qemu/gdbstub/user.c
Ilya Leoshkevich 046f143c51 gdbstub: Implement catching syscalls
GDB supports stopping on syscall entry and exit using the "catch
syscall" command. It relies on 3 packets, which are currently not
supported by QEMU:

* qSupported:QCatchSyscalls+ [1]
* QCatchSyscalls: [2]
* T05syscall_entry: and T05syscall_return: [3]

Implement generation and handling of these packets.

[1] https://sourceware.org/gdb/current/onlinedocs/gdb.html/General-Query-Packets.html#qSupported
[2] https://sourceware.org/gdb/current/onlinedocs/gdb.html/General-Query-Packets.html#QCatchSyscalls
[3] https://sourceware.org/gdb/current/onlinedocs/gdb.html/Stop-Reply-Packets.html

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20240202152506.279476-5-iii@linux.ibm.com>
[AJB: GString -> g_strdup_printf]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240207163812.3231697-14-alex.bennee@linaro.org>
2024-02-09 17:52:40 +00:00

604 lines
14 KiB
C

/*
* gdbstub user-mode helper routines.
*
* We know for user-mode we are using TCG so we can call stuff directly.
*
* Copyright (c) 2003-2005 Fabrice Bellard
* Copyright (c) 2022 Linaro Ltd
*
* SPDX-License-Identifier: LGPL-2.0+
*/
#include "qemu/osdep.h"
#include "qemu/bitops.h"
#include "qemu/cutils.h"
#include "qemu/sockets.h"
#include "exec/hwaddr.h"
#include "exec/tb-flush.h"
#include "exec/gdbstub.h"
#include "gdbstub/syscalls.h"
#include "gdbstub/user.h"
#include "hw/core/cpu.h"
#include "trace.h"
#include "internals.h"
#define GDB_NR_SYSCALLS 1024
typedef unsigned long GDBSyscallsMask[BITS_TO_LONGS(GDB_NR_SYSCALLS)];
/* User-mode specific state */
typedef struct {
int fd;
char *socket_path;
int running_state;
/*
* Store syscalls mask without memory allocation in order to avoid
* implementing synchronization.
*/
bool catch_all_syscalls;
GDBSyscallsMask catch_syscalls_mask;
} GDBUserState;
static GDBUserState gdbserver_user_state;
int gdb_get_char(void)
{
uint8_t ch;
int ret;
for (;;) {
ret = recv(gdbserver_user_state.fd, &ch, 1, 0);
if (ret < 0) {
if (errno == ECONNRESET) {
gdbserver_user_state.fd = -1;
}
if (errno != EINTR) {
return -1;
}
} else if (ret == 0) {
close(gdbserver_user_state.fd);
gdbserver_user_state.fd = -1;
return -1;
} else {
break;
}
}
return ch;
}
bool gdb_got_immediate_ack(void)
{
int i;
i = gdb_get_char();
if (i < 0) {
/* no response, continue anyway */
return true;
}
if (i == '+') {
/* received correctly, continue */
return true;
}
/* anything else, including '-' then try again */
return false;
}
void gdb_put_buffer(const uint8_t *buf, int len)
{
int ret;
while (len > 0) {
ret = send(gdbserver_user_state.fd, buf, len, 0);
if (ret < 0) {
if (errno != EINTR) {
return;
}
} else {
buf += ret;
len -= ret;
}
}
}
/* Tell the remote gdb that the process has exited. */
void gdb_exit(int code)
{
char buf[4];
if (!gdbserver_state.init) {
return;
}
if (gdbserver_user_state.socket_path) {
unlink(gdbserver_user_state.socket_path);
}
if (gdbserver_user_state.fd < 0) {
return;
}
trace_gdbstub_op_exiting((uint8_t)code);
if (gdbserver_state.allow_stop_reply) {
snprintf(buf, sizeof(buf), "W%02x", (uint8_t)code);
gdb_put_packet(buf);
gdbserver_state.allow_stop_reply = false;
}
}
void gdb_qemu_exit(int code)
{
exit(code);
}
int gdb_handlesig_reason(CPUState *cpu, int sig, const char *reason)
{
char buf[256];
int n;
if (!gdbserver_state.init || gdbserver_user_state.fd < 0) {
return sig;
}
/* disable single step if it was enabled */
cpu_single_step(cpu, 0);
tb_flush(cpu);
if (sig != 0) {
gdb_set_stop_cpu(cpu);
if (gdbserver_state.allow_stop_reply) {
g_string_printf(gdbserver_state.str_buf,
"T%02xthread:", gdb_target_signal_to_gdb(sig));
gdb_append_thread_id(cpu, gdbserver_state.str_buf);
g_string_append_c(gdbserver_state.str_buf, ';');
if (reason) {
g_string_append(gdbserver_state.str_buf, reason);
}
gdb_put_strbuf();
gdbserver_state.allow_stop_reply = false;
}
}
/*
* gdb_put_packet() might have detected that the peer terminated the
* connection.
