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

[Andy Lutomirski]

On Jul 23, 2014 10:17 PM, "AKASHI Takahiro" <takahiro.akashi@xxxxxxxxxx> wrote:
>
> On 07/24/2014 01:41 PM, Kees Cook wrote:
>>
>> On Wed, Jul 23, 2014 at 8:40 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> 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@xxxxxxxx>
>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
>>>> ---
>>>>    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@xxxxxxxxxx>
>>>> + *
>>>> + * 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.

It seems odd that the header would be added without any users.  I
guess it's okay, since arm64 uses it in the followup patch.

>
>> 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?

If that works, yes.

--Andy

>
> -Takahiro AKASHI
>>
>>
>> -Kees
>>
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