From: Tim Chen <tim.c.chen@linux.intel.com>
Date: Fri, 15 Dec 2017 12:25:03 +0000 (-0800)
Subject: x86: Add macro that does not save rax, rcx, rdx on stack to disable IBRS
X-Git-Tag: v4.1.12-124.31.3~1415
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=86eb701a9cc2a4b6e602d77b2b3f12a5e1e267f3;p=users%2Fjedix%2Flinux-maple.git

x86: Add macro that does not save rax, rcx, rdx on stack to disable IBRS


Orabug: 27344012
CVE: CVE-2017-5715

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>
---

diff --git a/arch/x86/include/asm/spec_ctrl.h b/arch/x86/include/asm/spec_ctrl.h
index de4ce9ee4de8..3080f33fbd08 100644
--- a/arch/x86/include/asm/spec_ctrl.h
+++ b/arch/x86/include/asm/spec_ctrl.h
@@ -46,6 +46,11 @@
 	popq %rdx;				\
 	popq %rcx;				\
 	popq %rax
+#define __ASM_DISABLE_IBRS_CLOBBER		\
+	movl $MSR_IA32_SPEC_CTRL, %ecx;		\
+	movl $0, %edx;				\
+	movl $0, %eax;				\
+	wrmsr;
 
 .macro ENABLE_IBRS
 ALTERNATIVE "", __stringify(__ASM_ENABLE_IBRS), X86_FEATURE_SPEC_CTRL
@@ -66,5 +71,9 @@ ALTERNATIVE "", __stringify(__ASM_DISABLE_IBRS), X86_FEATURE_SPEC_CTRL
 ALTERNATIVE "", __stringify(__ASM_SET_IBPB), X86_FEATURE_SPEC_CTRL
 .endm
 
+.macro DISABLE_IBRS_CLOBBER
+ALTERNATIVE "", __stringify(__ASM_DISABLE_IBRS_CLOBBER), X86_FEATURE_SPEC_CTRL
+.endm
+
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_SPEC_CTRL_H */