ppc-stub.c

底层驱动开发

	/* In case GDB is started before us, ack any packets (presumably
	 * "$?#xx") sitting there.
	 *
	 * I've found this code causes more problems than it solves,
	 * so that's why it's commented out.  GDB seems to work fine
	 * now starting either before or after the kernel   -bwb
	 */

	while((c = getDebugChar()) != '$');
	while((c = getDebugChar()) != '#');
	c = getDebugChar(); /* eat first csum byte */
	c = getDebugChar(); /* eat second csum byte */
	putDebugChar('+'); /* ack it */
#endif
	debugger = kgdb;
	debugger_bpt = kgdb_bpt;
	debugger_sstep = kgdb_sstep;
	debugger_iabr_match = kgdb_iabr_match;
	debugger_dabr_match = kgdb_dabr_match;

	initialized = 1;
}

static void kgdb_fault_handler(struct pt_regs *regs)
{
	kgdb_longjmp((long*)fault_jmp_buf, 1);
}

int kgdb_bpt(struct pt_regs *regs)
{
	return handle_exception(regs);
}

int kgdb_sstep(struct pt_regs *regs)
{
	return handle_exception(regs);
}

void kgdb(struct pt_regs *regs)
{
	handle_exception(regs);
}

int kgdb_iabr_match(struct pt_regs *regs)
{
	printk(KERN_ERR "kgdb doesn't support iabr, what?!?\n");
	return handle_exception(regs);
}

int kgdb_dabr_match(struct pt_regs *regs)
{
	printk(KERN_ERR "kgdb doesn't support dabr, what?!?\n");
	return handle_exception(regs);
}

/* Convert the hardware trap type code to a unix signal number. */
/*
 * This table contains the mapping between PowerPC hardware trap types, and
 * signals, which are primarily what GDB understands.
 */
static struct hard_trap_info
{
	unsigned int tt;		/* Trap type code for powerpc */
	unsigned char signo;		/* Signal that we map this trap into */
} hard_trap_info[] = {
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
	{ 0x100, SIGINT  },		/* critical input interrupt */
	{ 0x200, SIGSEGV },		/* machine check */
	{ 0x300, SIGSEGV },		/* data storage */
	{ 0x400, SIGBUS  },		/* instruction storage */
	{ 0x500, SIGINT  },		/* interrupt */
	{ 0x600, SIGBUS  },		/* alignment */
	{ 0x700, SIGILL  },		/* program */
	{ 0x800, SIGILL  },		/* reserved */
	{ 0x900, SIGILL  },		/* reserved */
	{ 0xa00, SIGILL  },		/* reserved */
	{ 0xb00, SIGILL  },		/* reserved */
	{ 0xc00, SIGCHLD },		/* syscall */
	{ 0xd00, SIGILL  },		/* reserved */
	{ 0xe00, SIGILL  },		/* reserved */
	{ 0xf00, SIGILL  },		/* reserved */
	/*
	** 0x1000  PIT
	** 0x1010  FIT
	** 0x1020  watchdog
	** 0x1100  data TLB miss
	** 0x1200  instruction TLB miss
	*/
	{ 0x2002, SIGTRAP},		/* debug */
#else
	{ 0x200, SIGSEGV },		/* machine check */
	{ 0x300, SIGSEGV },		/* address error (store) */
	{ 0x400, SIGBUS },		/* instruction bus error */
	{ 0x500, SIGINT },		/* interrupt */
	{ 0x600, SIGBUS },		/* alingment */
	{ 0x700, SIGTRAP },		/* breakpoint trap */
	{ 0x800, SIGFPE },		/* fpu unavail */
	{ 0x900, SIGALRM },		/* decrementer */
	{ 0xa00, SIGILL },		/* reserved */
	{ 0xb00, SIGILL },		/* reserved */
	{ 0xc00, SIGCHLD },		/* syscall */
	{ 0xd00, SIGTRAP },		/* single-step/watch */
	{ 0xe00, SIGFPE },		/* fp assist */
#endif
	{ 0, 0}				/* Must be last */

};

static int computeSignal(unsigned int tt)
{
	struct hard_trap_info *ht;

	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
		if (ht->tt == tt)
			return ht->signo;

	return SIGHUP; /* default for things we don't know about */
}

#define PC_REGNUM 64
#define SP_REGNUM 1

/*
 * This function does all command processing for interfacing to gdb.
 */
static int
handle_exception (struct pt_regs *regs)
{
	int sigval;
	int addr;
	int length;
	char *ptr;
	unsigned int msr;

	/* We don't handle user-mode breakpoints. */
	if (user_mode(regs))
		return 0;

	if (debugger_fault_handler) {
		debugger_fault_handler(regs);
		panic("kgdb longjump failed!\n");
	}
	if (kgdb_active) {
		printk(KERN_ERR "interrupt while in kgdb, returning\n");
		return 0;
	}

	kgdb_active = 1;
	kgdb_started = 1;

