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5de96121 MS |
1 | /* |
2 | * arch/microblaze/mm/fault.c | |
3 | * | |
4 | * Copyright (C) 2007 Xilinx, Inc. All rights reserved. | |
5 | * | |
6 | * Derived from "arch/ppc/mm/fault.c" | |
7 | * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) | |
8 | * | |
9 | * Derived from "arch/i386/mm/fault.c" | |
10 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds | |
11 | * | |
12 | * Modified by Cort Dougan and Paul Mackerras. | |
13 | * | |
14 | * This file is subject to the terms and conditions of the GNU General | |
15 | * Public License. See the file COPYING in the main directory of this | |
16 | * archive for more details. | |
17 | * | |
18 | */ | |
19 | ||
20 | #include <linux/module.h> | |
21 | #include <linux/signal.h> | |
22 | #include <linux/sched.h> | |
23 | #include <linux/kernel.h> | |
24 | #include <linux/errno.h> | |
25 | #include <linux/string.h> | |
26 | #include <linux/types.h> | |
27 | #include <linux/ptrace.h> | |
28 | #include <linux/mman.h> | |
29 | #include <linux/mm.h> | |
30 | #include <linux/interrupt.h> | |
31 | ||
32 | #include <asm/page.h> | |
33 | #include <asm/pgtable.h> | |
34 | #include <asm/mmu.h> | |
6bd55f0b | 35 | #include <linux/mmu_context.h> |
5de96121 MS |
36 | #include <linux/uaccess.h> |
37 | #include <asm/exceptions.h> | |
38 | ||
5de96121 MS |
39 | static unsigned long pte_misses; /* updated by do_page_fault() */ |
40 | static unsigned long pte_errors; /* updated by do_page_fault() */ | |
41 | ||
42 | /* | |
43 | * Check whether the instruction at regs->pc is a store using | |
44 | * an update addressing form which will update r1. | |
45 | */ | |
46 | static int store_updates_sp(struct pt_regs *regs) | |
47 | { | |
48 | unsigned int inst; | |
49 | ||
5213a9c3 | 50 | if (get_user(inst, (unsigned int __user *)regs->pc)) |
5de96121 MS |
51 | return 0; |
52 | /* check for 1 in the rD field */ | |
53 | if (((inst >> 21) & 0x1f) != 1) | |
54 | return 0; | |
55 | /* check for store opcodes */ | |
56 | if ((inst & 0xd0000000) == 0xd0000000) | |
57 | return 1; | |
58 | return 0; | |
59 | } | |
60 | ||
61 | ||
62 | /* | |
63 | * bad_page_fault is called when we have a bad access from the kernel. | |
64 | * It is called from do_page_fault above and from some of the procedures | |
65 | * in traps.c. | |
66 | */ | |
3863dbce | 67 | void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) |
5de96121 MS |
68 | { |
69 | const struct exception_table_entry *fixup; | |
70 | /* MS: no context */ | |
71 | /* Are we prepared to handle this fault? */ | |
72 | fixup = search_exception_tables(regs->pc); | |
73 | if (fixup) { | |
74 | regs->pc = fixup->fixup; | |
75 | return; | |
76 | } | |
77 | ||
78 | /* kernel has accessed a bad area */ | |
5de96121 MS |
79 | die("kernel access of bad area", regs, sig); |
80 | } | |
81 | ||
82 | /* | |
83 | * The error_code parameter is ESR for a data fault, | |
84 | * 0 for an instruction fault. | |
85 | */ | |
86 | void do_page_fault(struct pt_regs *regs, unsigned long address, | |
87 | unsigned long error_code) | |
88 | { | |
89 | struct vm_area_struct *vma; | |
90 | struct mm_struct *mm = current->mm; | |
91 | siginfo_t info; | |
92 | int code = SEGV_MAPERR; | |
93 | int is_write = error_code & ESR_S; | |
94 | int fault; | |
759496ba | 95 | unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
5de96121 MS |
96 | |
97 | regs->ear = address; | |
98 | regs->esr = error_code; | |
99 | ||
100 | /* On a kernel SLB miss we can only check for a valid exception entry */ | |
78ebfa88 | 101 | if (unlikely(kernel_mode(regs) && (address >= TASK_SIZE))) { |
6bd55f0b | 102 | pr_warn("kernel task_size exceed"); |
5de96121 MS |
103 | _exception(SIGSEGV, regs, code, address); |
104 | } | |
105 | ||
