commit 0998e4228aca046fbd747c3fed909791d52e88eb
author Zachary Amsden <zach@vmware.com> Sat Sep 03 15:56:43 2005 -0700
committer Linus Torvalds <torvalds@evo.osdl.org> Mon Sep 05 00:06:12 2005 -0700
tree 314cb04a6223100bf468cc420985bfe7e3680d44
parent f2ab4461249df85b20930a7a57b54f39c5ae291a

[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>

arch/i386/kernel/traps.c

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 1144df0..b2b4bb8 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -210,7 +210,7 @@
 	unsigned short ss;
 
 	esp = (unsigned long) (&regs->esp);
-	ss = __KERNEL_DS;
+	savesegment(ss, ss);
 	if (user_mode(regs)) {
 		in_kernel = 0;
 		esp = regs->esp;
@@ -267,9 +267,6 @@
 	char c;
 	unsigned long eip;
 
-	if (user_mode(regs))
-		goto no_bug;		/* Not in kernel */
-
 	eip = regs->eip;
 
 	if (eip < PAGE_OFFSET)