*/
if (gdbserver_user_state.fd < 0) {
return sig;
}
sig = 0;
gdbserver_state.state = RS_IDLE;
gdbserver_user_state.running_state = 0;
while (gdbserver_user_state.running_state == 0) {
n = read(gdbserver_user_state.fd, buf, 256);
if (n > 0) {
int i;
for (i = 0; i < n; i++) {
gdb_read_byte(buf[i]);
}
} else {
/*
* XXX: Connection closed. Should probably wait for another
* connection before continuing.
*/
if (n == 0) {
close(gdbserver_user_state.fd);
}
gdbserver_user_state.fd = -1;
return sig;
}
}
sig = gdbserver_state.signal;
gdbserver_state.signal = 0;
return sig;
}
/* Tell the remote gdb that the process has exited due to SIG. */
void gdb_signalled(CPUArchState *env, int sig)
{
char buf[4];
if (!gdbserver_state.init || gdbserver_user_state.fd < 0 ||
!gdbserver_state.allow_stop_reply) {
return;
}
snprintf(buf, sizeof(buf), "X%02x", gdb_target_signal_to_gdb(sig));
gdb_put_packet(buf);
gdbserver_state.allow_stop_reply = false;
}
static void gdb_accept_init(int fd)
{
gdb_init_gdbserver_state();
gdb_create_default_process(&gdbserver_state);
gdbserver_state.processes[0].attached = true;
gdbserver_state.c_cpu = gdb_first_attached_cpu();
gdbserver_state.g_cpu = gdbserver_state.c_cpu;
gdbserver_user_state.fd = fd;
}
static bool gdb_accept_socket(int gdb_fd)
{
int fd;
for (;;) {
fd = accept(gdb_fd, NULL, NULL);
if (fd < 0 && errno != EINTR) {
perror("accept socket");
return false;
} else if (fd >= 0) {
qemu_set_cloexec(fd);
break;
}
}
gdb_accept_init(fd);
return true;
}
static int gdbserver_open_socket(const char *path)
{
struct sockaddr_un sockaddr = {};
int fd, ret;
fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (fd < 0) {
perror("create socket");
return -1;
}
sockaddr.sun_family = AF_UNIX;
pstrcpy(sockaddr.sun_path, sizeof(sockaddr.sun_path) - 1, path);
ret = bind(fd, (struct sockaddr *)&sockaddr, sizeof(sockaddr));
if (ret < 0) {
perror("bind socket");
close(fd);
return -1;
}
ret = listen(fd, 1);
if (ret < 0) {
perror("listen socket");
close(fd);
return -1;
}
return fd;
}
static bool gdb_accept_tcp(int gdb_fd)
{
struct sockaddr_in sockaddr = {};
socklen_t len;
int fd;
for (;;) {
len = sizeof(sockaddr);
fd = accept(gdb_fd, (struct sockaddr *)&sockaddr, &len);
if (fd < 0 && errno != EINTR) {
perror("accept");
return false;
} else if (fd >= 0) {
qemu_set_cloexec(fd);
break;
}
}
/* set short latency */
if (socket_set_nodelay(fd)) {
perror("setsockopt");
close(fd);
return false;
}
gdb_accept_init(fd);
return true;
}
static int gdbserver_open_port(int port)
{
struct sockaddr_in sockaddr;
int fd, ret;
fd = socket(PF_INET, SOCK_STREAM, 0);
if (fd < 0) {
perror("socket");
return -1;
}
qemu_set_cloexec(fd);
socket_set_fast_reuse(fd);
sockaddr.sin_family = AF_INET;
sockaddr.sin_port = htons(port);
sockaddr.sin_addr.s_addr = 0;
ret = bind(fd, (struct sockaddr *)&sockaddr, sizeof(sockaddr));
if (ret < 0) {
perror("bind");
close(fd);
return -1;
}
ret = listen(fd, 1);
if (ret < 0) {
perror("listen");
close(fd);
return -1;
}
return fd;
}
int gdbserver_start(const char *port_or_path)
{
int port = g_ascii_strtoull(port_or_path, NULL, 10);
