Commit | Line | Data |
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14cf11af | 1 | /* |
14cf11af PM |
2 | * PowerPC version |
3 | * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) | |
4 | * | |
5 | * Derived from "arch/i386/mm/fault.c" | |
6 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds | |
7 | * | |
8 | * Modified by Cort Dougan and Paul Mackerras. | |
9 | * | |
10 | * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) | |
11 | * | |
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. | |
16 | */ | |
17 | ||
14cf11af PM |
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> | |
26 | #include <linux/mm.h> | |
27 | #include <linux/interrupt.h> | |
28 | #include <linux/highmem.h> | |
29 | #include <linux/module.h> | |
30 | #include <linux/kprobes.h> | |
1eeb66a1 | 31 | #include <linux/kdebug.h> |
14cf11af PM |
32 | |
33 | #include <asm/page.h> | |
34 | #include <asm/pgtable.h> | |
35 | #include <asm/mmu.h> | |
36 | #include <asm/mmu_context.h> | |
37 | #include <asm/system.h> | |
38 | #include <asm/uaccess.h> | |
39 | #include <asm/tlbflush.h> | |
14cf11af PM |
40 | #include <asm/siginfo.h> |
41 | ||
4f9e87c0 | 42 | |
9f90b997 CH |
43 | #ifdef CONFIG_KPROBES |
44 | static inline int notify_page_fault(struct pt_regs *regs) | |
4f9e87c0 | 45 | { |
9f90b997 CH |
46 | int ret = 0; |
47 | ||
48 | /* kprobe_running() needs smp_processor_id() */ | |
49 | if (!user_mode(regs)) { | |
50 | preempt_disable(); | |
51 | if (kprobe_running() && kprobe_fault_handler(regs, 11)) | |
52 | ret = 1; | |
53 | preempt_enable(); | |
54 | } | |
4f9e87c0 | 55 | |
9f90b997 | 56 | return ret; |
4f9e87c0 AK |
57 | } |
58 | #else | |
9f90b997 | 59 | static inline int notify_page_fault(struct pt_regs *regs) |
4f9e87c0 | 60 | { |
9f90b997 | 61 | return 0; |
4f9e87c0 AK |
62 | } |
63 | #endif | |
64 | ||
14cf11af PM |
65 | /* |
66 | * Check whether the instruction at regs->nip is a store using | |
67 | * an update addressing form which will update r1. | |
68 | */ | |
69 | static int store_updates_sp(struct pt_regs *regs) | |
70 | { | |
71 | unsigned int inst; | |
72 | ||
73 | if (get_user(inst, (unsigned int __user *)regs->nip)) | |
74 | return 0; | |
75 | /* check for 1 in the rA field */ | |
76 | if (((inst >> 16) & 0x1f) != 1) | |
77 | return 0; | |
78 | /* check major opcode */ | |
79 | switch (inst >> 26) { | |
80 | case 37: /* stwu */ | |
81 | case 39: /* stbu */ | |
82 | case 45: /* sthu */ | |
83 | case 53: /* stfsu */ | |
84 | case 55: /* stfdu */ | |
85 | return 1; | |
86 | case 62: /* std or stdu */ | |
87 | return (inst & 3) == 1; | |
88 | case 31: | |
89 | /* check minor opcode */ | |
90 | switch ((inst >> 1) & 0x3ff) { | |
91 | case 181: /* stdux */ | |
92 | case 183: /* stwux */ | |
93 | case 247: /* stbux */ | |
94 | case 439: /* sthux */ | |
95 | case 695: /* stfsux */ | |
96 | case 759: /* stfdux */ | |
97 | return 1; | |
98 | } | |
99 | } | |
100 | return 0; | |
101 | } | |
102 | ||
14cf11af PM |
103 | /* |
104 | * For 600- and 800-family processors, the error_code parameter is DSISR | |
105 | * for a data fault, SRR1 for an instruction fault. For 400-family processors | |
106 | * the error_code parameter is ESR for a data fault, 0 for an instruction | |
107 | * fault. | |
108 | * For 64-bit processors, the error_code parameter is | |
109 | * - DSISR for a non-SLB data access fault, | |
110 | * - SRR1 & 0x08000000 for a non-SLB instruction access fault | |
111 | * - 0 any SLB fault. | |
112 | * | |
113 | * The return value is 0 if the fault was handled, or the signal | |
114 | * number if this is a kernel fault that can't be handled here. | |
115 | */ | |
116 | int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, | |
117 | unsigned long error_code) | |
