3 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
5 * Derived from "arch/i386/mm/fault.c"
6 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * Modified by Cort Dougan and Paul Mackerras.
10 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version
15 * 2 of the License, or (at your option) any later version.
18 #include <linux/signal.h>
19 #include <linux/sched.h>
20 #include <linux/kernel.h>
21 #include <linux/errno.h>
22 #include <linux/string.h>
23 #include <linux/types.h>
24 #include <linux/ptrace.h>
25 #include <linux/mman.h>
27 #include <linux/interrupt.h>
28 #include <linux/highmem.h>
29 #include <linux/module.h>
30 #include <linux/kprobes.h>
31 #include <linux/kdebug.h>
32 #include <linux/perf_event.h>
33 #include <linux/magic.h>
34 #include <linux/ratelimit.h>
36 #include <asm/firmware.h>
38 #include <asm/pgtable.h>
40 #include <asm/mmu_context.h>
41 #include <asm/uaccess.h>
42 #include <asm/tlbflush.h>
43 #include <asm/siginfo.h>
44 #include <asm/debug.h>
45 #include <mm/mmu_decl.h>
50 static inline int notify_page_fault(struct pt_regs
*regs
)
54 /* kprobe_running() needs smp_processor_id() */
55 if (!user_mode(regs
)) {
57 if (kprobe_running() && kprobe_fault_handler(regs
, 11))
65 static inline int notify_page_fault(struct pt_regs
*regs
)
72 * Check whether the instruction at regs->nip is a store using
73 * an update addressing form which will update r1.
75 static int store_updates_sp(struct pt_regs
*regs
)
79 if (get_user(inst
, (unsigned int __user
*)regs
->nip
))
81 /* check for 1 in the rA field */
82 if (((inst
>> 16) & 0x1f) != 1)
84 /* check major opcode */
92 case 62: /* std or stdu */
93 return (inst
& 3) == 1;
95 /* check minor opcode */
96 switch ((inst
>> 1) & 0x3ff) {
100 case 439: /* sthux */
101 case 695: /* stfsux */
102 case 759: /* stfdux */
109 * do_page_fault error handling helpers
112 #define MM_FAULT_RETURN 0
113 #define MM_FAULT_CONTINUE -1
114 #define MM_FAULT_ERR(sig) (sig)
116 static int do_sigbus(struct pt_regs
*regs
, unsigned long address
)
120 up_read(¤t
->mm
->mmap_sem
);
122 if (user_mode(regs
)) {
123 current
->thread
.trap_nr
= BUS_ADRERR
;
124 info
.si_signo
= SIGBUS
;
126 info
.si_code
= BUS_ADRERR
;
127 info
.si_addr
= (void __user
*)address
;
128 force_sig_info(SIGBUS
, &info
, current
);
129 return MM_FAULT_RETURN
;
131 return MM_FAULT_ERR(SIGBUS
);
134 static int mm_fault_error(struct pt_regs
*regs
, unsigned long addr
, int fault
)
137 * Pagefault was interrupted by SIGKILL. We have no reason to
138 * continue the pagefault.
140 if (fatal_signal_pending(current
)) {
142 * If we have retry set, the mmap semaphore will have
143 * alrady been released in __lock_page_or_retry(). Else
146 if (!(fault
& VM_FAULT_RETRY
))
147 up_read(¤t
->mm
->mmap_sem
);
148 /* Coming from kernel, we need to deal with uaccess fixups */
150 return MM_FAULT_RETURN
;
151 return MM_FAULT_ERR(SIGKILL
);
154 /* No fault: be happy */
155 if (!(fault
& VM_FAULT_ERROR
))
156 return MM_FAULT_CONTINUE
;
159 if (fault
& VM_FAULT_OOM
) {
160 up_read(¤t
->mm
->mmap_sem
);
163 * We ran out of memory, or some other thing happened to us that
164 * made us unable to handle the page fault gracefully.
166 if (!user_mode(regs
))
167 return MM_FAULT_ERR(SIGKILL
);
168 pagefault_out_of_memory();
169 return MM_FAULT_RETURN
;
172 /* Bus error. x86 handles HWPOISON here, we'll add this if/when
173 * we support the feature in HW
175 if (fault
& VM_FAULT_SIGBUS
)
176 return do_sigbus(regs
, addr
);
178 /* We don't understand the fault code, this is fatal */
180 return MM_FAULT_CONTINUE
;
184 * For 600- and 800-family processors, the error_code parameter is DSISR
185 * for a data fault, SRR1 for an instruction fault. For 400-family processors
186 * the error_code parameter is ESR for a data fault, 0 for an instruction
188 * For 64-bit processors, the error_code parameter is
189 * - DSISR for a non-SLB data access fault,
190 * - SRR1 & 0x08000000 for a non-SLB instruction access fault
193 * The return value is 0 if the fault was handled, or the signal
194 * number if this is a kernel fault that can't be handled here.
