linux-kernel - Re: [PATCH v3 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp

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Date:   Wed, 30 Sep 2020 16:21:21 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     YiFei Zhu <zhuyifei1999@...il.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        YiFei Zhu <yifeifz2@...inois.edu>, bpf <bpf@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        David Laight <David.Laight@...lab.com>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Jack Chen <jianyan2@...inois.edu>,
        Josep Torrellas <torrella@...inois.edu>,
        Tianyin Xu <tyxu@...inois.edu>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Tycho Andersen <tycho@...ho.pizza>,
        Valentin Rothberg <vrothber@...hat.com>,
        Will Drewry <wad@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH v3 seccomp 5/5] seccomp/cache: Report cache data through
 /proc/pid/seccomp_cache

On Thu, Oct 01, 2020 at 01:08:04AM +0200, Jann Horn wrote:
> [adding x86 folks to enhance bikeshedding]
> 
> On Thu, Oct 1, 2020 at 12:59 AM Kees Cook <keescook@...omium.org> wrote:
> > On Wed, Sep 30, 2020 at 10:19:16AM -0500, YiFei Zhu wrote:
> > > From: YiFei Zhu <yifeifz2@...inois.edu>
> > >
> > > Currently the kernel does not provide an infrastructure to translate
> > > architecture numbers to a human-readable name. Translating syscall
> > > numbers to syscall names is possible through FTRACE_SYSCALL
> > > infrastructure but it does not provide support for compat syscalls.
> > >
> > > This will create a file for each PID as /proc/pid/seccomp_cache.
> > > The file will be empty when no seccomp filters are loaded, or be
> > > in the format of:
> > > <arch name> <decimal syscall number> <ALLOW | FILTER>
> > > where ALLOW means the cache is guaranteed to allow the syscall,
> > > and filter means the cache will pass the syscall to the BPF filter.
> > >
> > > For the docker default profile on x86_64 it looks like:
> > > x86_64 0 ALLOW
> > > x86_64 1 ALLOW
> > > x86_64 2 ALLOW
> > > x86_64 3 ALLOW
> > > [...]
> > > x86_64 132 ALLOW
> > > x86_64 133 ALLOW
> > > x86_64 134 FILTER
> > > x86_64 135 FILTER
> > > x86_64 136 FILTER
> > > x86_64 137 ALLOW
> > > x86_64 138 ALLOW
> > > x86_64 139 FILTER
> > > x86_64 140 ALLOW
> > > x86_64 141 ALLOW
> [...]
> > > diff --git a/arch/x86/include/asm/seccomp.h b/arch/x86/include/asm/seccomp.h
> > > index 7b3a58271656..33ccc074be7a 100644
> > > --- a/arch/x86/include/asm/seccomp.h
> > > +++ b/arch/x86/include/asm/seccomp.h
> > > @@ -19,13 +19,16 @@
> > >  #ifdef CONFIG_X86_64
> > >  # define SECCOMP_ARCH_DEFAULT                        AUDIT_ARCH_X86_64
> > >  # define SECCOMP_ARCH_DEFAULT_NR             NR_syscalls
> > > +# define SECCOMP_ARCH_DEFAULT_NAME           "x86_64"
> > >  # ifdef CONFIG_COMPAT
> > >  #  define SECCOMP_ARCH_COMPAT                        AUDIT_ARCH_I386
> > >  #  define SECCOMP_ARCH_COMPAT_NR             IA32_NR_syscalls
> > > +#  define SECCOMP_ARCH_COMPAT_NAME           "x86_32"
> >
> > I think this should be "ia32"? Is there a good definitive guide on this
> > naming convention?
> 
> "man 2 syscall" calls them "x86-64" and "i386". The syscall table
> files use ABI names "i386" and "64". The syscall stub prefixes use
> "x64" and "ia32".
> 
> I don't think we have a good consistent naming strategy here. :P

Agreed. And with "i386" being so hopelessly inaccurate, I prefer
"ia32" ... *shrug*

I would hope we don't have to be super-pedantic and call them "x86-64" and "IA-32". :P

-- 
Kees Cook