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From: =?UTF-8?q?Alex=20Benn=C3=A9e?= <alex.bennee@linaro.org>
To: qemu-devel@nongnu.org
Cc: qemu-ppc@nongnu.org, Mahmoud Mandour <ma.mandourr@gmail.com>,
Thomas Huth <thuth@redhat.com>,
Daniel Henrique Barboza <danielhb413@gmail.com>,
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Laurent Vivier <laurent@vivier.eu>, Riku Voipio <riku.voipio@iki.fi>,
Bin Meng <bmeng.cn@gmail.com>, qemu-rust@nongnu.org,
Laurent Vivier <lvivier@redhat.com>,
Liu Zhiwei <zhiwei_liu@linux.alibaba.com>, Weiwei Li <liwei1518@gmail.com>,
qemu-riscv@nongnu.org, Fabiano Rosas <farosas@suse.de>,
Tyrone Ting <kfting@nuvoton.com>, Paolo Bonzini <pbonzini@redhat.com>,
Nicholas Piggin <npiggin@gmail.com>, Alexandre Iooss <erdnaxe@crans.org>,
Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH 15/18] gdbstub: Allow late attachment
Date: Mon, 3 Feb 2025 14:40:45 +0000
Message-Id: <20250203144048.2131117-16-alex.bennee@linaro.org>
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From: Ilya Leoshkevich <iii@linux.ibm.com>
Allow debugging individual processes in multi-process applications by
starting them with export QEMU_GDB=3D/tmp/qemu-%d.sock,suspend=3Dn.
Currently one would have to attach to every process to ensure the app
makes progress.
In case suspend=3Dn is not specified, the flow remains unchanged. If it
is specified, then accepting the client connection is delegated to a
thread. In the future this machinery may be reused for handling
reconnections and interruptions.
On accepting a connection, the thread schedules gdb_handlesig() on the
first CPU and wakes it up with host_interrupt_signal. Note that the
result of this gdb_handlesig() invocation is handled, as opposed to
many other existing call sites. These other call sites probably need to
be fixed separately.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20250117001542.8290-7-iii@linux.ibm.com>
Signed-off-by: Alex Benn=C3=A9e <alex.bennee@linaro.org>
---
bsd-user/main.c | 1 -
gdbstub/user.c | 115 +++++++++++++++++++++++++++++++++++++++++-----
linux-user/main.c | 1 -
3 files changed, 103 insertions(+), 14 deletions(-)
diff --git a/bsd-user/main.c b/bsd-user/main.c
index b2f6a9be2f..fdb160bed0 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -629,7 +629,6 @@ int main(int argc, char **argv)
=20
if (gdbstub) {
gdbserver_start(gdbstub, &error_fatal);
- gdb_handlesig(cpu, 0, NULL, NULL, 0);
}
cpu_loop(env);
/* never exits */
diff --git a/gdbstub/user.c b/gdbstub/user.c
index 8225b70280..3730f32c41 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -22,6 +22,7 @@
#include "gdbstub/user.h"
#include "gdbstub/enums.h"
#include "hw/core/cpu.h"
+#include "user/signal.h"
#include "trace.h"
#include "internals.h"
=20
@@ -393,32 +394,122 @@ static int gdbserver_open_port(int port, Error **err=
p)
return fd;
}
=20
-bool gdbserver_start(const char *port_or_path, Error **errp)
+static bool gdbserver_accept(int port, int gdb_fd, const char *path)
{
- int port =3D g_ascii_strtoull(port_or_path, NULL, 10);
+ bool ret;
+
+ if (port > 0) {
+ ret =3D gdb_accept_tcp(gdb_fd);
+ } else {
