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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. v2: Fully fold repeat_nmi into the normal code flow (adding a single redundant instruction to the "normal" code path), thus retaining the special protection of all instructions between repeat_nmi and end_repeat_nmi. Link: http://lkml.kernel.org/r/4F478B630200007800074A31@nat28.tlf.novell.com Signed-off-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -1530,6 +1530,7 @@ ENTRY(nmi)
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/* Use %rdx as out temp variable throughout */
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pushq_cfi %rdx
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CFI_REL_OFFSET rdx, 0
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/*
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* If %cs was not the kernel segment, then the NMI triggered in user
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@ -1554,6 +1555,7 @@ ENTRY(nmi)
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*/
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lea 6*8(%rsp), %rdx
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test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
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CFI_REMEMBER_STATE
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nested_nmi:
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/*
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@ -1585,10 +1587,12 @@ nested_nmi:
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nested_nmi_out:
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popq_cfi %rdx
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CFI_RESTORE rdx
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/* No need to check faults here */
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INTERRUPT_RETURN
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CFI_RESTORE_STATE
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first_nmi:
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/*
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* Because nested NMIs will use the pushed location that we
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@ -1624,6 +1628,10 @@ first_nmi:
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* NMI may zero out. The original stack frame and the temp storage
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* is also used by nested NMIs and can not be trusted on exit.
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*/
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/* Do not pop rdx, nested NMIs will corrupt it */
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movq (%rsp), %rdx
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CFI_RESTORE rdx
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/* Set the NMI executing variable on the stack. */
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pushq_cfi $1
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@ -1631,14 +1639,31 @@ first_nmi:
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.rept 5
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pushq_cfi 6*8(%rsp)
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.endr
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CFI_DEF_CFA_OFFSET SS+8-RIP
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/*
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* If there was a nested NMI, the first NMI's iret will return
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* here. But NMIs are still enabled and we can take another
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* nested NMI. The nested NMI checks the interrupted RIP to see
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* if it is between repeat_nmi and end_repeat_nmi, and if so
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* it will just return, as we are about to repeat an NMI anyway.
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* This makes it safe to copy to the stack frame that a nested
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* NMI will update.
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*/
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repeat_nmi:
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/*
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* Update the stack variable to say we are still in NMI (the update
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* is benign for the non-repeat case, where 1 was pushed just above
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* to this very stack slot).
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*/
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movq $1, 5*8(%rsp)
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/* Make another copy, this one may be modified by nested NMIs */
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.rept 5
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pushq_cfi 4*8(%rsp)
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.endr
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/* Do not pop rdx, nested NMIs will corrupt it */
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movq 11*8(%rsp), %rdx
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CFI_DEF_CFA_OFFSET SS+8-RIP
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end_repeat_nmi:
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/*
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* Everything below this point can be preempted by a nested
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@ -1646,7 +1671,6 @@ first_nmi:
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* caused by an exception and nested NMI will start here, and
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* can still be preempted by another NMI.
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*/
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restart_nmi:
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pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
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subq $ORIG_RAX-R15, %rsp
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CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
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@ -1675,26 +1699,6 @@ nmi_restore:
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CFI_ENDPROC
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END(nmi)
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/*
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* If an NMI hit an iret because of an exception or breakpoint,
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* it can lose its NMI context, and a nested NMI may come in.
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* In that case, the nested NMI will change the preempted NMI's
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* stack to jump to here when it does the final iret.
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*/
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repeat_nmi:
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INTR_FRAME
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/* Update the stack variable to say we are still in NMI */
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movq $1, 5*8(%rsp)
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/* copy the saved stack back to copy stack */
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.rept 5
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pushq_cfi 4*8(%rsp)
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.endr
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jmp restart_nmi
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CFI_ENDPROC
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end_repeat_nmi:
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ENTRY(ignore_sysret)
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CFI_STARTPROC
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mov $-ENOSYS,%eax
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