On 2/20/20 4:58 PM, Changbin Du wrote:
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
You actually fixed this for all architectures :) This has been annoying me on MIPS since more than a year... I haven't checked the GDB protocol spec, but so far: Tested-by: Philippe Mathieu-Daudé <phi...@redhat.com>
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); }
