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Linux/arch/mips/mm/fault.c

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Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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/signal.h>
  9 #include <linux/sched.h>
 10 #include <linux/interrupt.h>
 11 #include <linux/kernel.h>
 12 #include <linux/errno.h>
 13 #include <linux/string.h>
 14 #include <linux/types.h>
 15 #include <linux/ptrace.h>
 16 #include <linux/mman.h>
 17 #include <linux/mm.h>
 18 #include <linux/smp.h>
 19 #include <linux/module.h>
 20 #include <linux/kprobes.h>
 21 #include <linux/perf_event.h>
 22 
 23 #include <asm/branch.h>
 24 #include <asm/mmu_context.h>
 25 #include <asm/uaccess.h>
 26 #include <asm/ptrace.h>
 27 #include <asm/highmem.h>                /* For VMALLOC_END */
 28 #include <linux/kdebug.h>
 29 
 30 /*
 31  * This routine handles page faults.  It determines the address,
 32  * and the problem, and then passes it off to one of the appropriate
 33  * routines.
 34  */
 35 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, unsigned long write,
 36                               unsigned long address)
 37 {
 38         struct vm_area_struct * vma = NULL;
 39         struct task_struct *tsk = current;
 40         struct mm_struct *mm = tsk->mm;
 41         const int field = sizeof(unsigned long) * 2;
 42         siginfo_t info;
 43         int fault;
 44         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
 45                                                  (write ? FAULT_FLAG_WRITE : 0);
 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 retry:
 96         down_read(&mm->mmap_sem);
 97         vma = find_vma(mm, address);
 98         if (!vma)
 99                 goto bad_area;
100         if (vma->vm_start <= address)
101                 goto good_area;
102         if (!(vma->vm_flags & VM_GROWSDOWN))
103                 goto bad_area;
104         if (expand_stack(vma, address))
105                 goto bad_area;
106 /*
107  * Ok, we have a good vm_area for this memory access, so
108  * we can handle it..
109  */
110 good_area:
111         info.si_code = SEGV_ACCERR;
112 
113         if (write) {
114                 if (!(vma->vm_flags & VM_WRITE))
115                         goto bad_area;
116         } else {
117                 if (kernel_uses_smartmips_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 #if 0
130                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
131                                           raw_smp_processor_id(),
132                                           current->comm, current->pid,
133                                           field, address, write,
134                                           field, regs->cp0_epc);
135 #endif
136                                 goto bad_area;
137                         }
138                 } else {
139                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
140                                 goto bad_area;
141                 }
142         }
143 
144         /*
145          * If for any reason at all we couldn't handle the fault,
146          * make sure we exit gracefully rather than endlessly redo
147          * the fault.
148          */
149         fault = handle_mm_fault(mm, vma, address, flags);
150 
151         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
152                 return;
153 
154         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
155         if (unlikely(fault & VM_FAULT_ERROR)) {
156                 if (fault & VM_FAULT_OOM)
157                         goto out_of_memory;
158                 else if (fault & VM_FAULT_SIGBUS)
159                         goto do_sigbus;
160                 BUG();
161         }
162         if (flags & FAULT_FLAG_ALLOW_RETRY) {
163                 if (fault & VM_FAULT_MAJOR) {
164                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
165                                                   regs, address);
166                         tsk->maj_flt++;
167                 } else {
168                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
169                                                   regs, address);
170                         tsk->min_flt++;
171                 }
172                 if (fault & VM_FAULT_RETRY) {
173                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
174 
175                         /*
176                          * No need to up_read(&mm->mmap_sem) 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 
185         up_read(&mm->mmap_sem);
186         return;
187 
188 /*
189  * Something tried to access memory that isn't in our memory map..
190  * Fix it, but check if it's kernel or user first..
191  */
192 bad_area:
193         up_read(&mm->mmap_sem);
194 
195 bad_area_nosemaphore:
196         /* User mode accesses just cause a SIGSEGV */
197         if (user_mode(regs)) {
198                 tsk->thread.cp0_badvaddr = address;
199                 tsk->thread.error_code = write;
200 #if 0
201                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
202                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
203                        tsk->comm,
204                        write ? "write access to" : "read access from",
205                        field, address,
206                        field, (unsigned long) regs->cp0_epc,
207                        field, (unsigned long) regs->regs[31]);
208 #endif
209                 info.si_signo = SIGSEGV;
210                 info.si_errno = 0;
211                 /* info.si_code has been set above */
212                 info.si_addr = (void __user *) address;
213                 force_sig_info(SIGSEGV, &info, tsk);
214                 return;
215         }
216 
217 no_context:
218         /* Are we prepared to handle this kernel fault?  */
219         if (fixup_exception(regs)) {
220                 current->thread.cp0_baduaddr = address;
221                 return;
222         }
223 
224         /*
225          * Oops. The kernel tried to access some bad page. We'll have to
226          * terminate things with extreme prejudice.
227          */
228         bust_spinlocks(1);
229 
230         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
231                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
232                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
233                field,  regs->regs[31]);
234         die("Oops", regs);
235 
236 out_of_memory:
237         /*
238          * We ran out of memory, call the OOM killer, and return the userspace
239          * (which will retry the fault, or kill us if we got oom-killed).
240          */
241         up_read(&mm->mmap_sem);
242         pagefault_out_of_memory();
243         return;
244 
245 do_sigbus:
246         up_read(&mm->mmap_sem);
247 
248         /* Kernel mode? Handle exceptions or die */
249         if (!user_mode(regs))
250                 goto no_context;
251         else
252         /*
253          * Send a sigbus, regardless of whether we were in kernel
254          * or user mode.
255          */
256 #if 0
257                 printk("do_page_fault() #3: sending SIGBUS to %s for "
258                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
259                        tsk->comm,
260                        write ? "write access to" : "read access from",
261                        field, address,
262                        field, (unsigned long) regs->cp0_epc,
263                        field, (unsigned long) regs->regs[31]);
264 #endif
265         tsk->thread.cp0_badvaddr = address;
266         info.si_signo = SIGBUS;
267         info.si_errno = 0;
268         info.si_code = BUS_ADRERR;
269         info.si_addr = (void __user *) address;
270         force_sig_info(SIGBUS, &info, tsk);
271 
272         return;
273 #ifndef CONFIG_64BIT
274 vmalloc_fault:
275         {
276                 /*
277                  * Synchronize this task's top level page-table
278                  * with the 'reference' page table.
279                  *
280                  * Do _not_ use "tsk" here. We might be inside
281                  * an interrupt in the middle of a task switch..
282                  */
283                 int offset = __pgd_offset(address);
284                 pgd_t *pgd, *pgd_k;
285                 pud_t *pud, *pud_k;
286                 pmd_t *pmd, *pmd_k;
287                 pte_t *pte_k;
288 
289                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
290                 pgd_k = init_mm.pgd + offset;
291 
292                 if (!pgd_present(*pgd_k))
293                         goto no_context;
294                 set_pgd(pgd, *pgd_k);
295 
296                 pud = pud_offset(pgd, address);
297                 pud_k = pud_offset(pgd_k, address);
298                 if (!pud_present(*pud_k))
299                         goto no_context;
300 
301                 pmd = pmd_offset(pud, address);
302                 pmd_k = pmd_offset(pud_k, address);
303                 if (!pmd_present(*pmd_k))
304                         goto no_context;
305                 set_pmd(pmd, *pmd_k);
306 
307                 pte_k = pte_offset_kernel(pmd_k, address);
308                 if (!pte_present(*pte_k))
309                         goto no_context;
310                 return;
311         }
312 #endif
313 }
314 

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