stepping problem with sh4, gdbserver
peter garrone <pgarrone <at> linuxmail.org>
2005-02-02 06:51:44 GMT
While debugging remotely with gdbserver and stepping the gdb (6.3) test program "break.c" at line 96, the
"next" command causes a segfault at frame.c line 1244 (frame->next != NULL) because frame is null. The
relevant backtrace is:
get_frame_pc(frame = 0) frame.c:1244
Tracing the execution of gdb itself, handle_inferior_event is invoked one instruction before and then at
the point of calling the function marker1, according to the value of stop_pc at infrun.c:1547. This
second invocation of handle_inferior_event inserts a breakpoint at the return point (stop_pc + 4) and
returns. Then handle_inferior_event is invoked again, this time stop_pc is set to the address of the very
first instruction of the marker1 function. The test at infrun.c:2285 if(frame_id_eq(.....)) returns
true and the block following is taken.
Execution proceeds to line 2449
"insert_step_resume_breakpoint_at_frame(get_prev_frame(get_current_frame())" where the error occurs.
I dont understand why gdb would set a breakpoint in marker1 when it is stepping over the function. At the
first instruction of marker1, the stack would still be unchanged from its value in the top function, since
the sh4 does not change the stack when it calls a subroutine, so perhaps this has something to do with it.
I am using gdb 6.3, but have seen a similar error on previous versions. Configuration is for
sh4-xxx-linux-gnu, gdb_target=linux, --enable-shared, --enable-threads
The only relevant source change is an include in gdbserver/linux-sh-low.c where #include <sys/reg.h> is
Any help appreciated.