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 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-retpoline-support-retpoline-builds-with-clang.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 87358710c1fb4f1bf96bbe2349975ff9953fc9b2 Mon Sep 17 00:00:00 2001

From: David Woodhouse dwmw@amazon.co.uk Date: Mon, 19 Feb 2018 10:50:57 +0000 Subject: x86/retpoline: Support retpoline builds with Clang

From: David Woodhouse dwmw@amazon.co.uk

commit 87358710c1fb4f1bf96bbe2349975ff9953fc9b2 upstream.

Signed-off-by: David Woodhouse dwmw@amazon.co.uk Reviewed-by: Thomas Gleixner tglx@linutronix.de Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: arjan.van.de.ven@intel.com Cc: bp@alien8.de Cc: dave.hansen@intel.com Cc: jmattson@google.com Cc: karahmed@amazon.de Cc: kvm@vger.kernel.org Cc: pbonzini@redhat.com Cc: rkrcmar@redhat.com Link: http://lkml.kernel.org/r/1519037457-7643-5-git-send-email-dwmw@amazon.co.uk Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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 @@ -232,7 +232,10 @@ KBUILD_CFLAGS += -fno-asynchronous-unwin

# 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 @@ -19,3 +19,8 @@

#define randomized_struct_fields_start struct { #define randomized_struct_fields_end }; + +/* 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 @@ -93,6 +93,10 @@ #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 @@ -6,10 +6,10 @@ #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 @@ -47,7 +47,7 @@

/* These are for everybody (although not all archs will actually discard it in modules) */ -#define __init __section(.init.text) __cold __inittrace __latent_entropy __noretpoline +#define __init __section(.init.text) __cold __inittrace __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@amazon.co.uk are

queue-4.14/x86-retpoline-support-retpoline-builds-with-clang.patch queue-4.14/revert-x86-retpoline-simplify-vmexit_fill_rsb.patch queue-4.14/x86-speculation-use-ibrs-if-available-before-calling-into-firmware.patch queue-4.14/x86-speculation-objtool-annotate-indirect-calls-jumps-for-objtool.patch