1 | /* |
2 | * This file is subject to the terms and conditions of the GNU General Public |
3 | * License. See the file "COPYING" in the main directory of this archive |
4 | * for more details. |
5 | * |
6 | * Copyright (C) 1995 - 2000 by Ralf Baechle |
7 | */ |
8 | #include <linux/context_tracking.h> |
9 | #include <linux/signal.h> |
10 | #include <linux/sched.h> |
11 | #include <linux/interrupt.h> |
12 | #include <linux/kernel.h> |
13 | #include <linux/errno.h> |
14 | #include <linux/string.h> |
15 | #include <linux/types.h> |
16 | #include <linux/ptrace.h> |
17 | #include <linux/ratelimit.h> |
18 | #include <linux/mman.h> |
19 | #include <linux/mm.h> |
20 | #include <linux/smp.h> |
21 | #include <linux/kprobes.h> |
22 | #include <linux/perf_event.h> |
23 | #include <linux/uaccess.h> |
24 | |
25 | #include <asm/branch.h> |
26 | #include <asm/mmu_context.h> |
27 | #include <asm/ptrace.h> |
28 | #include <asm/highmem.h> /* For VMALLOC_END */ |
29 | #include <asm/traps.h> |
30 | #include <linux/kdebug.h> |
31 | |
32 | int show_unhandled_signals = 1; |
33 | |
34 | /* |
35 | * This routine handles page faults. It determines the address, |
36 | * and the problem, and then passes it off to one of the appropriate |
37 | * routines. |
38 | */ |
39 | static void __do_page_fault(struct pt_regs *regs, unsigned long write, |
40 | unsigned long address) |
41 | { |
42 | struct vm_area_struct * vma = NULL; |
43 | struct task_struct *tsk = current; |
44 | struct mm_struct *mm = tsk->mm; |
45 | const int field = sizeof(unsigned long) * 2; |
46 | int si_code; |
47 | vm_fault_t fault; |
48 | unsigned int flags = FAULT_FLAG_DEFAULT; |
49 | |
50 | static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10); |
51 | |
52 | #if 0 |
53 | printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n" , raw_smp_processor_id(), |
54 | current->comm, current->pid, field, address, write, |
55 | field, regs->cp0_epc); |
56 | #endif |
57 | |
58 | #ifdef CONFIG_KPROBES |
59 | /* |
60 | * This is to notify the fault handler of the kprobes. |
61 | */ |
62 | if (notify_die(val: DIE_PAGE_FAULT, str: "page fault" , regs, err: -1, |
63 | current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) |
64 | return; |
65 | #endif |
66 | |
67 | si_code = SEGV_MAPERR; |
68 | |
69 | /* |
70 | * We fault-in kernel-space virtual memory on-demand. The |
71 | * 'reference' page table is init_mm.pgd. |
72 | * |
73 | * NOTE! We MUST NOT take any locks for this case. We may |
74 | * be in an interrupt or a critical region, and should |
75 | * only copy the information from the master page table, |
76 | * nothing more. |
77 | */ |
78 | #ifdef CONFIG_64BIT |
79 | # define VMALLOC_FAULT_TARGET no_context |
80 | #else |
81 | # define VMALLOC_FAULT_TARGET vmalloc_fault |
82 | #endif |
83 | |
84 | if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) |
85 | goto VMALLOC_FAULT_TARGET; |
86 | #ifdef MODULE_START |
87 | if (unlikely(address >= MODULE_START && address < MODULE_END)) |
88 | goto VMALLOC_FAULT_TARGET; |
89 | #endif |
90 | |
91 | /* |
92 | * If we're in an interrupt or have no user |
93 | * context, we must not take the fault.. |
94 | */ |
95 | if (faulthandler_disabled() || !mm) |
96 | goto bad_area_nosemaphore; |
97 | |
98 | if (user_mode(regs)) |
99 | flags |= FAULT_FLAG_USER; |
100 | |
101 | perf_sw_event(event_id: PERF_COUNT_SW_PAGE_FAULTS, nr: 1, regs, addr: address); |
102 | retry: |
103 | vma = lock_mm_and_find_vma(mm, address, regs); |
104 | if (!vma) |
105 | goto bad_area_nosemaphore; |
106 | /* |
