Introduce [compat_]save_altstack_ex() to unbreak x86 SMAP
For performance reasons, when SMAP is in use, SMAP is left open for an
entire put_user_try { ... } put_user_catch(); block, however, calling
__put_user() in the middle of that block will close SMAP as the
STAC..CLAC constructs intentionally do not nest.
Furthermore, using __put_user() rather than put_user_ex() here is bad
for performance.
Thus, introduce new [compat_]save_altstack_ex() helpers that replace
__[compat_]save_altstack() for x86, being currently the only
architecture which supports put_user_try { ... } put_user_catch().
Reported-by: H. Peter Anvin <[email protected]>
Signed-off-by: Al Viro <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Cc: <[email protected]> # v3.8+
Link: http://lkml.kernel.org/n/[email protected]
4 files changed
