Date:	Fri, 24 Feb 2012 12:06:43 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<srostedt@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86-64: fix CFI annotations for NMI nesting code

The saving and restoring of %rdx wasn't annotated at all, and the
jumping over sections where state gets partly restored wasn't handled
either.

Further, by folding the pushing of the previous frame in repeat_nmi
into that which so far was immediately preceding restart_nmi (after
moving the restore of %rdx ahead of that, since it doesn't get used
anymore when pushing prior frames), annotations of the replicated
frame creations can be made consistent too.

Finally, the END()/CFI_ENDPROC marker of nmi should be at the very
end, rather than giving repeat_nmi its own frame (as this isn't a
separate function).

Signed-off-by: Jan Beulich <jbeulich@...e.com>
Cc: Steven Rostedt <srostedt@...hat.com>

---
 arch/x86/kernel/entry_64.S |   27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

--- 3.3-rc4/arch/x86/kernel/entry_64.S
+++ 3.3-rc4-x86_64-nmi-cfi/arch/x86/kernel/entry_64.S
@@ -1530,6 +1530,7 @@ ENTRY(nmi)
 
 	/* Use %rdx as out temp variable throughout */
 	pushq_cfi %rdx
+	CFI_REL_OFFSET rdx, 0
 
 	/*
 	 * Check the special variable on the stack to see if NMIs are
@@ -1547,6 +1548,7 @@ ENTRY(nmi)
 	 */
 	lea 6*8(%rsp), %rdx
 	test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
+	CFI_REMEMBER_STATE
 
 nested_nmi:
 	/*
@@ -1578,10 +1580,12 @@ nested_nmi:
 
 nested_nmi_out:
 	popq_cfi %rdx
+	CFI_RESTORE rdx
 
 	/* No need to check faults here */
 	INTERRUPT_RETURN
 
+	CFI_RESTORE_STATE
 first_nmi:
 	/*
 	 * Because nested NMIs will use the pushed location that we
@@ -1617,6 +1621,10 @@ first_nmi:
 	 * NMI may zero out. The original stack frame and the temp storage
 	 * is also used by nested NMIs and can not be trusted on exit.
 	 */
+	/* Do not pop rdx, nested NMIs will corrupt it */
+	movq (%rsp), %rdx
+	CFI_RESTORE rdx
+
 	/* Set the NMI executing variable on the stack. */
 	pushq_cfi $1
 
@@ -1624,14 +1632,14 @@ first_nmi:
 	.rept 5
 	pushq_cfi 6*8(%rsp)
 	.endr
+	CFI_DEF_CFA_OFFSET SS+8-RIP
 
+restart_nmi:
 	/* Make another copy, this one may be modified by nested NMIs */
 	.rept 5
 	pushq_cfi 4*8(%rsp)
 	.endr
-
-	/* Do not pop rdx, nested NMIs will corrupt it */
-	movq 11*8(%rsp), %rdx
+	CFI_DEF_CFA_OFFSET SS+8-RIP
 
 	/*
 	 * Everything below this point can be preempted by a nested
@@ -1639,7 +1647,6 @@ first_nmi:
 	 * caused by an exception and nested NMI will start here, and
 	 * can still be preempted by another NMI.
 	 */
-restart_nmi:
 	pushq_cfi $-1		/* ORIG_RAX: no syscall to restart */
 	subq $ORIG_RAX-R15, %rsp
 	CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
@@ -1665,8 +1672,6 @@ nmi_restore:
 	/* Clear the NMI executing stack variable */
 	movq $0, 10*8(%rsp)
 	jmp irq_return
-	CFI_ENDPROC
-END(nmi)
 
 	/*
 	 * If an NMI hit an iret because of an exception or breakpoint,
@@ -1675,18 +1680,12 @@ END(nmi)
 	 * stack to jump to here when it does the final iret.
 	 */
 repeat_nmi:
-	INTR_FRAME
 	/* Update the stack variable to say we are still in NMI */
 	movq $1, 5*8(%rsp)
-
-	/* copy the saved stack back to copy stack */
-	.rept 5
-	pushq_cfi 4*8(%rsp)
-	.endr
-
 	jmp restart_nmi
-	CFI_ENDPROC
 end_repeat_nmi:
+	CFI_ENDPROC
+END(nmi)
 
 ENTRY(ignore_sysret)
 	CFI_STARTPROC



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