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traps.c

/*
 *  linux/arch/arm26/kernel/traps.c
 *
 *  Copyright (C) 1995-2002 Russell King
 *  Fragments that appear the same as linux/arch/i386/kernel/traps.c (C) Linus Torvalds
 *  Copyright (C) 2003 Ian Molton (ARM26)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  'traps.c' handles hardware exceptions after we have saved some state in
 *  'linux/arch/arm26/lib/traps.S'.  Mostly a debugging aid, but will probably
 *  kill the offending process.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/personality.h>
#include <linux/ptrace.h>
#include <linux/elf.h>
#include <linux/interrupt.h>
#include <linux/init.h>

#include <asm/atomic.h>
#include <asm/io.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <linux/mutex.h>

#include "ptrace.h"

extern void c_backtrace (unsigned long fp, int pmode);
extern void show_pte(struct mm_struct *mm, unsigned long addr);

const char *processor_modes[] = { "USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" };

static const char *handler[]= { "prefetch abort", "data abort", "address exception", "interrupt" "*bad reason*"};

/*
 * Stack pointers should always be within the kernels view of
 * physical memory.  If it is not there, then we can't dump
 * out any information relating to the stack.
 */
static int verify_stack(unsigned long sp)
{
      if (sp < PAGE_OFFSET || (sp > (unsigned long)high_memory && high_memory != 0))
            return -EFAULT;

      return 0;
}

/*
 * Dump out the contents of some memory nicely...
 */
static void dump_mem(const char *str, unsigned long bottom, unsigned long top)
{
      unsigned long p = bottom & ~31;
      mm_segment_t fs;
      int i;

      /*
       * We need to switch to kernel mode so that we can use __get_user
       * to safely read from kernel space.  Note that we now dump the
       * code first, just in case the backtrace kills us.
       */
      fs = get_fs();
      set_fs(KERNEL_DS);

      printk("%s", str);
      printk("(0x%08lx to 0x%08lx)\n", bottom, top);

      for (p = bottom & ~31; p < top;) {
            printk("%04lx: ", p & 0xffff);

            for (i = 0; i < 8; i++, p += 4) {
                  unsigned int val;

                  if (p < bottom || p >= top)
                        printk("         ");
                  else {
                        __get_user(val, (unsigned long *)p);
                        printk("%08x ", val);
                  }
            }
            printk ("\n");
      }

      set_fs(fs);
}

static void dump_instr(struct pt_regs *regs)
{
      unsigned long addr = instruction_pointer(regs);
      const int width = 8;
      mm_segment_t fs;
      int i;

      /*
       * We need to switch to kernel mode so that we can use __get_user
       * to safely read from kernel space.  Note that we now dump the
       * code first, just in case the backtrace kills us.
       */
      fs = get_fs();
      set_fs(KERNEL_DS);

      printk("Code: ");
      for (i = -4; i < 1; i++) {
            unsigned int val, bad;

            bad = __get_user(val, &((u32 *)addr)[i]);

            if (!bad)
                  printk(i == 0 ? "(%0*x) " : "%0*x ", width, val);
            else {
                  printk("bad PC value.");
                  break;
            }
      }
      printk("\n");

      set_fs(fs);
}

/*static*/ void __dump_stack(struct task_struct *tsk, unsigned long sp)
{
      dump_mem("Stack: ", sp, 8192+(unsigned long)task_stack_page(tsk));
}

void dump_stack(void)
{
#ifdef CONFIG_DEBUG_ERRORS
        __backtrace();
#endif
}

EXPORT_SYMBOL(dump_stack);

//FIXME - was a static fn
void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
      unsigned int fp;
      int ok = 1;

      printk("Backtrace: ");
      fp = regs->ARM_fp;
      if (!fp) {
            printk("no frame pointer");
            ok = 0;
      } else if (verify_stack(fp)) {
            printk("invalid frame pointer 0x%08x", fp);
            ok = 0;
      } else if (fp < (unsigned long)end_of_stack(tsk))
            printk("frame pointer underflow");
      printk("\n");

      if (ok)
            c_backtrace(fp, processor_mode(regs));
}

/* FIXME - this is probably wrong.. */
void show_stack(struct task_struct *task, unsigned long *sp) {
      dump_mem("Stack: ", (unsigned long)sp, 8192+(unsigned long)task_stack_page(task));
}

DEFINE_SPINLOCK(die_lock);

