From: Michael Brown <mbrown@fensystems.co.uk>
To: Maarten Lankhorst <maarten.lankhorst@canonical.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Matt Fleming <matt@console-pimps.org>
Cc: Ulf Winkelvos <ulf@winkelvos.de>,
Matt Fleming <matt.fleming@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
Seth Forshee <seth.forshee@canonical.com>,
Matthew Garrett <mjg59@srcf.ucam.org>
Subject: Re: [REGRESSION] "efi: efistub: Convert into static library" and preparation patches
Date: Thu, 04 Sep 2014 13:54:09 +0100 [thread overview]
Message-ID: <540860F1.6060801@fensystems.co.uk> (raw)
In-Reply-To: <54084376.8090002@canonical.com>
On 04/09/14 11:48, Maarten Lankhorst wrote:
>>> If not, Ard please go ahead with option #2 above. Overkill yes, but I've
>>> done the single __attribute__() hacks in other projects and someone
>>> (usually me) always eventually forgets to tag some instance.
>>>
>> It appears we just got lucky on arm64, since we don't have any global
>> variables, but the issue does exist there as well.
>>
> FWIW, visibility pushing doesn't seem to work for functions declared with extern.
> Following seems to get rid of all GOTPCREL:
Are you sure? The iPXE build process relies on this:
/* Force visibility of all symbols to "hidden", i.e. inform gcc that
* all symbol references resolve strictly within our final binary.
* This avoids unnecessary PLT/GOT entries on x86_64.
*
* This is a stronger claim than specifying "-fvisibility=hidden",
* since it also affects symbols marked with "extern".
*/
#ifndef ASSEMBLY
#if __GNUC__ >= 4
#pragma GCC visibility push(hidden)
#endif
#endif /* ASSEMBLY */
and https://gcc.gnu.org/wiki/Visibility states that
"#pragma GCC visibility is stronger than -fvisibility; it affects
extern declarations as well. -fvisibility only affects definitions, so
that existing code can be recompiled with minimal changes. This is more
true for C than C++; C++ interfaces tend use classes, which are affected
by -fvisibility."
Michael
WARNING: multiple messages have this Message-ID (diff)
From: Michael Brown <mbrown-OViyBiuKJBuK421+ScFKDQ@public.gmane.org>
To: Maarten Lankhorst
<maarten.lankhorst-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
Ard Biesheuvel
<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
Matt Fleming
<matt-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>
Cc: Ulf Winkelvos <ulf-rS3t9PEbhQ0OIzVOb1FTxg@public.gmane.org>,
Matt Fleming
<matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org"
<x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Seth Forshee
<seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
Subject: Re: [REGRESSION] "efi: efistub: Convert into static library" and preparation patches
Date: Thu, 04 Sep 2014 13:54:09 +0100 [thread overview]
Message-ID: <540860F1.6060801@fensystems.co.uk> (raw)
In-Reply-To: <54084376.8090002-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
On 04/09/14 11:48, Maarten Lankhorst wrote:
>>> If not, Ard please go ahead with option #2 above. Overkill yes, but I've
>>> done the single __attribute__() hacks in other projects and someone
>>> (usually me) always eventually forgets to tag some instance.
>>>
>> It appears we just got lucky on arm64, since we don't have any global
>> variables, but the issue does exist there as well.
>>
> FWIW, visibility pushing doesn't seem to work for functions declared with extern.
> Following seems to get rid of all GOTPCREL:
Are you sure? The iPXE build process relies on this:
/* Force visibility of all symbols to "hidden", i.e. inform gcc that
* all symbol references resolve strictly within our final binary.
* This avoids unnecessary PLT/GOT entries on x86_64.
*
* This is a stronger claim than specifying "-fvisibility=hidden",
* since it also affects symbols marked with "extern".
*/
#ifndef ASSEMBLY
#if __GNUC__ >= 4
#pragma GCC visibility push(hidden)
#endif
#endif /* ASSEMBLY */
and https://gcc.gnu.org/wiki/Visibility states that
"#pragma GCC visibility is stronger than -fvisibility; it affects
extern declarations as well. -fvisibility only affects definitions, so
that existing code can be recompiled with minimal changes. This is more
true for C than C++; C++ interfaces tend use classes, which are affected
by -fvisibility."
Michael
next prev parent reply other threads:[~2014-09-04 12:54 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 15:25 [REGRESSION] "efi: efistub: Convert into static library" and preparation patches Maarten Lankhorst
2014-09-02 15:25 ` Maarten Lankhorst
2014-09-02 19:29 ` Matt Fleming
2014-09-03 6:06 ` Ard Biesheuvel
2014-09-03 8:27 ` Maarten Lankhorst
2014-09-03 8:27 ` Maarten Lankhorst
2014-09-03 12:18 ` Ard Biesheuvel
2014-09-03 12:18 ` Ard Biesheuvel
2014-09-03 15:30 ` Maarten Lankhorst
2014-09-03 15:37 ` Ard Biesheuvel
2014-09-03 15:37 ` Ard Biesheuvel
2014-09-03 17:59 ` Matt Fleming
2014-09-03 17:59 ` Matt Fleming
2014-09-03 19:57 ` Ard Biesheuvel
2014-09-03 19:57 ` Ard Biesheuvel
2014-09-03 21:28 ` H. Peter Anvin
2014-09-03 21:28 ` H. Peter Anvin
2014-09-04 10:48 ` Maarten Lankhorst
2014-09-04 10:48 ` Maarten Lankhorst
2014-09-04 11:19 ` Ard Biesheuvel
2014-09-04 11:19 ` Ard Biesheuvel
2014-09-04 11:24 ` Maarten Lankhorst
2014-09-04 11:24 ` Maarten Lankhorst
2014-09-04 12:54 ` Michael Brown [this message]
2014-09-04 12:54 ` Michael Brown
2014-09-04 19:12 ` Ard Biesheuvel
2014-09-04 19:12 ` Ard Biesheuvel
2014-09-04 21:25 ` Ard Biesheuvel
2014-09-04 21:37 ` Matt Fleming
2014-09-04 21:37 ` Matt Fleming
2014-09-05 20:27 ` Matt Fleming
2014-09-05 20:27 ` Matt Fleming
2014-09-08 12:55 ` Ard Biesheuvel
2014-09-08 12:55 ` Ard Biesheuvel
2014-09-08 13:01 ` Maarten Lankhorst
2014-09-08 13:01 ` Maarten Lankhorst
2014-09-08 13:16 ` Matt Fleming
2014-09-22 18:44 ` Josh Boyer
2014-09-22 21:07 ` Matt Fleming
2014-09-22 21:24 ` Josh Boyer
2014-09-03 21:47 ` H. Peter Anvin
2014-09-03 21:47 ` H. Peter Anvin
2014-09-04 6:47 ` Ard Biesheuvel
2014-09-04 6:47 ` Ard Biesheuvel
2014-09-04 7:40 ` Matt Fleming
2014-09-04 7:50 ` Maarten Lankhorst
2014-09-04 7:29 ` Matt Fleming
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