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From:   Andy Lutomirski <luto@amacapital.net>
Date:   Fri, 9 Oct 2020 10:25:00 -0700
Message-ID: <CALCETrUD7z3-zL_rATzTyDUzgerOzXJHdn-hntNMG=vnX8ZF2w@mail.gmail.com>
Subject: Re: [PATCH v4 seccomp 3/5] x86: Enable seccomp architecture tracking
To:     YiFei Zhu <zhuyifei1999@gmail.com>
Cc:     Linux Containers <containers@lists.linux-foundation.org>,
        YiFei Zhu <yifeifz2@illinois.edu>, bpf <bpf@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        David Laight <David.Laight@aculab.com>,
        Dimitrios Skarlatos <dskarlat@cs.cmu.edu>,
        Giuseppe Scrivano <gscrivan@redhat.com>,
        Hubertus Franke <frankeh@us.ibm.com>,
        Jack Chen <jianyan2@illinois.edu>,
        Jann Horn <jannh@google.com>,
        Josep Torrellas <torrella@illinois.edu>,
        Kees Cook <keescook@chromium.org>,
        Tianyin Xu <tyxu@illinois.edu>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Tycho Andersen <tycho@tycho.pizza>,
        Valentin Rothberg <vrothber@redhat.com>,
        Will Drewry <wad@chromium.org>
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On Fri, Oct 9, 2020 at 10:15 AM YiFei Zhu <zhuyifei1999@gmail.com> wrote:
>
> From: Kees Cook <keescook@chromium.org>
>
> Provide seccomp internals with the details to calculate which syscall
> table the running kernel is expecting to deal with. This allows for
> efficient architecture pinning and paves the way for constant-action
> bitmaps.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Co-developed-by: YiFei Zhu <yifeifz2@illinois.edu>
> Signed-off-by: YiFei Zhu <yifeifz2@illinois.edu>
> ---
>  arch/x86/include/asm/seccomp.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/arch/x86/include/asm/seccomp.h b/arch/x86/include/asm/seccomp.h
> index 2bd1338de236..03365af6165d 100644
> --- a/arch/x86/include/asm/seccomp.h
> +++ b/arch/x86/include/asm/seccomp.h
> @@ -16,6 +16,18 @@
>  #define __NR_seccomp_sigreturn_32      __NR_ia32_sigreturn
>  #endif
>
> +#ifdef CONFIG_X86_64
> +# define SECCOMP_ARCH_NATIVE           AUDIT_ARCH_X86_64
> +# define SECCOMP_ARCH_NATIVE_NR                NR_syscalls
> +# ifdef CONFIG_COMPAT
> +#  define SECCOMP_ARCH_COMPAT          AUDIT_ARCH_I386
> +#  define SECCOMP_ARCH_COMPAT_NR       IA32_NR_syscalls
> +# endif
> +#else /* !CONFIG_X86_64 */
> +# define SECCOMP_ARCH_NATIVE           AUDIT_ARCH_I386
> +# define SECCOMP_ARCH_NATIVE_NR                NR_syscalls
> +#endif

Is the idea that any syscall that's out of range for this (e.g. all of
the x32 syscalls) is unoptimized?  I'm okay with this, but I think it
could use a comment.

> +
>  #include <asm-generic/seccomp.h>
>
>  #endif /* _ASM_X86_SECCOMP_H */
> --
> 2.28.0
>


-- 
Andy Lutomirski
AMA Capital Management, LLC