[BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes implementation on arm

[BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes implementation on arm

[Jon Medhurst (Tixy)]

On Wed, 2017-02-15 at 09:27 +0900, Masami Hiramatsu wrote:
> Hi,
> 
> Here is the 2nd version of the patches which improve kprobe
> on arm implementation (a kind of bugfix). Version 1 is here;
> 
> https://lkml.org/lkml/2017/2/13/538
> 
> In this version I didn't update the code, just update the
> patch description according to Tixy's comment and add his Ack.
> 
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (3):
>       kprobes/arm: Allow to handle reentered kprobe on single-stepping
>       kprobes/arm: Skip single-stepping in recursing path if possible
>       kprobes/arm: Fix the return address of multiple kretprobes
> 

Thanks for doing these. Am I correct in assuming we don't need to
consider these fixes urgent or critical? Only the first looks like it
could be serious, and the x86 fix for that is 3 years old and ARM has
gone without it all this time. So I'm guessing it's fine to wait for the
normal development process and deal with it after the about to open
merge window is completed?

If so, I propose that I put the patches in a branch for Russell to pull
later (unless he pipes up with objections or says otherwise). Meantime
I'll investigate the kprobes test failures I see (which actually looks
like cache/TLB issues and not test code problems after all).

BTW, I added the?ARM kernel list to the CC. I spotted you didn't add it
to you patch postings, which means people interested in ARM (other than
Russell) wouldn't have seen them.

Thanks

-- 
Tixy

[BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes implementation on arm

[Masami Hiramatsu]

On Fri, 17 Feb 2017 11:01:10 +0000
"Jon Medhurst (Tixy)" <tixy@linaro.org> wrote:

> On Wed, 2017-02-15 at 09:27 +0900, Masami Hiramatsu wrote:
> > Hi,
> > 
> > Here is the 2nd version of the patches which improve kprobe
> > on arm implementation (a kind of bugfix). Version 1 is here;
> > 
> > https://lkml.org/lkml/2017/2/13/538
> > 
> > In this version I didn't update the code, just update the
> > patch description according to Tixy's comment and add his Ack.
> > 
> > Thank you,
> > 
> > ---
> > 
> > Masami Hiramatsu (3):
> >       kprobes/arm: Allow to handle reentered kprobe on single-stepping
> >       kprobes/arm: Skip single-stepping in recursing path if possible
> >       kprobes/arm: Fix the return address of multiple kretprobes
> > 
> 
> Thanks for doing these. Am I correct in assuming we don't need to
> consider these fixes urgent or critical? Only the first looks like it
> could be serious, and the x86 fix for that is 3 years old and ARM has
> gone without it all this time. So I'm guessing it's fine to wait for the
> normal development process and deal with it after the about to open
> merge window is completed?

Agreed. I'm not sure how frequently FIQ is used in ARM, but anyway
it happens only when root user intensively uses kprobes on FIQ handlers.

> If so, I propose that I put the patches in a branch for Russell to pull
> later (unless he pipes up with objections or says otherwise). Meantime
> I'll investigate the kprobes test failures I see (which actually looks
> like cache/TLB issues and not test code problems after all).

OK, btw, I couldn't reproduce the kprobes test failure with
CONFIG_DEBUG_RODATA=y on qemu...

> 
> BTW, I added the?ARM kernel list to the CC. I spotted you didn't add it
> to you patch postings, which means people interested in ARM (other than
> Russell) wouldn't have seen them.

Ah, I forgot that, Thank you!

> 
> Thanks
> 
> -- 
> Tixy


-- 
Masami Hiramatsu <mhiramat@kernel.org>

[BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes implementation on arm

[Jon Medhurst (Tixy)]

On Sat, 2017-02-18 at 06:43 +0900, Masami Hiramatsu wrote:
> On Fri, 17 Feb 2017 11:01:10 +0000
> "Jon Medhurst (Tixy)" <tixy@linaro.org> wrote:
[...]
> > Meantime
> > I'll investigate the kprobes test failures I see (which actually looks
> > like cache/TLB issues and not test code problems after all).
> 
> OK, btw, I couldn't reproduce the kprobes test failure with
> CONFIG_DEBUG_RODATA=y on qemu...

That's because it's a problem with caches which qemu doesn't emulate.
I worked out the cause and posted a patch...
http://lists.infradead.org/pipermail/linux-arm-kernel/2017-February/489517.html

-- 
Tixy

[BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes implementation on arm

[Masami Hiramatsu]

On Wed, 22 Feb 2017 15:58:49 +0000
"Jon Medhurst (Tixy)" <tixy@linaro.org> wrote:

> On Sat, 2017-02-18 at 06:43 +0900, Masami Hiramatsu wrote:
> > On Fri, 17 Feb 2017 11:01:10 +0000
> > "Jon Medhurst (Tixy)" <tixy@linaro.org> wrote:
> [...]
> > > Meantime
> > > I'll investigate the kprobes test failures I see (which actually looks
> > > like cache/TLB issues and not test code problems after all).
> > 
> > OK, btw, I couldn't reproduce the kprobes test failure with
> > CONFIG_DEBUG_RODATA=y on qemu...
> 
> That's because it's a problem with caches which qemu doesn't emulate.
> I worked out the cause and posted a patch...
> http://lists.infradead.org/pipermail/linux-arm-kernel/2017-February/489517.html

OK, I see.

Thanks! 

-- 
Masami Hiramatsu <mhiramat@kernel.org>