Re: [PATCH] kcov: mark in_softirq_really() as __always_inline

[Josh Poimboeuf]

On Tue, Dec 17, 2024 at 09:30:24AM +0100, Marco Elver wrote:
> On Tue, 17 Dec 2024 at 08:18, Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> >
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > If gcc decides not to inline in_softirq_really(), objtool warns about
> > a function call with UACCESS enabled:
> >
> > kernel/kcov.o: warning: objtool: __sanitizer_cov_trace_pc+0x1e: call to in_softirq_really() with UACCESS enabled
> > kernel/kcov.o: warning: objtool: check_kcov_mode+0x11: call to in_softirq_really() with UACCESS enabled
> >
> > Mark this as __always_inline to avoid the problem.
> >
> > Fixes: 7d4df2dad312 ("kcov: properly check for softirq context")
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> 
> __always_inline is the usual approach for code that can be
> instrumented - but I thought we explicitly never instrument
> kernel/kcov.c with anything. So I'm rather puzzled why gcc would not
> inline this function. In any case "inline" guarantees nothing, so:

I'm guessing CONFIG_DEBUG_SECTION_MISMATCH was enabled, which enables
-fno-inline-functions-called-once which ends up being the cause of a lot
of these __always_inline patches.

I had a patch to get rid of that at some point, guess it got lost...

-- 
Josh