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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> | |
35 | #include <asm/mmu_context.h> | |
36 | #include <asm/system.h> | |
37 | #include <linux/uaccess.h> | |
38 | #include <asm/exceptions.h> | |
39 | ||
40 | #if defined(CONFIG_KGDB) | |
41 | int debugger_kernel_faults = 1; | |
42 | #endif | |
43 | ||
44 | static unsigned long pte_misses; /* updated by do_page_fault() */ | |
45 | static unsigned long pte_errors; /* updated by do_page_fault() */ | |
46 | ||
47 | /* | |
48 | * Check whether the instruction at regs->pc is a store using | |
49 | * an update addressing form which will update r1. | |
50 | */ | |
51 | static int store_updates_sp(struct pt_regs *regs) | |
52 | { | |
53 | unsigned int inst; | |
54 | ||
55 | if (get_user(inst, (unsigned int *)regs->pc)) | |
56 | return 0; | |
57 | /* check for 1 in the rD field */ | |
58 | if (((inst >> 21) & 0x1f) != 1) | |
59 | return 0; | |
60 | /* check for store opcodes */ | |
61 | if ((inst & 0xd0000000) == 0xd0000000) | |
62 | return 1; | |
63 | return 0; | |
64 | } | |
65 | ||
66 | ||
67 | /* | |
68 | * bad_page_fault is called when we have a bad access from the kernel. | |
69 | * It is called from do_page_fault above and from some of the procedures | |
70 | * in traps.c. | |
71 | */ | |
3863dbce | 72 | void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) |
5de96121 MS |
73 | { |
74 | const struct exception_table_entry *fixup; | |
75 | /* MS: no context */ | |
76 | /* Are we prepared to handle this fault? */ | |
77 | fixup = search_exception_tables(regs->pc); | |
78 | if (fixup) { | |
79 | regs->pc = fixup->fixup; | |
80 | return; | |
81 | } | |
82 | ||
83 | /* kernel has accessed a bad area */ | |
84 | #if defined(CONFIG_KGDB) | |
85 | if (debugger_kernel_faults) | |
86 | debugger(regs); | |
87 | #endif | |
88 | die("kernel access of bad area", regs, sig); | |
89 | } | |
90 | ||
91 | /* | |
92 | * The error_code parameter is ESR for a data fault, | |
93 | * 0 for an instruction fault. | |
94 | */ | |
95 | void do_page_fault(struct pt_regs *regs, unsigned long address, | |
96 | unsigned long error_code) | |
97 | { | |
98 | struct vm_area_struct *vma; | |
99 | struct mm_struct *mm = current->mm; | |
100 | siginfo_t info; | |
101 | int code = SEGV_MAPERR; | |
102 | int is_write = error_code & ESR_S; | |
103 | int fault; | |
104 | ||
105 | regs->ear = address; | |
106 | regs->esr = error_code; | |
107 | ||
108 | /* On a kernel SLB miss we can only check for a valid exception entry */ | |
109 | if (kernel_mode(regs) && (address >= TASK_SIZE)) { | |
110 | printk(KERN_WARNING "kernel task_size exceed"); | |
111 | _exception(SIGSEGV, regs, code, address); | |
112 | } | |
113 | ||
114 | /* for instr TLB miss and instr storage exception ESR_S is undefined */ | |
115 | if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11) | |
116 | is_write = 0; | |
117 | ||
118 | #if defined(CONFIG_KGDB) | |
119 | if (debugger_fault_handler && regs->trap == 0x300) { | |
120 | debugger_fault_handler(regs); | |
121 | return; | |
122 | } | |
123 | #endif /* CONFIG_KGDB */ | |
124 | ||
f10eca6e MS |
125 | if (in_atomic() || !mm) { |
126 | if (kernel_mode(regs)) | |
127 | goto bad_area_nosemaphore; | |
128 | ||
5de96121 MS |
129 | /* in_atomic() in user mode is really bad, |
130 | as is current->mm == NULL. */ | |
131 | printk(KERN_EMERG "Page fault in user mode with " | |
132 | "in_atomic(), mm = %p\n", mm); | |
133 | printk(KERN_EMERG "r15 = %lx MSR = %lx\n", | |
134 | regs->r15, regs->msr); | |
135 | die("Weird page fault", regs, SIGSEGV); | |
136 | } | |
137 | ||
138 | /* When running in the kernel we expect faults to occur only to | |
139 | * addresses in user space. All other faults represent errors in the | |
140 | * kernel and should generate an OOPS. Unfortunately, in the case of an | |
141 | * erroneous fault occurring in a code path which already holds mmap_sem | |
142 | * we will deadlock attempting to validate the fault against the | |
143 | * address space. Luckily the kernel only validly references user | |
144 | * space from well defined areas of code, which are listed in the | |
145 | * exceptions table. | |
146 | * | |
147 | * As the vast majority of faults will be valid we will only perform | |
148 | * the source reference check when there is a possibility of a deadlock. | |
149 | * Attempt to lock the address space, if we cannot we then validate the | |
150 | * source. If this is invalid we can skip the address space check, | |
151 | * thus avoiding the deadlock. | |
152 | */ | |
153 | if (!down_read_trylock(&mm->mmap_sem)) { | |
154 | if (kernel_mode(regs) && !search_exception_tables(regs->pc)) | |