/*
 * This function is protected against re-entrancy.
 */
NORET_TYPE void die(const char *str, struct pt_regs *regs, int err)
{
      struct task_struct *tsk = current;

      console_verbose();
      spin_lock_irq(&die_lock);

      printk("Internal error: %s: %x\n", str, err);
      printk("CPU: %d\n", smp_processor_id());
      show_regs(regs);
      printk("Process %s (pid: %d, stack limit = 0x%p)\n",
            current->comm, current->pid, end_of_stack(tsk));

      if (!user_mode(regs) || in_interrupt()) {
            __dump_stack(tsk, (unsigned long)(regs + 1));
            dump_backtrace(regs, tsk);
            dump_instr(regs);
      }
while(1);
      spin_unlock_irq(&die_lock);
      do_exit(SIGSEGV);
}

void die_if_kernel(const char *str, struct pt_regs *regs, int err)
{
      if (user_mode(regs))
            return;

      die(str, regs, err);
}

static DEFINE_MUTEX(undef_mutex);
static int (*undef_hook)(struct pt_regs *);

int request_undef_hook(int (*fn)(struct pt_regs *))
{
      int ret = -EBUSY;

      mutex_lock(&undef_mutex);
      if (undef_hook == NULL) {
            undef_hook = fn;
            ret = 0;
      }
      mutex_unlock(&undef_mutex);

      return ret;
}

int release_undef_hook(int (*fn)(struct pt_regs *))
{
      int ret = -EINVAL;

      mutex_lock(&undef_mutex);
      if (undef_hook == fn) {
            undef_hook = NULL;
            ret = 0;
      }
      mutex_unlock(&undef_mutex);

      return ret;
}

static int undefined_extension(struct pt_regs *regs, unsigned int op)
{
      switch (op) {
      case 1:     /* 0xde01 / 0x?7f001f0 */
            ptrace_break(current, regs);
            return 0;
      }
      return 1;
}

asmlinkage void do_undefinstr(struct pt_regs *regs)
{
      siginfo_t info;
      void *pc;

      regs->ARM_pc -= 4;

      pc = (unsigned long *)instruction_pointer(regs); /* strip PSR */

      if (user_mode(regs)) {
            u32 instr;

            get_user(instr, (u32 *)pc);

            if ((instr & 0x0fff00ff) == 0x07f000f0 &&
                undefined_extension(regs, (instr >> 8) & 255) == 0) {
                  regs->ARM_pc += 4;
                  return;
            }
      } else {
            if (undef_hook && undef_hook(regs) == 0) {
                  regs->ARM_pc += 4;
                  return;
            }
      }

#ifdef CONFIG_DEBUG_USER
      printk(KERN_INFO "%s (%d): undefined instruction: pc=%p\n",
            current->comm, current->pid, pc);
      dump_instr(regs);
#endif

      current->thread.error_code = 0;
      current->thread.trap_no = 6;

      info.si_signo = SIGILL;
      info.si_errno = 0;
      info.si_code  = ILL_ILLOPC;
      info.si_addr  = pc;

      force_sig_info(SIGILL, &info, current);

      die_if_kernel("Oops - undefined instruction", regs, 0);
}

asmlinkage void do_excpt(unsigned long address, struct pt_regs *regs, int mode)
{
      siginfo_t info;

#ifdef CONFIG_DEBUG_USER
      printk(KERN_INFO "%s (%d): address exception: pc=%08lx\n",
            current->comm, current->pid, instruction_pointer(regs));
      dump_instr(regs);
#endif

      current->thread.error_code = 0;
      current->thread.trap_no = 11;

      info.si_signo = SIGBUS;
      info.si_errno = 0;
      info.si_code  = BUS_ADRERR;
      info.si_addr  = (void *)address;

      force_sig_info(SIGBUS, &info, current);

      die_if_kernel("Oops - address exception", regs, mode);
}

asmlinkage void do_unexp_fiq (struct pt_regs *regs)
{
#ifndef CONFIG_IGNORE_FIQ
      printk("Hmm.  Unexpected FIQ received, but trying to continue\n");
      printk("You may have a hardware problem...\n");
#endif
}

/*
 * bad_mode handles the impossible case in the vectors.  If you see one of
 * these, then it's extremely serious, and could mean you have buggy hardware.
 * It never returns, and never tries to sync.  We hope that we can at least
 * dump out some state information...
 */
asmlinkage void bad_mode(struct pt_regs *regs, int reason, int proc_mode)
{
      unsigned int vectors = vectors_base();

      console_verbose();

      printk(KERN_CRIT "Bad mode in %s handler detected: mode %s\n",
            handler[reason<5?reason:4], processor_modes[proc_mode]);

      /*
       * Dump out the vectors and stub routines.  Maybe a better solution
       * would be to dump them out only if we detect that they are corrupted.
       */
      dump_mem(KERN_CRIT "Vectors: ", vectors, vectors + 0x40);
      dump_mem(KERN_CRIT "Stubs: ", vectors + 0x200, vectors + 0x4b8);

      die("Oops", regs, 0);
      local_irq_disable();
      panic("bad mode");
}

static int bad_syscall(int n, struct pt_regs *regs)
{
      struct thread_info *thread = current_thread_info();
      siginfo_t info;

      if (current->personality != PER_LINUX && thread->exec_domain->handler) {
            thread->exec_domain->handler(n, regs);
            return regs->ARM_r0;
      }

