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Linux/arch/nios2/mm/fault.c

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  1 /*
  2  * Copyright (C) 2009 Wind River Systems Inc
  3  *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
  4  *
  5  * based on arch/mips/mm/fault.c which is:
  6  *
  7  * Copyright (C) 1995-2000 Ralf Baechle
  8  *
  9  * This file is subject to the terms and conditions of the GNU General Public
 10  * License.  See the file "COPYING" in the main directory of this archive
 11  * for more details.
 12  */
 13 
 14 #include <linux/signal.h>
 15 #include <linux/sched.h>
 16 #include <linux/sched/debug.h>
 17 #include <linux/interrupt.h>
 18 #include <linux/kernel.h>
 19 #include <linux/errno.h>
 20 #include <linux/string.h>
 21 #include <linux/types.h>
 22 #include <linux/ptrace.h>
 23 #include <linux/mman.h>
 24 #include <linux/mm.h>
 25 #include <linux/extable.h>
 26 #include <linux/uaccess.h>
 27 
 28 #include <asm/mmu_context.h>
 29 #include <asm/traps.h>
 30 
 31 #define EXC_SUPERV_INSN_ACCESS  9  /* Supervisor only instruction address */
 32 #define EXC_SUPERV_DATA_ACCESS  11 /* Supervisor only data address */
 33 #define EXC_X_PROTECTION_FAULT  13 /* TLB permission violation (x) */
 34 #define EXC_R_PROTECTION_FAULT  14 /* TLB permission violation (r) */
 35 #define EXC_W_PROTECTION_FAULT  15 /* TLB permission violation (w) */
 36 
 37 /*
 38  * This routine handles page faults.  It determines the address,
 39  * and the problem, and then passes it off to one of the appropriate
 40  * routines.
 41  */
 42 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 43                                 unsigned long address)
 44 {
 45         struct vm_area_struct *vma = NULL;
 46         struct task_struct *tsk = current;
 47         struct mm_struct *mm = tsk->mm;
 48         int code = SEGV_MAPERR;
 49         vm_fault_t fault;
 50         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 51 
 52         cause >>= 2;
 53 
 54         /* Restart the instruction */
 55         regs->ea -= 4;
 56 
 57         /*
 58          * We fault-in kernel-space virtual memory on-demand. The
 59          * 'reference' page table is init_mm.pgd.
 60          *
 61          * NOTE! We MUST NOT take any locks for this case. We may
 62          * be in an interrupt or a critical region, and should
 63          * only copy the information from the master page table,
 64          * nothing more.
 65          */
 66         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
 67                 if (user_mode(regs))
 68                         goto bad_area_nosemaphore;
 69                 else
 70                         goto vmalloc_fault;
 71         }
 72 
 73         if (unlikely(address >= TASK_SIZE))
 74                 goto bad_area_nosemaphore;
 75 
 76         /*
 77          * If we're in an interrupt or have no user
 78          * context, we must not take the fault..
 79          */
 80         if (faulthandler_disabled() || !mm)
 81                 goto bad_area_nosemaphore;
 82 
 83         if (user_mode(regs))
 84                 flags |= FAULT_FLAG_USER;
 85 
 86         if (!down_read_trylock(&mm->mmap_sem)) {
 87                 if (!user_mode(regs) && !search_exception_tables(regs->ea))
 88                         goto bad_area_nosemaphore;
 89 retry:
 90                 down_read(&mm->mmap_sem);
 91         }
 92 
 93         vma = find_vma(mm, address);
 94         if (!vma)
 95                 goto bad_area;
 96         if (vma->vm_start <= address)
 97                 goto good_area;
 98         if (!(vma->vm_flags & VM_GROWSDOWN))
 99                 goto bad_area;
100         if (expand_stack(vma, address))
101                 goto bad_area;
102 /*
103  * Ok, we have a good vm_area for this memory access, so
104  * we can handle it..
105  */
106 good_area:
107         code = SEGV_ACCERR;
108 
109         switch (cause) {
110         case EXC_SUPERV_INSN_ACCESS:
111                 goto bad_area;
112         case EXC_SUPERV_DATA_ACCESS:
113                 goto bad_area;
114         case EXC_X_PROTECTION_FAULT:
115                 if (!(vma->vm_flags & VM_EXEC))
116                         goto bad_area;
117                 break;
118         case EXC_R_PROTECTION_FAULT:
119                 if (!(vma->vm_flags & VM_READ))
120                         goto bad_area;
121                 break;
122         case EXC_W_PROTECTION_FAULT:
123                 if (!(vma->vm_flags & VM_WRITE))
124                         goto bad_area;
125                 flags = FAULT_FLAG_WRITE;
126                 break;
127         }
128 
129         /*
130          * If for any reason at all we couldn't handle the fault,
131          * make sure we exit gracefully rather than endlessly redo
132          * the fault.
