1 /*
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
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>
31 #include <linux/kdebug.h>
32
33 #include <asm/firmware.h>
34 #include <asm/page.h>
35 #include <asm/pgtable.h>
36 #include <asm/mmu.h>
37 #include <asm/mmu_context.h>
38 #include <asm/system.h>
39 #include <asm/uaccess.h>
40 #include <asm/tlbflush.h>
41 #include <asm/siginfo.h>
42
43
44 #ifdef CONFIG_KPROBES
notify_page_fault(struct pt_regs * regs)45 static inline int notify_page_fault(struct pt_regs *regs)
46 {
47 int ret = 0;
48
49 /* kprobe_running() needs smp_processor_id() */
50 if (!user_mode(regs)) {
51 preempt_disable();
52 if (kprobe_running() && kprobe_fault_handler(regs, 11))
53 ret = 1;
54 preempt_enable();
55 }
56
57 return ret;
58 }
59 #else
notify_page_fault(struct pt_regs * regs)60 static inline int notify_page_fault(struct pt_regs *regs)
61 {
62 return 0;
63 }
64 #endif
65
66 /*
67 * Check whether the instruction at regs->nip is a store using
68 * an update addressing form which will update r1.
69 */
store_updates_sp(struct pt_regs * regs)70 static int store_updates_sp(struct pt_regs *regs)
71 {
72 unsigned int inst;
73
74 if (get_user(inst, (unsigned int __user *)regs->nip))
75 return 0;
76 /* check for 1 in the rA field */
77 if (((inst >> 16) & 0x1f) != 1)
78 return 0;
79 /* check major opcode */
80 switch (inst >> 26) {
81 case 37: /* stwu */
82 case 39: /* stbu */
83 case 45: /* sthu */
84 case 53: /* stfsu */
85 case 55: /* stfdu */
86 return 1;
87 case 62: /* std or stdu */
88 return (inst & 3) == 1;
89 case 31:
90 /* check minor opcode */
91 switch ((inst >> 1) & 0x3ff) {
92 case 181: /* stdux */
93 case 183: /* stwux */
94 case 247: /* stbux */
95 case 439: /* sthux */
96 case 695: /* stfsux */
97 case 759: /* stfdux */
98 return 1;
99 }
100 }
101 return 0;
102 }
103
104 /*
105 * For 600- and 800-family processors, the error_code parameter is DSISR
106 * for a data fault, SRR1 for an instruction fault. For 400-family processors
107 * the error_code parameter is ESR for a data fault, 0 for an instruction
108 * fault.
109 * For 64-bit processors, the error_code parameter is
110 * - DSISR for a non-SLB data access fault,
111 * - SRR1 & 0x08000000 for a non-SLB instruction access fault
112 * - 0 any SLB fault.
113 *
114 * The return value is 0 if the fault was handled, or the signal
115 * number if this is a kernel fault that can't be handled here.
116 */
do_page_fault(struct pt_regs * regs,unsigned long address,unsigned long error_code)117 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
118 unsigned long error_code)
119 {
120 struct vm_area_struct * vma;
121 struct mm_struct *mm = current->mm;
122 siginfo_t info;
123 int code = SEGV_MAPERR;
124 int is_write = 0, ret;
125 int trap = TRAP(regs);
126 int is_exec = trap == 0x400;
127
128 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
129 /*
130 * Fortunately the bit assignments in SRR1 for an instruction
131 * fault and DSISR for a data fault are mostly the same for the
132 * bits we are interested in. But there are some bits which
133 * indicate errors in DSISR but can validly be set in SRR1.
134 */
135 if (trap == 0x400)
136 error_code &= 0x48200000;
137 else
138 is_write = error_code & DSISR_ISSTORE;
139 #else
140 is_write = error_code & ESR_DST;
141 #endif /* CONFIG_4xx || CONFIG_BOOKE */
142
143 if (notify_page_fault(regs))
144 return 0;
145
146 if (unlikely(debugger_fault_handler(regs)))
147 return 0;
148
149 /* On a kernel SLB miss we can only check for a valid exception entry */
150 if (!user_mode(regs) && (address >= TASK_SIZE))
151 return SIGSEGV;
152
153 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
154 if (error_code & DSISR_DABRMATCH) {
155 /* DABR match */
156 do_dabr(regs, address, error_code);
157 return 0;
158 }
159 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
160
161 if (in_atomic() || mm == NULL) {
162 if (!user_mode(regs))
163 return SIGSEGV;
164 /* in_atomic() in user mode is really bad,
165 as is current->mm == NULL. */
166 printk(KERN_EMERG "Page fault in user mode with "
167 "in_atomic() = %d mm = %p\n", in_atomic(), mm);
168 printk(KERN_EMERG "NIP = %lx MSR = %lx\n",
169 regs->nip, regs->msr);
170 die("Weird page fault", regs, SIGSEGV);
171 }
172
173 /* When running in the kernel we expect faults to occur only to
174 * addresses in user space. All other faults represent errors in the
175 * kernel and should generate an OOPS. Unfortunately, in the case of an
176 * erroneous fault occurring in a code path which already holds mmap_sem
177 * we will deadlock attempting to validate the fault against the
178 * address space. Luckily the kernel only validly references user
179 * space from well defined areas of code, which are listed in the
180 * exceptions table.
