x86/retpoline: Support retpoline builds with Clang
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>
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@ -232,7 +232,10 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
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# Avoid indirect branches in kernel to deal with Spectre
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ifdef CONFIG_RETPOLINE
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RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
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RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
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RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
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RETPOLINE_CFLAGS += $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
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ifneq ($(RETPOLINE_CFLAGS),)
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KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
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endif
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@ -27,3 +27,8 @@
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#if __has_feature(address_sanitizer)
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#define __SANITIZE_ADDRESS__
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#endif
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/* Clang doesn't have a way to turn it off per-function, yet. */
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#ifdef __noretpoline
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#undef __noretpoline
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#endif
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@ -93,6 +93,10 @@
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#define __weak __attribute__((weak))
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#define __alias(symbol) __attribute__((alias(#symbol)))
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#ifdef RETPOLINE
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#define __noretpoline __attribute__((indirect_branch("keep")))
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#endif
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/*
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* it doesn't make sense on ARM (currently the only user of __naked)
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* to trace naked functions because then mcount is called without
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@ -6,10 +6,10 @@
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#include <linux/types.h>
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/* Built-in __init functions needn't be compiled with retpoline */
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#if defined(RETPOLINE) && !defined(MODULE)
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#define __noretpoline __attribute__((indirect_branch("keep")))
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#if defined(__noretpoline) && !defined(MODULE)
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#define __noinitretpoline __noretpoline
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#else
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#define __noretpoline
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#define __noinitretpoline
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#endif
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/* These macros are used to mark some functions or
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@ -47,7 +47,7 @@
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/* These are for everybody (although not all archs will actually
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discard it in modules) */
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#define __init __section(.init.text) __cold __latent_entropy __noretpoline
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#define __init __section(.init.text) __cold __latent_entropy __noinitretpoline
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#define __initdata __section(.init.data)
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#define __initconst __section(.init.rodata)
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#define __exitdata __section(.exit.data)
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