From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Peter Zijlstra <peterz@infradead.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Kees Cook <keescook@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Craig Topper <craig.topper@intel.com>,
Alexander Potapenko <glider@google.com>,
Bill Wendling <morbo@google.com>,
Stephen Hines <srhines@google.com>
Subject: Re: objtool warnings in prerelease clang-9
Date: Sat, 6 Jul 2019 10:50:01 -0500 [thread overview]
Message-ID: <20190706155001.yrfxqj7c2bmqtbid@treble> (raw)
In-Reply-To: <alpine.DEB.2.21.1907022332000.1802@nanos.tec.linutronix.de>
On Tue, Jul 02, 2019 at 11:58:27PM +0200, Thomas Gleixner wrote:
> platform-quirks.o:
>
> if (x86_platform.set_legacy_features)
> 74: 4c 8b 1d 00 00 00 00 mov 0x0(%rip),%r11 # 7b <x86_early_init_platform_quirks+0x7b>
> 7b: 4d 85 db test %r11,%r11
> 7e: 0f 85 00 00 00 00 jne 84 <x86_early_init_platform_quirks+0x84>
> x86_platform.set_legacy_features();
> }
> 84: c3 retq
>
> That jne jumps to __x86_indirect_thunk_r11, aka. ratpoutine.
>
> No idea why objtool thinks that the instruction at 0x84 is not
> reachable. Josh?
That's a conditional tail call, which is something GCC never does.
Objtool doesn't understand that, so we'll need to fix it.
--
Josh
next prev parent reply other threads:[~2019-07-06 15:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-02 20:53 objtool warnings in prerelease clang-9 Nick Desaulniers
2019-07-02 21:58 ` Thomas Gleixner
2019-07-02 22:09 ` Nick Desaulniers
2019-07-02 22:20 ` Thomas Gleixner
2019-07-02 22:33 ` Nick Desaulniers
2019-07-06 15:50 ` Josh Poimboeuf [this message]
2019-07-10 23:22 ` Josh Poimboeuf
2019-07-10 23:42 ` Nick Desaulniers
2019-07-11 0:04 ` Josh Poimboeuf
2019-07-02 22:07 ` Peter Zijlstra
2019-07-03 0:30 ` Nick Desaulniers
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