[PATCH v3 0/5] Software breakpoints support for ARM linux in GDBServer.

Antoine Tremblay
2015-10-20T16:48:21Z

In this v3 :

The main change is that the functions breakpoint_from_pc and
breakpoint_from_kind are now called : breakpoint_kind_from_pc and
sw_breakpoint_from_kind.

As suggested in : https://sourceware.org/ml/gdb-patches/2015-10/msg00287.html

Thank you Pedro the patch set is really more clear now.

Thus the patchset is restructured for that, patches have been renamed and
reordered.

Patches that have changed have their own v3 comment.

Original comment is updated :

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This patch series adds software breakpoint support for ARM on linux in
GDBServer.

This is a subset of a previous patchset :
https://sourceware.org/ml/gdb-patches/2015-09/msg00221.html

Other patches in that previous patchset will be sent after.

The problematic with ARM software breakpoints is that it can have 3 different
breakpoints one for each instruction set : arm, thumb, thumb2.

So we need to be able to set different kinds of breakpoints when GDBServer sets
its own breakpoints or when a breakpoint is set using GDB's Z0 packet.

In order to allow that the patches :

[PATCH v3 1/5] Add the target_ops needed for software breakpoints in GDBServer.

Adds new target operations to replace the static breakpoint and breakpoint_len
operation so that the target can return the proper GDBServer breakpoint.

[PATCH v3 2/5] Support breakpoint kinds for software breakpoints in GDBServer.

This is the main patch of the set, it handles GDBServer's software
breakpoints by calling the breakpoint_kind_from_pc operation and
sw_breakpoint_from_kind.

[PATCH v3 3/5] Implement breakpoint_kind_from_pc and sw_breakpoint_from_kind for
ARM in GDBServer.

This patch adds the ARM implementation of these target operation, selecting the
thumb, thumb2, or arm breakpoint based on the PC address and the flags encoded
in it.

[PATCH v3 4/5] Refactor the breakpoint definitions in linux-arm-low.c.

This patch refactors the breakpoint definitions a bit to be more clear
.
[PATCH v3 5/5] Support software breakpoints for ARM linux in GDBServer.

And finally software breakpoints via Z0 packets are enabled for ARM.

This patchset has no regressions observed, tested on ubuntu 14.04 ARMv7 and x86.
With gdbserver-{native,extended} / { -marm -mthumb }

Note also that while I could not test directly thumbv1 instructions with gcc
-marmv4t , manual testing of the software breakpoints was done for thumbv1
instructions.