Hi, We need the `qqemu.Pid` packet only for the QEMU system part in order to figure out the page tables and to do it efficiently. We do have a fallback to using `monitor info mem` but it is slow, (iirc) doesn't provide all the necessary information and (iirc) isn't implemented on all architectures.
Also, is the QEMU own pid leak such a problem? There are worse issues than that available with current features though I believe they are not really security issues. I will detail this in a private email to you. Best, Dominik 'Disconnect3d' Czarnota On Fri, 2 May 2025 at 15:18, Alex Bennée <[email protected]> wrote: > Dominik 'Disconnect3d' Czarnota <[email protected]> writes: > > > This patch adds support for the `qqemu.Pid` packet to the qemu > > gdbstub which can be used by clients to get the QEMU process PID. > > > > This is useful for plugins like Pwndbg [0] or gdb-pt-dump in order to > > inspect the QEMU process memory through the /proc/self/{maps,mem} > > interfaces. Without this feature, they have to rely on doing an > > unreliable pgrep/ps output processing. > > That seems a little thin a reason for QEMU to expose its own PID. For > user-mode you can already get that detail through anything using > gdb_append_thread_id(). > > For system-mode leaking QEMU's own pid seems like an information leak at > best. There are modes like semihosting which give a remote even more > power but you need to at least opt in to that. > > > > > This patch has been developed by Patryk, who I included in the > > Co-authored-by and who asked me to send the patch. > > > > [0] https://github.com/pwndbg/pwndbg > > [1] https://github.com/martinradev/gdb-pt-dump > > > > Co-authored-by: Patryk 'patryk4815' Sondej <[email protected]> > > Signed-off-by: Dominik 'Disconnect3d' Czarnota < > [email protected]> > > --- > > gdbstub/gdbstub.c | 10 ++++++++++ > > 1 file changed, 10 insertions(+) > > > > diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c > > index 282e13e163..a077c2c5ed 100644 > > --- a/gdbstub/gdbstub.c > > +++ b/gdbstub/gdbstub.c > > @@ -1746,6 +1746,12 @@ static void handle_query_qemu_supported(GArray > *params, void *user_ctx) > > gdb_put_strbuf(); > > } > > > > +static void handle_query_qemu_pid(GArray *params, void *user_ctx) > > +{ > > + g_string_printf(gdbserver_state.str_buf, "F%x", getpid()); > > + gdb_put_strbuf(); > > +} > > + > > static const GdbCmdParseEntry gdb_gen_query_set_common_table[] = { > > /* Order is important if has same prefix */ > > { > > @@ -1902,6 +1908,10 @@ static const GdbCmdParseEntry > gdb_gen_query_table[] = { > > .handler = handle_query_qemu_supported, > > .cmd = "qemu.Supported", > > }, > > + { > > + .handler = handle_query_qemu_pid, > > + .cmd = "qemu.Pid", > > + }, > > #ifndef CONFIG_USER_ONLY > > { > > .handler = gdb_handle_query_qemu_phy_mem_mode, > > -- > Alex Bennée > Virtualisation Tech Lead @ Linaro >
