From: Hugh Dickins <hughd@google.com>
Date: Fri, 22 Sep 2017 03:39:56 +0000 (-0700)
Subject: kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER
X-Git-Tag: archive/raspbian/4.9.80-2+rpi1~8^2^2~40
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=0fcf765837fb4c4ab508a3487249584a701a5e74;p=linux-4.9.git

kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER

pjt has observed that nmi's second (nmi_from_kernel) call to do_nmi()
adjusted the %rdi regs arg, rightly when CONFIG_KAISER, but wrongly
when not CONFIG_KAISER.

Although the minimal change is to add an #ifdef CONFIG_KAISER around
the addq line, that looks cluttered, and I prefer how the first call
to do_nmi() handled it: prepare args in %rdi and %rsi before getting
into the CONFIG_KAISER block, since it does not touch them at all.

And while we're here, place the "#ifdef CONFIG_KAISER" that follows
each, to enclose the "Unconditionally restore CR3" comment: matching
how the "Unconditionally use kernel CR3" comment above is enclosed.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Gbp-Pq: Topic features/all/kpti
Gbp-Pq: Name kaiser-fix-regs-to-do_nmi-ifndef-config_kaiser.patch
---

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 5874e3280135..2f9eb09210a3 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1337,12 +1337,13 @@ ENTRY(nmi)
 	movq	%rax, %cr3
 #endif
 	call	do_nmi
+
+#ifdef CONFIG_KAISER
 	/*
 	 * Unconditionally restore CR3.  I know we return to
 	 * kernel code that needs user CR3, but do we ever return
 	 * to "user mode" where we need the kernel CR3?
 	 */
-#ifdef CONFIG_KAISER
 	popq	%rax
 	mov	%rax, %cr3
 #endif
@@ -1566,6 +1567,8 @@ end_repeat_nmi:
 	SWAPGS
 	xorl	%ebx, %ebx
 1:
+	movq	%rsp, %rdi
+	movq	$-1, %rsi
 #ifdef CONFIG_KAISER
 	/* Unconditionally use kernel CR3 for do_nmi() */
 	/* %rax is saved above, so OK to clobber here */
@@ -1578,16 +1581,14 @@ end_repeat_nmi:
 #endif
 
 	/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
-	movq	%rsp, %rdi
-	addq	$8, %rdi /* point %rdi at ptregs, fixed up for CR3 */
-	movq	$-1, %rsi
 	call	do_nmi
+
+#ifdef CONFIG_KAISER
 	/*
 	 * Unconditionally restore CR3.  We might be returning to
 	 * kernel code that needs user CR3, like just just before
 	 * a sysret.
 	 */
-#ifdef CONFIG_KAISER
 	popq	%rax
 	mov	%rax, %cr3
 #endif