On Thu, Feb 20, 2020 at 06:47:26PM +0100, Philippe Mathieu-Daudé wrote: > 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> > Thanks for your feedback. :)
-- Cheers, Changbin Du
