root/arch/xtensa/mm/fault.c

DEFINITIONS

1. do_page_fault
2. bad_page_fault

   1 // TODO VM_EXEC flag work-around, cache aliasing
   2 /*
   3  * arch/xtensa/mm/fault.c
   4  *
   5  * This file is subject to the terms and conditions of the GNU General Public
   6  * License.  See the file "COPYING" in the main directory of this archive
   7  * for more details.
   8  *
   9  * Copyright (C) 2001 - 2010 Tensilica Inc.
  10  *
  11  * Chris Zankel <chris@zankel.net>
  12  * Joe Taylor   <joe@tensilica.com, joetylr@yahoo.com>
  13  */
  14 
  15 #include <linux/mm.h>
  16 #include <linux/extable.h>
  17 #include <linux/hardirq.h>
  18 #include <linux/perf_event.h>
  19 #include <linux/uaccess.h>
  20 #include <asm/mmu_context.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/hardirq.h>
  23 #include <asm/pgalloc.h>
  24 
  25 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
  26 void bad_page_fault(struct pt_regs*, unsigned long, int);
  27 
  28 /*
  29  * This routine handles page faults.  It determines the address,
  30  * and the problem, and then passes it off to one of the appropriate
  31  * routines.
  32  *
  33  * Note: does not handle Miss and MultiHit.
  34  */
  35 
  36 void do_page_fault(struct pt_regs *regs)
  37 {
  38         struct vm_area_struct * vma;
  39         struct mm_struct *mm = current->mm;
  40         unsigned int exccause = regs->exccause;
  41         unsigned int address = regs->excvaddr;
  42         int code;
  43 
  44         int is_write, is_exec;
  45         vm_fault_t fault;
  46         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  47 
  48         code = SEGV_MAPERR;
  49 
  50         /* We fault-in kernel-space virtual memory on-demand. The
  51          * 'reference' page table is init_mm.pgd.
  52          */
  53         if (address >= TASK_SIZE && !user_mode(regs))
  54                 goto vmalloc_fault;
  55 
  56         /* If we're in an interrupt or have no user
  57          * context, we must not take the fault..
  58          */
  59         if (faulthandler_disabled() || !mm) {
  60                 bad_page_fault(regs, address, SIGSEGV);
  61                 return;
  62         }
  63 
  64         is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  65         is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
  66                     exccause == EXCCAUSE_ITLB_MISS ||
  67                     exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  68 
  69         pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
  70                  current->comm, current->pid,
  71                  address, exccause, regs->pc,
  72                  is_write ? "w" : "", is_exec ? "x" : "");
  73 
  74         if (user_mode(regs))
  75                 flags |= FAULT_FLAG_USER;
  76 retry:
  77         down_read(&mm->mmap_sem);
  78         vma = find_vma(mm, address);
  79 
  80         if (!vma)
  81                 goto bad_area;
  82         if (vma->vm_start <= address)
  83                 goto good_area;
  84         if (!(vma->vm_flags & VM_GROWSDOWN))
  85                 goto bad_area;
  86         if (expand_stack(vma, address))
  87                 goto bad_area;
  88 
  89         /* Ok, we have a good vm_area for this memory access, so
  90          * we can handle it..
  91          */
  92 
  93 good_area:
  94         code = SEGV_ACCERR;
  95 
  96         if (is_write) {
  97                 if (!(vma->vm_flags & VM_WRITE))
  98                         goto bad_area;
  99                 flags |= FAULT_FLAG_WRITE;
 100         } else if (is_exec) {
 101                 if (!(vma->vm_flags & VM_EXEC))
 102                         goto bad_area;
 103         } else  /* Allow read even from write-only pages. */
 104                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 105                         goto bad_area;
 106 
 107         /* If for any reason at all we couldn't handle the fault,
 108          * make sure we exit gracefully rather than endlessly redo
 109          * the fault.
 110          */
 111         fault = handle_mm_fault(vma, address, flags);
 112 
 113         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 114                 return;
 115 
 116         if (unlikely(fault & VM_FAULT_ERROR)) {
 117                 if (fault & VM_FAULT_OOM)
 118                         goto out_of_memory;
 119                 else if (fault & VM_FAULT_SIGSEGV)
 120                         goto bad_area;
 121                 else if (fault & VM_FAULT_SIGBUS)
 122                         goto do_sigbus;
 123                 BUG();
 124         }
 125         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 126                 if (fault & VM_FAULT_MAJOR)
 127                         current->maj_flt++;
 128                 else