+ ret =3D gdb_accept_socket(gdb_fd);
+ if (ret) {
+ gdbserver_user_state.socket_path =3D g_strdup(path);
+ }
+ }
+
+ if (!ret) {
+ close(gdb_fd);
+ }
+
+ return ret;
+}
+
+struct {
+ int port;
int gdb_fd;
+ char *path;
+} gdbserver_args;
+
+static void do_gdb_handlesig(CPUState *cs, run_on_cpu_data arg)
+{
+ int sig;
+
+ sig =3D target_to_host_signal(gdb_handlesig(cs, 0, NULL, NULL, 0));
+ if (sig >=3D 1 && sig < NSIG) {
+ qemu_kill_thread(gdb_get_cpu_index(cs), sig);
+ }
+}
+
+static void *gdbserver_accept_thread(void *arg)
+{
+ if (gdbserver_accept(gdbserver_args.port, gdbserver_args.gdb_fd,
+ gdbserver_args.path)) {
+ CPUState *cs =3D first_cpu;
+
+ async_safe_run_on_cpu(cs, do_gdb_handlesig, RUN_ON_CPU_NULL);
+ qemu_kill_thread(gdb_get_cpu_index(cs), host_interrupt_signal);
+ }
+
+ g_free(gdbserver_args.path);
+ gdbserver_args.path =3D NULL;
+
+ return NULL;
+}
=20
+#define USAGE "\nUsage: -g {port|path}[,suspend=3D{y|n}]"
+
+bool gdbserver_start(const char *args, Error **errp)
+{
+ g_auto(GStrv) argv =3D g_strsplit(args, ",", 0);
+ const char *port_or_path =3D NULL;
+ bool suspend =3D true;
+ int gdb_fd, port;
+ GStrv arg;
+
+ for (arg =3D argv; *arg; arg++) {
+ g_auto(GStrv) tokens =3D g_strsplit(*arg, "=3D", 2);
+
+ if (g_strcmp0(tokens[0], "suspend") =3D=3D 0) {
+ if (tokens[1] =3D=3D NULL) {
+ error_setg(errp,
+ "gdbstub: missing \"suspend\" option value" USA=
GE);
+ return false;
+ } else if (!qapi_bool_parse(tokens[0], tokens[1],
+ &suspend, errp)) {
+ return false;
+ }
+ } else {
+ if (port_or_path) {
+ error_setg(errp, "gdbstub: unknown option \"%s\"" USAGE, *=
arg);
+ return false;
+ }
+ port_or_path =3D *arg;
+ }
+ }
+ if (!port_or_path) {
+ error_setg(errp, "gdbstub: port or path not specified" USAGE);
+ return false;
+ }
+
+ port =3D g_ascii_strtoull(port_or_path, NULL, 10);
if (port > 0) {
gdb_fd =3D gdbserver_open_port(port, errp);
} else {
gdb_fd =3D gdbserver_open_socket(port_or_path, errp);
}
-
if (gdb_fd < 0) {
return false;
}
=20
- if (port > 0 && gdb_accept_tcp(gdb_fd)) {
- return true;
- } else if (gdb_accept_socket(gdb_fd)) {
- gdbserver_user_state.socket_path =3D g_strdup(port_or_path);
+ if (suspend) {
+ if (gdbserver_accept(port, gdb_fd, port_or_path)) {
+ gdb_handlesig(first_cpu, 0, NULL, NULL, 0);
+ return true;
+ } else {
+ error_setg(errp, "gdbstub: failed to accept connection");
+ return false;
+ }
+ } else {
+ QemuThread thread;
+
+ gdbserver_args.port =3D port;
+ gdbserver_args.gdb_fd =3D gdb_fd;
+ gdbserver_args.path =3D g_strdup(port_or_path);
+ qemu_thread_create(&thread, "gdb-accept",
+ &gdbserver_accept_thread, NULL,
+ QEMU_THREAD_DETACHED);
return true;
}
-
- /* gone wrong */
- close(gdb_fd);
- error_setg(errp, "gdbstub: failed to accept connection");
- return false;
}
=20
void gdbserver_fork_start(void)
diff --git a/linux-user/main.c b/linux-user/main.c
index 7198fa0986..5c74c52cc5 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -1024,7 +1024,6 @@ int main(int argc, char **argv, char **envp)
=20
if (gdbstub) {
gdbserver_start(gdbstub, &error_fatal);
- gdb_handlesig(cpu, 0, NULL, NULL, 0);
}
=20
#ifdef CONFIG_SEMIHOSTING
--=20
2.39.5