No code changes.
Changes since v1: added comments as requested by Steven Rostedt
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Oleg Nesterov <o...@redhat.com>
CC: Borislav Petkov <b...@alien8.de>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Andy Lutomirski <l...@amacapital.net>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: X86 ML <x...@kernel.org>
CC: Alexei Starovoitov <a...@plumgrid.com>
CC: Will Drewry <w...@chromium.org>
CC: Kees Cook <keesc...@chromium.org>
CC: Steven Rostedt <rost...@goodmis.org>
CC: linux-kernel@vger.kernel.org
---
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
--
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