Re: [PATCH] MIPS: uprobes: Restore thread.trap_nr

[Tiezhu Yang]

Cc:
Oleg Nesterov <oleg@xxxxxxxxxx>
Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>

On 04/23/2023 11:08 AM, Bagas Sanjaya wrote:
> On Sun, Apr 23, 2023 at 09:38:03AM +0800, Tiezhu Yang wrote:
> > thread.trap_nr is saved in arch_uprobe_pre_xol(), it should be restored
> > in arch_uprobe_{post,abort}_xol() accordingly, actually it was only done
> > in the post function, just do it in the abort function too, this change
> > is similar with x86 and powerpc.
>
> I'm confused (please fix up grammar, spelling, and punctuation). Can you
> explain why thread.trap_nr should be restored somewhere else? Also, what
> x86/powerpc changes as reference?

Here is the related first commit for x86 in 2012:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0326f5a94dde

When xol insn itself triggers the signal, restart the original insn,
in this case, UTASK_SSTEP_TRAPPED is set [1], it does *abort_xol()
instead of *post_xol() [2], then should do the restore operations.

Maybe Oleg and Srikar could give more detailed backgrounds, thank you.
https://lore.kernel.org/lkml/1682213883-3654-1-git-send-email-yangtiezhu@xxxxxxxxxxx/

[1] 
https://elixir.bootlin.com/linux/latest/source/kernel/events/uprobes.c#L1980
[2] 
https://elixir.bootlin.com/linux/latest/source/kernel/events/uprobes.c#L2268

Thanks,
Tiezhu