2 * linux/arch/i386/mm/fault.c
4 * Copyright (C) 1995 Linus Torvalds
7 #include <linux/signal.h>
8 #include <linux/sched.h>
9 #include <linux/kernel.h>
10 #include <linux/errno.h>
11 #include <linux/string.h>
12 #include <linux/types.h>
13 #include <linux/ptrace.h>
14 #include <linux/mman.h>
16 #include <linux/smp.h>
17 #include <linux/smp_lock.h>
18 #include <linux/interrupt.h>
19 #include <linux/init.h>
20 #include <linux/tty.h>
21 #include <linux/vt_kern.h> /* For unblank_screen() */
22 #include <linux/highmem.h>
23 #include <linux/module.h>
25 #include <asm/system.h>
26 #include <asm/uaccess.h>
28 #include <asm/kdebug.h>
30 extern void die(const char *,struct pt_regs
*,long);
33 * Unlock any spinlocks which will prevent us from getting the
36 void bust_spinlocks(int yes
)
38 int loglevel_save
= console_loglevel
;
49 * OK, the message is on the console. Now we call printk()
50 * without oops_in_progress set so that printk will give klogd
51 * a poke. Hold onto your hats...
53 console_loglevel
= 15; /* NMI oopser may have shut the console up */
55 console_loglevel
= loglevel_save
;
59 * Return EIP plus the CS segment base. The segment limit is also
60 * adjusted, clamped to the kernel/user address space (whichever is
61 * appropriate), and returned in *eip_limit.
63 * The segment is checked, because it might have been changed by another
64 * task between the original faulting instruction and here.
66 * If CS is no longer a valid code segment, or if EIP is beyond the
67 * limit, or if it is a kernel address when CS is not a kernel segment,
68 * then the returned value will be greater than *eip_limit.
70 * This is slow, but is very rarely executed.
72 static inline unsigned long get_segment_eip(struct pt_regs
*regs
,
73 unsigned long *eip_limit
)
75 unsigned long eip
= regs
->eip
;
76 unsigned seg
= regs
->xcs
& 0xffff;
77 u32 seg_ar
, seg_limit
, base
, *desc
;
79 /* The standard kernel/user address space limit. */
80 *eip_limit
= (seg
& 3) ? USER_DS
.seg
: KERNEL_DS
.seg
;
82 /* Unlikely, but must come before segment checks. */
83 if (unlikely((regs
->eflags
& VM_MASK
) != 0))
84 return eip
+ (seg
<< 4);
86 /* By far the most common cases. */
87 if (likely(seg
== __USER_CS
|| seg
== __KERNEL_CS
))
90 /* Check the segment exists, is within the current LDT/GDT size,
91 that kernel/user (ring 0..3) has the appropriate privilege,
92 that it's a code segment, and get the limit. */
93 __asm__ ("larl %3,%0; lsll %3,%1"
94 : "=&r" (seg_ar
), "=r" (seg_limit
) : "0" (0), "rm" (seg
));
95 if ((~seg_ar
& 0x9800) || eip
> seg_limit
) {
97 return 1; /* So that returned eip > *eip_limit. */
100 /* Get the GDT/LDT descriptor base.
101 When you look for races in this code remember that
102 LDT and other horrors are only used in user space. */
104 /* Must lock the LDT while reading it. */
105 down(¤t
->mm
->context
.sem
);
106 desc
= current
->mm
->context
.ldt
;
107 desc
= (void *)desc
+ (seg
& ~7);
109 /* Must disable preemption while reading the GDT. */
110 desc
= (u32
*)&per_cpu(cpu_gdt_table
, get_cpu());
111 desc
= (void *)desc
+ (seg
& ~7);
114 /* Decode the code segment base from the descriptor */
115 base
= (desc
[0] >> 16) |
116 ((desc
[1] & 0xff) << 16) |
117 (desc
[1] & 0xff000000);
120 up(¤t
->mm
->context
.sem
);
124 /* Adjust EIP and segment limit, and clamp at the kernel limit.
125 It's legitimate for segments to wrap at 0xffffffff. */
127 if (seg_limit
< *eip_limit
&& seg_limit
>= base
)
128 *eip_limit
= seg_limit
;
133 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
134 * Check that here and ignore it.
