From 4f71086665360eb15cb0cc3392bd5063f26ee934 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 15 May 2018 19:19:58 +0100 Subject: [PATCH] gdbstub: Clarify what gdb_handlesig() is doing gdb_handlesig()'s behaviour is not entirely obvious at first glance. Add a doc comment for it, and also add a comment explaining why it's ok for gdb_do_syscallv() to ignore gdb_handlesig()'s return value. (Coverity complains about this: CID 1390850.) Signed-off-by: Peter Maydell Message-Id: <20180515181958.25837-1-peter.maydell@linaro.org> Signed-off-by: Laurent Vivier --- gdbstub.c | 6 ++++++ include/exec/gdbstub.h | 15 +++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/gdbstub.c b/gdbstub.c index e4ece2f5bc..6081e719c5 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1558,6 +1558,12 @@ void gdb_do_syscallv(gdb_syscall_complete_cb cb, const char *fmt, va_list va) *p = 0; #ifdef CONFIG_USER_ONLY put_packet(s, s->syscall_buf); + /* 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). + */ gdb_handlesig(s->c_cpu, 0); #else /* In this case wait to send the syscall packet until notification that diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h index 2e8a4b83b9..08363969c1 100644 --- a/include/exec/gdbstub.h +++ b/include/exec/gdbstub.h @@ -48,6 +48,21 @@ int use_gdb_syscalls(void); void gdb_set_stop_cpu(CPUState *cpu); void gdb_exit(CPUArchState *, int); #ifdef CONFIG_USER_ONLY +/** + * gdb_handlesig: yield control to gdb + * @cpu: CPU + * @sig: if non-zero, the signal number which caused us to stop + * + * This function yields control to gdb, when a user-mode-only target + * needs to stop execution. If @sig is non-zero, then we will send a + * stop packet to tell gdb that we have stopped because of this signal. + * + * This function will block (handling protocol requests from gdb) + * until gdb tells us to continue target execution. When it does + * return, the return value is a signal to deliver to the target, + * or 0 if no signal should be delivered, ie the signal that caused + * us to stop should be ignored. + */ int gdb_handlesig(CPUState *, int); void gdb_signalled(CPUArchState *, int); void gdbserver_fork(CPUState *);