 KiB
C
555 lines
14 KiB
C
/*
|
|
* linux/arch/i386/mm/fault.c
|
|
*
|
|
* Copyright (C) 1995 Linus Torvalds
|
|
*/
|
|
|
|
#include <linux/signal.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/string.h>
|
|
#include <linux/types.h>
|
|
#include <linux/ptrace.h>
|
|
#include <linux/mman.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/smp.h>
|
|
#include <linux/smp_lock.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/init.h>
|
|
#include <linux/tty.h>
|
|
#include <linux/vt_kern.h> /* For unblank_screen() */
|
|
#include <linux/highmem.h>
|
|
#include <linux/module.h>
|
|
|
|
#include <asm/system.h>
|
|
#include <asm/uaccess.h>
|
|
#include <asm/desc.h>
|
|
#include <asm/kdebug.h>
|
|
|
|
extern void die(const char *,struct pt_regs *,long);
|
|
|
|
/*
|
|
* Unlock any spinlocks which will prevent us from getting the
|
|
* message out
|
|
*/
|
|
void bust_spinlocks(int yes)
|
|
{
|
|
int loglevel_save = console_loglevel;
|
|
|
|
if (yes) {
|
|
oops_in_progress = 1;
|
|
return;
|
|
}
|
|
#ifdef CONFIG_VT
|
|
unblank_screen();
|
|
#endif
|
|
oops_in_progress = 0;
|
|
/*
|
|
* OK, the message is on the console. Now we call printk()
|
|
* without oops_in_progress set so that printk will give klogd
|
|
* a poke. Hold onto your hats...
|
|
*/
|
|
console_loglevel = 15; /* NMI oopser may have shut the console up */
|
|
printk(" ");
|
|
console_loglevel = loglevel_save;
|
|
}
|
|
|
|
/*
|
|
* Return EIP plus the CS segment base. The segment limit is also
|
|
* adjusted, clamped to the kernel/user address space (whichever is
|
|
* appropriate), and returned in *eip_limit.
|
|
*
|
|
* The segment is checked, because it might have been changed by another
|
|
* task between the original faulting instruction and here.
|
|
*
|
|
* If CS is no longer a valid code segment, or if EIP is beyond the
|
|
* limit, or if it is a kernel address when CS is not a kernel segment,
|
|
* then the returned value will be greater than *eip_limit.
|
|
*
|
|
* This is slow, but is very rarely executed.
|
|
*/
|
|
static inline unsigned long get_segment_eip(struct pt_regs *regs,
|
|
unsigned long *eip_limit)
|
|
{
|
|
unsigned long eip = regs->eip;
|
|
unsigned seg = regs->xcs & 0xffff;
|
|
u32 seg_ar, seg_limit, base, *desc;
|
|
|
|
/* The standard kernel/user address space limit. */
|
|
*eip_limit = (seg & 3) ? USER_DS.seg : KERNEL_DS.seg;
|
|
|
|
/* Unlikely, but must come before segment checks. */
|
|
if (unlikely((regs->eflags & VM_MASK) != 0))
|
|
return eip + (seg << 4);
|
|
|
|
/* By far the most common cases. */
|
|
if (likely(seg == __USER_CS || seg == __KERNEL_CS))
|
|
return eip;
|
|
|
|
/* Check the segment exists, is within the current LDT/GDT size,
|
|
that kernel/user (ring 0..3) has the appropriate privilege,
|
|
that it's a code segment, and get the limit. */
|
|
__asm__ ("larl %3,%0; lsll %3,%1"
|
|
: "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg));
|
|
if ((~seg_ar & 0x9800) || eip > seg_limit) {
|
|
*eip_limit = 0;
|
|
return 1; /* So that returned eip > *eip_limit. */
|
|
}
|
|
|
|
/* Get the GDT/LDT descriptor base.
|
|
When you look for races in this code remember that
|
|
LDT and other horrors are only used in user space. */
|
|
if (seg & (1<<2)) {
|
|
/* Must lock the LDT while reading it. */
|
|
down(¤t->mm->context.sem);
|
|
desc = current->mm->context.ldt;
|
|
desc = (void *)desc + (seg & ~7);
|
|
} else {
|
|
/* Must disable preemption while reading the GDT. */
|
|
desc = (u32 *)&per_cpu(cpu_gdt_table, get_cpu());
|
|
desc = (void *)desc + (seg & ~7);
|
|
}
|
|
|
|
/* Decode the code segment base from the descriptor */
|
|
base = get_desc_base((unsigned long *)desc);
|
|
|
|
if (seg & (1<<2)) {
|
|
up(¤t->mm->context.sem);
|
|
} else
|
|
put_cpu();
|
|
|
|
/* Adjust EIP and segment limit, and clamp at the kernel limit.