181 *
182 * As the vast majority of faults will be valid we will only perform
183 * the source reference check when there is a possibility of a deadlock.
184 * Attempt to lock the address space, if we cannot we then validate the
185 * source. If this is invalid we can skip the address space check,
186 * thus avoiding the deadlock.
187 */
188 if (!down_read_trylock(&mm->mmap_sem)) {
189 if (!user_mode(regs) && !search_exception_tables(regs->nip))
190 goto bad_area_nosemaphore;
191
192 down_read(&mm->mmap_sem);
193 }
194
195 vma = find_vma(mm, address);
196 if (!vma)
197 goto bad_area;
198 if (vma->vm_start <= address)
199 goto good_area;
200 if (!(vma->vm_flags & VM_GROWSDOWN))
201 goto bad_area;
202
203 /*
204 * N.B. The POWER/Open ABI allows programs to access up to
205 * 288 bytes below the stack pointer.
206 * The kernel signal delivery code writes up to about 1.5kB
207 * below the stack pointer (r1) before decrementing it.
208 * The exec code can write slightly over 640kB to the stack
209 * before setting the user r1. Thus we allow the stack to
210 * expand to 1MB without further checks.
211 */
212 if (address + 0x100000 < vma->vm_end) {
213 /* get user regs even if this fault is in kernel mode */
214 struct pt_regs *uregs = current->thread.regs;
215 if (uregs == NULL)
216 goto bad_area;
217
218 /*
219 * A user-mode access to an address a long way below
220 * the stack pointer is only valid if the instruction
221 * is one which would update the stack pointer to the
222 * address accessed if the instruction completed,
223 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
224 * (or the byte, halfword, float or double forms).
225 *
226 * If we don't check this then any write to the area
227 * between the last mapped region and the stack will
228 * expand the stack rather than segfaulting.
229 */
230 if (address + 2048 < uregs->gpr[1]
231 && (!user_mode(regs) || !store_updates_sp(regs)))
232 goto bad_area;
233 }
234 if (expand_stack(vma, address))
235 goto bad_area;
236
237 good_area:
238 code = SEGV_ACCERR;
239 #if defined(CONFIG_6xx)
240 if (error_code & 0x95700000)
241 /* an error such as lwarx to I/O controller space,
242 address matching DABR, eciwx, etc. */
243 goto bad_area;
244 #endif /* CONFIG_6xx */
245 #if defined(CONFIG_8xx)
246 /* The MPC8xx seems to always set 0x80000000, which is
247 * "undefined". Of those that can be set, this is the only
248 * one which seems bad.
249 */
250 if (error_code & 0x10000000)
251 /* Guarded storage error. */
252 goto bad_area;
253 #endif /* CONFIG_8xx */
254
255 if (is_exec) {
256 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
257 /* protection fault */
258 if (error_code & DSISR_PROTFAULT)
259 goto bad_area;
260 /*
261 * Allow execution from readable areas if the MMU does not
262 * provide separate controls over reading and executing.