int gdb_fd;
if (port > 0) {
gdb_fd = gdbserver_open_port(port);
} else {
gdb_fd = gdbserver_open_socket(port_or_path);
}
if (gdb_fd < 0) {
return -1;
}
if (port > 0 && gdb_accept_tcp(gdb_fd)) {
return 0;
} else if (gdb_accept_socket(gdb_fd)) {
gdbserver_user_state.socket_path = g_strdup(port_or_path);
return 0;
}
/* gone wrong */
close(gdb_fd);
return -1;
}
/* Disable gdb stub for child processes. */
void gdbserver_fork(CPUState *cpu)
{
if (!gdbserver_state.init || gdbserver_user_state.fd < 0) {
return;
}
close(gdbserver_user_state.fd);
gdbserver_user_state.fd = -1;
cpu_breakpoint_remove_all(cpu, BP_GDB);
/* no cpu_watchpoint_remove_all for user-mode */
}
/*
* Execution state helpers
*/
void gdb_handle_query_attached(GArray *params, void *user_ctx)
{
gdb_put_packet("0");
}
void gdb_continue(void)
{
gdbserver_user_state.running_state = 1;
trace_gdbstub_op_continue();
}
/*
* Resume execution, for user-mode emulation it's equivalent to
* gdb_continue.
*/
int gdb_continue_partial(char *newstates)
{
CPUState *cpu;
int res = 0;
/*
* This is not exactly accurate, but it's an improvement compared to the
* previous situation, where only one CPU would be single-stepped.
*/
CPU_FOREACH(cpu) {
if (newstates[cpu->cpu_index] == 's') {
trace_gdbstub_op_stepping(cpu->cpu_index);
cpu_single_step(cpu, gdbserver_state.sstep_flags);
}
}
gdbserver_user_state.running_state = 1;
return res;
}
/*
* Memory access helpers
*/
int gdb_target_memory_rw_debug(CPUState *cpu, hwaddr addr,
uint8_t *buf, int len, bool is_write)
{
CPUClass *cc;
cc = CPU_GET_CLASS(cpu);
if (cc->memory_rw_debug) {
return cc->memory_rw_debug(cpu, addr, buf, len, is_write);
}
return cpu_memory_rw_debug(cpu, addr, buf, len, is_write);
}
/*
* cpu helpers
*/
unsigned int gdb_get_max_cpus(void)
{
CPUState *cpu;
unsigned int max_cpus = 1;
CPU_FOREACH(cpu) {
max_cpus = max_cpus <= cpu->cpu_index ? cpu->cpu_index + 1 : max_cpus;
}
return max_cpus;
}
/* replay not supported for user-mode */
bool gdb_can_reverse(void)
{
return false;
}
/*
* Break/Watch point helpers
*/
bool gdb_supports_guest_debug(void)
{
/* user-mode == TCG == supported */
return true;
}
int gdb_breakpoint_insert(CPUState *cs, int type, vaddr addr, vaddr len)
{
CPUState *cpu;
int err = 0;
switch (type) {
case GDB_BREAKPOINT_SW:
case GDB_BREAKPOINT_HW:
CPU_FOREACH(cpu) {
err = cpu_breakpoint_insert(cpu, addr, BP_GDB, NULL);
if (err) {
break;
}
}
return err;
default:
/* user-mode doesn't support watchpoints */
return -ENOSYS;
}
}
int gdb_breakpoint_remove(CPUState *cs, int type, vaddr addr, vaddr len)
{
CPUState *cpu;
int err = 0;
switch (type) {
case GDB_BREAKPOINT_SW:
case GDB_BREAKPOINT_HW:
CPU_FOREACH(cpu) {
err = cpu_breakpoint_remove(cpu, addr, BP_GDB);
if (err) {
break;
}
}
return err;
default:
/* user-mode doesn't support watchpoints */
return -ENOSYS;
}
}
void gdb_breakpoint_remove_all(CPUState *cs)
{
cpu_breakpoint_remove_all(cs, BP_GDB);
}
/*
* For user-mode syscall support we send the system call immediately
* and then return control to gdb for it to process the syscall request.