#ifdef CONFIG_DEBUG_USER
      printk(KERN_ERR "[%d] %s: obsolete system call %08x.\n",
            current->pid, current->comm, n);
      dump_instr(regs);
#endif

      info.si_signo = SIGILL;
      info.si_errno = 0;
      info.si_code  = ILL_ILLTRP;
      info.si_addr  = (void *)instruction_pointer(regs) - 4;

      force_sig_info(SIGILL, &info, current);
      die_if_kernel("Oops", regs, n);
      return regs->ARM_r0;
}

static inline void
do_cache_op(unsigned long start, unsigned long end, int flags)
{
      struct vm_area_struct *vma;

      if (end < start)
            return;

      vma = find_vma(current->active_mm, start);
      if (vma && vma->vm_start < end) {
            if (start < vma->vm_start)
                  start = vma->vm_start;
            if (end > vma->vm_end)
                  end = vma->vm_end;
      }
}

/*
 * Handle all unrecognised system calls.
 *  0x9f0000 - 0x9fffff are some more esoteric system calls
 */
#define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
asmlinkage int arm_syscall(int no, struct pt_regs *regs)
{
      siginfo_t info;

      if ((no >> 16) != 0x9f)
            return bad_syscall(no, regs);

      switch (no & 0xffff) {
      case 0: /* branch through 0 */
            info.si_signo = SIGSEGV;
            info.si_errno = 0;
            info.si_code  = SEGV_MAPERR;
            info.si_addr  = NULL;

            force_sig_info(SIGSEGV, &info, current);

            die_if_kernel("branch through zero", regs, 0);
            return 0;

      case NR(breakpoint): /* SWI BREAK_POINT */
            ptrace_break(current, regs);
            return regs->ARM_r0;

      case NR(cacheflush):
            return 0;

      case NR(usr26):
            break;

      default:
            /* Calls 9f00xx..9f07ff are defined to return -ENOSYS
               if not implemented, rather than raising SIGILL.  This
               way the calling program can gracefully determine whether
               a feature is supported.  */
            if (no <= 0x7ff)
                  return -ENOSYS;
            break;
      }
#ifdef CONFIG_DEBUG_USER
      /*
       * experience shows that these seem to indicate that
       * something catastrophic has happened
       */
      printk("[%d] %s: arm syscall %d\n", current->pid, current->comm, no);
      dump_instr(regs);
      if (user_mode(regs)) {
            show_regs(regs);
            c_backtrace(regs->ARM_fp, processor_mode(regs));
      }
#endif
      info.si_signo = SIGILL;
      info.si_errno = 0;
      info.si_code  = ILL_ILLTRP;
      info.si_addr  = (void *)instruction_pointer(regs) - 4;

      force_sig_info(SIGILL, &info, current);
      die_if_kernel("Oops", regs, no);
      return 0;
}

void __bad_xchg(volatile void *ptr, int size)
{
      printk("xchg: bad data size: pc 0x%p, ptr 0x%p, size %d\n",
            __builtin_return_address(0), ptr, size);
      BUG();
}

/*
 * A data abort trap was taken, but we did not handle the instruction.
 * Try to abort the user program, or panic if it was the kernel.
 */
asmlinkage void
baddataabort(int code, unsigned long instr, struct pt_regs *regs)
{
      unsigned long addr = instruction_pointer(regs);
      siginfo_t info;

#ifdef CONFIG_DEBUG_USER
      printk(KERN_ERR "[%d] %s: bad data abort: code %d instr 0x%08lx\n",
            current->pid, current->comm, code, instr);
      dump_instr(regs);
      show_pte(current->mm, addr);
#endif

      info.si_signo = SIGILL;
      info.si_errno = 0;
      info.si_code  = ILL_ILLOPC;
      info.si_addr  = (void *)addr;

      force_sig_info(SIGILL, &info, current);
      die_if_kernel("unknown data abort code", regs, instr);
}

volatile void __bug(const char *file, int line, void *data)
{
      printk(KERN_CRIT"kernel BUG at %s:%d!", file, line);
      if (data)
            printk(KERN_CRIT" - extra data = %p", data);
      printk("\n");
      *(int *)0 = 0;
}

void __readwrite_bug(const char *fn)
{
      printk("%s called, but not implemented", fn);
      BUG();
}

void __pte_error(const char *file, int line, unsigned long val)
{
      printk("%s:%d: bad pte %08lx.\n", file, line, val);
}

void __pmd_error(const char *file, int line, unsigned long val)
{
      printk("%s:%d: bad pmd %08lx.\n", file, line, val);
}

void __pgd_error(const char *file, int line, unsigned long val)
{
      printk("%s:%d: bad pgd %08lx.\n", file, line, val);
}

asmlinkage void __div0(void)
{
      printk("Division by zero in kernel.\n");
      dump_stack();
}

void abort(void)
{
      BUG();

      /* if that doesn't kill us, halt */
      panic("Oops failed to kill thread");
}

void __init trap_init(void)
{
      extern void __trap_init(unsigned long);
      unsigned long base = vectors_base();

      __trap_init(base);
      if (base != 0)
            printk(KERN_DEBUG "Relocating machine vectors to 0x%08lx\n",
                  base);
}

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