traps.c

一个2.4.21版本的嵌入式linux内核

		/* Run the emulator */
		sig = fpu_emulator_cop1Handler (0, regs,
			&current->thread.fpu.soft);

		/*
		 * We can't allow the emulated instruction to leave any of
		 * the cause bit set in $fcr31.
		 */
		current->thread.fpu.soft.sr &= ~FPU_CSR_ALL_X;

		/* Restore the hardware register state */
		restore_fp(current);

		/* If something went wrong, signal */
		if (sig)
		{
			/*
			 * Return EPC is not calculated in the FPU emulator,
			 * if a signal is being send. So we calculate it here.
			 */
			compute_return_epc(regs);
			force_sig(sig, current);
		}

		return;
	}

	if (compute_return_epc(regs))
		return;
	force_sig(SIGFPE, current);
}

static inline int get_insn_opcode(struct pt_regs *regs, unsigned int *opcode)
{
	unsigned long *epc;

	epc = (unsigned long *) regs->cp0_epc +
	      ((regs->cp0_cause & CAUSEF_BD) != 0);
	if (!get_user(opcode, epc))
		return 0;

	force_sig(SIGSEGV, current);
	return 1;
}

asmlinkage void do_bp(struct pt_regs *regs)
{
	unsigned int opcode, bcode;
	siginfo_t info;

	if (get_insn_opcode(regs, &opcode))
		return;

	/*
	 * There is the ancient bug in the MIPS assemblers that the break
	 * code starts left to bit 16 instead to bit 6 in the opcode.
	 * Gas is bug-compatible ...
	 */
	bcode = ((opcode >> 16) & ((1 << 20) - 1));

	/*
	 * (A short test says that IRIX 5.3 sends SIGTRAP for all break
	 * insns, even for break codes that indicate arithmetic failures.
	 * Weird ...)
	 * But should we continue the brokenness???  --macro
	 */
	switch (bcode) {
	case 6:
	case 7:
		if (bcode == 7)
			info.si_code = FPE_INTDIV;
		else
			info.si_code = FPE_INTOVF;
		info.si_signo = SIGFPE;
		info.si_errno = 0;
		info.si_addr = (void *)regs->cp0_epc;
		force_sig_info(SIGFPE, &info, current);
		break;
	default:
		force_sig(SIGTRAP, current);
	}
}

asmlinkage void do_tr(struct pt_regs *regs)
{
	unsigned int opcode, tcode = 0;
	siginfo_t info;

	if (get_insn_opcode(regs, &opcode))
		return;

        /* Immediate versions don't provide a code.  */
	if (!(opcode & OPCODE))
		tcode = ((opcode >> 6) & ((1 << 20) - 1));

	/*
	 * (A short test says that IRIX 5.3 sends SIGTRAP for all trap
	 * insns, even for trap codes that indicate arithmetic failures.
	 * Weird ...)
	 * But should we continue the brokenness???  --macro
	 */
	switch (tcode) {
	case 6:
	case 7:
		if (tcode == 7)
			info.si_code = FPE_INTDIV;
		else
			info.si_code = FPE_INTOVF;
		info.si_signo = SIGFPE;
		info.si_errno = 0;
		info.si_addr = (void *)regs->cp0_epc;
		force_sig_info(SIGFPE, &info, current);
		break;
	default:
		force_sig(SIGTRAP, current);
	}
}

asmlinkage void do_ri(struct pt_regs *regs)
{
	die_if_kernel("Reserved instruction in kernel code", regs);

	if (compute_return_epc(regs))
		return;

	force_sig(SIGILL, current);
}

asmlinkage void do_cpu(struct pt_regs *regs)
{
	unsigned int cpid;
	void fpu_emulator_init_fpu(void);
	int sig;

	cpid = (regs->cp0_cause >> CAUSEB_CE) & 3;
	if (cpid != 1)
		goto bad_cid;

	if (!(mips_cpu.options & MIPS_CPU_FPU))
		goto fp_emul;

	regs->cp0_status |= ST0_CU1;