|
|
It's legitimate for segments to wrap at 0xffffffff. */
|
|
seg_limit += base;
|
|
if (seg_limit < *eip_limit && seg_limit >= base)
|
|
*eip_limit = seg_limit;
|
|
return eip + base;
|
|
}
|
|
|
|
/*
|
|
* Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
|
|
* Check that here and ignore it.
|
|
*/
|
|
static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
|
|
{
|
|
unsigned long limit;
|
|
unsigned long instr = get_segment_eip (regs, &limit);
|
|
int scan_more = 1;
|
|
int prefetch = 0;
|
|
int i;
|
|
|
|
for (i = 0; scan_more && i < 15; i++) {
|
|
unsigned char opcode;
|
|
unsigned char instr_hi;
|
|
unsigned char instr_lo;
|
|
|
|
if (instr > limit)
|
|
break;
|
|
if (__get_user(opcode, (unsigned char *) instr))
|
|
break;
|
|
|
|
instr_hi = opcode & 0xf0;
|
|
instr_lo = opcode & 0x0f;
|
|
instr++;
|
|
|
|
switch (instr_hi) {
|
|
case 0x20:
|
|
case 0x30:
|
|
/* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
|
|
scan_more = ((instr_lo & 7) == 0x6);
|
|
break;
|
|
|
|
case 0x60:
|
|
/* 0x64 thru 0x67 are valid prefixes in all modes. */
|
|
scan_more = (instr_lo & 0xC) == 0x4;
|
|
break;
|
|
case 0xF0:
|
|
/* 0xF0, 0xF2, and 0xF3 are valid prefixes */
|
|
scan_more = !instr_lo || (instr_lo>>1) == 1;
|
|
break;
|
|
case 0x00:
|
|
/* Prefetch instruction is 0x0F0D or 0x0F18 */
|
|
scan_more = 0;
|
|
if (instr > limit)
|
|
break;
|
|
if (__get_user(opcode, (unsigned char *) instr))
|
|
break;
|
|
prefetch = (instr_lo == 0xF) &&
|
|
(opcode == 0x0D || opcode == 0x18);
|
|
break;
|
|
default:
|
|
scan_more = 0;
|
|
break;
|
|
}
|
|
}
|
|
return prefetch;
|
|
}
|
|
|
|
static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
|
|
unsigned long error_code)
|
|
{
|
|
if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
|
|
boot_cpu_data.x86 >= 6)) {
|
|
/* Catch an obscure case of prefetch inside an NX page. */
|
|
if (nx_enabled && (error_code & 16))
|
|
return 0;
|
|
return __is_prefetch(regs, addr);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
fastcall void do_invalid_op(struct pt_regs *, unsigned long);
|
|
|
|
/*
|
|
* This routine handles page faults. It determines the address,
|
|
* and the problem, and then passes it off to one of the appropriate
|
|
* routines.
|
|
*
|
|
* error_code:
|
|
* bit 0 == 0 means no page found, 1 means protection fault
|
|
* bit 1 == 0 means read, 1 means write
|
|
* bit 2 == 0 means kernel, 1 means user-mode
|
|
*/
|
|
fastcall void do_page_fault(struct pt_regs *regs, unsigned long error_code)
|
|
{
|
|
struct task_struct *tsk;
|
|
struct mm_struct *mm;
|
|
struct vm_area_struct * vma;
|
|
unsigned long address;
|
|
unsigned long page;
|
|
int write;
|
|
siginfo_t info;
|
|
|
|
/* get the address */
|
|
__asm__("movl %%cr2,%0":"=r" (address));
|
|
|
|
if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
|
|
SIGSEGV) == NOTIFY_STOP)
|
|
return;
|
|
/* It's safe to allow irq's after cr2 has been saved */
|
|
if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
|
|
local_irq_enable();
|
|
|
|
tsk = current;
|
|
|
|
info.si_code = SEGV_MAPERR;
|
|
|
|
/*
|
|
* We fault-in kernel-space virtual memory on-demand. The
|
|
* 'reference' page table is init_mm.pgd.
|
|
*
|
|
* NOTE! We MUST NOT take any locks for this case. We may
|
|
* be in an interrupt or a critical region, and should
|
|
* only copy the information from the master page table,
|
|
* nothing more.
