| 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) |