107 | * Ok, we have a good vm_area for this memory access, so |
108 | * we can handle it.. |
109 | */ |
110 | si_code = SEGV_ACCERR; |
111 | |
112 | if (write) { |
113 | if (!(vma->vm_flags & VM_WRITE)) |
114 | goto bad_area; |
115 | flags |= FAULT_FLAG_WRITE; |
116 | } else { |
117 | if (cpu_has_rixi) { |
118 | if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) { |
119 | #if 0 |
120 | pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n" , |
121 | raw_smp_processor_id(), |
122 | current->comm, current->pid, |
123 | field, address, write, |
124 | field, regs->cp0_epc); |
125 | #endif |
126 | goto bad_area; |
127 | } |
128 | if (!(vma->vm_flags & VM_READ) && |
129 | exception_epc(regs) != address) { |
130 | #if 0 |
131 | pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n" , |
132 | raw_smp_processor_id(), |
133 | current->comm, current->pid, |
134 | field, address, write, |
135 | field, regs->cp0_epc); |
136 | #endif |
137 | goto bad_area; |
138 | } |
139 | } else { |
140 | if (unlikely(!vma_is_accessible(vma))) |
141 | goto bad_area; |
142 | } |
143 | } |
144 | |
145 | /* |
146 | * If for any reason at all we couldn't handle the fault, |
147 | * make sure we exit gracefully rather than endlessly redo |
148 | * the fault. |
149 | */ |
150 | fault = handle_mm_fault(vma, address, flags, regs); |
151 | |
152 | if (fault_signal_pending(fault_flags: fault, regs)) { |
153 | if (!user_mode(regs)) |
154 | goto no_context; |
155 | return; |
156 | } |
157 | |
158 | /* The fault is fully completed (including releasing mmap lock) */ |
159 | if (fault & VM_FAULT_COMPLETED) |
160 | return; |
161 | |
162 | if (unlikely(fault & VM_FAULT_ERROR)) { |
163 | if (fault & VM_FAULT_OOM) |
164 | goto out_of_memory; |
165 | else if (fault & VM_FAULT_SIGSEGV) |
166 | goto bad_area; |
167 | else if (fault & VM_FAULT_SIGBUS) |
168 | goto do_sigbus; |
169 | BUG(); |
170 | } |
171 | |
172 | if (fault & VM_FAULT_RETRY) { |
173 | flags |= FAULT_FLAG_TRIED; |
174 | |
175 | /* |
176 | * No need to mmap_read_unlock(mm) as we would |
177 | * have already released it in __lock_page_or_retry |
178 | * in mm/filemap.c. |
179 | */ |
180 | |
181 | goto retry; |
182 | } |
183 | |
184 | mmap_read_unlock(mm); |
185 | return; |
186 | |
187 | /* |
188 | * Something tried to access memory that isn't in our memory map.. |
189 | * Fix it, but check if it's kernel or user first.. |
190 | */ |
191 | bad_area: |
192 | mmap_read_unlock(mm); |
193 | |
194 | bad_area_nosemaphore: |
195 | /* User mode accesses just cause a SIGSEGV */ |
196 | if (user_mode(regs)) { |
197 | tsk->thread.cp0_badvaddr = address; |
198 | tsk->thread.error_code = write; |
199 | if (show_unhandled_signals && |
200 | unhandled_signal(tsk, SIGSEGV) && |
201 | __ratelimit(&ratelimit_state)) { |
202 | pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n" , |
203 | tsk->comm, |
204 | write ? "write access to" : "read access from" , |
205 | field, address); |
206 | pr_info("epc = %0*lx in" , field, |
207 | (unsigned long) regs->cp0_epc); |
208 | print_vma_addr(KERN_CONT " " , rip: regs->cp0_epc); |
209 | pr_cont("\n" ); |
210 | pr_info("ra = %0*lx in" , field, |
211 | (unsigned long) regs->regs[31]); |
212 | print_vma_addr(KERN_CONT " " , rip: regs->regs[31]); |
213 | pr_cont("\n" ); |
214 | } |
215 | current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; |
216 | force_sig_fault(SIGSEGV, code: si_code, addr: (void __user *)address); |
217 | return; |
218 | } |
219 | |
220 | no_context: |
221 | /* Are we prepared to handle this kernel fault? */ |
