arch/arm26/mm/fault.c

   1 /*
   2  *  linux/arch/arm26/mm/fault.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *  Modifications for ARM processor (c) 1995-2001 Russell King
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/config.h>
  12 #include <linux/signal.h>
  13 #include <linux/sched.h>
  14 #include <linux/kernel.h>
  15 #include <linux/errno.h>
  16 #include <linux/string.h>
  17 #include <linux/types.h>
  18 #include <linux/ptrace.h>
  19 #include <linux/mman.h>
  20 #include <linux/mm.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/proc_fs.h>
  23 #include <linux/init.h>
  24
  25 #include <asm/system.h>
  26 #include <asm/pgtable.h>
  27 #include <asm/uaccess.h> //FIXME this header may be bogusly included
  28
  29 #include "fault.h"
  30
  31 #define FAULT_CODE_LDRSTRPOST   0x80
  32 #define FAULT_CODE_LDRSTRPRE    0x40
  33 #define FAULT_CODE_LDRSTRREG    0x20
  34 #define FAULT_CODE_LDMSTM       0x10
  35 #define FAULT_CODE_LDCSTC       0x08
  36 #define FAULT_CODE_PREFETCH     0x04
  37 #define FAULT_CODE_WRITE        0x02
  38 #define FAULT_CODE_FORCECOW     0x01
  39
  40 #define DO_COW(m)               ((m) & (FAULT_CODE_WRITE|FAULT_CODE_FORCECOW))
  41 #define READ_FAULT(m)           (!((m) & FAULT_CODE_WRITE))
  42 #define DEBUG
  43 /*
  44  * This is useful to dump out the page tables associated with
  45  * 'addr' in mm 'mm'.
  46  */
  47 void show_pte(struct mm_struct *mm, unsigned long addr)
  48 {
  49         pgd_t *pgd;
  50
  51         if (!mm)
  52                 mm = &init_mm;
  53
  54         printk(KERN_ALERT "pgd = %p\n", mm->pgd);
  55         pgd = pgd_offset(mm, addr);
  56         printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
  57
  58         do {
  59                 pmd_t *pmd;
  60                 pte_t *pte;
  61
  62                 pmd = pmd_offset(pgd, addr);
  63
  64                 if (pmd_none(*pmd))
  65                         break;
  66
  67                 if (pmd_bad(*pmd)) {
  68                         printk("(bad)");
  69                         break;
  70                 }
  71
  72                 /* We must not map this if we have highmem enabled */
  73                 /* FIXME */
  74                 pte = pte_offset_map(pmd, addr);
  75                 printk(", *pte=%08lx", pte_val(*pte));
  76                 pte_unmap(pte);
  77         } while(0);
  78
  79         printk("\n");
  80 }
  81
  82 /*
  83  * Oops.  The kernel tried to access some page that wasn't present.
  84  */
  85 static void
  86 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
  87                   struct pt_regs *regs)
  88 {
  89         /*
  90          * Are we prepared to handle this kernel fault?
  91          */
  92         if (fixup_exception(regs))
  93                 return;
  94
  95         /*
  96          * No handler, we'll have to terminate things with extreme prejudice.
  97          */
  98         bust_spinlocks(1);
  99         printk(KERN_ALERT
 100                 "Unable to handle kernel %s at virtual address %08lx\n",
 101                 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 102                 "paging request", addr);
 103
 104         show_pte(mm, addr);
 105         die("Oops", regs, fsr);
 106         bust_spinlocks(0);
 107         do_exit(SIGKILL);
 108 }
 109
 110 /*
 111  * Something tried to access memory that isn't in our memory map..
 112  * User mode accesses just cause a SIGSEGV
 113  */
 114 static void
 115 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 116                 unsigned int fsr, int code, struct pt_regs *regs)
 117 {
 118         struct siginfo si;
 119
 120 #ifdef CONFIG_DEBUG_USER
 121         printk("%s: unhandled page fault at 0x%08lx, code 0x%03x\n",
 122                tsk->comm, addr, fsr);
 123         show_pte(tsk->mm, addr);
 124         show_regs(regs);
 125         //dump_backtrace(regs, tsk); // FIXME ARM32 dropped this - why?
 126         while(1); //FIXME - hack to stop debug going nutso
 127 #endif
 128
 129         tsk->thread.address = addr;
 130         tsk->thread.error_code = fsr;
 131         tsk->thread.trap_no = 14;
 132         si.si_signo = SIGSEGV;
 133         si.si_errno = 0;
 134         si.si_code = code;
 135         si.si_addr = (void *)addr;
 136         force_sig_info(SIGSEGV, &si, tsk);
 137 }
 138
 139 static int
 140 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 141                 struct task_struct *tsk)
 142 {
 143         struct vm_area_struct *vma;
 144         int fault, mask;
 145
 146         vma = find_vma(mm, addr);
 147         fault = -2; /* bad map area */
 148         if (!vma)
 149                 goto out;
 150         if (vma->vm_start > addr)
 151                 goto check_stack;
 152
 153         /*
 154          * Ok, we have a good vm_area for this
 155          * memory access, so we can handle it.
