kgdb_stub.c

linux-2.6.15.6

/*
 * May be copied or modified under the terms of the GNU General Public
 * License.  See linux/COPYING for more information.
 *
 * Containes extracts from code by Glenn Engel, Jim Kingdon,
 * David Grothe <[e-mail]>, Tigran Aivazian <[e-mail]>,
 * Amit S. Kale <[e-mail]>,  William Gatliff <[e-mail]>,
 * Ben Lee, Steve Chamberlain and Benoit Miller <[e-mail]>.
 * 
 * This version by Henry Bell <[e-mail]>
 * Minor modifications by Jeremy Siegel <[e-mail]>
 * 
 * Contains low-level support for remote debug using GDB. 
 *
 * To enable debugger support, two things need to happen. A call to
 * set_debug_traps() is necessary in order to allow any breakpoints
 * or error conditions to be properly intercepted and reported to gdb.
 * A breakpoint also needs to be generated to begin communication.  This
 * is most easily accomplished by a call to breakpoint() which does
 * a trapa if the initialisation phase has been successfully completed.
 *
 * In this case, set_debug_traps() is not used to "take over" exceptions;
 * other kernel code is modified instead to enter the kgdb functions here
 * when appropriate (see entry.S for breakpoint traps and NMI interrupts,
 * see traps.c for kernel error exceptions).
 *
 * The following gdb commands are supported:
 *
 *    Command       Function                               Return value
 *
 *    g             return the value of the CPU registers  hex data or ENN
 *    G             set the value of the CPU registers     OK or ENN
 *
 *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
 *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
 *    XAA..AA,LLLL: Same, but data is binary (not hex)     OK or ENN
 *
 *    c             Resume at current address              SNN   ( signal NN)
 *    cAA..AA       Continue at address AA..AA             SNN
 *    CNN;          Resume at current address with signal  SNN
 *    CNN;AA..AA    Resume at address AA..AA with signal   SNN
 *
 *    s             Step one instruction                   SNN
 *    sAA..AA       Step one instruction from AA..AA       SNN
 *    SNN;          Step one instruction with signal       SNN
 *    SNNAA..AA     Step one instruction from AA..AA w/NN  SNN
 *
 *    k             kill (Detach GDB)
 *
 *    d             Toggle debug flag
 *    D             Detach GDB 
 *
 *    Hct           Set thread t for operations,           OK or ENN
 *                  c = 'c' (step, cont), c = 'g' (other
 *                  operations)
 *
 *    qC            Query current thread ID                QCpid
 *    qfThreadInfo  Get list of current threads (first)    m<id>
 *    qsThreadInfo   "    "  "     "      "   (subsequent)
 *    qOffsets      Get section offsets                  Text=x;Data=y;Bss=z
 * 
 *    TXX           Find if thread XX is alive             OK or ENN
 *    ?             What was the last sigval ?             SNN   (signal NN)
 *    O             Output to GDB console
 *
 * Remote communication protocol.
 *
 *    A debug packet whose contents are <data> is encapsulated for
 *    transmission in the form:
 *
 *       $ <data> # CSUM1 CSUM2
 *
 *       <data> must be ASCII alphanumeric and cannot include characters
 *       '$' or '#'.  If <data> starts with two characters followed by
 *       ':', then the existing stubs interpret this as a sequence number.
 *
 *       CSUM1 and CSUM2 are ascii hex representation of an 8-bit 
 *       checksum of <data>, the most significant nibble is sent first.
 *       the hex digits 0-9,a-f are used.
 *
 *    Receiver responds with:
 *
 *       +       - if CSUM is correct and ready for next packet
 *       -       - if CSUM is incorrect
 *
 * Responses can be run-length encoded to save space.  A '*' means that
 * the next character is an ASCII encoding giving a repeat count which
 * stands for that many repititions of the character preceding the '*'.
 * The encoding is n+29, yielding a printable character where n >=3 
 * (which is where RLE starts to win).  Don't use an n > 126. 
 *
 * So "0* " means the same as "0000".
 */

#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/delay.h>
#include <linux/linkage.h>
#include <linux/init.h>

