linux-kernel - Re: [PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS

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Message-ID: <20150227102644.18a0ea5f@canb.auug.org.au>
Date:	Fri, 27 Feb 2015 10:26:44 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Hector Marco Gisbert <hecmargi@....es>,
	Kees Cook <keescook@...omium.org>,
	LKML <linux-kernel@...r.kernel.org>,
	ismael Ripoll <iripoll@....es>, <x86@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS

Hi Andrew,

[Just resending to correct addresses - sorry for those who get a duplicate]

On Thu, 26 Feb 2015 14:38:15 -0800 Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> diff -puN fs/binfmt_elf.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix fs/binfmt_elf.c
> --- a/fs/binfmt_elf.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
> +++ a/fs/binfmt_elf.c
> @@ -22,6 +22,7 @@
>  #include <linux/slab.h>
>  #include <linux/personality.h>
>  #include <linux/elfcore.h>
> +#include <linux/elf-randomization.h>
>  #include <linux/init.h>
>  #include <linux/highuid.h>
>  #include <linux/compiler.h>
> @@ -2300,6 +2301,26 @@ out:
>  
>  #endif		/* CONFIG_ELF_CORE */
>  
> +/* Not all architectures implement mmap_rnd() */
> +unsigned long __weak mmap_rnd(void)
> +{
> +}
> +
> +/*
> + * Not all architectures use randomize_et_dyn(), so use __weak to let the
> + * linker omit it from vmlinux
> + */
> +unsigned long __weak randomize_et_dyn(unsigned long base)
> +{
> +	unsigned long ret;
> +
> +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> +		!(current->flags & PF_RANDOMIZE))
> +		return base;
> +	ret = base + mmap_rnd();
> +	return max(ret, base);
> +}
> +  

Didn't we have some trouble with some compilers when the weak function
(mmap_rnd) was defined and used in the same file i.e. the wrong one was
used?

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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