 156          */
 157 good_area:
 158         if (READ_FAULT(fsr)) /* read? */
 159                 mask = VM_READ|VM_EXEC;
 160         else
 161                 mask = VM_WRITE;
 162
 163         fault = -1; /* bad access type */
 164         if (!(vma->vm_flags & mask))
 165                 goto out;
 166
 167         /*
 168          * If for any reason at all we couldn't handle
 169          * the fault, make sure we exit gracefully rather
 170          * than endlessly redo the fault.
 171          */
 172 survive:
 173         fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, DO_COW(fsr));
 174
 175         /*
 176          * Handle the "normal" cases first - successful and sigbus
 177          */
 178         switch (fault) {
 179         case 2:
 180                 tsk->maj_flt++;
 181                 return fault;
 182         case 1:
 183                 tsk->min_flt++;
 184         case 0:
 185                 return fault;
 186         }
 187
 188         fault = -3; /* out of memory */
 189         if (tsk->pid != 1)
 190                 goto out;
 191
 192         /*
 193          * If we are out of memory for pid1,
 194          * sleep for a while and retry
 195          */
 196         yield();
 197         goto survive;
 198
 199 check_stack:
 200         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 201                 goto good_area;
 202 out:
 203         return fault;
 204 }
 205
 206 int do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 207 {
 208         struct task_struct *tsk;
 209         struct mm_struct *mm;
 210         int fault;
 211
 212         tsk = current;
 213         mm  = tsk->mm;
 214
 215         /*
 216          * If we're in an interrupt or have no user
 217          * context, we must not take the fault..
 218          */
 219         if (in_interrupt() || !mm)
 220                 goto no_context;
 221
 222         down_read(&mm->mmap_sem);
 223         fault = __do_page_fault(mm, addr, fsr, tsk);
 224         up_read(&mm->mmap_sem);
 225
 226         /*
 227          * Handle the "normal" case first
 228          */
 229         if (fault > 0)
 230                 return 0;
 231
 232         /*
 233          * We had some memory, but were unable to
 234          * successfully fix up this page fault.
 235          */
 236         if (fault == 0){
 237                 goto do_sigbus;
 238         }
 239
 240         /*
 241          * If we are in kernel mode at this point, we
 242          * have no context to handle this fault with.
 243          * FIXME - is this test right?
 244          */
 245         if (!user_mode(regs)){
 246                 goto no_context;
 247         }
 248
 249         if (fault == -3) {
 250                 /*
 251                  * We ran out of memory, or some other thing happened to
 252                  * us that made us unable to handle the page fault gracefully.
 253                  */
 254                 printk("VM: killing process %s\n", tsk->comm);
 255                 do_exit(SIGKILL);
 256         }
 257         else{
 258                 __do_user_fault(tsk, addr, fsr, fault == -1 ? SEGV_ACCERR : SEGV_MAPERR, regs);
 259         }
 260
 261         return 0;
 262
 263
 264 /*
 265  * We ran out of memory, or some other thing happened to us that made
 266  * us unable to handle the page fault gracefully.
 267  */
 268 do_sigbus:
 269         /*
 270          * Send a sigbus, regardless of whether we were in kernel
 271          * or user mode.
 272          */
 273         tsk->thread.address = addr;  //FIXME - need other bits setting?
 274         tsk->thread.error_code = fsr;
 275         tsk->thread.trap_no = 14;
 276         force_sig(SIGBUS, tsk);
 277 #ifdef CONFIG_DEBUG_USER
 278         printk(KERN_DEBUG "%s: sigbus at 0x%08lx, pc=0x%08lx\n",
 279                 current->comm, addr, instruction_pointer(regs));
 280 #endif
 281
 282         /* Kernel mode? Handle exceptions or die */
 283         if (user_mode(regs))
 284                 return 0;
 285
 286 no_context:
 287         __do_kernel_fault(mm, addr, fsr, regs);
 288         return 0;
 289 }
 290
 291 /*
 292  * Handle a data abort.  Note that we have to handle a range of addresses
 293  * on ARM2/3 for ldm.  If both pages are zero-mapped, then we have to force
 294  * a copy-on-write.  However, on the second page, we always force COW.
 295  */
 296 asmlinkage void
 297 do_DataAbort(unsigned long min_addr, unsigned long max_addr, int mode, struct pt_regs *regs)
 298 {
 299         do_page_fault(min_addr, mode, regs);
 300
 301         if ((min_addr ^ max_addr) >> PAGE_SHIFT){
 302                do_page_fault(max_addr, mode | FAULT_CODE_FORCECOW, regs);
 303         }
 304 }
 305
 306 asmlinkage int
 307 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
 308 {
 309 #if 0
 310         if (the memc mapping for this page exists) {
 311                 printk ("Page in, but got abort (undefined instruction?)\n");
 312                 return 0;
 313         }
 314 #endif
 315         do_page_fault(addr, FAULT_CODE_PREFETCH, regs);
 316         return 1;
 317 }
 318