#include <asm/system.h>
#include <asm/current.h>
#include <asm/signal.h>
#include <asm/pgtable.h>
#include <asm/ptrace.h>
#include <asm/kgdb.h>

#ifdef CONFIG_SH_KGDB_CONSOLE
#include <linux/console.h>
#endif

/* Function pointers for linkage */
kgdb_debug_hook_t *kgdb_debug_hook;
kgdb_bus_error_hook_t *kgdb_bus_err_hook;

int (*kgdb_getchar)(void);
void (*kgdb_putchar)(int);

static void put_debug_char(int c)
{
	if (!kgdb_putchar)
		return;
	(*kgdb_putchar)(c);
}
static int get_debug_char(void)
{
	if (!kgdb_getchar)
		return -1;
	return (*kgdb_getchar)();
}

/* Num chars in in/out bound buffers, register packets need NUMREGBYTES * 2 */
#define BUFMAX 1024
#define NUMREGBYTES (MAXREG*4)
#define OUTBUFMAX (NUMREGBYTES*2+512)

enum regs {
	R0 = 0, R1,  R2,  R3,   R4,   R5,  R6, R7,
	R8, R9, R10, R11, R12,  R13,  R14, R15,
	PC, PR, GBR, VBR, MACH, MACL, SR,
	/*  */
	MAXREG
};

static unsigned int registers[MAXREG];
struct kgdb_regs trap_registers;

char kgdb_in_gdb_mode;
char in_nmi;			/* Set during NMI to prevent reentry */
int kgdb_nofault;		/* Boolean to ignore bus errs (i.e. in GDB) */
int kgdb_enabled = 1;		/* Default to enabled, cmdline can disable */
int kgdb_halt;

/* Exposed for user access */
struct task_struct *kgdb_current;
unsigned int kgdb_g_imask;
int kgdb_trapa_val;
int kgdb_excode;

/* Default values for SCI (can override via kernel args in setup.c) */
#ifndef CONFIG_KGDB_DEFPORT
#define CONFIG_KGDB_DEFPORT 1
#endif

#ifndef CONFIG_KGDB_DEFBAUD
#define CONFIG_KGDB_DEFBAUD 115200
#endif

#if defined(CONFIG_KGDB_DEFPARITY_E)
#define CONFIG_KGDB_DEFPARITY 'E'
#elif defined(CONFIG_KGDB_DEFPARITY_O)
#define CONFIG_KGDB_DEFPARITY 'O'
#else /* CONFIG_KGDB_DEFPARITY_N */
#define CONFIG_KGDB_DEFPARITY 'N'
#endif

#ifdef CONFIG_KGDB_DEFBITS_7
#define CONFIG_KGDB_DEFBITS '7'
#else /* CONFIG_KGDB_DEFBITS_8 */
#define CONFIG_KGDB_DEFBITS '8'
#endif

/* SCI/UART settings, used in kgdb_console_setup() */
int  kgdb_portnum = CONFIG_KGDB_DEFPORT;
int  kgdb_baud = CONFIG_KGDB_DEFBAUD;
char kgdb_parity = CONFIG_KGDB_DEFPARITY;
char kgdb_bits = CONFIG_KGDB_DEFBITS;

/* Jump buffer for setjmp/longjmp */
static jmp_buf rem_com_env;

/* TRA differs sh3/4 */
#if defined(CONFIG_CPU_SH3)
#define TRA 0xffffffd0
#elif defined(CONFIG_CPU_SH4)
#define TRA 0xff000020
#endif

