From 7eb895307f53af3435440d3fe67c0e4e679d99b2 Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Mon, 23 May 2016 17:32:56 +0100 Subject: Skip unwritable frames in command "finish" Nowadays, GDB can't insert breakpoint on the return address of the exception handler on ARM M-profile, because the address is a magic one 0xfffffff9, (gdb) bt #0 CT32B1_IRQHandler () at ../src/timer.c:67 #1 #2 main () at ../src/timer.c:127 (gdb) info frame Stack level 0, frame at 0x200ffa8: pc = 0x4ec in CT32B1_IRQHandler (../src/timer.c:67); saved pc = 0xfffffff9 called by frame at 0x200ffc8 source language c. Arglist at 0x200ffa0, args: Locals at 0x200ffa0, Previous frame's sp is 0x200ffa8 Saved registers: r7 at 0x200ffa0, lr at 0x200ffa4 (gdb) x/x 0xfffffff9 0xfffffff9: Cannot access memory at address 0xfffffff9 (gdb) finish Run till exit from #0 CT32B1_IRQHandler () at ../src/timer.c:67 Ed:15: Target error from Set break/watch: Et:96: Pseudo-address (0xFFFFFFxx) for EXC_RETURN is invalid (GDB error?) Warning: Cannot insert hardware breakpoint 0. Could not insert hardware breakpoints: You may have requested too many hardware breakpoints/watchpoints. Command aborted. even some debug probe can't set hardware breakpoint on the magic address too, (gdb) hbreak *0xfffffff9 Hardware assisted breakpoint 2 at 0xfffffff9 (gdb) c Continuing. Ed:15: Target error from Set break/watch: Et:96: Pseudo-address (0xFFFFFFxx) for EXC_RETURN is invalid (GDB error?) Warning: Cannot insert hardware breakpoint 2. Could not insert hardware breakpoints: You may have requested too many hardware breakpoints/watchpoints. Command aborted. The problem described above is quite similar to PR 8841, in which GDB can't set breakpoint on signal trampoline, which is mapped to a read-only page by kernel. The rationale of this patch is to skip "unwritable" frames when looking for caller frames in command "finish", and a new gdbarch method code_of_frame_writable is added. This patch fixes the problem on ARM cortex-m target, but it can be used to fix PR 8841 too. gdb: 2016-05-10 Yao Qi * arch-utils.c (default_code_of_frame_writable): New function. * arch-utils.h (default_code_of_frame_writable): Declare. * arm-tdep.c (arm_code_of_frame_writable): New function. (arm_gdbarch_init): Install gdbarch method code_of_frame_writable if the target is M-profile. * frame.c (skip_unwritable_frames): New function. * frame.h (skip_unwritable_frames): Declare. * gdbarch.sh (code_of_frame_writable): New. * gdbarch.c, gdbarch.h: Re-generated. * infcmd.c (finish_command): Call skip_unwritable_frames. --- gdb/frame.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'gdb/frame.h') diff --git a/gdb/frame.h b/gdb/frame.h index 8ee64f1..5f21bb8 100644 --- a/gdb/frame.h +++ b/gdb/frame.h @@ -826,4 +826,9 @@ extern enum language get_frame_language (struct frame_info *frame); extern struct frame_info *skip_tailcall_frames (struct frame_info *frame); +/* Return the first frame above FRAME or FRAME of which the code is + writable. */ + +extern struct frame_info *skip_unwritable_frames (struct frame_info *frame); + #endif /* !defined (FRAME_H) */ -- cgit v1.1