Hardware watchpoints on GNU/Linux AArch64

Florian Weimer fweimer@redhat.com
Mon Jan 2 17:59:19 GMT 2023


* Florian Weimer:

> * Andrew Pinski:
>
>> On Mon, Jan 2, 2023 at 8:49 AM Florian Weimer via Gdb
>> <gdb@sourceware.org> wrote:
>>>
>>> Running
>>>
>>> gdb-12.1-10.fc38.aarch64
>>> kernel-6.2.0-0.rc1.20221230gitbff687b3dad6.15.fc38.aarch64
>>>
>>> I do not seem to be able to use hardware watchpoints.  GDB just logs
>>> warnings:
>>>
>>> warning: Unable to determine the number of hardware watchpoints available.
>>> warning: Unable to determine the number of hardware breakpoints available.
>>
>> This shows up when the ptrace either fails or ptrace returns an
>> unknown value for AARCH64_DEBUG_ARCH value.
>> In the boot log there should be a message saying how many HW
>> breakpoint and watchpoints there are and what version of the debug
>> arch is there.
>
> I only see this in the kernel log:
>
> hw-breakpoint: found 6 breakpoint and 4 watchpoint registers.
>
> Nothing else in the vicinity.

GDB on bare-metal (on a different machine, not the hypervisor) has
hardware watchpoint support, as expected.

Probably the next step is to figure out what software is running on the
hypervisor.

Thanks,
Florian



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