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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@suse.com>
Cc: Steven Rostedt <srostedt@redhat.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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