linux-kernel - Re: [PATCH] x86, relocs: add more per-cpu gold special cases

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Message-ID: <CAGXu5jJJGxad=cJ52Jzja55Aj+nrkHSAJqUt+He0Bs7GViz=Bg@mail.gmail.com>
Date:	Thu, 10 Oct 2013 17:13:38 -0700
From:	Kees Cook <keescook@...omium.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>, Cong Ding <dinggnu@...il.com>
Subject: Re: [PATCH] x86, relocs: add more per-cpu gold special cases

On Tue, Oct 1, 2013 at 12:22 PM, Kees Cook <keescook@...omium.org> wrote:
> The "gold" linker doesn't seem to put some additional per-cpu cases in
> the right place. Add these to the per-cpu check. Without this, the kASLR
> patch series fails to correctly apply relocations, and fails to boot.
>
> Found and fixed by Michael Davidson.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Ping on this patch. Can this get picked up for tip?

-Kees

> ---
>  arch/x86/tools/relocs.c |   18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
> index f7bab68..71a2533 100644
> --- a/arch/x86/tools/relocs.c
> +++ b/arch/x86/tools/relocs.c
> @@ -722,15 +722,23 @@ static void percpu_init(void)
>
>  /*
>   * Check to see if a symbol lies in the .data..percpu section.
> - * For some as yet not understood reason the "__init_begin"
> - * symbol which immediately preceeds the .data..percpu section
> - * also shows up as it it were part of it so we do an explict
> - * check for that symbol name and ignore it.
> + *
> + * The linker incorrectly associates some symbols with the
> + * .data..percpu section so we also need to check the symbol
> + * name to make sure that we classify the symbol correctly.
> + *
> + * The GNU linker incorrectly associates:
> + *     __init_begin
> + *
> + * The "gold" linker incorrectly associates:
> + *     init_per_cpu__irq_stack_union
> + *     init_per_cpu__gdt_page
>   */
>  static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
>  {
>         return (sym->st_shndx == per_cpu_shndx) &&
> -               strcmp(symname, "__init_begin");
> +               strcmp(symname, "__init_begin") &&
> +               strncmp(symname, "init_per_cpu_", 13);
>  }
>
>
> --
> 1.7.9.5
>
>
> --
> Kees Cook
> Chrome OS Security



-- 
Kees Cook
Chrome OS Security
--
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