linux-kernel - Re: [PATCH] x86, relocs: add percpu fixup for GNU ld 2.23

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Message-ID: <CAGXu5j+EUA_5E=-r+hhGYarMvt2PWp8Eu==6EP9ZKp9c5VjtYg@mail.gmail.com>
Date:	Wed, 16 Oct 2013 07:55:15 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>,
	Michael Davidson <md@...gle.com>, Cong Ding <dinggnu@...il.com>
Subject: Re: [PATCH] x86, relocs: add percpu fixup for GNU ld 2.23

On Tue, Oct 15, 2013 at 11:51 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 10/15/2013 11:43 PM, Kees Cook wrote:
>> The GNU linker tries to put __per_cpu_load into the percpu area, resulting
>> in a lack of its relocation. Force this symbol to be relocated. Seen
>> starting with GNU ld 2.23 and later.
>>
>> Reported-by: Ingo Molnar <mingo@...nel.org>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>>  arch/x86/tools/relocs.c |    2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
>> index 1fa291f..7a85f29 100644
>> --- a/arch/x86/tools/relocs.c
>> +++ b/arch/x86/tools/relocs.c
>> @@ -729,6 +729,7 @@ static void percpu_init(void)
>>   *
>>   * The GNU linker incorrectly associates:
>>   *   __init_begin
>> + *   __per_cpu_load
>>   *
>>   * The "gold" linker incorrectly associates:
>>   *   init_per_cpu__irq_stack_union
>> @@ -738,6 +739,7 @@ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
>>  {
>>       return (sym->st_shndx == per_cpu_shndx) &&
>>               strcmp(symname, "__init_begin") &&
>> +             strcmp(symname, "__per_cpu_load") &&
>>               strncmp(symname, "init_per_cpu_", 13);
>>  }
>>
>>
>
> Why isn't this list using a regex like other symbol classes?

I assume because it was initially a single item and it has grown
slowly. Would you like me to convert it to a regex instead?

-Kees

-- 
Kees Cook
Chrome OS Security
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