traps.c

linux-2.4.29操作系统的源码

 *  SH4:
 *   - PC always points to delayed branch
 * - return 0 if handled, -EFAULT if failed (may not return if in kernel)
 */

/* Macros to determine offset from current PC for branch instructions */
/* Explicit type coercion is used to force sign extension where needed */
#define SH_PC_8BIT_OFFSET(instr) ((((signed char)(instr))*2) + 4)
#define SH_PC_12BIT_OFFSET(instr) ((((signed short)(instr<<4))>>3) + 4)

static int handle_unaligned_access(u16 instruction, struct pt_regs *regs)
{
	u_int rm;
	int ret, index;

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

	/* shout about the first ten userspace fixups */
	if (user_mode(regs) && handle_unaligned_notify_count>0) {
		handle_unaligned_notify_count--;

		printk("Fixing up unaligned userspace access in \"%s\" pid=%d pc=0x%p ins=0x%04hx\n",
		       current->comm,current->pid,(u16*)regs->pc,instruction);
	}

	ret = -EFAULT;
	switch (instruction&0xF000) {
	case 0x0000:
		if (instruction==0x000B) {
			/* rts */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0)
				regs->pc = regs->pr;
		}
		else if ((instruction&0x00FF)==0x0023) {
			/* braf @Rm */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0)
				regs->pc += rm + 4;
		}
		else if ((instruction&0x00FF)==0x0003) {
			/* bsrf @Rm */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0) {
				regs->pr = regs->pc + 4;
				regs->pc += rm + 4;
			}
		}
		else {
			/* mov.[bwl] to/from memory via r0+rn */
			goto simple;
		}
		break;

	case 0x1000: /* mov.l Rm,@(disp,Rn) */
		goto simple;

	case 0x2000: /* mov.[bwl] to memory, possibly with pre-decrement */
		goto simple;

	case 0x4000:
		if ((instruction&0x00FF)==0x002B) {
			/* jmp @Rm */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0)
				regs->pc = rm;
		}
		else if ((instruction&0x00FF)==0x000B) {
			/* jsr @Rm */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0) {
				regs->pr = regs->pc + 4;
				regs->pc = rm;
			}
		}
		else {
			/* mov.[bwl] to/from memory via r0+rn */
			goto simple;
		}
		break;

	case 0x5000: /* mov.l @(disp,Rm),Rn */
		goto simple;

	case 0x6000: /* mov.[bwl] from memory, possibly with post-increment */
		goto simple;

	case 0x8000: /* bf lab, bf/s lab, bt lab, bt/s lab */
		switch (instruction&0x0F00) {
		case 0x0100: /* mov.w R0,@(disp,Rm) */
			goto simple;
		case 0x0500: /* mov.w @(disp,Rm),R0 */
			goto simple;
		case 0x0B00: /* bf   lab - no delayslot*/
			break;
		case 0x0F00: /* bf/s lab */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0) {
#if defined(__SH4__)
				if ((regs->sr & 0x00000001) != 0)
					regs->pc += 4; /* next after slot */
				else
#endif
					regs->pc += SH_PC_8BIT_OFFSET(instruction);
			}
			break;
		case 0x0900: /* bt   lab - no delayslot */
			break;
		case 0x0D00: /* bt/s lab */
			ret = handle_unaligned_delayslot(regs);
			if (ret==0) {
#if defined(__SH4__)
				if ((regs->sr & 0x00000001) == 0)
					regs->pc += 4; /* next after slot */
				else
#endif
					regs->pc += SH_PC_8BIT_OFFSET(instruction);
			}
			break;
		}
		break;

	case 0xA000: /* bra label */
		ret = handle_unaligned_delayslot(regs);
		if (ret==0)
			regs->pc += SH_PC_12BIT_OFFSET(instruction);
		break;

	case 0xB000: /* bsr label */
		ret = handle_unaligned_delayslot(regs);
		if (ret==0) {
			regs->pr = regs->pc + 4;
			regs->pc += SH_PC_12BIT_OFFSET(instruction);
		}
		break;
	}
	return ret;

	/* handle non-delay-slot instruction */
 simple:
	ret = handle_unaligned_ins(instruction,regs);
	if (ret==0)
		regs->pc += 2;
	return ret;
}

/*
 * Handle various address error exceptions
 */
asmlinkage void do_address_error(struct pt_regs *regs, 
				 unsigned long writeaccess,
				 unsigned long address)
{
	unsigned long error_code;
	mm_segment_t oldfs;
	u16 instruction;
	int tmp;

	asm volatile("stc       r2_bank,%0": "=r" (error_code));

	oldfs = get_fs();

	if (user_mode(regs)) {
		sti();
		current->thread.error_code = error_code;
		current->thread.trap_no = (writeaccess) ? 8 : 7;

