traps.c

linux-2.4.29操作系统的源码

/* $Id: traps.c,v 1.1.1.1.2.5 2003/10/23 22:08:56 yoshii Exp $
 *
 *  linux/arch/sh/traps.c
 *
 *  SuperH version: Copyright (C) 1999 Niibe Yutaka
 *                  Copyright (C) 2000 Philipp Rumpf
 *                  Copyright (C) 2000 David Howells
 *                  Copyright (C) 2002 Paul Mundt
 */

/*
 * 'Traps.c' handles hardware traps and faults after we have saved some
 * state in 'entry.S'.
 */
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/spinlock.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/atomic.h>
#include <asm/processor.h>

#ifdef CONFIG_SH_KGDB
#include <asm/kgdb.h>
#define CHK_REMOTE_DEBUG(regs)                                               \
{                                                                            \
  if ((kgdb_debug_hook != (kgdb_debug_hook_t *) NULL) && (!user_mode(regs))) \
  {                                                                          \
    (*kgdb_debug_hook)(regs);                                                \
  }                                                                          \
}
#else
#define CHK_REMOTE_DEBUG(regs)
#endif

#define DO_ERROR(trapnr, signr, str, name, tsk) \
asmlinkage void do_##name(unsigned long r4, unsigned long r5, \
			  unsigned long r6, unsigned long r7, \
			  struct pt_regs regs) \
{ \
	unsigned long error_code; \
 \
	/* Check if it's a DSP instruction */ \
 	if (is_dsp_inst(&regs)) { \
		/* Enable DSP mode, and restart instruction. */ \
		regs.sr |= SR_DSP; \
		return; \
	} \
 \
	asm volatile("stc	r2_bank, %0": "=r" (error_code)); \
	sti(); \
	tsk->thread.error_code = error_code; \
	tsk->thread.trap_no = trapnr; \
        CHK_REMOTE_DEBUG(&regs); \
	force_sig(signr, tsk); \
	die_if_no_fixup(str,&regs,error_code); \
}

/*
 * These constants are for searching for possible module text
 * segments.  VMALLOC_OFFSET comes from mm/vmalloc.c; MODULE_RANGE is
 * a guess of how much space is likely to be vmalloced.
 */
#define VMALLOC_OFFSET (8*1024*1024)
#define MODULE_RANGE (8*1024*1024)

spinlock_t die_lock;

void die(const char * str, struct pt_regs * regs, long err)
{
	console_verbose();
	spin_lock_irq(&die_lock);
	printk("%s: %04lx\n", str, err & 0xffff);
	CHK_REMOTE_DEBUG(regs);
	show_regs(regs);
	spin_unlock_irq(&die_lock);
	do_exit(SIGSEGV);
}

static inline void die_if_kernel(const char * str, struct pt_regs * regs, long err)
{
	if (!user_mode(regs))
		die(str, regs, err);
}

static int handle_unaligned_notify_count = 10;

/*
 * try and fix up kernelspace address errors
 * - userspace errors just cause EFAULT to be returned, resulting in SEGV
 * - kernel/userspace interfaces cause a jump to an appropriate handler
 * - other kernel errors are bad
 * - return 0 if fixed-up, -EFAULT if non-fatal (to the kernel) fault
 */
static int die_if_no_fixup(const char * str, struct pt_regs * regs, long err)
{
	if (!user_mode(regs))
	{
		unsigned long fixup;
		fixup = search_exception_table(regs->pc);
		if (fixup) {
			regs->pc = fixup;
			return 0;
		}
		die(str, regs, err);
	}
	return -EFAULT;
}

/*
 * handle an instruction that does an unaligned memory access by emulating the
 * desired behaviour
 * - note that PC _may not_ point to the faulting instruction
 *   (if that instruction is in a branch delay slot)
 * - return 0 if emulation okay, -EFAULT on existential error
 */
static int handle_unaligned_ins(u16 instruction, struct pt_regs *regs)
{
	int ret, index, count;
	unsigned long *rm, *rn;
	unsigned char *src, *dst;

	index = (instruction>>8)&15;	/* 0x0F00 */
	rn = &regs->regs[index];

	index = (instruction>>4)&15;	/* 0x00F0 */
	rm = &regs->regs[index];

	count = 1<<(instruction&3);

	ret = -EFAULT;
	switch (instruction>>12) {
	case 0: /* mov.[bwl] to/from memory via r0+rn */
		if (instruction & 8) {
			/* from memory */
			src = (unsigned char*) *rm;
			src += regs->regs[0];
			dst = (unsigned char*) rn;
			*(unsigned long*)dst = 0;