#ifdef CONFIG_SMP
	if (current->used_math) {
		lazy_fpu_switch(0, current);
	} else {
		init_fpu();
		current->used_math = 1;
	}
	current->flags |= PF_USEDFPU;
#else
	if (last_task_used_math == current)
		return;

	if (current->used_math) {		/* Using the FPU again.  */
		lazy_fpu_switch(last_task_used_math, current);
	} else {				/* First time FPU user.  */
		lazy_fpu_switch(last_task_used_math, 0);
		init_fpu();
		current->used_math = 1;
	}
	last_task_used_math = current;
#endif
	return;

fp_emul:
	if (last_task_used_math != current) {
		if (!current->used_math) {
			fpu_emulator_init_fpu();
			current->used_math = 1;
		}
	}
	sig = fpu_emulator_cop1Handler(0, regs, &current->thread.fpu.soft);
	last_task_used_math = current;
	if (sig) {
		/*
		 * Return EPC is not calculated in the FPU emulator, if
		 * a signal is being send. So we calculate it here.
		 */
		compute_return_epc(regs);
		force_sig(sig, current);
	}
	return;

bad_cid:
	compute_return_epc(regs);
	force_sig(SIGILL, current);
}

asmlinkage void do_watch(struct pt_regs *regs)
{
	extern void dump_tlb_all(void);

	/*
	 * We use the watch exception where available to detect stack
	 * overflows.
	 */
	dump_tlb_all();
	show_regs(regs);
	panic("Caught WATCH exception - probably caused by stack overflow.");
}

asmlinkage void do_mcheck(struct pt_regs *regs)
{
	show_regs(regs);
	dump_tlb_all();
	/*
	 * Some chips may have other causes of machine check (e.g. SB1
	 * graduation timer)
	 */
	panic("Caught Machine Check exception - %scaused by multiple "
	      "matching entries in the TLB.",
	      (regs->cp0_status & ST0_TS) ? "" : "not ");
}

asmlinkage void do_reserved(struct pt_regs *regs)
{
	/*
	 * Game over - no way to handle this if it ever occurs.  Most probably
	 * caused by a new unknown cpu type or after another deadly
	 * hard/software error.
	 */
	panic("Caught reserved exception %ld - should not happen.",
	      (regs->cp0_cause & 0x1f) >> 2);
}

static inline void watch_init(unsigned long cputype)
{
	switch(cputype) {
	case CPU_R10000:
	case CPU_R4000MC:
	case CPU_R4400MC:
	case CPU_R4000SC:
	case CPU_R4400SC:
	case CPU_R4000PC:
	case CPU_R4400PC:
	case CPU_R4200:
	case CPU_R4300:
		set_except_vector(23, handle_watch);
		watch_available = 1;
		break;
	}
}

unsigned long exception_handlers[32];

/*
 * As a side effect of the way this is implemented we're limited
 * to interrupt handlers in the address range from
 * KSEG0 <= x < KSEG0 + 256mb on the Nevada.  Oh well ...
 */
void *set_except_vector(int n, void *addr)
{
	unsigned long handler = (unsigned long) addr;
	unsigned long old_handler = exception_handlers[n];

	exception_handlers[n] = handler;
	if (n == 0 && mips_cpu.options & MIPS_CPU_DIVEC) {
		*(volatile u32 *)(KSEG0+0x200) = 0x08000000 |
		                                 (0x03ffffff & (handler >> 2));
		flush_icache_range(KSEG0+0x200, KSEG0 + 0x204);
	}
	return (void *)old_handler;
}

asmlinkage int (*save_fp_context)(struct sigcontext *sc);
asmlinkage int (*restore_fp_context)(struct sigcontext *sc);
extern asmlinkage int _save_fp_context(struct sigcontext *sc);
extern asmlinkage int _restore_fp_context(struct sigcontext *sc);

extern asmlinkage int fpu_emulator_save_context(struct sigcontext *sc);
extern asmlinkage int fpu_emulator_restore_context(struct sigcontext *sc);

void __init per_cpu_trap_init(void)
{
	unsigned int cpu = smp_processor_id();

	/* Some firmware leaves the BEV flag set, clear it.  */
	clear_cp0_status(ST0_CU1|ST0_CU2|ST0_CU3|ST0_BEV);
	set_cp0_status(ST0_CU0|ST0_FR|ST0_KX|ST0_SX|ST0_UX);

	/*
	 * Some MIPS CPUs have a dedicated interrupt vector which reduces the
	 * interrupt processing overhead.  Use it where available.
	 */
	if (mips_cpu.options & MIPS_CPU_DIVEC)
		set_cp0_cause(CAUSEF_IV);

	cpu_data[cpu].asid_cache = ASID_FIRST_VERSION;
	set_context(((long)(&pgd_current[cpu])) << 23);
	set_wired(0);
}

void __init trap_init(void)
{
	extern char except_vec0;
	extern char except_vec1_r4k;
	extern char except_vec1_r10k;
	extern char except_vec2_generic;
	extern char except_vec3_generic, except_vec3_r4000;
	extern char except_vec4;
	unsigned long i;
	int dummy;

	per_cpu_trap_init();