196 int __kprobes
do_page_fault(struct pt_regs
*regs
, unsigned long address
,
197 unsigned long error_code
)
199 struct vm_area_struct
* vma
;
200 struct mm_struct
*mm
= current
->mm
;
201 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
202 int code
= SEGV_MAPERR
;
204 int trap
= TRAP(regs
);
205 int is_exec
= trap
== 0x400;
208 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
210 * Fortunately the bit assignments in SRR1 for an instruction
211 * fault and DSISR for a data fault are mostly the same for the
212 * bits we are interested in. But there are some bits which
213 * indicate errors in DSISR but can validly be set in SRR1.
216 error_code
&= 0x48200000;
218 is_write
= error_code
& DSISR_ISSTORE
;
220 is_write
= error_code
& ESR_DST
;
221 #endif /* CONFIG_4xx || CONFIG_BOOKE */
224 flags
|= FAULT_FLAG_WRITE
;
226 #ifdef CONFIG_PPC_ICSWX
228 * we need to do this early because this "data storage
229 * interrupt" does not update the DAR/DEAR so we don't want to
232 if (error_code
& ICSWX_DSI_UCT
) {
233 int rc
= acop_handle_fault(regs
, address
, error_code
);
237 #endif /* CONFIG_PPC_ICSWX */
239 if (notify_page_fault(regs
))
242 if (unlikely(debugger_fault_handler(regs
)))
245 /* On a kernel SLB miss we can only check for a valid exception entry */
246 if (!user_mode(regs
) && (address
>= TASK_SIZE
))
249 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
250 defined(CONFIG_PPC_BOOK3S_64))
251 if (error_code
& DSISR_DABRMATCH
) {
253 do_dabr(regs
, address
, error_code
);
258 /* We restore the interrupt state now */
259 if (!arch_irq_disabled_regs(regs
))
262 if (in_atomic() || mm
== NULL
) {
263 if (!user_mode(regs
))
265 /* in_atomic() in user mode is really bad,
266 as is current->mm == NULL. */
267 printk(KERN_EMERG
"Page fault in user mode with "
268 "in_atomic() = %d mm = %p\n", in_atomic(), mm
);
269 printk(KERN_EMERG
"NIP = %lx MSR = %lx\n",
270 regs
->nip
, regs
->msr
);
271 die("Weird page fault", regs
, SIGSEGV
);
274 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
276 /* When running in the kernel we expect faults to occur only to
277 * addresses in user space. All other faults represent errors in the
278 * kernel and should generate an OOPS. Unfortunately, in the case of an
279 * erroneous fault occurring in a code path which already holds mmap_sem
280 * we will deadlock attempting to validate the fault against the
281 * address space. Luckily the kernel only validly references user
282 * space from well defined areas of code, which are listed in the
285 * As the vast majority of faults will be valid we will only perform
286 * the source reference check when there is a possibility of a deadlock.
287 * Attempt to lock the address space, if we cannot we then validate the
288 * source. If this is invalid we can skip the address space check,
289 * thus avoiding the deadlock.
291 if (!down_read_trylock(&mm
->mmap_sem
)) {
292 if (!user_mode(regs
) && !search_exception_tables(regs
->nip
))
293 goto bad_area_nosemaphore
;
296 down_read(&mm
->mmap_sem
);
299 * The above down_read_trylock() might have succeeded in
300 * which case we'll have missed the might_sleep() from
306 vma
= find_vma(mm
, address
);
309 if (vma
->vm_start
<= address
)
311 if (!(vma
->vm_flags
& VM_GROWSDOWN
))
315 * N.B. The POWER/Open ABI allows programs to access up to
316 * 288 bytes below the stack pointer.
317 * The kernel signal delivery code writes up to about 1.5kB
318 * below the stack pointer (r1) before decrementing it.
319 * The exec code can write slightly over 640kB to the stack
320 * before setting the user r1. Thus we allow the stack to
321 * expand to 1MB without further checks.
323 if (address
+ 0x100000 < vma
->vm_end
) {
324 /* get user regs even if this fault is in kernel mode */
325 struct pt_regs
*uregs
= current
->thread
.regs
;
330 * A user-mode access to an address a long way below
331 * the stack pointer is only valid if the instruction
332 * is one which would update the stack pointer to the
333 * address accessed if the instruction completed,
334 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
335 * (or the byte, halfword, float or double forms).
337 * If we don't check this then any write to the area
338 * between the last mapped region and the stack will
339 * expand the stack rather than segfaulting.
341 if (address
+ 2048 < uregs
->gpr
[1]
342 && (!user_mode(regs
) || !store_updates_sp(regs
)))
345 if (expand_stack(vma
, address
))
350 #if defined(CONFIG_6xx)
351 if (error_code
& 0x95700000)
352 /* an error such as lwarx to I/O controller space,
353 address matching DABR, eciwx, etc. */
355 #endif /* CONFIG_6xx */
356 #if defined(CONFIG_8xx)
357 /* 8xx sometimes need to load a invalid/non-present TLBs.