106 | /* for instr TLB miss and instr storage exception ESR_S is undefined */ | |
107 | if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11) | |
108 | is_write = 0; | |
109 | ||
70ffdb93 | 110 | if (unlikely(faulthandler_disabled() || !mm)) { |
f10eca6e MS |
111 | if (kernel_mode(regs)) |
112 | goto bad_area_nosemaphore; | |
113 | ||
70ffdb93 | 114 | /* faulthandler_disabled() in user mode is really bad, |
5de96121 | 115 | as is current->mm == NULL. */ |
70ffdb93 DH |
116 | pr_emerg("Page fault in user mode with faulthandler_disabled(), mm = %p\n", |
117 | mm); | |
6bd55f0b | 118 | pr_emerg("r15 = %lx MSR = %lx\n", |
5de96121 MS |
119 | regs->r15, regs->msr); |
120 | die("Weird page fault", regs, SIGSEGV); | |
121 | } | |
122 | ||
759496ba JW |
123 | if (user_mode(regs)) |
124 | flags |= FAULT_FLAG_USER; | |
125 | ||
5de96121 MS |
126 | /* When running in the kernel we expect faults to occur only to |
127 | * addresses in user space. All other faults represent errors in the | |
128 | * kernel and should generate an OOPS. Unfortunately, in the case of an | |
129 | * erroneous fault occurring in a code path which already holds mmap_sem | |
130 | * we will deadlock attempting to validate the fault against the | |
131 | * address space. Luckily the kernel only validly references user | |
132 | * space from well defined areas of code, which are listed in the | |
133 | * exceptions table. | |
134 | * | |
135 | * As the vast majority of faults will be valid we will only perform | |
136 | * the source reference check when there is a possibility of a deadlock. | |
137 | * Attempt to lock the address space, if we cannot we then validate the | |
138 | * source. If this is invalid we can skip the address space check, | |
139 | * thus avoiding the deadlock. | |
140 | */ | |
78ebfa88 | 141 | if (unlikely(!down_read_trylock(&mm->mmap_sem))) { |
5de96121 MS |
142 | if (kernel_mode(regs) && !search_exception_tables(regs->pc)) |
143 | goto bad_area_nosemaphore; | |
144 | ||
f397c077 | 145 | retry: |
5de96121 MS |
146 | down_read(&mm->mmap_sem); |
147 | } | |
148 | ||
149 | vma = find_vma(mm, address); | |
78ebfa88 | 150 | if (unlikely(!vma)) |
5de96121 MS |
151 | goto bad_area; |
152 | ||
153 | if (vma->vm_start <= address) | |
154 | goto good_area; | |
155 | ||
78ebfa88 | 156 | if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) |
5de96121 MS |
157 | goto bad_area; |
158 | ||
78ebfa88 | 159 | if (unlikely(!is_write)) |
5de96121 MS |
160 | goto bad_area; |
161 | ||
162 | /* | |
163 | * N.B. The ABI allows programs to access up to | |
164 | * a few hundred bytes below the stack pointer (TBD). | |
165 | * The kernel signal delivery code writes up to about 1.5kB | |
166 | * below the stack pointer (r1) before decrementing it. | |
167 | * The exec code can write slightly over 640kB to the stack | |
168 | * before setting the user r1. Thus we allow the stack to | |
169 | * expand to 1MB without further checks. | |
170 | */ | |
78ebfa88 | 171 | if (unlikely(address + 0x100000 < vma->vm_end)) { |
5de96121 MS |
172 | |
173 | /* get user regs even if this fault is in kernel mode */ | |
174 | struct pt_regs *uregs = current->thread.regs; | |
175 | if (uregs == NULL) | |
176 | goto bad_area; | |
177 | ||
178 | /* | |
179 | * A user-mode access to an address a long way below | |
180 | * the stack pointer is only valid if the instruction | |
181 | * is one which would update the stack pointer to the | |
182 | * address accessed if the instruction completed, | |
183 | * i.e. either stwu rs,n(r1) or stwux rs,r1,rb | |
184 | * (or the byte, halfword, float or double forms). | |
185 | * | |
186 | * If we don't check this then any write to the area | |
187 | * between the last mapped region and the stack will | |