/* Macros for single step instruction identification */
#define OPCODE_BT(op)         (((op) & 0xff00) == 0x8900)
#define OPCODE_BF(op)         (((op) & 0xff00) == 0x8b00)
#define OPCODE_BTF_DISP(op)   (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
			      (((op) & 0x7f ) << 1))
#define OPCODE_BFS(op)        (((op) & 0xff00) == 0x8f00)
#define OPCODE_BTS(op)        (((op) & 0xff00) == 0x8d00)
#define OPCODE_BRA(op)        (((op) & 0xf000) == 0xa000)
#define OPCODE_BRA_DISP(op)   (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
			      (((op) & 0x7ff) << 1))
#define OPCODE_BRAF(op)       (((op) & 0xf0ff) == 0x0023)
#define OPCODE_BRAF_REG(op)   (((op) & 0x0f00) >> 8)
#define OPCODE_BSR(op)        (((op) & 0xf000) == 0xb000)
#define OPCODE_BSR_DISP(op)   (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
			      (((op) & 0x7ff) << 1))
#define OPCODE_BSRF(op)       (((op) & 0xf0ff) == 0x0003)
#define OPCODE_BSRF_REG(op)   (((op) >> 8) & 0xf)
#define OPCODE_JMP(op)        (((op) & 0xf0ff) == 0x402b)
#define OPCODE_JMP_REG(op)    (((op) >> 8) & 0xf)
#define OPCODE_JSR(op)        (((op) & 0xf0ff) == 0x400b)
#define OPCODE_JSR_REG(op)    (((op) >> 8) & 0xf)
#define OPCODE_RTS(op)        ((op) == 0xb)
#define OPCODE_RTE(op)        ((op) == 0x2b)

#define SR_T_BIT_MASK           0x1
#define STEP_OPCODE             0xc320
#define BIOS_CALL_TRAP          0x3f

/* Exception codes as per SH-4 core manual */
#define ADDRESS_ERROR_LOAD_VEC   7
#define ADDRESS_ERROR_STORE_VEC  8
#define TRAP_VEC                 11
#define INVALID_INSN_VEC         12
#define INVALID_SLOT_VEC         13
#define NMI_VEC                  14
#define USER_BREAK_VEC           15
#define SERIAL_BREAK_VEC         58

/* Misc static */
static int stepped_address;
static short stepped_opcode;
static const char hexchars[] = "0123456789abcdef";
static char in_buffer[BUFMAX];
static char out_buffer[OUTBUFMAX];

static void kgdb_to_gdb(const char *s);

#ifdef CONFIG_KGDB_THREAD
static struct task_struct *trapped_thread;
static struct task_struct *current_thread;
typedef unsigned char threadref[8];
#define BUF_THREAD_ID_SIZE 16
#endif

/* Return addr as a real volatile address */
static inline unsigned int ctrl_inl(const unsigned long addr)
{
	return *(volatile unsigned long *) addr;
}

/* Correctly set *addr using volatile */
static inline void ctrl_outl(const unsigned int b, unsigned long addr)
{
	*(volatile unsigned long *) addr = b;
}

/* Get high hex bits */
static char highhex(const int x)
{
	return hexchars[(x >> 4) & 0xf];
}

/* Get low hex bits */
static char lowhex(const int x)
{
	return hexchars[x & 0xf];
}

/* Convert ch to hex */
static int hex(const char ch)
{
	if ((ch >= 'a') && (ch <= 'f'))
		return (ch - 'a' + 10);
	if ((ch >= '0') && (ch <= '9'))
		return (ch - '0');
	if ((ch >= 'A') && (ch <= 'F'))
		return (ch - 'A' + 10);
	return (-1);
}

/* Convert the memory pointed to by mem into hex, placing result in buf.
   Returns a pointer to the last char put in buf (null) */
static char *mem_to_hex(const char *mem, char *buf, const int count)
{
	int i;
	int ch;
	unsigned short s_val;
	unsigned long l_val;

	/* Check for 16 or 32 */
	if (count == 2 && ((long) mem & 1) == 0) {
		s_val = *(unsigned short *) mem;
		mem = (char *) &s_val;
	} else if (count == 4 && ((long) mem & 3) == 0) {
		l_val = *(unsigned long *) mem;
		mem = (char *) &l_val;
	}
	for (i = 0; i < count; i++) {
		ch = *mem++;
		*buf++ = highhex(ch);
		*buf++ = lowhex(ch);
	}
	*buf = 0;
	return (buf);
}

/* Convert the hex array pointed to by buf into binary, to be placed in mem.
   Return a pointer to the character after the last byte written */
static char *hex_to_mem(const char *buf, char *mem, const int count)
{
	int i;
	unsigned char ch;

	for (i = 0; i < count; i++) {
		ch = hex(*buf++) << 4;
		ch = ch + hex(*buf++);
		*mem++ = ch;
	}
	return (mem);
}