	/* Copy the generic exception handlers to their final destination. */
	memcpy((void *)(KSEG0 + 0x100), &except_vec2_generic, 0x80);
	memcpy((void *)(KSEG0 + 0x180), &except_vec3_generic, 0x80);

	/*
	 * Setup default vectors
	 */
	for(i = 0; i <= 31; i++)
		set_except_vector(i, handle_reserved);

	/*
	 * Only some CPUs have the watch exceptions or a dedicated
	 * interrupt vector.
	 */
	watch_init(mips_cpu.cputype);

	/*
	 * Some MIPS CPUs have a dedicated interrupt vector which reduces the
	 * interrupt processing overhead.  Use it where available.
	 */
	memcpy((void *)(KSEG0 + 0x200), &except_vec4, 8);

	if (mips_cpu.options & MIPS_CPU_MCHECK)
		set_except_vector(24, handle_mcheck);

	/*
	 * The Data Bus Errors / Instruction Bus Errors are signaled
	 * by external hardware.  Therefore these two exceptions
	 * may have board specific handlers.
	 */
	bus_error_init();

	/*
	 * Handling the following exceptions depends mostly of the cpu type
	 */
	switch(mips_cpu.cputype) {
        case CPU_SB1:
#ifdef CONFIG_SB1_CACHE_ERROR
		{
		/* Special cache error handler for SB1 */
		extern char except_vec2_sb1;
		memcpy((void *)(KSEG0 + 0x100), &except_vec2_sb1, 0x80);
		memcpy((void *)(KSEG1 + 0x100), &except_vec2_sb1, 0x80);
		}
#endif
		/* Enable timer interrupt and scd mapped interrupt */
		clear_cp0_status(0xf000);
		set_cp0_status(0xc00);

		/* Fall through. */
	case CPU_R10000:
	case CPU_R4000MC:
	case CPU_R4400MC:
	case CPU_R4000SC:
	case CPU_R4400SC:
	case CPU_R4000PC:
	case CPU_R4400PC:
	case CPU_R4200:
	case CPU_R4300:
	case CPU_R4600:
	case CPU_R5000:
	case CPU_NEVADA:
	case CPU_5KC:
	case CPU_20KC:
	case CPU_RM7000:
		/* Debug TLB refill handler.  */
		memcpy((void *)KSEG0, &except_vec0, 0x80);
		if ((mips_cpu.options & MIPS_CPU_4KEX)
		    && (mips_cpu.options & MIPS_CPU_4KTLB)) {
			memcpy((void *)KSEG0 + 0x080, &except_vec1_r4k, 0x80);
		} else {
			memcpy((void *)KSEG0 + 0x080, &except_vec1_r10k, 0x80);
		}
		if (mips_cpu.options & MIPS_CPU_VCE) {
			memcpy((void *)(KSEG0 + 0x180), &except_vec3_r4000,
			       0x80);
		} else {
			memcpy((void *)(KSEG0 + 0x180), &except_vec3_generic,
			       0x80);
		}

		set_except_vector(1, __xtlb_mod);
		set_except_vector(2, __xtlb_tlbl);
		set_except_vector(3, __xtlb_tlbs);
		set_except_vector(4, handle_adel);
		set_except_vector(5, handle_ades);

		set_except_vector(6, handle_ibe);
		set_except_vector(7, handle_dbe);

		set_except_vector(8, handle_sys);
		set_except_vector(9, handle_bp);
		set_except_vector(10, handle_ri);
		set_except_vector(11, handle_cpu);
		set_except_vector(12, handle_ov);
		set_except_vector(13, handle_tr);
		set_except_vector(15, handle_fpe);
		break;

	case CPU_R8000:
		panic("R8000 is unsupported");
		break;

	case CPU_UNKNOWN:
	default:
		panic("Unknown CPU type");
	}
	flush_icache_range(KSEG0, KSEG0 + 0x200);

	if (mips_cpu.options & MIPS_CPU_FPU) {
	        save_fp_context = _save_fp_context;
		restore_fp_context = _restore_fp_context;
	} else {
		save_fp_context = fpu_emulator_save_context;
		restore_fp_context = fpu_emulator_restore_context;
	}

	if (mips_cpu.isa_level == MIPS_CPU_ISA_IV)
		set_cp0_status(ST0_XX);

	atomic_inc(&init_mm.mm_count);	/* XXX UP?  */
	current->active_mm = &init_mm;
}