118 | { | |
119 | struct vm_area_struct * vma; | |
120 | struct mm_struct *mm = current->mm; | |
121 | siginfo_t info; | |
122 | int code = SEGV_MAPERR; | |
83c54070 | 123 | int is_write = 0, ret; |
14cf11af PM |
124 | int trap = TRAP(regs); |
125 | int is_exec = trap == 0x400; | |
126 | ||
127 | #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) | |
128 | /* | |
129 | * Fortunately the bit assignments in SRR1 for an instruction | |
130 | * fault and DSISR for a data fault are mostly the same for the | |
131 | * bits we are interested in. But there are some bits which | |
132 | * indicate errors in DSISR but can validly be set in SRR1. | |
133 | */ | |
134 | if (trap == 0x400) | |
135 | error_code &= 0x48200000; | |
136 | else | |
137 | is_write = error_code & DSISR_ISSTORE; | |
138 | #else | |
139 | is_write = error_code & ESR_DST; | |
140 | #endif /* CONFIG_4xx || CONFIG_BOOKE */ | |
141 | ||
9f90b997 | 142 | if (notify_page_fault(regs)) |
14cf11af PM |
143 | return 0; |
144 | ||
c3b75bd7 MN |
145 | if (unlikely(debugger_fault_handler(regs))) |
146 | return 0; | |
14cf11af PM |
147 | |
148 | /* On a kernel SLB miss we can only check for a valid exception entry */ | |
149 | if (!user_mode(regs) && (address >= TASK_SIZE)) | |
150 | return SIGSEGV; | |
151 | ||
152 | #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) | |
153 | if (error_code & DSISR_DABRMATCH) { | |
154 | /* DABR match */ | |
bce6c5fd | 155 | do_dabr(regs, address, error_code); |
14cf11af PM |
156 | return 0; |
157 | } | |
158 | #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ | |
159 | ||
160 | if (in_atomic() || mm == NULL) { | |
161 | if (!user_mode(regs)) | |
162 | return SIGSEGV; | |
163 | /* in_atomic() in user mode is really bad, | |
164 | as is current->mm == NULL. */ | |
df3c9019 | 165 | printk(KERN_EMERG "Page fault in user mode with " |
14cf11af PM |
166 | "in_atomic() = %d mm = %p\n", in_atomic(), mm); |
167 | printk(KERN_EMERG "NIP = %lx MSR = %lx\n", | |
168 | regs->nip, regs->msr); | |
169 | die("Weird page fault", regs, SIGSEGV); | |
170 | } | |
171 | ||
172 | /* When running in the kernel we expect faults to occur only to | |
173 | * addresses in user space. All other faults represent errors in the | |
fc5266ea AB |
174 | * kernel and should generate an OOPS. Unfortunately, in the case of an |
175 | * erroneous fault occurring in a code path which already holds mmap_sem | |
14cf11af PM |
176 | * we will deadlock attempting to validate the fault against the |
177 | * address space. Luckily the kernel only validly references user | |
178 | * space from well defined areas of code, which are listed in the | |
179 | * exceptions table. | |
180 | * | |
181 | * As the vast majority of faults will be valid we will only perform | |
fc5266ea | 182 | * the source reference check when there is a possibility of a deadlock. |
14cf11af PM |
183 | * Attempt to lock the address space, if we cannot we then validate the |
184 | * source. If this is invalid we can skip the address space check, | |
185 | * thus avoiding the deadlock. | |
186 | */ | |
187 | if (!down_read_trylock(&mm->mmap_sem)) { | |
188 | if (!user_mode(regs) && !search_exception_tables(regs->nip)) | |
189 | goto bad_area_nosemaphore; | |
190 | ||
191 | down_read(&mm->mmap_sem); | |
192 | } | |
193 | ||
194 | vma = find_vma(mm, address); | |
195 | if (!vma) | |
196 | goto bad_area; | |
197 | if (vma->vm_start <= address) | |
198 | goto good_area; | |
199 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
200 | goto bad_area; | |
201 | ||
202 | /* | |
203 | * N.B. The POWER/Open ABI allows programs to access up to | |
204 | * 288 bytes below the stack pointer. | |
205 | * The kernel signal delivery code writes up to about 1.5kB | |