|
|
*
|
|
* This verifies that the fault happens in kernel space
|
|
* (error_code & 4) == 0, and that the fault was not a
|
|
* protection error (error_code & 1) == 0.
|
|
*/
|
|
if (unlikely(address >= TASK_SIZE)) {
|
|
if (!(error_code & 5))
|
|
goto vmalloc_fault;
|
|
/*
|
|
* Don't take the mm semaphore here. If we fixup a prefetch
|
|
* fault we could otherwise deadlock.
|
|
*/
|
|
goto bad_area_nosemaphore;
|
|
}
|
|
|
|
mm = tsk->mm;
|
|
|
|
/*
|
|
* If we're in an interrupt, have no user context or are running in an
|
|
* atomic region then we must not take the fault..
|
|
*/
|
|
if (in_atomic() || !mm)
|
|
goto bad_area_nosemaphore;
|
|
|
|
/* When running in the kernel we expect faults to occur only to
|
|
* addresses in user space. All other faults represent errors in the
|
|
* kernel and should generate an OOPS. Unfortunatly, in the case of an
|
|
* erroneous fault occuring in a code path which already holds mmap_sem
|
|
* we will deadlock attempting to validate the fault against the
|
|
* address space. Luckily the kernel only validly references user
|
|
* space from well defined areas of code, which are listed in the
|
|
* exceptions table.
|
|
*
|
|
* As the vast majority of faults will be valid we will only perform
|
|
* the source reference check when there is a possibilty of a deadlock.
|
|
* Attempt to lock the address space, if we cannot we then validate the
|
|
* source. If this is invalid we can skip the address space check,
|
|
* thus avoiding the deadlock.
|
|
*/
|
|
if (!down_read_trylock(&mm->mmap_sem)) {
|
|
if ((error_code & 4) == 0 &&
|
|
!search_exception_tables(regs->eip))
|
|
goto bad_area_nosemaphore;
|
|
down_read(&mm->mmap_sem);
|
|
}
|
|
|
|
vma = find_vma(mm, address);
|
|
if (!vma)
|
|
goto bad_area;
|
|
if (vma->vm_start <= address)
|
|
goto good_area;
|
|
if (!(vma->vm_flags & VM_GROWSDOWN))
|
|
goto bad_area;
|
|
if (error_code & 4) {
|
|
/*
|
|
* accessing the stack below %esp is always a bug.
|
|
* The "+ 32" is there due to some instructions (like
|
|
* pusha) doing post-decrement on the stack and that
|
|
* doesn't show up until later..
|
|
*/
|
|
if (address + 32 < regs->esp)
|
|
goto bad_area;
|
|
}
|
|
if (expand_stack(vma, address))
|
|
goto bad_area;
|
|
/*
|
|
* Ok, we have a good vm_area for this memory access, so
|
|
* we can handle it..
|
|
*/
|
|
good_area:
|
|
info.si_code = SEGV_ACCERR;
|
|
write = 0;
|
|
switch (error_code & 3) {
|
|
default: /* 3: write, present */
|
|
#ifdef TEST_VERIFY_AREA
|
|
if (regs->cs == KERNEL_CS)
|
|
printk("WP fault at %08lx\n", regs->eip);
|
|
#endif
|
|
/* fall through */
|
|
case 2: /* write, not present */
|
|
if (!(vma->vm_flags & VM_WRITE))
|
|
goto bad_area;
|
|
write++;
|
|
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;
|
|
info.si_signo = SIGSEGV;
|
|
info.si_errno = 0;
|
|
/* info.si_code has been set above */
|
|
info.si_addr = (void __user *)address;
|
|
force_sig_info(SIGSEGV, &info, tsk);
|
|
return;
|
|
}
|
|
|
|
#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);
|
|
asm("movl %%cr3,%0":"=r" (page));
|
|
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;
|
|
info.si_signo = SIGBUS;
|
|
info.si_errno = 0;
|
|
info.si_code = BUS_ADRERR;
|
|
info.si_addr = (void __user *)address;
|
|
force_sig_info(SIGBUS, &info, tsk);
|
|
return;
|
|
|
|
vmalloc_fault:
|
|
{
|
|
/*
|
|
* Synchronize this task's top level page-table
|
|
* with the 'reference' page table.
|
|
*
|
|
* Do _not_ use "tsk" here. We might be inside
|
|
* an interrupt in the middle of a task switch..
|
|
*/
|
|
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;
|
|
}
|
|
}
|