 129                         current->min_flt++;
 130                 if (fault & VM_FAULT_RETRY) {
 131                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 132                         flags |= FAULT_FLAG_TRIED;
 133 
 134                          /* No need to up_read(&mm->mmap_sem) as we would
 135                          * have already released it in __lock_page_or_retry
 136                          * in mm/filemap.c.
 137                          */
 138 
 139                         goto retry;
 140                 }
 141         }
 142 
 143         up_read(&mm->mmap_sem);
 144         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 145         if (flags & VM_FAULT_MAJOR)
 146                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
 147         else
 148                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
 149 
 150         return;
 151 
 152         /* Something tried to access memory that isn't in our memory map..
 153          * Fix it, but check if it's kernel or user first..
 154          */
 155 bad_area:
 156         up_read(&mm->mmap_sem);
 157         if (user_mode(regs)) {
 158                 current->thread.bad_vaddr = address;
 159                 current->thread.error_code = is_write;
 160                 force_sig_fault(SIGSEGV, code, (void *) address);
 161                 return;
 162         }
 163         bad_page_fault(regs, address, SIGSEGV);
 164         return;
 165 
 166 
 167         /* We ran out of memory, or some other thing happened to us that made
 168          * us unable to handle the page fault gracefully.
 169          */
 170 out_of_memory:
 171         up_read(&mm->mmap_sem);
 172         if (!user_mode(regs))
 173                 bad_page_fault(regs, address, SIGKILL);
 174         else
 175                 pagefault_out_of_memory();
 176         return;
 177 
 178 do_sigbus:
 179         up_read(&mm->mmap_sem);
 180 
 181         /* Send a sigbus, regardless of whether we were in kernel
 182          * or user mode.
 183          */
 184         current->thread.bad_vaddr = address;
 185         force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
 186 
 187         /* Kernel mode? Handle exceptions or die */
 188         if (!user_mode(regs))
 189                 bad_page_fault(regs, address, SIGBUS);
 190         return;
 191 
 192 vmalloc_fault:
 193         {
 194                 /* Synchronize this task's top level page-table
 195                  * with the 'reference' page table.
 196                  */
 197                 struct mm_struct *act_mm = current->active_mm;
 198                 int index = pgd_index(address);
 199                 pgd_t *pgd, *pgd_k;
 200                 pmd_t *pmd, *pmd_k;
 201                 pte_t *pte_k;
 202 
 203                 if (act_mm == NULL)
 204                         goto bad_page_fault;
 205 
 206                 pgd = act_mm->pgd + index;
 207                 pgd_k = init_mm.pgd + index;
 208 
 209                 if (!pgd_present(*pgd_k))
 210                         goto bad_page_fault;
 211 
 212                 pgd_val(*pgd) = pgd_val(*pgd_k);
 213 
 214                 pmd = pmd_offset(pgd, address);
 215                 pmd_k = pmd_offset(pgd_k, address);
 216                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 217                         goto bad_page_fault;
 218 
 219                 pmd_val(*pmd) = pmd_val(*pmd_k);
 220                 pte_k = pte_offset_kernel(pmd_k, address);
 221 
 222                 if (!pte_present(*pte_k))
 223                         goto bad_page_fault;
 224                 return;
 225         }
 226 bad_page_fault:
 227         bad_page_fault(regs, address, SIGKILL);
 228         return;
 229 }
 230 
 231 
 232 void
 233 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 234 {
 235         extern void die(const char*, struct pt_regs*, long);
 236         const struct exception_table_entry *entry;
 237 
 238         /* Are we prepared to handle this kernel fault?  */
 239         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 240                 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
 241                          current->comm, regs->pc, entry->fixup);
 242                 current->thread.bad_uaddr = address;
 243                 regs->pc = entry->fixup;
 244                 return;
 245         }
 246 
 247         /* Oops. The kernel tried to access some bad page. We'll have to
 248          * terminate things with extreme prejudice.
 249          */
 250         pr_alert("Unable to handle kernel paging request at virtual "
 251                  "address %08lx\n pc = %08lx, ra = %08lx\n",
 252                  address, regs->pc, regs->areg[0]);
 253         die("Oops", regs, sig);
 254         do_exit(sig);
 255 }