#ifdef KGDB_DEBUG
	printk("kgdb: entering handle_exception; trap [0x%x]\n",
			(unsigned int)regs->trap);
#endif

	kgdb_interruptible(0);
	lock_kernel();
	msr = mfmsr();
	mtmsr(msr & ~MSR_EE);	/* disable interrupts */

	if (regs->nip == (unsigned long)breakinst) {
		/* Skip over breakpoint trap insn */
		regs->nip += 4;
	}

	/* reply to host that an exception has occurred */
	sigval = computeSignal(regs->trap);
	ptr = remcomOutBuffer;

	*ptr++ = 'T';
	*ptr++ = hexchars[sigval >> 4];
	*ptr++ = hexchars[sigval & 0xf];
	*ptr++ = hexchars[PC_REGNUM >> 4];
	*ptr++ = hexchars[PC_REGNUM & 0xf];
	*ptr++ = ':';
	ptr = mem2hex((char *)&regs->nip, ptr, 4);
	*ptr++ = ';';
	*ptr++ = hexchars[SP_REGNUM >> 4];
	*ptr++ = hexchars[SP_REGNUM & 0xf];
	*ptr++ = ':';
	ptr = mem2hex(((char *)regs) + SP_REGNUM*4, ptr, 4);
	*ptr++ = ';';
	*ptr++ = 0;

	putpacket(remcomOutBuffer);
	if (kdebug)
		printk("remcomOutBuffer: %s\n", remcomOutBuffer);

	/* XXX We may want to add some features dealing with poking the
	 * XXX page tables, ... (look at sparc-stub.c for more info)
	 * XXX also required hacking to the gdb sources directly...
	 */

	while (1) {
		remcomOutBuffer[0] = 0;

		getpacket(remcomInBuffer);
		switch (remcomInBuffer[0]) {
		case '?': /* report most recent signal */
			remcomOutBuffer[0] = 'S';
			remcomOutBuffer[1] = hexchars[sigval >> 4];
			remcomOutBuffer[2] = hexchars[sigval & 0xf];
			remcomOutBuffer[3] = 0;
			break;
#if 0
		case 'q': /* this screws up gdb for some reason...*/
		{
			extern long _start, sdata, __bss_start;

			ptr = &remcomInBuffer[1];
			if (strncmp(ptr, "Offsets", 7) != 0)
				break;

			ptr = remcomOutBuffer;
			sprintf(ptr, "Text=%8.8x;Data=%8.8x;Bss=%8.8x",
				&_start, &sdata, &__bss_start);
			break;
		}
#endif
		case 'd':
			/* toggle debug flag */
			kdebug ^= 1;
			break;

		case 'g':	/* return the value of the CPU registers.
				 * some of them are non-PowerPC names :(
				 * they are stored in gdb like:
				 * struct {
				 *     u32 gpr[32];
				 *     f64 fpr[32];
				 *     u32 pc, ps, cnd, lr; (ps=msr)
				 *     u32 cnt, xer, mq;
				 * }
				 */
		{
			int i;
			ptr = remcomOutBuffer;
			/* General Purpose Regs */
			ptr = mem2hex((char *)regs, ptr, 32 * 4);
			/* Floating Point Regs - FIXME */
			/*ptr = mem2hex((char *), ptr, 32 * 8);*/
			for(i=0; i<(32*8*2); i++) { /* 2chars/byte */
				ptr[i] = '0';
			}
			ptr += 32*8*2;
			/* pc, msr, cr, lr, ctr, xer, (mq is unused) */
			ptr = mem2hex((char *)&regs->nip, ptr, 4);
			ptr = mem2hex((char *)&regs->msr, ptr, 4);
			ptr = mem2hex((char *)&regs->ccr, ptr, 4);
			ptr = mem2hex((char *)&regs->link, ptr, 4);
			ptr = mem2hex((char *)&regs->ctr, ptr, 4);
			ptr = mem2hex((char *)&regs->xer, ptr, 4);
		}
			break;

		case 'G': /* set the value of the CPU registers */
		{
			ptr = &remcomInBuffer[1];

			/*
			 * If the stack pointer has moved, you should pray.
			 * (cause only god can help you).
			 */

			/* General Purpose Regs */
			hex2mem(ptr, (char *)regs, 32 * 4);

			/* Floating Point Regs - FIXME?? */
			/*ptr = hex2mem(ptr, ??, 32 * 8);*/
			ptr += 32*8*2;

