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Linux/arch/metag/mm/fault.c

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  1 /*
  2  *  Meta page fault handling.
  3  *
  4  *  Copyright (C) 2005-2012 Imagination Technologies Ltd.
  5  */
  6 
  7 #include <linux/mman.h>
  8 #include <linux/mm.h>
  9 #include <linux/kernel.h>
 10 #include <linux/ptrace.h>
 11 #include <linux/interrupt.h>
 12 #include <linux/uaccess.h>
 13 
 14 #include <asm/tlbflush.h>
 15 #include <asm/mmu.h>
 16 #include <asm/traps.h>
 17 
 18 /* Clear any pending catch buffer state. */
 19 static void clear_cbuf_entry(struct pt_regs *regs, unsigned long addr,
 20                              unsigned int trapno)
 21 {
 22         PTBICTXEXTCB0 cbuf = regs->extcb0;
 23 
 24         switch (trapno) {
 25                 /* Instruction fetch faults leave no catch buffer state. */
 26         case TBIXXF_SIGNUM_IGF:
 27         case TBIXXF_SIGNUM_IPF:
 28                 return;
 29         default:
 30                 if (cbuf[0].CBAddr == addr) {
 31                         cbuf[0].CBAddr = 0;
 32                         cbuf[0].CBFlags &= ~TXCATCH0_FAULT_BITS;
 33 
 34                         /* And, as this is the ONLY catch entry, we
 35                          * need to clear the cbuf bit from the context!
 36                          */
 37                         regs->ctx.SaveMask &= ~(TBICTX_CBUF_BIT |
 38                                                 TBICTX_XCBF_BIT);
 39 
 40                         return;
 41                 }
 42                 pr_err("Failed to clear cbuf entry!\n");
 43         }
 44 }
 45 
 46 int show_unhandled_signals = 1;
 47 
 48 int do_page_fault(struct pt_regs *regs, unsigned long address,
 49                   unsigned int write_access, unsigned int trapno)
 50 {
 51         struct task_struct *tsk;
 52         struct mm_struct *mm;
 53         struct vm_area_struct *vma, *prev_vma;
 54         siginfo_t info;
 55         int fault;
 56         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 57 
 58         tsk = current;
 59 
 60         if ((address >= VMALLOC_START) && (address < VMALLOC_END)) {
 61                 /*
 62                  * Synchronize this task's top level page-table
 63                  * with the 'reference' page table.
 64                  *
 65                  * Do _not_ use "tsk" here. We might be inside
 66                  * an interrupt in the middle of a task switch..
 67                  */
 68                 int offset = pgd_index(address);
 69                 pgd_t *pgd, *pgd_k;
 70                 pud_t *pud, *pud_k;
 71                 pmd_t *pmd, *pmd_k;
 72                 pte_t *pte_k;
 73 
 74                 pgd = ((pgd_t *)mmu_get_base()) + offset;
 75                 pgd_k = swapper_pg_dir + offset;
 76 
 77                 /* This will never happen with the folded page table. */
 78                 if (!pgd_present(*pgd)) {
 79                         if (!pgd_present(*pgd_k))
 80                                 goto bad_area_nosemaphore;
 81                         set_pgd(pgd, *pgd_k);
 82                         return 0;
 83                 }
 84 
 85                 pud = pud_offset(pgd, address);
 86                 pud_k = pud_offset(pgd_k, address);
 87                 if (!pud_present(*pud_k))
 88                         goto bad_area_nosemaphore;
 89                 set_pud(pud, *pud_k);
 90 
 91                 pmd = pmd_offset(pud, address);
 92                 pmd_k = pmd_offset(pud_k, address);
 93                 if (!pmd_present(*pmd_k))
 94                         goto bad_area_nosemaphore;
 95                 set_pmd(pmd, *pmd_k);
 96 
 97                 pte_k = pte_offset_kernel(pmd_k, address);
 98                 if (!pte_present(*pte_k))
 99                         goto bad_area_nosemaphore;
100 
101                 /* May only be needed on Chorus2 */
102                 flush_tlb_all();
103                 return 0;
104         }
105 
106         mm = tsk->mm;
107 
108         if (faulthandler_disabled() || !mm)
109                 goto no_context;
110 
111         if (user_mode(regs))
112                 flags |= FAULT_FLAG_USER;
113 retry:
114         down_read(&mm->mmap_sem);
115 
116         vma = find_vma_prev(mm, address, &prev_vma);
117 
118         if (!vma || address < vma->vm_start)
119                 goto check_expansion;
120 
121 good_area:
122         if (write_access) {
123                 if (!(vma->vm_flags & VM_WRITE))
124                         goto bad_area;
125                 flags |= FAULT_FLAG_WRITE;
126         } else {
127                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
128                         goto bad_area;
129         }
130 
131         /*
132          * If for any reason at all we couldn't handle the fault,
133          * make sure we exit gracefully rather than endlessly redo
134          * the fault.