136 static int __is_prefetch(struct pt_regs
*regs
, unsigned long addr
)
139 unsigned long instr
= get_segment_eip (regs
, &limit
);
144 for (i
= 0; scan_more
&& i
< 15; i
++) {
145 unsigned char opcode
;
146 unsigned char instr_hi
;
147 unsigned char instr_lo
;
151 if (__get_user(opcode
, (unsigned char *) instr
))
154 instr_hi
= opcode
& 0xf0;
155 instr_lo
= opcode
& 0x0f;
161 /* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
162 scan_more
= ((instr_lo
& 7) == 0x6);
166 /* 0x64 thru 0x67 are valid prefixes in all modes. */
167 scan_more
= (instr_lo
& 0xC) == 0x4;
170 /* 0xF0, 0xF2, and 0xF3 are valid prefixes */
171 scan_more
= !instr_lo
|| (instr_lo
>>1) == 1;
174 /* Prefetch instruction is 0x0F0D or 0x0F18 */
178 if (__get_user(opcode
, (unsigned char *) instr
))
180 prefetch
= (instr_lo
== 0xF) &&
181 (opcode
== 0x0D || opcode
== 0x18);
191 static inline int is_prefetch(struct pt_regs
*regs
, unsigned long addr
,
192 unsigned long error_code
)
194 if (unlikely(boot_cpu_data
.x86_vendor
== X86_VENDOR_AMD
&&
195 boot_cpu_data
.x86
>= 6)) {
196 /* Catch an obscure case of prefetch inside an NX page. */
197 if (nx_enabled
&& (error_code
& 16))
199 return __is_prefetch(regs
, addr
);
204 asmlinkage
void do_invalid_op(struct pt_regs
*, unsigned long);
207 * This routine handles page faults. It determines the address,
208 * and the problem, and then passes it off to one of the appropriate
212 * bit 0 == 0 means no page found, 1 means protection fault
213 * bit 1 == 0 means read, 1 means write
214 * bit 2 == 0 means kernel, 1 means user-mode
216 asmlinkage
void do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
218 struct task_struct
*tsk
;
219 struct mm_struct
*mm
;
220 struct vm_area_struct
* vma
;
221 unsigned long address
;
226 /* get the address */
227 __asm__("movl %%cr2,%0":"=r" (address
));
229 if (notify_die(DIE_PAGE_FAULT
, "page fault", regs
, error_code
, 14,
230 SIGSEGV
) == NOTIFY_STOP
)
232 /* It's safe to allow irq's after cr2 has been saved */
233 if (regs
->eflags
& (X86_EFLAGS_IF
|VM_MASK
))
238 info
.si_code
= SEGV_MAPERR
;
241 * We fault-in kernel-space virtual memory on-demand. The
242 * 'reference' page table is init_mm.pgd.
244 * NOTE! We MUST NOT take any locks for this case. We may
245 * be in an interrupt or a critical region, and should
246 * only copy the information from the master page table,
249 * This verifies that the fault happens in kernel space
250 * (error_code & 4) == 0, and that the fault was not a
251 * protection error (error_code & 1) == 0.
253 if (unlikely(address
>= TASK_SIZE
)) {
254 if (!(error_code
& 5))
257 * Don't take the mm semaphore here. If we fixup a prefetch
258 * fault we could otherwise deadlock.
260 goto bad_area_nosemaphore
;
266 * If we're in an interrupt, have no user context or are running in an
267 * atomic region then we must not take the fault..
269 if (in_atomic() || !mm
)
270 goto bad_area_nosemaphore
;
272 /* When running in the kernel we expect faults to occur only to
273 * addresses in user space. All other faults represent errors in the
274 * kernel and should generate an OOPS. Unfortunatly, in the case of an
275 * erroneous fault occuring in a code path which already holds mmap_sem
276 * we will deadlock attempting to validate the fault against the
277 * address space. Luckily the kernel only validly references user
278 * space from well defined areas of code, which are listed in the
281 * As the vast majority of faults will be valid we will only perform
282 * the source reference check when there is a possibilty of a deadlock.
283 * Attempt to lock the address space, if we cannot we then validate the
284 * source. If this is invalid we can skip the address space check,
285 * thus avoiding the deadlock.
287 if (!down_read_trylock(&mm
->mmap_sem
)) {
288 if ((error_code
& 4) == 0 &&
289 !search_exception_tables(regs
->eip
))
290 goto bad_area_nosemaphore
;
291 down_read(&mm
->mmap_sem
);
294 vma
= find_vma(mm
, address
);
297 if (vma
->vm_start
<= address
)
299 if (!(vma
->vm_flags
& VM_GROWSDOWN
))
301 if (error_code
& 4) {
303 * accessing the stack below %esp is always a bug.
304 * The "+ 32" is there due to some instructions (like
305 * pusha) doing post-decrement on the stack and that
306 * doesn't show up until later..
308 if (address
+ 32 < regs
->esp
)
311 if (expand_stack(vma
, address
))
314 * Ok, we have a good vm_area for this memory access, so
318 info
.si_code
= SEGV_ACCERR
;
320 switch (error_code
& 3) {
321 default: /* 3: write, present */
322 #ifdef TEST_VERIFY_AREA
323 if (regs
->cs
== KERNEL_CS
)
324 printk("WP fault at %08lx\n", regs
->eip
);
327 case 2: /* write, not present */
328 if (!(vma
->vm_flags
& VM_WRITE
))
332 case 1: /* read, present */
334 case 0: /* read, not present */
335 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
)))
341 * If for any reason at all we couldn't handle the fault,
342 * make sure we exit gracefully rather than endlessly redo
345 switch (handle_mm_fault(mm
, vma
, address
, write
)) {
352 case VM_FAULT_SIGBUS
:
361 * Did it hit the DOS screen memory VA from vm86 mode?
