[PATCH] x86: privilege cleanup
Privilege checking cleanup. Originally, these diffs were much greater, but
recent cleanups in Linux have already done much of the cleanup. I added
some explanatory comments in places where the reasoning behind certain
tests is rather subtle.
Also, in traps.c, we can skip the user_mode check in handle_BUG(). The
reason is, there are only two call chains - one via die_if_kernel() and one
via do_page_fault(), both entering from die(). Both of these paths already
ensure that a kernel mode failure has happened. Also, the original check
here, if (user_mode(regs)) was insufficient anyways, since it would not
rule out BUG faults from V8086 mode execution.
Saving the %ss segment in show_regs() rather than assuming a fixed value
also gives better information about the current kernel state in the
register dump.
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c
index 7bcda6d..61eb0c8 100644
--- a/arch/i386/kernel/signal.c
+++ b/arch/i386/kernel/signal.c
@@ -604,7 +604,9 @@
* We want the common case to go fast, which
* is why we may in certain cases get here from
* kernel mode. Just return without doing anything
- * if so.
+ * if so. vm86 regs switched out by assembly code
+ * before reaching here, so testing against kernel
+ * CS suffices.
*/
if (!user_mode(regs))
return 1;