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Re: [committed, PATCH] Add -mshared option to x86 ELF assembler
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Markus Trippelsdorf <markus at trippelsdorf dot de>
- Cc: Binutils <binutils at sourceware dot org>, Andy Lutomirski <luto at kernel dot org>
- Date: Mon, 1 Jun 2015 04:05:45 -0700
- Subject: Re: [committed, PATCH] Add -mshared option to x86 ELF assembler
- Authentication-results: sourceware.org; auth=none
- References: <20150515103414 dot GA20518 at intel dot com> <20150601083214 dot GA381 at x4>
On Mon, Jun 1, 2015 at 1:32 AM, Markus Trippelsdorf
<markus@trippelsdorf.de> wrote:
> On 2015.05.15 at 03:34 -0700, H.J. Lu wrote:
>> This patch adds -mshared option to x86 ELF assembler. By default,
>> assembler will optimize out non-PLT relocations against defined non-weak
>> global branch targets with default visibility. The -mshared option tells
>> the assembler to generate code which may go into a shared library
>> where all non-weak global branch targets with default visibility can
>> be preempted. The resulting code is slightly bigger. This option
>> only affects the handling of branch instructions.
>>
>> This Linux kernel patch is needed to create a working x86 Linux kernel if
>> it hasn't been applied:
>>
>> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
>> index ae6588b..b91a00c 100644
>> --- a/arch/x86/kernel/head_64.S
>> +++ b/arch/x86/kernel/head_64.S
>> @@ -339,8 +339,8 @@ early_idt_handlers:
>> i = i + 1
>> .endr
>>
>> -/* This is global to keep gas from relaxing the jumps */
>> -ENTRY(early_idt_handler)
>> +/* This is weak to keep gas from relaxing the jumps */
>> +WEAK(early_idt_handler)
>> cld
>
> Have you posted the patch to LKML already?
> (I hit this issue today and it took me a while to figure out the cause.)
A kernel patch will be checked in soon.
--
H.J.