363 if (regs
->eflags
& VM_MASK
) {
364 unsigned long bit
= (address
- 0xA0000) >> PAGE_SHIFT
;
366 tsk
->thread
.screen_bitmap
|= 1 << bit
;
368 up_read(&mm
->mmap_sem
);
372 * Something tried to access memory that isn't in our memory map..
373 * Fix it, but check if it's kernel or user first..
376 up_read(&mm
->mmap_sem
);
378 bad_area_nosemaphore
:
379 /* User mode accesses just cause a SIGSEGV */
380 if (error_code
& 4) {
382 * Valid to do another page fault here because this one came
385 if (is_prefetch(regs
, address
, error_code
))
388 tsk
->thread
.cr2
= address
;
389 /* Kernel addresses are always protection faults */
390 tsk
->thread
.error_code
= error_code
| (address
>= TASK_SIZE
);
391 tsk
->thread
.trap_no
= 14;
392 info
.si_signo
= SIGSEGV
;
394 /* info.si_code has been set above */
395 info
.si_addr
= (void __user
*)address
;
396 force_sig_info(SIGSEGV
, &info
, tsk
);
400 #ifdef CONFIG_X86_F00F_BUG
402 * Pentium F0 0F C7 C8 bug workaround.
404 if (boot_cpu_data
.f00f_bug
) {
407 nr
= (address
- idt_descr
.address
) >> 3;
410 do_invalid_op(regs
, 0);
417 /* Are we prepared to handle this kernel fault? */
418 if (fixup_exception(regs
))
422 * Valid to do another page fault here, because if this fault
423 * had been triggered by is_prefetch fixup_exception would have
426 if (is_prefetch(regs
, address
, error_code
))
430 * Oops. The kernel tried to access some bad page. We'll have to
431 * terminate things with extreme prejudice.
436 #ifdef CONFIG_X86_PAE
437 if (error_code
& 16) {
438 pte_t
*pte
= lookup_address(address
);
440 if (pte
&& pte_present(*pte
) && !pte_exec_kernel(*pte
))
441 printk(KERN_CRIT
"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", current
->uid
);
444 if (address
< PAGE_SIZE
)
445 printk(KERN_ALERT
"Unable to handle kernel NULL pointer dereference");
447 printk(KERN_ALERT
"Unable to handle kernel paging request");
448 printk(" at virtual address %08lx\n",address
);
449 printk(KERN_ALERT
" printing eip:\n");
450 printk("%08lx\n", regs
->eip
);
451 asm("movl %%cr3,%0":"=r" (page
));
452 page
= ((unsigned long *) __va(page
))[address
>> 22];
453 printk(KERN_ALERT
"*pde = %08lx\n", page
);
455 * We must not directly access the pte in the highpte
456 * case, the page table might be allocated in highmem.
457 * And lets rather not kmap-atomic the pte, just in case
458 * it's allocated already.
460 #ifndef CONFIG_HIGHPTE
463 address
&= 0x003ff000;
464 page
= ((unsigned long *) __va(page
))[address
>> PAGE_SHIFT
];
465 printk(KERN_ALERT
"*pte = %08lx\n", page
);
468 die("Oops", regs
, error_code
);
473 * We ran out of memory, or some other thing happened to us that made
474 * us unable to handle the page fault gracefully.
477 up_read(&mm
->mmap_sem
);
480 down_read(&mm
->mmap_sem
);
483 printk("VM: killing process %s\n", tsk
->comm
);
489 up_read(&mm
->mmap_sem
);
491 /* Kernel mode? Handle exceptions or die */
492 if (!(error_code
& 4))
495 /* User space => ok to do another page fault */
496 if (is_prefetch(regs
, address
, error_code
))
499 tsk
->thread
.cr2
= address
;
500 tsk
->thread
.error_code
= error_code
;
501 tsk
->thread
.trap_no
= 14;
502 info
.si_signo
= SIGBUS
;
504 info
.si_code
= BUS_ADRERR
;
505 info
.si_addr
= (void __user
*)address
;
506 force_sig_info(SIGBUS
, &info
, tsk
);
512 * Synchronize this task's top level page-table
513 * with the 'reference' page table.
515 * Do _not_ use "tsk" here. We might be inside
516 * an interrupt in the middle of a task switch..
518 int index
= pgd_index(address
);
519 unsigned long pgd_paddr
;
524 asm("movl %%cr3,%0":"=r" (pgd_paddr
));
525 pgd
= index
+ (pgd_t
*)__va(pgd_paddr
);
526 pgd_k
= init_mm
.pgd
+ index
;
528 if (!pgd_present(*pgd_k
))
532 * set_pgd(pgd, *pgd_k); here would be useless on PAE
533 * and redundant with the set_pmd() on non-PAE.
536 pmd
= pmd_offset(pgd
, address
);
537 pmd_k
= pmd_offset(pgd_k
, address
);
538 if (!pmd_present(*pmd_k
))
540 set_pmd(pmd
, *pmd_k
);
542 pte_k
= pte_offset_kernel(pmd_k
, address
);
543 if (!pte_present(*pte_k
))