2016-10-24 11:22:45

by Alexander Kuleshov

Subject: [PATCH] x86/entry64: move comment about informing of context tracking in right place

We are switching to kernel gsbase if an IRQ come from usermode with swpags.
Now there is comment which describes this:

IRQ from user mode. Switch to kernel gsbase and inform context tracking that
we're in kernel mode.

But now we execute swapgs, next TRACE_IRQS_OFF and only then the
CALL_enter_from_user_mode macro expands to the informing of
context tracking about this event. Let's move part of comment to
the right place where actual call to context tracing occured.

Signed-off-by: Alexander Kuleshov <[email protected]>
---
arch/x86/entry/entry_64.S | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index ef766a3..5e97642 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -474,8 +474,7 @@ END(irq_entries_start)
jz 1f

/*
- * IRQ from user mode. Switch to kernel gsbase and inform context
- * tracking that we're in kernel mode.
+ * IRQ from user mode. Switch to kernel gsbase.
*/
SWAPGS

@@ -489,6 +488,9 @@ END(irq_entries_start)
*/
TRACE_IRQS_OFF

+ /*
+ * Inform context tracking that we're in kernel mode.
+ */
CALL_enter_from_user_mode

1:
--
2.8.0.rc3.1353.gea9bdc0

2016-11-03 11:24:40

by Borislav Petkov

Subject: Re: [PATCH] x86/entry64: move comment about informing of context tracking in right place

On Mon, Oct 24, 2016 at 05:22:34PM +0600, Alexander Kuleshov wrote:
> We are switching to kernel gsbase if an IRQ come from usermode with swpags.

"... if an IRQ comes from ..."

Also, you mean SWAPGS. Instruction names in allcaps please and spelled
correctly please.

> Now there is comment which describes this:
>
> IRQ from user mode. Switch to kernel gsbase and inform context tracking that
> we're in kernel mode.
>
> But now we execute swapgs, next TRACE_IRQS_OFF and only then the
> CALL_enter_from_user_mode macro expands to the informing of
> context tracking about this event. Let's move part of comment to
> the right place where actual call to context tracing occured.

I don't agree with that change - SWAPGS is part of what the comment
explains so it looks just fine where it is.

For future patches:

Please integrate scripts/checkpatch.pl in your patch creation workflow:

WARNING: 'occured' may be misspelled - perhaps 'occurred'?
#27:
the right place where actual call to context tracing occured.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.