* Since the protocol requires that gdb hands control back to us
* using a "here are the results" F packet, we don't need to check
* gdb_handlesig's return value (which is the signal to deliver if
* execution was resumed via a continue packet).
*/
void gdb_syscall_handling(const char *syscall_packet)
{
gdb_put_packet(syscall_packet);
gdb_handlesig(gdbserver_state.c_cpu, 0);
}
static bool should_catch_syscall(int num)
{
if (gdbserver_user_state.catch_all_syscalls) {
return true;
}
if (num < 0 || num >= GDB_NR_SYSCALLS) {
return false;
}
return test_bit(num, gdbserver_user_state.catch_syscalls_mask);
}
void gdb_syscall_entry(CPUState *cs, int num)
{
if (should_catch_syscall(num)) {
g_autofree char *reason = g_strdup_printf("syscall_entry:%x;", num);
gdb_handlesig_reason(cs, gdb_target_sigtrap(), reason);
}
}
void gdb_syscall_return(CPUState *cs, int num)
{
if (should_catch_syscall(num)) {
g_autofree char *reason = g_strdup_printf("syscall_return:%x;", num);
gdb_handlesig_reason(cs, gdb_target_sigtrap(), reason);
}
}
void gdb_handle_set_catch_syscalls(GArray *params, void *user_ctx)
{
const char *param = get_param(params, 0)->data;
GDBSyscallsMask catch_syscalls_mask;
bool catch_all_syscalls;
unsigned int num;
const char *p;
/* "0" means not catching any syscalls. */
if (strcmp(param, "0") == 0) {
gdbserver_user_state.catch_all_syscalls = false;
memset(gdbserver_user_state.catch_syscalls_mask, 0,
sizeof(gdbserver_user_state.catch_syscalls_mask));
gdb_put_packet("OK");
return;
}
/* "1" means catching all syscalls. */
if (strcmp(param, "1") == 0) {
gdbserver_user_state.catch_all_syscalls = true;
gdb_put_packet("OK");
return;
}
/*
* "1;..." means catching only the specified syscalls.
* The syscall list must not be empty.
*/
if (param[0] == '1' && param[1] == ';') {
catch_all_syscalls = false;
memset(catch_syscalls_mask, 0, sizeof(catch_syscalls_mask));
for (p = &param[2];; p++) {
if (qemu_strtoui(p, &p, 16, &num) || (*p && *p != ';')) {
goto err;
}
if (num >= GDB_NR_SYSCALLS) {
/*
* Fall back to reporting all syscalls. Reporting extra
* syscalls is inefficient, but the spec explicitly allows it.
* Keep parsing in case there is a syntax error ahead.
*/
catch_all_syscalls = true;
} else {
set_bit(num, catch_syscalls_mask);
}
if (!*p) {
break;
}
}
gdbserver_user_state.catch_all_syscalls = catch_all_syscalls;
if (!catch_all_syscalls) {
memcpy(gdbserver_user_state.catch_syscalls_mask,
catch_syscalls_mask, sizeof(catch_syscalls_mask));
}
gdb_put_packet("OK");
return;
}
err:
gdb_put_packet("E00");
}