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/*
* Copyright 2014 Google Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but without any warranty; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <gdb.h>
#include <libpayload.h>
struct gdb_state gdb_state;
static u8 reply_buf[2048];
static u8 command_buf[2048];
static struct gdb_message command = {
.buf = command_buf,
.used = 0,
.size = sizeof(command_buf),
};
static struct gdb_message reply = {
.buf = reply_buf,
.used = 0,
.size = sizeof(reply_buf),
};
void gdb_command_loop(u8 signal)
{
if (gdb_state.resumed) {
/* We were just running. Send a stop reply. */
reply.used = 0;
gdb_message_add_string(&reply, "S");
gdb_message_encode_bytes(&reply, &signal, 1);
gdb_send_reply(&reply);
}
gdb_state.signal = signal;
gdb_state.resumed = 0;
gdb_state.connected = 1;
while (1) {
int i;
gdb_get_command(&command);
reply.used = 0;
for (i = 0; i < gdb_command_count; i++) {
int clen = strlen(gdb_commands[i].str);
if (!strncmp(gdb_commands[i].str, (char *)command.buf,
MIN(clen, command.used))) {
gdb_commands[i].handler(&command, clen, &reply);
break;
}
}
/* If we're resuming, we won't send a reply until we stop. */
if (gdb_state.resumed)
return;
gdb_send_reply(&reply);
}
}
static void gdb_output_write(const void *buffer, size_t count)
{
if (!gdb_state.resumed) {
/* Must be a die_if() in GDB (or a bug), so bail out and die. */
gdb_exit(-1);
video_console_init();
puts("GDB died, redirecting its last words to the screen:\n");
console_write(buffer, count);
} else {
reply.used = 0;
reply.buf[reply.used++] = 'O';
gdb_message_encode_bytes(&reply, buffer, count);
gdb_send_reply(&reply);
}
}
static struct console_output_driver gdb_output_driver = {
.write = &gdb_output_write
};
static void gdb_init(void)
{
printf("Ready for GDB connection.\n");
gdb_transport_init();
gdb_arch_init();
console_add_output_driver(&gdb_output_driver);
}
void gdb_enter(void)
{
if (!gdb_state.connected)
gdb_init();
gdb_arch_enter();
}
void gdb_exit(s8 exit_status)
{
if (!gdb_state.connected)
return;
reply.used = 0;
gdb_message_add_string(&reply, "W");
gdb_message_encode_bytes(&reply, &exit_status, 1);
gdb_send_reply(&reply);
console_remove_output_driver(&gdb_output_write);
gdb_transport_teardown();
gdb_state.connected = 0;
printf("Detached from GDB connection.\n");
}
/*
* This is a check architecture backends can run before entering the GDB command
* loop during exception handling. If it returns true, GDB was already running
* and must have caused an exception itself, which may happen if the GDB server
* tells us to do something stupid (e.g. write to an unmapped address). In that
* case, all we can do is blindly send a generic error code (since we're not
* sure which command caused the exception) and continue serving commands. When
* GDB eventually tells us to resume, we'll return from this function to the
* architecture backend which will have to do a "super exception return" that
* returns right back from the original (outermost) exception, "jumping over"
* all the intermediate exception frames we may have accumulated since. (This is
* the best we can do because our architecture backends generally don't support
* "full", unlimited exception reentrancy.)
*/
int gdb_handle_reentrant_exception(void)
{
if (!gdb_state.connected || gdb_state.resumed)
return 0; /* This is not a reentrant exception. */
static const char error_code[] = "E22"; /* EINVAL? */
static const struct gdb_message tmp_reply = {
.buf = (u8 *)error_code,
.used = sizeof(error_code),
.size = sizeof(error_code),
};
gdb_send_reply(&tmp_reply);
gdb_command_loop(gdb_state.signal); /* preserve old signal */
return 1;
}
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