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x86/retpoline: Support retpoline builds with Clang

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Signed-off-by: David Woodhouse <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
David Woodhouse authored and Ingo Molnar committed 2018-02-20 11:17:58 +01:00
1 parent dd84441a79
commit 87358710c1
4 files changed
+17 -5
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arch/x86/Makefile
+4 -1
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@@ -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
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@@ -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
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@@ -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
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@@ -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)