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