This is a note to let you know that I've just added the patch titled
x86/retpoline: Support retpoline builds with Clang
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-retpoline-support-retpoline-builds-with-clang.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 87358710c1fb4f1bf96bbe2349975ff9953fc9b2 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
Date: Mon, 19 Feb 2018 10:50:57 +0000
Subject: x86/retpoline: Support retpoline builds with Clang
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
commit 87358710c1fb4f1bf96bbe2349975ff9953fc9b2 upstream.
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: arjan.van.de.ven@xxxxxxxxx
Cc: bp@xxxxxxxxx
Cc: dave.hansen@xxxxxxxxx
Cc: jmattson@xxxxxxxxxx
Cc: karahmed@xxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: pbonzini@xxxxxxxxxx
Cc: rkrcmar@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1519037457-7643-5-git-send-email-dwmw@xxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/Makefile | 5 ++++-
include/linux/compiler-clang.h | 5 +++++
include/linux/compiler-gcc.h | 4 ++++
include/linux/init.h | 8 ++++----
4 files changed, 17 insertions(+), 5 deletions(-)
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -184,7 +184,10 @@ KBUILD_AFLAGS += $(mflags-y)
# Avoid indirect branches in kernel to deal with Spectre
ifdef CONFIG_RETPOLINE
- RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
+ RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
+ RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
+
+ RETPOLINE_CFLAGS += $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
ifneq ($(RETPOLINE_CFLAGS),)
KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
endif
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -15,3 +15,8 @@
* with any version that can compile the kernel
*/
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+/* Clang doesn't have a way to turn it off per-function, yet. */
+#ifdef __noretpoline
+#undef __noretpoline
+#endif
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -88,6 +88,10 @@
#define __weak __attribute__((weak))
#define __alias(symbol) __attribute__((alias(#symbol)))
+#ifdef RETPOLINE
+#define __noretpoline __attribute__((indirect_branch("keep")))
+#endif
+
/*
* it doesn't make sense on ARM (currently the only user of __naked)
* to trace naked functions because then mcount is called without
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -5,10 +5,10 @@
#include <linux/types.h>
/* Built-in __init functions needn't be compiled with retpoline */
-#if defined(RETPOLINE) && !defined(MODULE)
-#define __noretpoline __attribute__((indirect_branch("keep")))
+#if defined(__noretpoline) && !defined(MODULE)
+#define __noinitretpoline __noretpoline
#else
-#define __noretpoline
+#define __noinitretpoline
#endif
/* These macros are used to mark some functions or
@@ -46,7 +46,7 @@
/* These are for everybody (although not all archs will actually
discard it in modules) */
-#define __init __section(.init.text) __cold notrace __latent_entropy __noretpoline
+#define __init __section(.init.text) __cold notrace __latent_entropy __noinitretpoline
#define __initdata __section(.init.data)
#define __initconst __section(.init.rodata)
#define __exitdata __section(.exit.data)
Patches currently in stable-queue which might be from dwmw@xxxxxxxxxxxx are
queue-4.9/x86-retpoline-support-retpoline-builds-with-clang.patch
queue-4.9/revert-x86-retpoline-simplify-vmexit_fill_rsb.patch
queue-4.9/x86-speculation-use-ibrs-if-available-before-calling-into-firmware.patch
queue-4.9/x86-speculation-objtool-annotate-indirect-calls-jumps-for-objtool.patch