206 | * below the stack pointer (r1) before decrementing it. | |
207 | * The exec code can write slightly over 640kB to the stack | |
208 | * before setting the user r1. Thus we allow the stack to | |
209 | * expand to 1MB without further checks. | |
210 | */ | |
211 | if (address + 0x100000 < vma->vm_end) { | |
212 | /* get user regs even if this fault is in kernel mode */ | |
213 | struct pt_regs *uregs = current->thread.regs; | |
214 | if (uregs == NULL) | |
215 | goto bad_area; | |
216 | ||
217 | /* | |
218 | * A user-mode access to an address a long way below | |
219 | * the stack pointer is only valid if the instruction | |
220 | * is one which would update the stack pointer to the | |
221 | * address accessed if the instruction completed, | |
222 | * i.e. either stwu rs,n(r1) or stwux rs,r1,rb | |
223 | * (or the byte, halfword, float or double forms). | |
224 | * | |
225 | * If we don't check this then any write to the area | |
226 | * between the last mapped region and the stack will | |
227 | * expand the stack rather than segfaulting. | |
228 | */ | |
229 | if (address + 2048 < uregs->gpr[1] | |
230 | && (!user_mode(regs) || !store_updates_sp(regs))) | |
231 | goto bad_area; | |
232 | } | |
233 | if (expand_stack(vma, address)) | |
234 | goto bad_area; | |
235 | ||
236 | good_area: | |
237 | code = SEGV_ACCERR; | |
238 | #if defined(CONFIG_6xx) | |
239 | if (error_code & 0x95700000) | |
240 | /* an error such as lwarx to I/O controller space, | |
241 | address matching DABR, eciwx, etc. */ | |
242 | goto bad_area; | |
243 | #endif /* CONFIG_6xx */ | |
244 | #if defined(CONFIG_8xx) | |
245 | /* The MPC8xx seems to always set 0x80000000, which is | |
246 | * "undefined". Of those that can be set, this is the only | |
247 | * one which seems bad. | |
248 | */ | |
249 | if (error_code & 0x10000000) | |
250 | /* Guarded storage error. */ | |
251 | goto bad_area; | |
252 | #endif /* CONFIG_8xx */ | |
253 | ||
254 | if (is_exec) { | |
9ba4ace3 | 255 | #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) |
14cf11af PM |
256 | /* protection fault */ |
257 | if (error_code & DSISR_PROTFAULT) | |
258 | goto bad_area; | |
08ae6cc1 PM |
259 | /* |
260 | * Allow execution from readable areas if the MMU does not | |
261 | * provide separate controls over reading and executing. | |
262 | */ | |
263 | if (!(vma->vm_flags & VM_EXEC) && | |
264 | (cpu_has_feature(CPU_FTR_NOEXECUTE) || | |
265 | !(vma->vm_flags & (VM_READ | VM_WRITE)))) | |
14cf11af | 266 | goto bad_area; |
9ba4ace3 | 267 | #else |
14cf11af | 268 | pte_t *ptep; |
bab70a4a | 269 | pmd_t *pmdp; |
14cf11af PM |
270 | |
271 | /* Since 4xx/Book-E supports per-page execute permission, | |
272 | * we lazily flush dcache to icache. */ | |
273 | ptep = NULL; | |
bab70a4a ES |
274 | if (get_pteptr(mm, address, &ptep, &pmdp)) { |
275 | spinlock_t *ptl = pte_lockptr(mm, pmdp); | |
276 | spin_lock(ptl); | |
277 | if (pte_present(*ptep)) { | |
278 | struct page *page = pte_page(*ptep); | |
14cf11af | 279 | |
bab70a4a ES |
280 | if (!test_bit(PG_arch_1, &page->flags)) { |
281 | flush_dcache_icache_page(page); | |
282 | set_bit(PG_arch_1, &page->flags); | |
283 | } | |
1bc54c03 BH |
284 | pte_update(ptep, 0, _PAGE_HWEXEC | |
285 | _PAGE_ACCESSED); | |
e701d269 | 286 | _tlbie(address, mm->context.id); |
bab70a4a ES |
287 | pte_unmap_unlock(ptep, ptl); |
288 | up_read(&mm->mmap_sem); | |
289 | return 0; | |
14cf11af | 290 | } |
bab70a4a | 291 | pte_unmap_unlock(ptep, ptl); |
14cf11af | 292 | } |
14cf11af PM |
293 | #endif |
294 | /* a write */ | |
295 | } else if (is_write) { | |
296 | if (!(vma->vm_flags & VM_WRITE)) | |
297 | goto bad_area; | |
298 | /* a read */ | |
299 | } else { | |
300 | /* protection fault */ | |
