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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 <exception.h>
#include <gdb.h>
#include <libpayload.h>
struct gdb_regs
{
u32 r[16];
struct fp_reg
{
u8 byte[12];
} __packed f[8];
u32 fps;
u32 cpsr;
} __packed;
static const u8 type_to_signal[] = {
[EXC_UNDEF] = GDB_SIGILL,
[EXC_SWI] = GDB_SIGTRAP,
[EXC_PABORT] = GDB_SIGSEGV,
[EXC_DABORT] = GDB_SIGSEGV,
};
/* Scratch value to write reentrant exception states to. We never read it. */
static struct exception_state sentinel_exception_state;
static int gdb_exception_hook(u32 type)
{
/*
* If we were not resumed we are in deep trouble here. GDB probably told
* us to do something stupid and caused a reentrant exception. All we
* can do is just blindly send an error code and keep going. Eventually
* GDB will tell us to resume and we return right back to the original
* exception state ("jumping over" all the nested ones).
*/
if (gdb_state.connected && !gdb_state.resumed) {
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 */
} else {
if (type >= ARRAY_SIZE(type_to_signal) || !type_to_signal[type])
return 0;
exception_state_ptr = &sentinel_exception_state;
gdb_command_loop(type_to_signal[type]);
}
exception_state_ptr = &exception_state;
return 1;
}
void gdb_arch_init(void)
{
exception_install_hook(&gdb_exception_hook);
}
void gdb_arch_enter(void)
{
u32 *sp;
asm volatile ("mov %0, %%sp" : "=r"(sp) );
/* Avoid reentrant exceptions, just call the hook if in one already. */
if (sp >= exception_stack && sp <= exception_stack_end)
gdb_exception_hook(EXC_SWI);
else
asm volatile ("svc #0");
}
int gdb_arch_set_single_step(int on)
{
/* GDB seems to only need this on x86, ARM works fine without it. */
return -1;
}
void gdb_arch_encode_regs(struct gdb_message *message)
{
gdb_message_encode_bytes(message, exception_state.regs,
sizeof(exception_state.regs));
gdb_message_encode_zero_bytes(message,
offsetof(struct gdb_regs, cpsr) - offsetof(struct gdb_regs, f));
gdb_message_encode_bytes(message, &exception_state.cpsr,
sizeof(exception_state.cpsr));
}
void gdb_arch_decode_regs(int offset, struct gdb_message *message)
{
const int cpsr_hex_offset = offsetof(struct gdb_regs, cpsr) * 2;
gdb_message_decode_bytes(message, offset,
exception_state.regs, sizeof(exception_state.regs));
gdb_message_decode_bytes(message, offset + cpsr_hex_offset,
&exception_state.cpsr, sizeof(exception_state.cpsr));
}
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