x86, fs: Fix x86 procfs stack information for threads on 64-bit

x86, fs: Fix x86 procfs stack information for threads on 64-bit

This patch fixes two issues in the procfs stack information on
x86-64 linux.

The 32 bit loader compat_do_execve did not store stack
start. (this was figured out by Alexey Dobriyan).

The stack information on a x64_64 kernel always shows 0 kbyte
stack usage, because of a missing implementation of the KSTK_ESP
macro which always returned -1.

The new implementation now returns the right value.

Signed-off-by: Stefani Seibold <[email protected]>
Cc: Americo Wang <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrew Morton <[email protected]>
LKML-Reference: <1257240160.4889.24.camel@wall-e>
Signed-off-by: Ingo Molnar <[email protected]>