pve-edge-kernel/patches/kernel/0092-x86-entry-64-Merge-the-fast-and-slow-SYSRET-paths.patch

From c48697564de6da427f1e97a38192f4d456223942 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <[email protected]>
Date: Thu, 2 Nov 2017 00:59:04 -0700
Subject: [PATCH 092/231] x86/entry/64: Merge the fast and slow SYSRET paths
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CVE-2017-5754

They did almost the same thing.  Remove a bunch of pointless
instructions (mostly hidden in macros) and reduce cognitive load by
merging them.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/1204e20233fcab9130a1ba80b3b1879b5db3fc1f.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>
(cherry picked from commit a512210643da8082cb44181dba8b18e752bd68f0)
Signed-off-by: Andy Whitcroft <[email protected]>
Signed-off-by: Kleber Sacilotto de Souza <[email protected]>
(cherry picked from commit 7c4575d8bb2d01960ba9b9840fa22460e0179eca)
Signed-off-by: Fabian Grünbichler <[email protected]>
---
 arch/x86/entry/entry_64.S | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 33a416c7df2d..87be1cd1fa88 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -220,10 +220,9 @@ entry_SYSCALL_64_fastpath:
 	TRACE_IRQS_ON		/* user mode is traced as IRQs on */
 	movq	RIP(%rsp), %rcx
 	movq	EFLAGS(%rsp), %r11
-	RESTORE_C_REGS_EXCEPT_RCX_R11
-	movq	RSP(%rsp), %rsp
+	addq	$6*8, %rsp	/* skip extra regs -- they were preserved */
 	UNWIND_HINT_EMPTY
-	USERGS_SYSRET64
+	jmp	.Lpop_c_regs_except_rcx_r11_and_sysret
 
 1:
 	/*
@@ -317,6 +316,7 @@ syscall_return_via_sysret:
 	/* rcx and r11 are already restored (see code above) */
 	UNWIND_HINT_EMPTY
 	POP_EXTRA_REGS
+.Lpop_c_regs_except_rcx_r11_and_sysret:
 	popq	%rsi	/* skip r11 */
 	popq	%r10
 	popq	%r9
-- 
2.14.2