188 | * expand the stack rather than segfaulting. | |
189 | */ | |
190 | if (address + 2048 < uregs->r1 | |
191 | && (kernel_mode(regs) || !store_updates_sp(regs))) | |
192 | goto bad_area; | |
193 | } | |
194 | if (expand_stack(vma, address)) | |
195 | goto bad_area; | |
196 | ||
197 | good_area: | |
198 | code = SEGV_ACCERR; | |
199 | ||
200 | /* a write */ | |
78ebfa88 MS |
201 | if (unlikely(is_write)) { |
202 | if (unlikely(!(vma->vm_flags & VM_WRITE))) | |
5de96121 | 203 | goto bad_area; |
759496ba | 204 | flags |= FAULT_FLAG_WRITE; |
5de96121 MS |
205 | /* a read */ |
206 | } else { | |
207 | /* protection fault */ | |
78ebfa88 | 208 | if (unlikely(error_code & 0x08000000)) |
5de96121 | 209 | goto bad_area; |
78ebfa88 | 210 | if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC)))) |
5de96121 MS |
211 | goto bad_area; |
212 | } | |
213 | ||
214 | /* | |
215 | * If for any reason at all we couldn't handle the fault, | |
216 | * make sure we exit gracefully rather than endlessly redo | |
217 | * the fault. | |
218 | */ | |
f397c077 KC |
219 | fault = handle_mm_fault(mm, vma, address, flags); |
220 | ||
221 | if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) | |
222 | return; | |
223 | ||
5de96121 MS |
224 | if (unlikely(fault & VM_FAULT_ERROR)) { |
225 | if (fault & VM_FAULT_OOM) | |
226 | goto out_of_memory; | |
33692f27 LT |
227 | else if (fault & VM_FAULT_SIGSEGV) |
228 | goto bad_area; | |
5de96121 MS |
229 | else if (fault & VM_FAULT_SIGBUS) |
230 | goto do_sigbus; | |
231 | BUG(); | |
232 | } | |
f397c077 KC |
233 | |
234 | if (flags & FAULT_FLAG_ALLOW_RETRY) { | |
235 | if (unlikely(fault & VM_FAULT_MAJOR)) | |
236 | current->maj_flt++; | |
237 | else | |
238 | current->min_flt++; | |
239 | if (fault & VM_FAULT_RETRY) { | |
240 | flags &= ~FAULT_FLAG_ALLOW_RETRY; | |
45cac65b | 241 | flags |= FAULT_FLAG_TRIED; |
f397c077 KC |
242 | |
243 | /* | |
244 | * No need to up_read(&mm->mmap_sem) as we would | |
245 | * have already released it in __lock_page_or_retry | |
246 | * in mm/filemap.c. | |
247 | */ | |
248 | ||
249 | goto retry; | |
250 | } | |
251 | } | |
252 | ||
5de96121 | 253 | up_read(&mm->mmap_sem); |
f397c077 | 254 | |
5de96121 MS |
255 | /* |
256 | * keep track of tlb+htab misses that are good addrs but | |
257 | * just need pte's created via handle_mm_fault() | |
258 | * -- Cort | |
259 | */ | |
260 | pte_misses++; | |
261 | return; | |
262 | ||
263 | bad_area: | |
264 | up_read(&mm->mmap_sem); | |
265 | ||
266 | bad_area_nosemaphore: | |
267 | pte_errors++; | |
268 | ||
269 | /* User mode accesses cause a SIGSEGV */ | |
270 | if (user_mode(regs)) { | |
271 | _exception(SIGSEGV, regs, code, address); | |
272 | /* info.si_signo = SIGSEGV; | |
273 | info.si_errno = 0; | |
274 | info.si_code = code; | |
275 | info.si_addr = (void *) address; | |
276 | force_sig_info(SIGSEGV, &info, current);*/ | |
277 | return; | |
278 | } | |
279 | ||
280 | bad_page_fault(regs, address, SIGSEGV); | |
281 | return; | |
282 | ||
283 | /* | |
284 | * We ran out of memory, or some other thing happened to us that made | |
285 | * us unable to handle the page fault gracefully. | |
286 | */ | |
287 | out_of_memory: | |
5de96121 | 288 | up_read(&mm->mmap_sem); |
21e1c936 NP |
289 | if (!user_mode(regs)) |
290 | bad_page_fault(regs, address, SIGKILL); | |
291 | else | |
292 | pagefault_out_of_memory(); | |
5de96121 MS |
293 | return; |
294 | ||
295 | do_sigbus: | |
296 | up_read(&mm->mmap_sem); | |
297 | if (user_mode(regs)) { | |
298 | info.si_signo = SIGBUS; | |
299 | info.si_errno = 0; | |
300 | info.si_code = BUS_ADRERR; | |
301 | info.si_addr = (void __user *)address; | |
302 | force_sig_info(SIGBUS, &info, current); | |
303 | return; | |
304 | } | |
305 | bad_page_fault(regs, address, SIGBUS); | |
306 | } |