Le 20/02/2020 à 18:47, Philippe Mathieu-Daudé a écrit : > 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...
The problem started with an update of QEMU or of GDB? At one point it seemed to work, so what happened? Thanks, Laurent