#ifdef __LITTLE_ENDIAN__
			if (copy_from_user(dst, src, count))
				goto fetch_fault;

			if ((count == 2) && dst[1] & 0x80) {
				dst[2] = 0xff;
				dst[3] = 0xff;
			}
#else
			dst += 4-count;

			if (__copy_user(dst, src, count))
				goto fetch_fault;

			if ((count == 2) && dst[2] & 0x80) {
				dst[0] = 0xff;
				dst[1] = 0xff;
			}
#endif
		} else {
			/* to memory */
			src = (unsigned char*) rm;
#if !defined(__LITTLE_ENDIAN__)
			src += 4-count;
#endif
			dst = (unsigned char*) *rn;
			dst += regs->regs[0];

			if (copy_to_user(dst, src, count))
				goto fetch_fault;
		}
		ret = 0;
		break;

	case 1: /* mov.l Rm,@(disp,Rn) */
		src = (unsigned char*) rm;
		dst = (unsigned char*) *rn;
		dst += (instruction&0x000F)<<2;

		if (copy_to_user(dst,src,4))
			goto fetch_fault;
		ret = 0;
 		break;

	case 2: /* mov.[bwl] to memory, possibly with pre-decrement */
		if (instruction & 4)
			*rn -= count;
		src = (unsigned char*) rm;
		dst = (unsigned char*) *rn;
#if !defined(__LITTLE_ENDIAN__)
		src += 4-count;
#endif
		if (copy_to_user(dst, src, count))
			goto fetch_fault;
		ret = 0;
		break;

	case 5: /* mov.l @(disp,Rm),Rn */
		src = (unsigned char*) *rm;
		src += (instruction&0x000F)<<2;
		dst = (unsigned char*) rn;
		*(unsigned long*)dst = 0;

		if (copy_from_user(dst,src,4))
			goto fetch_fault;
		ret = 0;
 		break;

	case 6:	/* mov.[bwl] from memory, possibly with post-increment */
		src = (unsigned char*) *rm;
		if (instruction & 4)
			*rm += count;
		dst = (unsigned char*) rn;
		*(unsigned long*)dst = 0;
		
#ifdef __LITTLE_ENDIAN__
		if (copy_from_user(dst, src, count))
			goto fetch_fault;

		if ((count == 2) && dst[1] & 0x80) {
			dst[2] = 0xff;
			dst[3] = 0xff;
		}
#else
		dst += 4-count;
		
		if (copy_from_user(dst, src, count))
			goto fetch_fault;

		if ((count == 2) && dst[2] & 0x80) {
			dst[0] = 0xff;
			dst[1] = 0xff;
		}
#endif
		ret = 0;
		break;

	case 8:
		switch ((instruction&0xFF00)>>8) {
		case 0x81: /* mov.w R0,@(disp,Rn) */
			src = (unsigned char*) &regs->regs[0];
#if !defined(__LITTLE_ENDIAN__)
			src += 2;
#endif
			dst = (unsigned char*) *rm; /* called Rn in the spec */
			dst += (instruction&0x000F)<<1;

			if (copy_to_user(dst, src, 2))
				goto fetch_fault;
			ret = 0;
			break;

		case 0x85: /* mov.w @(disp,Rm),R0 */
			src = (unsigned char*) *rm;
			src += (instruction&0x000F)<<1;
			dst = (unsigned char*) &regs->regs[0];
			*(unsigned long*)dst = 0;

#if !defined(__LITTLE_ENDIAN__)
			dst += 2;
#endif

			if (copy_from_user(dst, src, 2))
				goto fetch_fault;

#ifdef __LITTLE_ENDIAN__
			if (dst[1] & 0x80) {
				dst[2] = 0xff;
				dst[3] = 0xff;
			}
#else
			if (dst[2] & 0x80) {
				dst[0] = 0xff;
				dst[1] = 0xff;
			}
#endif
			ret = 0;
			break;
		}
		break;
	}
	return ret;

 fetch_fault:
	/* Argh. Address not only misaligned but also non-existent.
	 * Raise an EFAULT and see if it's trapped
	 */
	return die_if_no_fixup("Fault in unaligned fixup", regs, 0);
}

/*
 * emulate the instruction in the delay slot
 * - fetches the instruction from PC+2
 */
static inline int handle_unaligned_delayslot(struct pt_regs *regs)
{
	u16 instruction;

	if (copy_from_user(&instruction, (u16 *)(regs->pc+2), 2)) {
		/* the instruction-fetch faulted */
		if (user_mode(regs))
			return -EFAULT;

		/* kernel */
		die("delay-slot-insn faulting in handle_unaligned_delayslot", regs, 0);
	}

	return handle_unaligned_ins(instruction,regs);
}

/*
 * handle an instruction that does an unaligned memory access
 * - have to be careful of branch delay-slot instructions that fault
 *  SH3:
 *   - if the branch would be taken PC points to the branch
 *   - if the branch would not be taken, PC points to delay-slot