[PATCH] fix crash in entry.S restore_all
Fix the access-above-bottom-of-stack crash.
1. Allows to preserve the valueable optimization
2. Works for NMIs
3. Doesn't care whether or not there are more of the like instances
where the stack is left empty.
4. Seems to work for me without the crashes:)
(akpm: this is still under discussion, although I _think_ it's OK. You might
want to hold off)
Signed-off-by: Stas Sergeev <stsp@aknet.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 1e45ff2..3c73dc8 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -245,6 +245,9 @@
restore_all:
movl EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
+ # Warning: OLDSS(%esp) contains the wrong/random values if we
+ # are returning to the kernel.
+ # See comments in process.c:copy_thread() for details.
movb OLDSS(%esp), %ah
movb CS(%esp), %al
andl $(VM_MASK | (4 << 8) | 3), %eax