155 | goto bad_area_nosemaphore; | |
156 | ||
157 | down_read(&mm->mmap_sem); | |
158 | } | |
159 | ||
160 | vma = find_vma(mm, address); | |
161 | if (!vma) | |
162 | goto bad_area; | |
163 | ||
164 | if (vma->vm_start <= address) | |
165 | goto good_area; | |
166 | ||
167 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
168 | goto bad_area; | |
169 | ||
170 | if (!is_write) | |
171 | goto bad_area; | |
172 | ||
173 | /* | |
174 | * N.B. The ABI allows programs to access up to | |
175 | * a few hundred bytes below the stack pointer (TBD). | |
176 | * The kernel signal delivery code writes up to about 1.5kB | |
177 | * below the stack pointer (r1) before decrementing it. | |
178 | * The exec code can write slightly over 640kB to the stack | |
179 | * before setting the user r1. Thus we allow the stack to | |
180 | * expand to 1MB without further checks. | |
181 | */ | |
182 | if (address + 0x100000 < vma->vm_end) { | |
183 | ||
184 | /* get user regs even if this fault is in kernel mode */ | |
185 | struct pt_regs *uregs = current->thread.regs; | |
186 | if (uregs == NULL) | |
187 | goto bad_area; | |
188 | ||
189 | /* | |
190 | * A user-mode access to an address a long way below | |
191 | * the stack pointer is only valid if the instruction | |
192 | * is one which would update the stack pointer to the | |
193 | * address accessed if the instruction completed, | |
194 | * i.e. either stwu rs,n(r1) or stwux rs,r1,rb | |
195 | * (or the byte, halfword, float or double forms). | |
196 | * | |
197 | * If we don't check this then any write to the area | |
198 | * between the last mapped region and the stack will | |
199 | * expand the stack rather than segfaulting. | |
200 | */ | |
201 | if (address + 2048 < uregs->r1 | |
202 | && (kernel_mode(regs) || !store_updates_sp(regs))) | |
203 | goto bad_area; | |
204 | } | |
205 | if (expand_stack(vma, address)) | |
206 | goto bad_area; | |
207 | ||
208 | good_area: | |
209 | code = SEGV_ACCERR; | |
210 | ||
211 | /* a write */ | |
212 | if (is_write) { | |
213 | if (!(vma->vm_flags & VM_WRITE)) | |
214 | goto bad_area; | |
215 | /* a read */ | |
216 | } else { | |
217 | /* protection fault */ | |
218 | if (error_code & 0x08000000) | |
219 | goto bad_area; | |
220 | if (!(vma->vm_flags & (VM_READ | VM_EXEC))) | |
221 | goto bad_area; | |
222 | } | |
223 | ||
224 | /* | |
225 | * If for any reason at all we couldn't handle the fault, | |
226 | * make sure we exit gracefully rather than endlessly redo | |
227 | * the fault. | |
228 | */ | |
229 | survive: | |
d06063cc | 230 | fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); |
5de96121 MS |
231 | if (unlikely(fault & VM_FAULT_ERROR)) { |
232 | if (fault & VM_FAULT_OOM) | |
233 | goto out_of_memory; | |
234 | else if (fault & VM_FAULT_SIGBUS) | |
235 | goto do_sigbus; | |
236 | BUG(); | |
237 | } | |
238 | if (fault & VM_FAULT_MAJOR) | |
239 | current->maj_flt++; | |
240 | else | |
241 | current->min_flt++; | |
242 | up_read(&mm->mmap_sem); | |
243 | /* | |
244 | * keep track of tlb+htab misses that are good addrs but | |
245 | * just need pte's created via handle_mm_fault() | |
246 | * -- Cort | |
247 | */ | |
248 | pte_misses++; | |
249 | return; | |
250 | ||
251 | bad_area: | |
252 | up_read(&mm->mmap_sem); | |
253 | ||
254 | bad_area_nosemaphore: | |
255 | pte_errors++; | |
256 | ||
257 | /* User mode accesses cause a SIGSEGV */ | |
258 | if (user_mode(regs)) { | |
259 | _exception(SIGSEGV, regs, code, address); | |
260 | /* info.si_signo = SIGSEGV; | |
261 | info.si_errno = 0; | |
262 | info.si_code = code; | |
263 | info.si_addr = (void *) address; | |
264 | force_sig_info(SIGSEGV, &info, current);*/ | |
265 | return; | |
266 | } | |
267 | ||
268 | bad_page_fault(regs, address, SIGSEGV); | |
269 | return; | |
270 | ||
271 | /* | |
272 | * We ran out of memory, or some other thing happened to us that made | |
273 | * us unable to handle the page fault gracefully. | |
274 | */ | |
275 | out_of_memory: | |
276 | if (current->pid == 1) { | |
277 | yield(); | |
278 | down_read(&mm->mmap_sem); | |
279 | goto survive; | |
280 | } | |
281 | up_read(&mm->mmap_sem); | |
282 | printk(KERN_WARNING "VM: killing process %s\n", current->comm); | |
283 | if (user_mode(regs)) | |
284 | do_exit(SIGKILL); | |
285 | bad_page_fault(regs, address, SIGKILL); | |
286 | return; | |
287 | ||
288 | do_sigbus: | |
289 | up_read(&mm->mmap_sem); | |
290 | if (user_mode(regs)) { | |
291 | info.si_signo = SIGBUS; | |
292 | info.si_errno = 0; | |
293 | info.si_code = BUS_ADRERR; | |
294 | info.si_addr = (void __user *)address; | |
295 | force_sig_info(SIGBUS, &info, current); | |
296 | return; | |
297 | } | |
298 | bad_page_fault(regs, address, SIGBUS); | |
299 | } |