133          */
134         fault = handle_mm_fault(vma, address, flags);
135 
136         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
137                 return;
138 
139         if (unlikely(fault & VM_FAULT_ERROR)) {
140                 if (fault & VM_FAULT_OOM)
141                         goto out_of_memory;
142                 else if (fault & VM_FAULT_SIGSEGV)
143                         goto bad_area;
144                 else if (fault & VM_FAULT_SIGBUS)
145                         goto do_sigbus;
146                 BUG();
147         }
148 
149         /*
150          * Major/minor page fault accounting is only done on the
151          * initial attempt. If we go through a retry, it is extremely
152          * likely that the page will be found in page cache at that point.
153          */
154         if (flags & FAULT_FLAG_ALLOW_RETRY) {
155                 if (fault & VM_FAULT_MAJOR)
156                         current->maj_flt++;
157                 else
158                         current->min_flt++;
159                 if (fault & VM_FAULT_RETRY) {
160                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
161                          * of starvation. */
162                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
163                         flags |= FAULT_FLAG_TRIED;
164 
165                         /*
166                          * No need to up_read(&mm->mmap_sem) as we would
167                          * have already released it in __lock_page_or_retry
168                          * in mm/filemap.c.
169                          */
170 
171                         goto retry;
172                 }
173         }
174 
175         up_read(&mm->mmap_sem);
176         return;
177 
178 /*
179  * Something tried to access memory that isn't in our memory map..
180  * Fix it, but check if it's kernel or user first..
181  */
182 bad_area:
183         up_read(&mm->mmap_sem);
184 
185 bad_area_nosemaphore:
186         /* User mode accesses just cause a SIGSEGV */
187         if (user_mode(regs)) {
188                 if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
189                         pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
190                                 "cause %ld\n", current->comm, SIGSEGV, address, cause);
191                         show_regs(regs);
192                 }
193                 _exception(SIGSEGV, regs, code, address);
194                 return;
195         }
196 
197 no_context:
198         /* Are we prepared to handle this kernel fault? */
199         if (fixup_exception(regs))
200                 return;
201 
202         /*
203          * Oops. The kernel tried to access some bad page. We'll have to
204          * terminate things with extreme prejudice.
205          */
206         bust_spinlocks(1);
207 
208         pr_alert("Unable to handle kernel %s at virtual address %08lx",
209                 address < PAGE_SIZE ? "NULL pointer dereference" :
210                 "paging request", address);
211         pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
212                 cause);
213         panic("Oops");
214         return;
215 
216 /*
217  * We ran out of memory, or some other thing happened to us that made
218  * us unable to handle the page fault gracefully.
219  */
220 out_of_memory:
221         up_read(&mm->mmap_sem);
222         if (!user_mode(regs))
223                 goto no_context;
224         pagefault_out_of_memory();
225         return;
226 
227 do_sigbus:
228         up_read(&mm->mmap_sem);
229 
230         /* Kernel mode? Handle exceptions or die */
231         if (!user_mode(regs))
232                 goto no_context;
233 
234         _exception(SIGBUS, regs, BUS_ADRERR, address);
235         return;
236 
237 vmalloc_fault:
238         {
239                 /*
240                  * Synchronize this task's top level page-table
241                  * with the 'reference' page table.
242                  *
243                  * Do _not_ use "tsk" here. We might be inside
244                  * an interrupt in the middle of a task switch..
245                  */
246                 int offset = pgd_index(address);
247                 pgd_t *pgd, *pgd_k;
248                 pud_t *pud, *pud_k;
249                 pmd_t *pmd, *pmd_k;
250                 pte_t *pte_k;
251 
252                 pgd = pgd_current + offset;
253                 pgd_k = init_mm.pgd + offset;
254 
255                 if (!pgd_present(*pgd_k))
256                         goto no_context;
257                 set_pgd(pgd, *pgd_k);
258 
259                 pud = pud_offset(pgd, address);
260                 pud_k = pud_offset(pgd_k, address);
261                 if (!pud_present(*pud_k))
262                         goto no_context;
263                 pmd = pmd_offset(pud, address);
264                 pmd_k = pmd_offset(pud_k, address);
265                 if (!pmd_present(*pmd_k))
266                         goto no_context;
267                 set_pmd(pmd, *pmd_k);
268 
269                 pte_k = pte_offset_kernel(pmd_k, address);
270                 if (!pte_present(*pte_k))
271                         goto no_context;
272 
273                 flush_tlb_kernel_page(address);
274                 return;
275         }
276 }
277 

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