135          */
136         fault = handle_mm_fault(mm, vma, address, flags);
137 
138         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
139                 return 0;
140 
141         if (unlikely(fault & VM_FAULT_ERROR)) {
142                 if (fault & VM_FAULT_OOM)
143                         goto out_of_memory;
144                 else if (fault & VM_FAULT_SIGSEGV)
145                         goto bad_area;
146                 else if (fault & VM_FAULT_SIGBUS)
147                         goto do_sigbus;
148                 BUG();
149         }
150         if (flags & FAULT_FLAG_ALLOW_RETRY) {
151                 if (fault & VM_FAULT_MAJOR)
152                         tsk->maj_flt++;
153                 else
154                         tsk->min_flt++;
155                 if (fault & VM_FAULT_RETRY) {
156                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
157                         flags |= FAULT_FLAG_TRIED;
158 
159                         /*
160                          * No need to up_read(&mm->mmap_sem) as we would
161                          * have already released it in __lock_page_or_retry
162                          * in mm/filemap.c.
163                          */
164 
165                         goto retry;
166                 }
167         }
168 
169         up_read(&mm->mmap_sem);
170         return 0;
171 
172 check_expansion:
173         vma = prev_vma;
174         if (vma && (expand_stack(vma, address) == 0))
175                 goto good_area;
176 
177 bad_area:
178         up_read(&mm->mmap_sem);
179 
180 bad_area_nosemaphore:
181         if (user_mode(regs)) {
182                 info.si_signo = SIGSEGV;
183                 info.si_errno = 0;
184                 info.si_code = SEGV_MAPERR;
185                 info.si_addr = (__force void __user *)address;
186                 info.si_trapno = trapno;
187 
188                 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
189                     printk_ratelimit()) {
190                         pr_info("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
191                                task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
192                                tsk->comm, task_pid_nr(tsk), address,
193                                regs->ctx.CurrPC, regs->ctx.AX[0].U0,
194                                write_access, trapno, trap_name(trapno));
195                         print_vma_addr(" in ", regs->ctx.CurrPC);
196                         print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
197                         printk("\n");
198                         show_regs(regs);
199                 }
200                 force_sig_info(SIGSEGV, &info, tsk);
201                 return 1;
202         }
203         goto no_context;
204 
205 do_sigbus:
206         up_read(&mm->mmap_sem);
207 
208         /*
209          * Send a sigbus, regardless of whether we were in kernel
210          * or user mode.
211          */
212         info.si_signo = SIGBUS;
213         info.si_errno = 0;
214         info.si_code = BUS_ADRERR;
215         info.si_addr = (__force void __user *)address;
216         info.si_trapno = trapno;
217         force_sig_info(SIGBUS, &info, tsk);
218 
219         /* Kernel mode? Handle exceptions or die */
220         if (!user_mode(regs))
221                 goto no_context;
222 
223         return 1;
224 
225         /*
226          * We ran out of memory, or some other thing happened to us that made
227          * us unable to handle the page fault gracefully.
228          */
229 out_of_memory:
230         up_read(&mm->mmap_sem);
231         if (user_mode(regs)) {
232                 pagefault_out_of_memory();
233                 return 1;
234         }
235 
236 no_context:
237         /* Are we prepared to handle this kernel fault?  */
238         if (fixup_exception(regs)) {
239                 clear_cbuf_entry(regs, address, trapno);
240                 return 1;
241         }
242 
243         die("Oops", regs, (write_access << 15) | trapno, address);
244         do_exit(SIGKILL);
245 }
246 

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