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Commit 87358710 authored by David Woodhouse's avatar David Woodhouse Committed by Ingo Molnar
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x86/retpoline: Support retpoline builds with Clang 



Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: default avatarThomas 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: default avatarIngo Molnar <mingo@kernel.org>
parent dd84441a

arch/x86/Makefile

+4 −1
Original line number Diff line number Diff line
@@ -232,7 +232,10 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables 


# 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

include/linux/compiler-clang.h

+5 −0
Original line number Diff line number Diff line
@@ -27,3 +27,8 @@ 
#if __has_feature(address_sanitizer)

#define __SANITIZE_ADDRESS__

#endif



/* Clang doesn't have a way to turn it off per-function, yet. */

#ifdef __noretpoline

#undef __noretpoline

#endif

include/linux/compiler-gcc.h

+4 −0
Original line number Diff line number Diff line
@@ -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

include/linux/init.h

+4 −4
Original line number Diff line number Diff line
@@ -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  __latent_entropy __noretpoline

#define __init		__section(.init.text) __cold  __latent_entropy __noinitretpoline

#define __initdata	__section(.init.data)

#define __initconst	__section(.init.rodata)

#define __exitdata	__section(.exit.data)