/* While finding valid hex chars, convert to an integer, then return it */
static int hex_to_int(char **ptr, int *int_value)
{
	int num_chars = 0;
	int hex_value;

	*int_value = 0;

	while (**ptr) {
		hex_value = hex(**ptr);
		if (hex_value >= 0) {
			*int_value = (*int_value << 4) | hex_value;
			num_chars++;
		} else
			break;
		(*ptr)++;
	}
	return num_chars;
}

/*  Copy the binary array pointed to by buf into mem.  Fix $, #,
    and 0x7d escaped with 0x7d.  Return a pointer to the character 
    after the last byte written. */
static char *ebin_to_mem(const char *buf, char *mem, int count)
{
	for (; count > 0; count--, buf++) {
		if (*buf == 0x7d)
			*mem++ = *(++buf) ^ 0x20;
		else
			*mem++ = *buf;
	}
	return mem;
}

/* Pack a hex byte */
static char *pack_hex_byte(char *pkt, int byte)
{
	*pkt++ = hexchars[(byte >> 4) & 0xf];
	*pkt++ = hexchars[(byte & 0xf)];
	return pkt;
}

#ifdef CONFIG_KGDB_THREAD

/* Pack a thread ID */
static char *pack_threadid(char *pkt, threadref * id)
{
	char *limit;
	unsigned char *altid;

	altid = (unsigned char *) id;

	limit = pkt + BUF_THREAD_ID_SIZE;
	while (pkt < limit)
		pkt = pack_hex_byte(pkt, *altid++);
	return pkt;
}

/* Convert an integer into our threadref */
static void int_to_threadref(threadref * id, const int value)
{
	unsigned char *scan = (unsigned char *) id;
	int i = 4;

	while (i--)
		*scan++ = 0;

	*scan++ = (value >> 24) & 0xff;
	*scan++ = (value >> 16) & 0xff;
	*scan++ = (value >> 8) & 0xff;
	*scan++ = (value & 0xff);
}

/* Return a task structure ptr for a particular pid */
static struct task_struct *get_thread(int pid)
{
	struct task_struct *thread;

	/* Use PID_MAX w/gdb for pid 0 */
	if (pid == PID_MAX) pid = 0;

	/* First check via PID */
	thread = find_task_by_pid(pid);

	if (thread)
		return thread;

	/* Start at the start */
	thread = init_tasks[0];

	/* Walk along the linked list of tasks */
	do {
		if (thread->pid == pid)
			return thread;
		thread = thread->next_task;
	} while (thread != init_tasks[0]);

	return NULL;
}

#endif /* CONFIG_KGDB_THREAD */

/* Scan for the start char '$', read the packet and check the checksum */
static void get_packet(char *buffer, int buflen)
{
	unsigned char checksum;
	unsigned char xmitcsum;
	int i;
	int count;
	char ch;

	do {
		/* Ignore everything until the start character */
		while ((ch = get_debug_char()) != '$');

		checksum = 0;
		xmitcsum = -1;
		count = 0;

		/* Now, read until a # or end of buffer is found */
		while (count < (buflen - 1)) {
			ch = get_debug_char();

			if (ch == '#')
				break;

			checksum = checksum + ch;
			buffer[count] = ch;
			count = count + 1;
		}

		buffer[count] = 0;

		/* Continue to read checksum following # */
		if (ch == '#') {
			xmitcsum = hex(get_debug_char()) << 4;
			xmitcsum += hex(get_debug_char());

			/* Checksum */
			if (checksum != xmitcsum)
				put_debug_char('-');	/* Failed checksum */
			else {
				/* Ack successful transfer */
				put_debug_char('+');

				/* If a sequence char is present, reply 
				   the sequence ID */
				if (buffer[2] == ':') {
					put_debug_char(buffer[0]);
					put_debug_char(buffer[1]);

					/* Remove sequence chars from buffer */
					count = strlen(buffer);
					for (i = 3; i <= count; i++)
						buffer[i - 3] = buffer[i];
				}
			}
		}
	}
	while (checksum != xmitcsum);	/* Keep trying while we fail */
}

/* Send the packet in the buffer with run-length encoding */
static void put_packet(char *buffer)
{
	int checksum;