		/* bad PC is not something we can fix */
		if (regs->pc & 1)
			goto uspace_segv;

		set_fs(USER_DS);
		if (copy_from_user(&instruction, (u16 *)(regs->pc), 2)) {
			/* Argh. Fault on the instruction itself.
			   This should never happen non-SMP
			*/
			set_fs(oldfs);
			goto uspace_segv;
		}

		tmp = handle_unaligned_access(instruction, regs);
		set_fs(oldfs);

		if (tmp==0)
			return; /* sorted */

	uspace_segv:
		printk(KERN_NOTICE "Killing process \"%s\" due to unaligned access\n", current->comm);
		force_sig(SIGSEGV, current);
	} else {
		if (regs->pc & 1)
			die("unaligned program counter", regs, error_code);

		set_fs(KERNEL_DS);
		if (copy_from_user(&instruction, (u16 *)(regs->pc), 2)) {
			/* Argh. Fault on the instruction itself.
			   This should never happen non-SMP
			*/
			set_fs(oldfs);
			die("insn faulting in do_address_error", regs, 0);
		}

		handle_unaligned_access(instruction, regs);
		set_fs(oldfs);
	}
}

#ifdef CONFIG_SH_DSP
/*
 *	SH-DSP support [e-mail].
 */
int is_dsp_inst(struct pt_regs *regs)
{
	unsigned short inst;

	get_user(inst, ((unsigned short *) regs->pc));

	inst &= 0xf000;

	/* Check for any type of DSP or support instruction */
	if ((inst == 0xf000) || (inst == 0x4000))
		return 1;

	return 0;
}
#else
#define is_dsp_inst(regs)	(0)
#endif /* CONFIG_SH_DSP */

DO_ERROR(12, SIGILL,  "reserved instruction", reserved_inst, current)
DO_ERROR(13, SIGILL,  "illegal slot instruction", illegal_slot_inst, current)

asmlinkage void do_exception_error(unsigned long r4, unsigned long r5,
				   unsigned long r6, unsigned long r7,
				   struct pt_regs regs)
{
	long ex;
	asm volatile("stc	r2_bank, %0" : "=r" (ex));
	die_if_kernel("exception", &regs, ex);
}

#if defined(CONFIG_SH_STANDARD_BIOS)
void *gdb_vbr_vector;
#endif

void __init trap_init(void)
{
	extern void *vbr_base;
	extern void *exception_handling_table[14];

	exception_handling_table[12] = (void *)do_reserved_inst;
	exception_handling_table[13] = (void *)do_illegal_slot_inst;

#if defined(CONFIG_SH_STANDARD_BIOS)
    	/*
	 * Read the old value of the VBR register to initialise
	 * the vector through which debug and BIOS traps are
	 * delegated by the Linux trap handler.
	 */
	{
	    register unsigned long vbr;
	    asm volatile("stc vbr, %0" : "=r" (vbr));
	    gdb_vbr_vector = (void *)(vbr + 0x100);
	    printk("Setting GDB trap vector to 0x%08lx\n",
	    	(unsigned long)gdb_vbr_vector);
	}
#endif

	/* NOTE: The VBR value should be at P1
	   (or P2, virtural "fixed" address space).
	   It's definitely should not in physical address.  */

	asm volatile("ldc	%0, vbr"
		     : /* no output */
		     : "r" (&vbr_base)
		     : "memory");
}

void show_task(unsigned long *sp)
{
	unsigned long *stack, addr;
	unsigned long module_start = VMALLOC_START;
	unsigned long module_end = VMALLOC_END;
	extern long _text, _etext;
	int i = 1;

	if (!sp) {
		__asm__ __volatile__ (
			"mov r15, %0\n\t"
			"stc r7_bank, %1\n\t"
			: "=r" (module_start),
			  "=r" (module_end)
		);
		
		sp = (unsigned long *)module_start;
	}

	stack = sp;

	printk("\nCall trace: ");

	while (((long)stack & (THREAD_SIZE - 1))) {
		if (__get_user(addr, stack)) {
			printk("Failing address 0x%lx\n", *stack);
			break;
		}
		stack++;

		if (((addr >= (unsigned long)&_text) &&
		     (addr <= (unsigned long)&_etext)) ||
		    ((addr >= module_start) && (addr <= module_end))) {
			if (i && ((i % 8) == 0))
				printk("\n       ");

			printk("[<%08lx>] ", addr);
			i++;
		}
	}

	printk("\n");
}

void show_trace_task(struct task_struct *tsk)
{
	show_task((unsigned long *)tsk->thread.sp);
}