Re: [PATCH] x86_64 signal handling for 64-bit apps w/ mixed 32-bit code - trivial fix

Andi Kleen
2005-10-06T16:46:50Z

Bryan Ford <baford@mit.edu> writes:

> The proposed patch doesn't affect any performance-critical paths (e.g.,
> syscall or interrupt entry/exit), and merely involves a couple more moves
> to/from user space on signal frame setup and sigreturn. It also doesn't
> affect the size or shape of the sigcontext at all, since there already was an
> (unused) slot for CS, and I've assigned the convenient __pad0 field as a slot
> for SS. The existing, unused slots for FS and GS remain unused for now, and
> I don't see any urgent need to change that. The only way this might break an
> existing app is if the app tries to cons up its own signal frame (not
> generated by the kernel) and pass it to sigreturn, but this is presumably a
> no-no anyway.

I see the point of saving/restore cs, but why ss and not es/ds ?

-Andi