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gdb_protocol.c
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gdb_protocol.c
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/*
ELF Loader - chargeur/implanteur d'exécutables au format ELF à but pédagogique
Copyright (C) 2012 Guillaume Huard
Ce programme est libre, vous pouvez le redistribuer et/ou le modifier selon les
termes de la Licence Publique Générale GNU publiée par la Free Software
Foundation (version 2 ou bien toute autre version ultérieure choisie par vous).
Ce programme est distribué car potentiellement utile, mais SANS AUCUNE
GARANTIE, ni explicite ni implicite, y compris les garanties de
commercialisation ou d'adaptation dans un but spécifique. Reportez-vous à la
Licence Publique Générale GNU pour plus de détails.
Vous devez avoir reçu une copie de la Licence Publique Générale GNU en même
temps que ce programme ; si ce n'est pas le cas, écrivez à la Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307,
États-Unis.
Contact: [email protected]
ENSIMAG - Laboratoire LIG
51 avenue Jean Kuntzmann
38330 Montbonnot Saint-Martin
*/
#include <stdio.h>
#include <assert.h>
#include <pthread.h>
#include "gdb_protocol.h"
#include "scanner.h"
#include "debug.h"
#include "csapp.h"
#include "util.h"
#define MAX_PACKET_SIZE 1024
#define MAX_BUFFER_SIZE (MAX_PACKET_SIZE-6)
struct gdb_protocol_data {
int fd;
char packet[MAX_PACKET_SIZE];
int len;
char *buffer;
char *answer;
int answer_len;
};
static void gdb_send_ack(gdb_protocol_data_t gdb) {
Rio_writen(gdb->fd, "+", 1);
}
static void gdb_send_buffer(gdb_protocol_data_t gdb) {
unsigned char check=0;
int i;
gdb->packet[0] = '$';
i = 1;
while (gdb->len--) {
check += gdb->packet[i];
i++;
}
gdb->packet[i++] = '#';
sprintf(gdb->packet+i, "%02x", check);
i += 2;
gdb->packet[i] = '\0';
gdb->len = i;
gdb_transmit_packet(gdb);
}
static void gdb_send_data(gdb_protocol_data_t gdb, char *data) {
strcpy(gdb->buffer, data);
gdb->len = strlen(data);
gdb_send_buffer(gdb);
}
static int gdb_get_answer(gdb_protocol_data_t gdb) {
int answer;
answer = gdb_get_packet(gdb);
// At this time, we don't have any good interpretation of the answer, just trace
// it as a debugging information
if (answer != EOF)
debug("Simulator answered: %s\n", gdb->answer);
else
debug("Simulator exited\n");
return answer;
}
/* Read and write to/from a string of bytes (in hexadecimal) in local byte
* order */
static void write_uint32(char *data, uint32_t value) {
int i, step;
int target_big_endian;
union {
unsigned char bytes[4];
uint32_t integer;
} mem;
mem.integer = value;
#ifdef BIG_ENDIAN_SIMULATOR
target_big_endian = 1;
#else
target_big_endian = 0;
#endif
if (is_big_endian() == target_big_endian) {
i = 0;
step = 1;
} else {
i = 3;
step = -1;
}
for (; (i<4) && (i>=0); i+=step) {
sprintf(data, "%02x", mem.bytes[i]);
data += 2;
}
*data = '\0';
}
/* Publicly accessible functions */
gdb_protocol_data_t gdb_init_data(int fd) {
gdb_protocol_data_t gdb;
gdb = malloc(sizeof(struct gdb_protocol_data));
if (gdb) {
gdb->fd = fd;
gdb->len = 0;
gdb->buffer = gdb->packet+1;
}
return gdb;
}
void gdb_destroy_data(gdb_protocol_data_t gdb) {
free(gdb);
}
void gdb_write_register(gdb_protocol_data_t gdb, uint8_t num, uint32_t value) {
char *buffer = gdb->buffer;
sprintf(buffer, "P%02x=", num);
write_uint32(buffer+4, value);
gdb->len = 12;
gdb_send_buffer(gdb);
gdb_get_answer(gdb);
}
void gdb_write_memory(gdb_protocol_data_t gdb, uint32_t address, void *buffer, size_t size) {
char *dest_buffer, *src_buffer;
int bytes_copied, buffer_size;
src_buffer = buffer;
while (size > 0) {
dest_buffer = gdb->buffer+19;
bytes_copied = 0;
buffer_size = 0;
while ((buffer_size < MAX_BUFFER_SIZE-1) &&
(bytes_copied < size)) {
switch (*src_buffer) {
case '$':
case '#':
case 0x7d:
*(dest_buffer++) = (char) 0x7d;
*dest_buffer = *src_buffer ^ (char) 0x20;
buffer_size++;
break;
default:
*dest_buffer = *src_buffer;
}
buffer_size++;
bytes_copied++;
dest_buffer++;
src_buffer++;
}
sprintf(gdb->buffer, "X%08x,%08x", address, bytes_copied);
gdb->buffer[18] = ':';
gdb->len = 19+buffer_size;
gdb_send_buffer(gdb);
gdb_get_answer(gdb);
address += bytes_copied;
size -= bytes_copied;
}
}
void gdb_cont(gdb_protocol_data_t gdb) {
int answer;
gdb_send_data(gdb, "c");
answer = gdb_get_answer(gdb);
if (answer != EOF)
debug("Unexpected packet after the end of the simulation: %s\n", gdb->packet);
}
int gdb_step(gdb_protocol_data_t gdb) {
int answer;
gdb_send_data(gdb, "s");
answer = gdb_get_answer(gdb);
return answer;
}
void gdb_require_retransmission(gdb_protocol_data_t gdb) {
Rio_writen(gdb->fd, "-", 1);
}
int gdb_packet_check(gdb_protocol_data_t gdb, char *packet, int length) {
int i;
unsigned char check=0;
unsigned int given;
for (i=1; i<length-3; i++)
check += packet[i];
sscanf(packet+i+1, "%x", &given);
debug("Received packet : ");
debug_raw_binary(packet, min(16, strlen(packet)));
if (check == given) {
debug_raw(", checksum ok\n");
gdb_send_ack(gdb);
} else {
debug_raw(", checksum failed, expected %02x got %02x\n", given, check);
debug("Requiring retransmission\n");
gdb_require_retransmission(gdb);
return 0;
}
gdb->answer = packet;
gdb->answer_len = length;
return 1;
}
void gdb_transmit_packet(gdb_protocol_data_t gdb) {
debug("Transmitting packet: %s\n", gdb->packet);
Rio_writen(gdb->fd, gdb->packet, gdb->len);
}