Recently when debugging an arm32 system on qemu, I found sometimes the
single-step command (stepi) is not working. This can be reproduced by
below steps:
1) start qemu-system-arm -s -S .. and wait for gdb connection.
2) start gdb and connect to qemu. In my case, gdb gets a wrong value
(0x60) for PC.
3) After connected, type 'stepi' and expect it will stop at next ins.
But, it has never stopped. This because:
1) We doesn't report ‘vContSupported’ feature to gdb explicitly and gdb
think we do not support it. In this case, gdb use a software breakpoint
to emulate single-step.
2) Since gdb gets a wrong initial value of PC, then gdb inserts a
breakpoint to wrong place (PC+4).
Since we do support ‘vContSupported’ query command, so let's tell gdb that
we support it.
Before this change, gdb send below 'Z0' packet to implement single-step:
gdb_handle_packet: Z0,4,4
After this change, gdb send "vCont;s.." which is expected:
gdb_handle_packet: vCont?
put_packet: vCont;c;C;s;S
gdb_handle_packet: vCont;s:p1.1;c:p1.-1
Signed-off-by: Changbin Du <changbin...@gmail.com>
---
gdbstub.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gdbstub.c b/gdbstub.c
index ce304ff482..adccd938e2 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -2111,7 +2111,7 @@ static void handle_query_supported(GdbCmdContext
*gdb_ctx, void *user_ctx)
gdb_ctx->s->multiprocess = true;
}
- pstrcat(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf), ";multiprocess+");
+ pstrcat(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf),
";vContSupported+;multiprocess+");
put_packet(gdb_ctx->s, gdb_ctx->str_buf);
}
--
2.25.0
