From: Thomas Gleixner <tglx@linutronix.de>
To: syzbot <syzbot+5245cb609175fb6e8122@syzkaller.appspotmail.com>,
bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
linux-kernel@vger.kernel.org, mingo@redhat.com,
syzkaller-bugs@googlegroups.com, x86@kernel.org,
Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Subject: Re: [syzbot] upstream build error (23)
Date: Tue, 29 Jul 2025 23:17:41 +0200 [thread overview]
Message-ID: <874iuuk87e.ffs@tglx> (raw)
In-Reply-To: <87cy9ikcwh.ffs@tglx>
On Tue, Jul 29 2025 at 21:36, Thomas Gleixner wrote:
> On Tue, Jul 29 2025 at 06:43, syzbot wrote:
> and to keep the call for efi_init() as a symbol for the linker to
> resolve, which obviously fails.
>
> If I change the efi_enabled() stub to __always_inline, it's optimized
> out.
Kees has addressed similar problems in:
8245d47cfaba ("x86: Handle KCOV __init vs inline mismatches")
65c430906eff ("arm64: Handle KCOV __init vs inline mismatches")
c64d6be1a6f8 ("s390: Handle KCOV __init vs inline mismatches")
2424fe1cac4f ("arm: Handle KCOV __init vs inline mismatches")
d01daf9d95c9 ("mips: Handle KCOV __init vs inline mismatch")
> Disabling CONFIG_KCOV_INSTRUMENT_ALL makes it go away. So GCC confuses
> the optimizer when CONFIG_KCOV_INSTRUMENT_ALL is on.
Seems to be GCC 12 specific. GCC13 does not have that problem.
> The kernel is full of such inline (not __always_inline) stub
> conditionals which evaluate to a constant....
And chasing all those stubs and convert them to __always_inline seems to
be a whack-a-mole game.
Can we just stop pretending that GCC12 is KCOV capable?
Thanks,
tglx
next prev parent reply other threads:[~2025-07-29 21:17 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-29 13:43 [syzbot] upstream build error (23) syzbot
2025-07-29 14:25 ` Borislav Petkov
2025-07-29 14:32 ` Aleksandr Nogikh
2025-07-29 14:48 ` Borislav Petkov
2025-07-29 19:36 ` Thomas Gleixner
2025-07-29 21:17 ` Thomas Gleixner [this message]
2025-07-29 21:38 ` Linus Torvalds
2025-07-29 21:52 ` Borislav Petkov
2025-07-29 22:11 ` Linus Torvalds
2025-07-29 22:27 ` Kees Cook
2025-07-29 22:12 ` Kees Cook
2025-07-30 10:44 ` Thomas Gleixner
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