			/* pc, msr, cr, lr, ctr, xer, (mq is unused) */
			ptr = hex2mem(ptr, (char *)&regs->nip, 4);
			ptr = hex2mem(ptr, (char *)&regs->msr, 4);
			ptr = hex2mem(ptr, (char *)&regs->ccr, 4);
			ptr = hex2mem(ptr, (char *)&regs->link, 4);
			ptr = hex2mem(ptr, (char *)&regs->ctr, 4);
			ptr = hex2mem(ptr, (char *)&regs->xer, 4);

			strcpy(remcomOutBuffer,"OK");
		}
			break;
		case 'H':
			/* don't do anything, yet, just acknowledge */
			hexToInt(&ptr, &addr);
			strcpy(remcomOutBuffer,"OK");
			break;

		case 'm':	/* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
				/* Try to read %x,%x.  */

			ptr = &remcomInBuffer[1];

			if (hexToInt(&ptr, &addr) && *ptr++ == ','
					&& hexToInt(&ptr, &length)) {
				if (mem2hex((char *)addr, remcomOutBuffer,
							length))
					break;
				strcpy(remcomOutBuffer, "E03");
			} else
				strcpy(remcomOutBuffer, "E01");
			break;

		case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
			/* Try to read '%x,%x:'.  */

			ptr = &remcomInBuffer[1];

			if (hexToInt(&ptr, &addr) && *ptr++ == ','
					&& hexToInt(&ptr, &length)
					&& *ptr++ == ':') {
				if (hex2mem(ptr, (char *)addr, length))
					strcpy(remcomOutBuffer, "OK");
				else
					strcpy(remcomOutBuffer, "E03");
				flush_icache_range(addr, addr+length);
			} else
				strcpy(remcomOutBuffer, "E02");
			break;


		case 'k': /* kill the program, actually just continue */
		case 'c': /* cAA..AA  Continue; address AA..AA optional */
			/* try to read optional parameter, pc unchanged if no parm */

			ptr = &remcomInBuffer[1];
			if (hexToInt(&ptr, &addr))
				regs->nip = addr;

/* Need to flush the instruction cache here, as we may have deposited a
 * breakpoint, and the icache probably has no way of knowing that a data ref to
 * some location may have changed something that is in the instruction cache.
 */
			kgdb_flush_cache_all();
			mtmsr(msr);

			kgdb_interruptible(1);
			unlock_kernel();
			kgdb_active = 0;
			if (kdebug) {
				printk("remcomInBuffer: %s\n", remcomInBuffer);
				printk("remcomOutBuffer: %s\n", remcomOutBuffer);
			}
			return 1;

		case 's':
			kgdb_flush_cache_all();
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
			mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC);
			regs->msr |= MSR_DE;
#else
			regs->msr |= MSR_SE;
#endif
			unlock_kernel();
			kgdb_active = 0;
			if (kdebug) {
				printk("remcomInBuffer: %s\n", remcomInBuffer);
				printk("remcomOutBuffer: %s\n", remcomOutBuffer);
			}
			return 1;

		case 'r':		/* Reset (if user process..exit ???)*/
			panic("kgdb reset.");
			break;
		}			/* switch */
		if (remcomOutBuffer[0] && kdebug) {
			printk("remcomInBuffer: %s\n", remcomInBuffer);
			printk("remcomOutBuffer: %s\n", remcomOutBuffer);
		}
		/* reply to the request */
		putpacket(remcomOutBuffer);
	} /* while(1) */
}

/* This function will generate a breakpoint exception.  It is used at the
   beginning of a program to sync up with a debugger and can be used
   otherwise as a quick means to stop program execution and "break" into
   the debugger. */

void
breakpoint(void)
{
	if (!initialized) {
		printk("breakpoint() called b4 kgdb init\n");
		return;
	}

	asm("	.globl breakinst	\n\
	     breakinst: .long 0x7d821008");
}

#ifdef CONFIG_KGDB_CONSOLE
/* Output string in GDB O-packet format if GDB has connected. If nothing
   output, returns 0 (caller must then handle output). */
int
kgdb_output_string (const char* s, unsigned int count)
{
	char buffer[512];

	if (!kgdb_started)
		return 0;

	count = (count <= (sizeof(buffer) / 2 - 2))
		? count : (sizeof(buffer) / 2 - 2);

	buffer[0] = 'O';
	mem2hex (s, &buffer[1], count);
	putpacket(buffer);

	return 1;
}
#endif

static void sysrq_handle_gdb(int key, struct pt_regs *pt_regs,
			     struct tty_struct *tty)
{
	printk("Entering GDB stub\n");
	breakpoint();
}
static struct sysrq_key_op sysrq_gdb_op = {
        .handler        = sysrq_handle_gdb,
        .help_msg       = "Gdb",
        .action_msg     = "GDB",
};

static int gdb_register_sysrq(void)
{
	printk("Registering GDB sysrq handler\n");
	register_sysrq_key('g', &sysrq_gdb_op);
	return 0;
}
module_init(gdb_register_sysrq);