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authorZachary Amsden <zach@vmware.com>2005-09-03 15:56:43 -0700
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 00:06:12 -0700
commit0998e4228aca046fbd747c3fed909791d52e88eb (patch)
tree314cb04a6223100bf468cc420985bfe7e3680d44 /include/asm-i386
parentf2ab4461249df85b20930a7a57b54f39c5ae291a (diff)
[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>
Diffstat (limited to 'include/asm-i386')
-rw-r--r--include/asm-i386/ptrace.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/asm-i386/ptrace.h b/include/asm-i386/ptrace.h
index 05532875e39..7e0f2945d17 100644
--- a/include/asm-i386/ptrace.h
+++ b/include/asm-i386/ptrace.h
@@ -61,6 +61,13 @@ struct pt_regs {
struct task_struct;
extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code);
+/*
+ * user_mode_vm(regs) determines whether a register set came from user mode.
+ * This is true if V8086 mode was enabled OR if the register set was from
+ * protected mode with RPL-3 CS value. This tricky test checks that with
+ * one comparison. Many places in the kernel can bypass this full check
+ * if they have already ruled out V8086 mode, so user_mode(regs) can be used.
+ */
static inline int user_mode(struct pt_regs *regs)
{
return (regs->xcs & 3) != 0;