222 | if (fixup_exception(regs)) { |
223 | current->thread.cp0_baduaddr = address; |
224 | return; |
225 | } |
226 | |
227 | /* |
228 | * Oops. The kernel tried to access some bad page. We'll have to |
229 | * terminate things with extreme prejudice. |
230 | */ |
231 | bust_spinlocks(yes: 1); |
232 | |
233 | printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " |
234 | "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n" , |
235 | raw_smp_processor_id(), field, address, field, regs->cp0_epc, |
236 | field, regs->regs[31]); |
237 | die("Oops" , regs); |
238 | |
239 | out_of_memory: |
240 | /* |
241 | * We ran out of memory, call the OOM killer, and return the userspace |
242 | * (which will retry the fault, or kill us if we got oom-killed). |
243 | */ |
244 | mmap_read_unlock(mm); |
245 | if (!user_mode(regs)) |
246 | goto no_context; |
247 | pagefault_out_of_memory(); |
248 | return; |
249 | |
250 | do_sigbus: |
251 | mmap_read_unlock(mm); |
252 | |
253 | /* Kernel mode? Handle exceptions or die */ |
254 | if (!user_mode(regs)) |
255 | goto no_context; |
256 | |
257 | /* |
258 | * Send a sigbus, regardless of whether we were in kernel |
259 | * or user mode. |
260 | */ |
261 | #if 0 |
262 | printk("do_page_fault() #3: sending SIGBUS to %s for " |
263 | "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n" , |
264 | tsk->comm, |
265 | write ? "write access to" : "read access from" , |
266 | field, address, |
267 | field, (unsigned long) regs->cp0_epc, |
268 | field, (unsigned long) regs->regs[31]); |
269 | #endif |
270 | current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; |
271 | tsk->thread.cp0_badvaddr = address; |
272 | force_sig_fault(SIGBUS, BUS_ADRERR, addr: (void __user *)address); |
273 | |
274 | return; |
275 | #ifndef CONFIG_64BIT |
276 | vmalloc_fault: |
277 | { |
278 | /* |
279 | * Synchronize this task's top level page-table |
280 | * with the 'reference' page table. |
281 | * |
282 | * Do _not_ use "tsk" here. We might be inside |
283 | * an interrupt in the middle of a task switch.. |
284 | */ |
285 | int offset = pgd_index(address); |
286 | pgd_t *pgd, *pgd_k; |
287 | p4d_t *p4d, *p4d_k; |
288 | pud_t *pud, *pud_k; |
289 | pmd_t *pmd, *pmd_k; |
290 | pte_t *pte_k; |
291 | |
292 | pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; |
293 | pgd_k = init_mm.pgd + offset; |
294 | |
295 | if (!pgd_present(*pgd_k)) |
296 | goto no_context; |
297 | set_pgd(pgd, *pgd_k); |
298 | |
299 | p4d = p4d_offset(pgd, address); |
300 | p4d_k = p4d_offset(pgd_k, address); |
301 | if (!p4d_present(*p4d_k)) |
302 | goto no_context; |
303 | |
304 | pud = pud_offset(p4d, address); |
305 | pud_k = pud_offset(p4d_k, address); |
306 | if (!pud_present(*pud_k)) |
307 | goto no_context; |
308 | |
309 | pmd = pmd_offset(pud, address); |
310 | pmd_k = pmd_offset(pud_k, address); |
311 | if (!pmd_present(*pmd_k)) |
312 | goto no_context; |
313 | set_pmd(pmd, *pmd_k); |
314 | |
315 | pte_k = pte_offset_kernel(pmd_k, address); |
316 | if (!pte_present(*pte_k)) |
317 | goto no_context; |
318 | return; |
319 | } |
320 | #endif |
321 | } |
322 | NOKPROBE_SYMBOL(__do_page_fault); |
323 | |
324 | asmlinkage void do_page_fault(struct pt_regs *regs, |
325 | unsigned long write, unsigned long address) |
326 | { |
327 | enum ctx_state prev_state; |
328 | |
329 | prev_state = exception_enter(); |
330 | __do_page_fault(regs, write, address); |
331 | exception_exit(prev_ctx: prev_state); |
332 | } |
333 | NOKPROBE_SYMBOL(do_page_fault); |
334 | |