358 * These must be invalidated separately as linux mm don't.
360 if (error_code
& 0x40000000) /* no translation? */
361 _tlbil_va(address
, 0, 0, 0);
363 /* The MPC8xx seems to always set 0x80000000, which is
364 * "undefined". Of those that can be set, this is the only
365 * one which seems bad.
367 if (error_code
& 0x10000000)
368 /* Guarded storage error. */
370 #endif /* CONFIG_8xx */
373 #ifdef CONFIG_PPC_STD_MMU
374 /* Protection fault on exec go straight to failure on
375 * Hash based MMUs as they either don't support per-page
376 * execute permission, or if they do, it's handled already
377 * at the hash level. This test would probably have to
378 * be removed if we change the way this works to make hash
379 * processors use the same I/D cache coherency mechanism
382 if (error_code
& DSISR_PROTFAULT
)
384 #endif /* CONFIG_PPC_STD_MMU */
387 * Allow execution from readable areas if the MMU does not
388 * provide separate controls over reading and executing.
390 * Note: That code used to not be enabled for 4xx/BookE.
391 * It is now as I/D cache coherency for these is done at
392 * set_pte_at() time and I see no reason why the test
393 * below wouldn't be valid on those processors. This -may-
394 * break programs compiled with a really old ABI though.
396 if (!(vma
->vm_flags
& VM_EXEC
) &&
397 (cpu_has_feature(CPU_FTR_NOEXECUTE
) ||
398 !(vma
->vm_flags
& (VM_READ
| VM_WRITE
))))
401 } else if (is_write
) {
402 if (!(vma
->vm_flags
& VM_WRITE
))
406 /* protection fault */
407 if (error_code
& 0x08000000)
409 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
414 * If for any reason at all we couldn't handle the fault,
415 * make sure we exit gracefully rather than endlessly redo
418 fault
= handle_mm_fault(mm
, vma
, address
, flags
);
419 if (unlikely(fault
& (VM_FAULT_RETRY
|VM_FAULT_ERROR
))) {
420 int rc
= mm_fault_error(regs
, address
, fault
);
421 if (rc
>= MM_FAULT_RETURN
)
426 * Major/minor page fault accounting is only done on the
427 * initial attempt. If we go through a retry, it is extremely
428 * likely that the page will be found in page cache at that point.
430 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
431 if (fault
& VM_FAULT_MAJOR
) {
433 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1,
435 #ifdef CONFIG_PPC_SMLPAR
436 if (firmware_has_feature(FW_FEATURE_CMO
)) {
438 get_lppaca()->page_ins
+= (1 << PAGE_FACTOR
);
441 #endif /* CONFIG_PPC_SMLPAR */
444 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1,
447 if (fault
& VM_FAULT_RETRY
) {
448 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
450 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
451 flags
|= FAULT_FLAG_TRIED
;
456 up_read(&mm
->mmap_sem
);
460 up_read(&mm
->mmap_sem
);
462 bad_area_nosemaphore
:
463 /* User mode accesses cause a SIGSEGV */
464 if (user_mode(regs
)) {
465 _exception(SIGSEGV
, regs
, code
, address
);
469 if (is_exec
&& (error_code
& DSISR_PROTFAULT
))
470 printk_ratelimited(KERN_CRIT
"kernel tried to execute NX-protected"
471 " page (%lx) - exploit attempt? (uid: %d)\n",
472 address
, from_kuid(&init_user_ns
, current_uid()));
479 * bad_page_fault is called when we have a bad access from the kernel.
480 * It is called from the DSI and ISI handlers in head.S and from some
481 * of the procedures in traps.c.
483 void bad_page_fault(struct pt_regs
*regs
, unsigned long address
, int sig
)
485 const struct exception_table_entry
*entry
;
486 unsigned long *stackend
;
488 /* Are we prepared to handle this fault? */
489 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
490 regs
->nip
= entry
->fixup
;
494 /* kernel has accessed a bad area */
496 switch (regs
->trap
) {
499 printk(KERN_ALERT
"Unable to handle kernel paging request for "
500 "data at address 0x%08lx\n", regs
->dar
);
504 printk(KERN_ALERT
"Unable to handle kernel paging request for "
505 "instruction fetch\n");
508 printk(KERN_ALERT
"Unable to handle kernel paging request for "
512 printk(KERN_ALERT
"Faulting instruction address: 0x%08lx\n",
515 stackend
= end_of_stack(current
);
516 if (current
!= &init_task
&& *stackend
!= STACK_END_MAGIC
)
517 printk(KERN_ALERT
"Thread overran stack, or stack corrupted\n");
519 die("Kernel access of bad area", regs
, sig
);