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Linux/arch/arc/mm/fault.c

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  1 /* Page Fault Handling for ARC (TLB Miss / ProtV)
  2  *
  3  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
  4  *
  5  * This program is free software; you can redistribute it and/or modify
  6  * it under the terms of the GNU General Public License version 2 as
  7  * published by the Free Software Foundation.
  8  */
  9 
 10 #include <linux/signal.h>
 11 #include <linux/interrupt.h>
 12 #include <linux/sched.h>
 13 #include <linux/errno.h>
 14 #include <linux/ptrace.h>
 15 #include <linux/uaccess.h>
 16 #include <linux/kdebug.h>
 17 #include <linux/perf_event.h>
 18 #include <asm/pgalloc.h>
 19 #include <asm/mmu.h>
 20 
 21 /*
 22  * kernel virtual address is required to implement vmalloc/pkmap/fixmap
 23  * Refer to asm/processor.h for System Memory Map
 24  *
 25  * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
 26  * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
 27  */
 28 noinline static int handle_kernel_vaddr_fault(unsigned long address)
 29 {
 30         /*
 31          * Synchronize this task's top level page-table
 32          * with the 'reference' page table.
 33          */
 34         pgd_t *pgd, *pgd_k;
 35         pud_t *pud, *pud_k;
 36         pmd_t *pmd, *pmd_k;
 37 
 38         pgd = pgd_offset_fast(current->active_mm, address);
 39         pgd_k = pgd_offset_k(address);
 40 
 41         if (!pgd_present(*pgd_k))
 42                 goto bad_area;
 43 
 44         pud = pud_offset(pgd, address);
 45         pud_k = pud_offset(pgd_k, address);
 46         if (!pud_present(*pud_k))
 47                 goto bad_area;
 48 
 49         pmd = pmd_offset(pud, address);
 50         pmd_k = pmd_offset(pud_k, address);
 51         if (!pmd_present(*pmd_k))
 52                 goto bad_area;
 53 
 54         set_pmd(pmd, *pmd_k);
 55 
 56         /* XXX: create the TLB entry here */
 57         return 0;
 58 
 59 bad_area:
 60         return 1;
 61 }
 62 
 63 void do_page_fault(unsigned long address, struct pt_regs *regs)
 64 {
 65         struct vm_area_struct *vma = NULL;
 66         struct task_struct *tsk = current;
 67         struct mm_struct *mm = tsk->mm;
 68         siginfo_t info;
 69         int fault, ret;
 70         int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
 71         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 72 
 73         /*
 74          * We fault-in kernel-space virtual memory on-demand. The
 75          * 'reference' page table is init_mm.pgd.
 76          *
 77          * NOTE! We MUST NOT take any locks for this case. We may
 78          * be in an interrupt or a critical region, and should
 79          * only copy the information from the master page table,
 80          * nothing more.
 81          */
 82         if (address >= VMALLOC_START) {
 83                 ret = handle_kernel_vaddr_fault(address);
 84                 if (unlikely(ret))
 85                         goto bad_area_nosemaphore;
 86                 else
 87                         return;
 88         }
 89 
 90         info.si_code = SEGV_MAPERR;
 91 
 92         /*
 93          * If we're in an interrupt or have no user
 94          * context, we must not take the fault..
 95          */
 96         if (faulthandler_disabled() || !mm)
 97                 goto no_context;
 98 
 99         if (user_mode(regs))
100                 flags |= FAULT_FLAG_USER;
101 retry:
102         down_read(&mm->mmap_sem);
103         vma = find_vma(mm, address);
104         if (!vma)
105                 goto bad_area;
106         if (vma->vm_start <= address)
107                 goto good_area;
108         if (!(vma->vm_flags & VM_GROWSDOWN))
109                 goto bad_area;
110         if (expand_stack(vma, address))
111                 goto bad_area;
112 
113         /*
114          * Ok, we have a good vm_area for this memory access, so
115          * we can handle it..
116          */
117 good_area:
118         info.si_code = SEGV_ACCERR;
119 
120         /* Handle protection violation, execute on heap or stack */
121 
122         if ((regs->ecr_vec == ECR_V_PROTV) &&
123             (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
124                 goto bad_area;
125 
126         if (write) {
127                 if (!(vma->vm_flags & VM_WRITE))
128                         goto bad_area;
129                 flags |= FAULT_FLAG_WRITE;
130         } else {
131                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
132                         goto bad_area;
133         }
134 
135         /*
136          * If for any reason at all we couldn't handle the fault,
137          * make sure we exit gracefully rather than endlessly redo
138          * the fault.
139          */
140         fault = handle_mm_fault(vma, address, flags);
141 
142         /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
143         if (unlikely(fatal_signal_pending(current))) {
144                 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
145                         up_read(&mm->mmap_sem);
146                 if (user_mode(regs))
147                         return;
148         }
149 
150         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
151 
152         if (likely(!(fault & VM_FAULT_ERROR))) {
153                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
154                         /* To avoid updating stats twice for retry case */
155                         if (fault & VM_FAULT_MAJOR) {
156                                 tsk->maj_flt++;
157                                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
158                                               regs, address);
159                         } else {
160                                 tsk->min_flt++;
161                                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
162                                               regs, address);
163                         }
164 
165                         if (fault & VM_FAULT_RETRY) {
166                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
167                                 flags |= FAULT_FLAG_TRIED;
168                                 goto retry;
169                         }
170                 }
171 
172                 /* Fault Handled Gracefully */
173                 up_read(&mm->mmap_sem);
174                 return;
175         }
176 
177         if (fault & VM_FAULT_OOM)
178                 goto out_of_memory;
179         else if (fault & VM_FAULT_SIGSEGV)
180                 goto bad_area;
181         else if (fault & VM_FAULT_SIGBUS)
182                 goto do_sigbus;
183 
184         /* no man's land */
185         BUG();
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         up_read(&mm->mmap_sem);
193 
194 bad_area_nosemaphore:
195         /* User mode accesses just cause a SIGSEGV */
196         if (user_mode(regs)) {
197                 tsk->thread.fault_address = address;
198                 info.si_signo = SIGSEGV;
199                 info.si_errno = 0;
200                 /* info.si_code has been set above */
201                 info.si_addr = (void __user *)address;
202                 force_sig_info(SIGSEGV, &info, tsk);
203                 return;
204         }
205 
206 no_context:
207         /* Are we prepared to handle this kernel fault?
208          *
209          * (The kernel has valid exception-points in the source
210          *  when it acesses user-memory. When it fails in one
211          *  of those points, we find it in a table and do a jump
212          *  to some fixup code that loads an appropriate error
213          *  code)
214          */
215         if (fixup_exception(regs))
216                 return;
217 
218         die("Oops", regs, address);
219 
220 out_of_memory:
221         up_read(&mm->mmap_sem);
222 
223         if (user_mode(regs)) {
224                 pagefault_out_of_memory();
225                 return;
226         }
227 
228         goto no_context;
229 
230 do_sigbus:
231         up_read(&mm->mmap_sem);
232 
233         if (!user_mode(regs))
234                 goto no_context;
235 
236         tsk->thread.fault_address = address;
237         info.si_signo = SIGBUS;
238         info.si_errno = 0;
239         info.si_code = BUS_ADRERR;
240         info.si_addr = (void __user *)address;
241         force_sig_info(SIGBUS, &info, tsk);
242 }
243 

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