Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering usingBPF

[Oleg Nesterov]

On 01/13, Will Drewry wrote:
>
> On Fri, Jan 13, 2012 at 1:01 PM, Will Drewry <wad@xxxxxxxxxxxx> wrote:
> > On Fri, Jan 13, 2012 at 11:31 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> >>
> >> Me too. I see no point in using user_regs_struct.
> >
> > I'll rev the change to use pt_regs and drop all the helper code.  If
> > no one says otherwise, that certainly seems ideal from a performance
> > perspective, and I see pt_regs exported to userland along with ptrace
> > abi register offset macros.
>
> On second thought, pt_regs is scary :)
>
> From looking at
>   http://lxr.linux.no/linux+v3.2.1/arch/x86/include/asm/syscall.h#L97
> and ia32syscall enty code, it appears that for x86, at least, the
> pt_regs for compat processes will be 8 bytes wide per register on the
> stack.  This means if a self-filtering 32-bit program runs on a 64-bit host in
> IA32_EMU, its filters will always index into pt_regs incorrectly.

Yes, thanks, I forgot about compat tasks again. But this is easy, just
we need regs_64_to_32().

Doesn't matter. I think Indan has a better suggestion.

Oleg.

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