On Mon, Nov 26, 2018 at 04:31:23PM -0800, Florian Fainelli wrote:
> breakpoint tests on the ARM 32-bit kernel are broken in several ways.
>
> The breakpoint length requested does not necessarily match whether the
> function address has the Thumb bit (bit 0) set or not, and this does
> matter to the ARM kernel hw_breakpoint infrastructure. See [1] for
> background.
>
> [1]: https://lkml.org/lkml/2018/11/15/205
>
> As Will indicated, the overflow handling would require single-stepping
> which is not supported at the moment. Just disable those tests for the
> ARM 32-bit platforms.
>
> Signed-off-by: Florian Fainelli <[email protected]>
> ---
> Changes in v2:
>
> - Fix comment above test per Will's feedback
>
> tools/perf/tests/bp_signal.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/tests/bp_signal.c b/tools/perf/tests/bp_signal.c
> index a467615c5a0e..05bf06f84a3b 100644
> --- a/tools/perf/tests/bp_signal.c
> +++ b/tools/perf/tests/bp_signal.c
> @@ -292,11 +292,11 @@ int test__bp_signal(struct test *test __maybe_unused,
> int subtest __maybe_unused
> bool test__bp_signal_is_supported(void)
> {
> /*
> - * The powerpc so far does not have support to even create
> + * powerpc, s390 and arm so far does not have support to even create
> * instruction breakpoint using the perf event interface.
> * Once it's there we can release this.
Sorry, Florian, but I still think this comment is bogus since you can
create instruction breakpoints via perf on arm. I think you need
something like:
/*
* PowerPC and S390 do not support creation of instruction
* breakpoints using the perf_event interface.
*
* ARM requires explicit rounding down of the instruction
* pointer in Thumb mode, and then requires the single-step
* to be handled explicitly in the overflow handler to avoid
* stepping into the SIGIO handler and getting stuck on the
* breakpointed instruction.
*
* Just disable the test for these architectures until these
* issues are resolved.
*/
Will
