Allow debugging individual processes in multi-process applications by
starting them with export QEMU_GDB=/tmp/qemu-%d.sock,suspend=n.
Currently one would have to attach to every process to ensure the app
makes progress.
In case suspend=n 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 Bennée <alex.bennee@linaro.org>
Message-Id: <20250207153112.3939799-16-alex.bennee@linaro.org>
In case an emulated process execve()s another emulated process, bind()
will fail, because the socket already exists. So try deleting it. Use
the existing unix_listen() function which does this. Link qemu-user
with qemu-sockets.c and add the monitor_get_fd() stub.
Note that it is not possible to handle this in do_execv(): deleting
gdbserver_user_state.socket_path before safe_execve() is not correct,
because the latter may fail, and afterwards we may lose control.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250117001542.8290-3-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250207153112.3939799-12-alex.bennee@linaro.org>
This started as a clean-up to properly pass a Error handler to the
gdbserver_start so we could do the right thing for command line and
HMP invocations.
Now that we have cleaned up foreach_device_config_or_exit() in earlier
patches we can further simplify by it by passing &error_fatal instead
of checking the return value. Having a return value is still useful
for HMP though so tweak the return to use a simple bool instead.
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250116160306.1709518-11-alex.bennee@linaro.org>
Move GdbCmdParseEntry and its associated types into a separate header
file to allow the use of GdbCmdParseEntry and other gdbstub command
functions outside of gdbstub.c.
Since GdbCmdParseEntry and get_param are now public, kdoc
GdbCmdParseEntry and rename get_param to gdb_get_cmd_param.
This commit also makes gdb_put_packet public since is used in gdbstub
command handling.
Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240628050850.536447-3-gustavo.romero@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240705084047.857176-32-alex.bennee@linaro.org>
When the terminal GDB_FORK_ENABLED state is reached, the coordination
socket is not needed anymore and is therefore closed. However, if there
is a communication error between QEMU gdbstub and GDB, the generic
error handling code attempts to close it again.
Fix by closing it later - before returning - instead.
Fixes: Coverity CID 1539966
Fixes: d547e711a8 ("gdbstub: Implement follow-fork-mode child")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240312001813.13720-1-iii@linux.ibm.com>
Add stub to handle Xfer:siginfo:read packet query that requests the
machine's siginfo data.
This is used when GDB user executes 'print $_siginfo' and when the
machine stops due to a signal, for instance, on SIGSEGV. The information
in siginfo allows GDB to determiner further details on the signal, like
the fault address/insn when the SIGSEGV is caught.
Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Message-Id: <20240309030901.1726211-5-gustavo.romero@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Currently it's not possible to use gdbstub for debugging linux-user
code that runs in a forked child, which is normally done using the `set
follow-fork-mode child` GDB command. Purely on the protocol level, the
missing piece is the fork-events feature.
However, a deeper problem is supporting $Hg switching between different
processes - right now it can do only threads. Implementing this for the
general case would be quite complicated, but, fortunately, for the
follow-fork-mode case there are a few factors that greatly simplify
things: fork() happens in the exclusive section, there are only two
processes involved, and before one of them is resumed, the second one
is detached.
This makes it possible to implement a simplified scheme: the parent and
the child share the gdbserver socket, it's used only by one of them at
any given time, which is coordinated through a separate socketpair. The
processes can read from the gdbserver socket only one byte at a time,
which is not great for performance, but, fortunately, the
follow-fork-mode handling involves only a few messages.
Advertise the fork-events support, and remember whether GDB has it
as well. Implement the state machine that is initialized on fork(),
decides the current owner of the gdbserver socket, and is terminated
when one of the two processes is detached. The logic for the parent and
the child is the same, only the initial state is different.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20240219141628.246823-12-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240305121005.3528075-13-alex.bennee@linaro.org>