263 */
264 if (!(vma->vm_flags & VM_EXEC) &&
265 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
266 !(vma->vm_flags & (VM_READ | VM_WRITE))))
267 goto bad_area;
268 #else
269 pte_t *ptep;
270 pmd_t *pmdp;
271
272 /* Since 4xx/Book-E supports per-page execute permission,
273 * we lazily flush dcache to icache. */
274 ptep = NULL;
275 if (get_pteptr(mm, address, &ptep, &pmdp)) {
276 spinlock_t *ptl = pte_lockptr(mm, pmdp);
277 spin_lock(ptl);
278 if (pte_present(*ptep)) {
279 struct page *page = pte_page(*ptep);
280
281 if (!test_bit(PG_arch_1, &page->flags)) {
282 flush_dcache_icache_page(page);
283 set_bit(PG_arch_1, &page->flags);
284 }
285 pte_update(ptep, 0, _PAGE_HWEXEC |
286 _PAGE_ACCESSED);
287 local_flush_tlb_page(vma, address);
288 pte_unmap_unlock(ptep, ptl);
289 up_read(&mm->mmap_sem);
290 return 0;
291 }
292 pte_unmap_unlock(ptep, ptl);
293 }
294 #endif
295 /* a write */
296 } else if (is_write) {
297 if (!(vma->vm_flags & VM_WRITE))
298 goto bad_area;
299 /* a read */
300 } else {
301 /* protection fault */
302 if (error_code & 0x08000000)
303 goto bad_area;
304 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
305 goto bad_area;
306 }
307
308 /*
309 * If for any reason at all we couldn't handle the fault,
310 * make sure we exit gracefully rather than endlessly redo
311 * the fault.
312 */
313 survive:
314 ret = handle_mm_fault(mm, vma, address, is_write);
315 if (unlikely(ret & VM_FAULT_ERROR)) {
316 if (ret & VM_FAULT_OOM)
317 goto out_of_memory;
318 else if (ret & VM_FAULT_SIGBUS)
319 goto do_sigbus;
320 BUG();
321 }
322 if (ret & VM_FAULT_MAJOR) {
323 current->maj_flt++;
324 #ifdef CONFIG_PPC_SMLPAR
325 if (firmware_has_feature(FW_FEATURE_CMO)) {
326 preempt_disable();
327 get_lppaca()->page_ins += (1 << PAGE_FACTOR);
328 preempt_enable();
329 }
330 #endif
331 } else
332 current->min_flt++;
333 up_read(&mm->mmap_sem);
334 return 0;
335
336 bad_area:
337 up_read(&mm->mmap_sem);
338
339 bad_area_nosemaphore:
340 /* User mode accesses cause a SIGSEGV */
341 if (user_mode(regs)) {
342 _exception(SIGSEGV, regs, code, address);
343 return 0;
344 }
345
346 if (is_exec && (error_code & DSISR_PROTFAULT)
347 && printk_ratelimit())
348 printk(KERN_CRIT "kernel tried to execute NX-protected"
349 " page (%lx) - exploit attempt? (uid: %d)\n",
350 address, current_uid());
351
352 return SIGSEGV;
353
354 /*
355 * We ran out of memory, or some other thing happened to us that made
356 * us unable to handle the page fault gracefully.
357 */
358 out_of_memory:
359 up_read(&mm->mmap_sem);
360 if (is_global_init(current)) {
361 yield();
362 down_read(&mm->mmap_sem);
363 goto survive;
364 }
365 printk("VM: killing process %s\n", current->comm);
366 if (user_mode(regs))
367 do_group_exit(SIGKILL);
368 return SIGKILL;
369
370 do_sigbus:
371 up_read(&mm->mmap_sem);
372 if (user_mode(regs)) {
373 info.si_signo = SIGBUS;
374 info.si_errno = 0;
375 info.si_code = BUS_ADRERR;
376 info.si_addr = (void __user *)address;
377 force_sig_info(SIGBUS, &info, current);
378 return 0;
379 }
380 return SIGBUS;
381 }
382
383 /*
384 * bad_page_fault is called when we have a bad access from the kernel.
385 * It is called from the DSI and ISI handlers in head.S and from some
386 * of the procedures in traps.c.
387 */
bad_page_fault(struct pt_regs * regs,unsigned long address,int sig)388 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
389 {
390 const struct exception_table_entry *entry;
391
392 /* Are we prepared to handle this fault? */
393 if ((entry = search_exception_tables(regs->nip)) != NULL) {
394 regs->nip = entry->fixup;
395 return;
396 }
397
398 /* kernel has accessed a bad area */
399
400 switch (regs->trap) {
401 case 0x300:
402 case 0x380:
403 printk(KERN_ALERT "Unable to handle kernel paging request for "
404 "data at address 0x%08lx\n", regs->dar);
405 break;
406 case 0x400:
407 case 0x480:
408 printk(KERN_ALERT "Unable to handle kernel paging request for "
409 "instruction fetch\n");
410 break;
411 default:
412 printk(KERN_ALERT "Unable to handle kernel paging request for "
413 "unknown fault\n");
414 break;
415 }
416 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
417 regs->nip);
418
419 die("Kernel access of bad area", regs, sig);
420 }
421