301 | if (error_code & 0x08000000) | |
302 | goto bad_area; | |
df67b3da | 303 | if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) |
14cf11af PM |
304 | goto bad_area; |
305 | } | |
306 | ||
307 | /* | |
308 | * If for any reason at all we couldn't handle the fault, | |
309 | * make sure we exit gracefully rather than endlessly redo | |
310 | * the fault. | |
311 | */ | |
312 | survive: | |
83c54070 NP |
313 | ret = handle_mm_fault(mm, vma, address, is_write); |
314 | if (unlikely(ret & VM_FAULT_ERROR)) { | |
315 | if (ret & VM_FAULT_OOM) | |
316 | goto out_of_memory; | |
317 | else if (ret & VM_FAULT_SIGBUS) | |
318 | goto do_sigbus; | |
14cf11af PM |
319 | BUG(); |
320 | } | |
83c54070 NP |
321 | if (ret & VM_FAULT_MAJOR) |
322 | current->maj_flt++; | |
323 | else | |
324 | current->min_flt++; | |
14cf11af PM |
325 | up_read(&mm->mmap_sem); |
326 | return 0; | |
327 | ||
328 | bad_area: | |
329 | up_read(&mm->mmap_sem); | |
330 | ||
331 | bad_area_nosemaphore: | |
332 | /* User mode accesses cause a SIGSEGV */ | |
333 | if (user_mode(regs)) { | |
334 | _exception(SIGSEGV, regs, code, address); | |
335 | return 0; | |
336 | } | |
337 | ||
338 | if (is_exec && (error_code & DSISR_PROTFAULT) | |
339 | && printk_ratelimit()) | |
340 | printk(KERN_CRIT "kernel tried to execute NX-protected" | |
341 | " page (%lx) - exploit attempt? (uid: %d)\n", | |
342 | address, current->uid); | |
343 | ||
344 | return SIGSEGV; | |
345 | ||
346 | /* | |
347 | * We ran out of memory, or some other thing happened to us that made | |
348 | * us unable to handle the page fault gracefully. | |
349 | */ | |
350 | out_of_memory: | |
351 | up_read(&mm->mmap_sem); | |
b460cbc5 | 352 | if (is_global_init(current)) { |
14cf11af PM |
353 | yield(); |
354 | down_read(&mm->mmap_sem); | |
355 | goto survive; | |
356 | } | |
357 | printk("VM: killing process %s\n", current->comm); | |
358 | if (user_mode(regs)) | |
effe24bd | 359 | do_group_exit(SIGKILL); |
14cf11af PM |
360 | return SIGKILL; |
361 | ||
362 | do_sigbus: | |
363 | up_read(&mm->mmap_sem); | |
364 | if (user_mode(regs)) { | |
365 | info.si_signo = SIGBUS; | |
366 | info.si_errno = 0; | |
367 | info.si_code = BUS_ADRERR; | |
368 | info.si_addr = (void __user *)address; | |
369 | force_sig_info(SIGBUS, &info, current); | |
370 | return 0; | |
371 | } | |
372 | return SIGBUS; | |
373 | } | |
374 | ||
375 | /* | |
376 | * bad_page_fault is called when we have a bad access from the kernel. | |
377 | * It is called from the DSI and ISI handlers in head.S and from some | |
378 | * of the procedures in traps.c. | |
379 | */ | |
380 | void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) | |
381 | { | |
382 | const struct exception_table_entry *entry; | |
383 | ||
384 | /* Are we prepared to handle this fault? */ | |
385 | if ((entry = search_exception_tables(regs->nip)) != NULL) { | |
386 | regs->nip = entry->fixup; | |
387 | return; | |
388 | } | |
389 | ||
390 | /* kernel has accessed a bad area */ | |
723925b7 | 391 | |
723925b7 | 392 | switch (regs->trap) { |
a416dd8d ME |
393 | case 0x300: |
394 | case 0x380: | |
395 | printk(KERN_ALERT "Unable to handle kernel paging request for " | |
396 | "data at address 0x%08lx\n", regs->dar); | |
397 | break; | |
398 | case 0x400: | |
399 | case 0x480: | |
400 | printk(KERN_ALERT "Unable to handle kernel paging request for " | |
401 | "instruction fetch\n"); | |
402 | break; | |
403 | default: | |
404 | printk(KERN_ALERT "Unable to handle kernel paging request for " | |
405 | "unknown fault\n"); | |
406 | break; | |
723925b7 OJ |
407 | } |
408 | printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", | |
409 | regs->nip); | |
410 | ||
14cf11af PM |
411 | die("Kernel access of bad area", regs, sig); |
412 | } |