Re: [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure computing mode 1

From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: Kees Cook <keescook@chromium.org>, Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	dsaxena@linaro.org,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	linaro-kernel@lists.linaro.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure computing mode 1
Date: Thu, 24 Jul 2014 14:17:04 +0900	[thread overview]
Message-ID: <53D096D0.2000708@linaro.org> (raw)
In-Reply-To: <CAGXu5j+GuoxR5o8CZZFZAEwQA=rRwBmBM-ZDU+nFAfHoqf8z9Q@mail.gmail.com>

On 07/24/2014 01:41 PM, Kees Cook wrote:
> On Wed, Jul 23, 2014 at 8:40 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>> On 07/22/2014 02:14 AM, AKASHI Takahiro wrote:
>>>
>>> Those values (__NR_seccomp_*) are used solely in secure_computing()
>>> to identify mode 1 system calls. If compat system calls have different
>>> syscall numbers, asm/seccomp.h may override them.
>>>
>>> Acked-by: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>> ---
>>>    include/asm-generic/seccomp.h |   28 ++++++++++++++++++++++++++++
>>>    1 file changed, 28 insertions(+)
>>>    create mode 100644 include/asm-generic/seccomp.h
>>>
>>> diff --git a/include/asm-generic/seccomp.h b/include/asm-generic/seccomp.h
>>> new file mode 100644
>>> index 0000000..5e97022
>>> --- /dev/null
>>> +++ b/include/asm-generic/seccomp.h
>>> @@ -0,0 +1,28 @@
>>> +/*
>>> + * include/asm-generic/seccomp.h
>>> + *
>>> + * Copyright (C) 2014 Linaro Limited
>>> + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +#ifndef _ASM_GENERIC_SECCOMP_H
>>> +#define _ASM_GENERIC_SECCOMP_H
>>> +
>>> +#include <asm-generic/unistd.h>
>>> +
>>> +#if defined(CONFIG_COMPAT) && !defined(__NR_seccomp_read_32)
>>> +#define __NR_seccomp_read_32           __NR_read
>>> +#define __NR_seccomp_write_32          __NR_write
>>> +#define __NR_seccomp_exit_32           __NR_exit
>>> +#define __NR_seccomp_sigreturn_32      __NR_rt_sigreturn
>>> +#endif /* CONFIG_COMPAT && ! already defined */
>>> +
>>> +#define __NR_seccomp_read              __NR_read
>>> +#define __NR_seccomp_write             __NR_write
>>> +#define __NR_seccomp_exit              __NR_exit
>>> +#define __NR_seccomp_sigreturn         __NR_rt_sigreturn
>>
>>
>> I don't like these names.  __NR_seccomp_read sounds like the number of a
>> syscall called seccomp_read.
>>
>> Also, shouldn't something be including this header?  I'm confused.
>
> Ah! Good catch. These names are correct (see kernel/seccomp.c's
> mode1_syscalls and mode1_syscalls_32 arrays), but the location of this
> change was unexpected. I was expecting this file to live in
> arch/*/include/asm/seccomp.h, not in include/asm-generic/seccomp.h.
>
> However, since it's always the same list, it might make sense to
> consolidate them into a single place as a default to make arch porting
> easier.

Yeah, that is why I put this file under include/asm-generic.

> However, I think that should be a separate patch.

Do you mean that the code for all the existing archs should also be changed
to use this (common) header?

-Takahiro AKASHI
>
> -Kees
>