From: Borislav Petkov <bp@alien8.de>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Rong Chen <rong.a.chen@intel.com>,
kernel test robot <lkp@intel.com>,
"Li, Philip" <philip.li@intel.com>, x86-ml <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Marco Elver <elver@google.com>
Subject: Re: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e
Date: Wed, 16 Sep 2020 13:34:49 +0200 [thread overview]
Message-ID: <20200916113449.GH2643@zn.tnic> (raw)
In-Reply-To: <20200915215054.GA1104608@rani.riverdale.lan>
On Tue, Sep 15, 2020 at 05:50:54PM -0400, Arvind Sankar wrote:
> On Tue, Sep 15, 2020 at 10:49:12PM +0200, Borislav Petkov wrote:
> >
> > (Btw, clang doesn't need to add that "xor %eax,%eax" - panic() should not be
> > returning, ever. :-))
> >
>
> I think this is because panic() is varargs, and clang doesn't support
> gcc's -mskip-rax-setup. The normal ABI requires the caller to set RAX to
> the number of arguments in vector registers.
>
> https://patchwork.ozlabs.org/project/gcc/patch/20141218131150.GA32638@intel.com/
Ah, good point. Found this in the ABI doc:
"For calls that may call functions that use varargs or stdargs
(prototype-less calls or calls to functions containing ellipsis (...) in
the declaration) %al is used as hidden argument to specify the number of
vector registers used. The contents of %al do not need to match exactly
the number of registers, but must be an upper bound on the number of
vector registers used and is in the range 0–8 inclusive."
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-09-16 21:01 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 13:42 [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e kernel test robot
2020-09-15 13:55 ` Borislav Petkov
2020-09-15 14:18 ` Rong Chen
2020-09-15 14:41 ` Borislav Petkov
2020-09-15 16:05 ` Borislav Petkov
2020-09-15 17:02 ` Josh Poimboeuf
2020-09-15 17:21 ` Borislav Petkov
2020-09-15 17:34 ` Borislav Petkov
2020-09-15 17:41 ` Nick Desaulniers
2020-09-15 18:01 ` Borislav Petkov
2020-09-15 18:04 ` Nick Desaulniers
2020-09-15 17:40 ` Nick Desaulniers
2020-09-15 18:09 ` Marco Elver
2020-09-16 8:30 ` peterz
2020-09-16 8:46 ` Marco Elver
2020-09-16 9:06 ` peterz
2020-09-16 9:33 ` Marco Elver
2020-09-16 18:22 ` Nick Desaulniers
2020-09-16 18:51 ` Marco Elver
2020-09-17 4:11 ` Fangrui Song
[not found] ` <333D40A0-4550-4309-9693-1ABA4AC75399@arm.com>
2020-09-17 11:04 ` Mark Rutland
2020-09-17 11:16 ` Daniel Kiss
2020-09-17 18:39 ` Josh Poimboeuf
2020-09-15 17:44 ` Nick Desaulniers
2020-09-15 20:12 ` Nick Desaulniers
2020-09-15 20:49 ` Borislav Petkov
2020-09-15 21:02 ` Josh Poimboeuf
2020-09-15 21:14 ` Borislav Petkov
2020-09-15 22:34 ` Nick Desaulniers
2020-09-16 7:03 ` Ilie Halip
2020-09-16 8:59 ` Marco Elver
2020-09-21 16:51 ` [tip: objtool/core] objtool: Ignore unreachable trap after call to noreturn functions tip-bot2 for Ilie Halip
2020-09-15 21:50 ` [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e Arvind Sankar
2020-09-15 21:59 ` Nick Desaulniers
2020-09-15 22:44 ` Arvind Sankar
2020-09-16 11:34 ` Borislav Petkov [this message]
2020-09-16 18:28 ` Nick Desaulniers
2020-09-16 18:48 ` Borislav Petkov
2020-09-15 21:13 ` Nick Desaulniers
2020-09-15 21:28 ` Josh Poimboeuf
2020-09-15 23:35 ` Marco Elver
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