Re: [PATCH 3/4] arm64: Allow hw watchpoint of length 3,5,6 and 7

From: Pratyush Anand
Date: Thu Oct 13 2016 - 06:22:38 EST

On Wednesday 12 October 2016 04:46 PM, Yao Qi wrote:
On Wed, Oct 12, 2016 at 6:58 AM, Pratyush Anand <panand@xxxxxxxxxx> wrote:
Since, arm64 can support all offset within a double word limit. Therefore,
now support other lengths within that range as well.

How does ptracer (like GDB) detect kernel has already supported all byte
address select values? I suppose ptrace(NT_ARM_HW_WATCH, ) with
len is 3 or 5 fail on current kernel but is of success after your patches

Thanks for testing these patches.

I do not know if we can know that other than the failure of ptrace(PTRACE_SETREGSET, .., NT_ARM_HW_WATCH, ..). I do not see any such option in `man ptrace`.

GDB is aware of the byte address select limitation in kernel, so it always
sets 1,2,4,8 in len in ctrl. GDB needs to know whether the limitation is still
there or not.

Not sure if other than "kernel version" anything will help here.