Re: [PATCH v3 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp_cache

Kees Cook
2020-09-30T23:21:26Z

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@chromium.org> wrote:
> > On Wed, Sep 30, 2020 at 10:19:16AM -0500, YiFei Zhu wrote:
> > > From: YiFei Zhu <yifeifz2@illinois.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