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Re: [committed, PATCH] Add -mshared option to x86 ELF assembler
- From: Markus Trippelsdorf <markus at trippelsdorf dot de>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: binutils at sourceware dot org, Andy Lutomirski <luto at kernel dot org>
- Date: Mon, 1 Jun 2015 10:32:14 +0200
- 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>
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.)
--
Markus