linux-kernel - Re: [PATCH] modpost: Add .irqentry.text to OTHER

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Message-ID: <CAK7LNARufW5wc=qBt5R=RJ9BkFirLKAgRgg_t=OmTTGbjLfsAg@mail.gmail.com>
Date: Wed, 4 Dec 2024 00:27:36 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 20241015061522.25288-1-rui.zhang@...el.com, 
	Zhang Rui <rui.zhang@...el.com>, hpa@...or.com, peterz@...radead.org, 
	thorsten.blum@...lux.com, yuntao.wang@...ux.dev, tony.luck@...el.com, 
	len.brown@...el.com, srinivas.pandruvada@...el.com, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org, mingo@...hat.com, 
	bp@...en8.de, dave.hansen@...ux.intel.com, rafael.j.wysocki@...el.com, 
	x86@...nel.org, linux-pm@...r.kernel.org, 
	Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] modpost: Add .irqentry.text to OTHER_SECTIONS

On Tue, Dec 3, 2024 at 6:03 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Mon, Dec 02 2024 at 11:02, Masahiro Yamada wrote:
> > On Sun, Dec 1, 2024 at 8:17 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> >>
> >> The compiler can fully inline the actual handler function of an interrupt
> >> entry into the .irqentry.text entry point. If such a function contains an
> >> access which has an exception table entry, modpost complains about a
> >> section mismatch:
> >>
> >>   WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference ...
> >>
> >>   The relocation at __ex_table+0x447c references section ".irqentry.text"
> >>   which is not in the list of authorized sections.
> >>
> >> Add .irqentry.text to OTHER_SECTIONS to cure the issue.
> >>
> >> Reported-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> >
> > I found the context in LKML.
> > Closes: https://lore.kernel.org/all/20241128111844.GE10431@google.com/
> >
> > However, is this still relevant to the mainline kernel?
> >
> > In Linux 5.4.y, I agree this because smp_apic_timer_interrupt()
> > is annotated as __irq_entry:
>
> Correct.
>
> > In this mainline kernel, DEFINE_IDTENTRY_SYSVEC()
> > expands to a normal .text function which is explicitly
> > annotated 'noinline'.
>
> It's not annotated noinline, it's annotated 'noinstr', which puts the
> code into the .noinstr.text section. That one is indeed covered.


The callsite of local_apic_timer_interrupt() is annotated 'noinline'
if I correctly understand this line:
  https://github.com/torvalds/linux/blob/v6.13-rc1/arch/x86/include/asm/idtentry.h#L272


It expands to:

static noinline void __sysvec_apic_timer_interrupt(struct pt_regs *regs)
{
       [snip]
       local_apic_timer_interrupt();
       [snip]
}



> So yes, the fix is only required for pre 5.8 kernels.

This never occurs on x86 after commit f0178fc01fe46,
but theoretically this may occur for other architectures.

Now applied to linux-kbuild.
Thanks.




>
> Thanks,
>
>         tglx



-- 
Best Regards
Masahiro Yamada