Re: [PATCH 1/8] kasan,x86: Frob kasan_report() in an exception

[Dmitry Vyukov]

On Wed, Mar 6, 2019 at 3:56 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Wed, Mar 06, 2019 at 03:40:51PM +0100, Dmitry Vyukov wrote:
> > On Wed, Mar 6, 2019 at 3:34 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> > > mm/kasan/generic_report.o: warning: objtool: __asan_report_load1_noabort()+0x0: call to __fentry__() with UACCESS enabled
>
> > But if it makes things simpler for the objtool, then I think we can
> > disable function tracer for generic_report.c too.
>
> It's not simpler; it is actually a correctness issue. Those functions
> must not call into the tracer with AC=1

You are right!
I assumed they are defined in kasan.c and then call into a report
function that is compiled with -pg.
We can either disable -pg for report.c, or move these callbacks into
kasan.c which already has -pg disabled. I don't have strong preference
either way as long as the option works in all cases.