2015-02-24 12:53:17

by Denys Vlasenko

Subject: [PATCH 4/6 v2] x86: entry_64.S: fold test_in_nmi macro into its only user

No code changes.

Changes since v1: added comments as requested by Steven Rostedt

Signed-off-by: Denys Vlasenko <[email protected]>
CC: Linus Torvalds <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: Borislav Petkov <[email protected]>
CC: "H. Peter Anvin" <[email protected]>
CC: Andy Lutomirski <[email protected]>
CC: Frederic Weisbecker <[email protected]>
CC: X86 ML <[email protected]>
CC: Alexei Starovoitov <[email protected]>
CC: Will Drewry <[email protected]>
CC: Kees Cook <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: [email protected]
---
arch/x86/kernel/entry_64.S | 30 ++++++++++++++----------------
1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 03498d0..0ec7928 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1378,19 +1378,7 @@ ENTRY(error_exit)
CFI_ENDPROC
END(error_exit)

-/*
- * Test if a given stack is an NMI stack or not.
- */
- .macro test_in_nmi reg stack nmi_ret normal_ret
- cmpq %\reg, \stack
- ja \normal_ret
- subq $EXCEPTION_STKSZ, %\reg
- cmpq %\reg, \stack
- jb \normal_ret
- jmp \nmi_ret
- .endm
-
- /* runs on exception stack */
+/* Runs on exception stack */
ENTRY(nmi)
INTR_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
@@ -1426,7 +1414,7 @@ ENTRY(nmi)
* NMI.
*/

- /* Use %rdx as out temp variable throughout */
+ /* Use %rdx as our temp variable throughout */
pushq_cfi %rdx
CFI_REL_OFFSET rdx, 0

@@ -1451,8 +1439,18 @@ ENTRY(nmi)
* We check the variable because the first NMI could be in a
* breakpoint routine using a breakpoint stack.
*/
- lea 6*8(%rsp), %rdx
- test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
+ lea 6*8(%rsp), %rdx
+ /* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */
+ cmpq %rdx, 4*8(%rsp)
+ /* If the stack pointer is above the NMI stack, this is a normal NMI */
+ ja first_nmi
+ subq $EXCEPTION_STKSZ, %rdx
+ cmpq %rdx, 4*8(%rsp)
+ /* If it is below the NMI stack, it is a normal NMI */
+ jb first_nmi
+ /* Ah, it is within the NMI stack, treat it as nested */
+ jmp nested_nmi
+
CFI_REMEMBER_STATE

nested_nmi:
--
1.8.1.4

2015-02-24 18:22:00

by Borislav Petkov

Subject: Re: [PATCH 4/6 v2] x86: entry_64.S: fold test_in_nmi macro into its only user

On Tue, Feb 24, 2015 at 01:52:38PM +0100, Denys Vlasenko wrote:
> No code changes.
>
> Changes since v1: added comments as requested by Steven Rostedt
>
> Signed-off-by: Denys Vlasenko <[email protected]>
> CC: Linus Torvalds <[email protected]>
> CC: Oleg Nesterov <[email protected]>
> CC: Borislav Petkov <[email protected]>
> CC: "H. Peter Anvin" <[email protected]>
> CC: Andy Lutomirski <[email protected]>
> CC: Frederic Weisbecker <[email protected]>
> CC: X86 ML <[email protected]>
> CC: Alexei Starovoitov <[email protected]>
> CC: Will Drewry <[email protected]>
> CC: Kees Cook <[email protected]>
> CC: Steven Rostedt <[email protected]>
> CC: [email protected]
> ---
> arch/x86/kernel/entry_64.S | 30 ++++++++++++++----------------
> 1 file changed, 14 insertions(+), 16 deletions(-)

Looks ok to me.

Acked-by: Borislav Petkov <[email protected]>

--
Regards/Gruss,
Boris.

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