Re: serious performance regression due to NX patch

Jakub Jelinek
2004-07-11T12:41:48Z

On Sun, Jul 11, 2004 at 05:52:59AM -0400, Ingo Molnar wrote:
>
> On Sun, 11 Jul 2004, Ingo Molnar wrote:
>
> > > ok, agreed. I'll check that it still does the right thing on x86.
> >
> > it doesnt seem to do the right thing for !PT_GNU_STACK applications on
> > x86:
>
> how about the patch below? This way we recognize the fact that x86 didnt
> have any executability check previously at the point where we discover
> that it's a 'legacy' binary.
>
> Ingo
>
> --- linux/fs/binfmt_elf.c.orig3
> +++ linux/fs/binfmt_elf.c
> @@ -627,8 +627,14 @@ static int load_elf_binary(struct linux_
> executable_stack = EXSTACK_DISABLE_X;
> break;
> }
> +#ifdef __i386_
> + /*
> + * Legacy x86 binaries have an expectation of executability for
> + * virtually all their address-space - turn executability on:
> + */
> if (i == elf_ex.e_phnum)
> def_flags |= VM_EXEC | VM_MAYEXEC;
> +#endif

This looks incorrect.
There are many arches where legacy binaries expect the executability for
virtually all their address-space (my guess is all but x86-64 and ia64),
and even on those two legacy binaries expected at least stack executable.

And on x86-64 and ia64 ia32 binaries (i.e. when binfmt_elf.c is included
in their binfmt_elf32.c or how is it called) should have VM_EXEC and
VM_MAYEXEC in def_flags.

Jakub