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authorZhenzhong Duan <zhenzhong.duan@oracle.com>2018-11-02 01:45:41 -0700
committerThomas Gleixner <tglx@linutronix.de>2018-11-28 11:57:03 +0100
commit4cd24de3a0980bf3100c9dcb08ef65ca7c31af48 (patch)
treee8358f10ec5689cdda1d7ad33491c607d15766c6
parent2e6e902d185027f8e3cb8b7305238f7e35d6a436 (diff)
x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support
Since retpoline capable compilers are widely available, make CONFIG_RETPOLINE hard depend on the compiler capability. Break the build when CONFIG_RETPOLINE is enabled and the compiler does not support it. Emit an error message in that case: "arch/x86/Makefile:226: *** You are building kernel with non-retpoline compiler, please update your compiler.. Stop." [dwmw: Fail the build with non-retpoline compiler] Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Borislav Petkov <bp@suse.de> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Michal Marek <michal.lkml@markovi.net> Cc: <srinivas.eeda@oracle.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/cca0cb20-f9e2-4094-840b-fb0f8810cd34@default
-rw-r--r--arch/x86/Kconfig4
-rw-r--r--arch/x86/Makefile5
-rw-r--r--arch/x86/include/asm/nospec-branch.h10
-rw-r--r--arch/x86/kernel/cpu/bugs.c2
-rw-r--r--scripts/Makefile.build2
5 files changed, 10 insertions, 13 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9d734f3c8234..b5286ad2a982 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -444,10 +444,6 @@ config RETPOLINE
branches. Requires a compiler with -mindirect-branch=thunk-extern
support for full protection. The kernel may run slower.
- Without compiler support, at least indirect branches in assembler
- code are eliminated. Since this includes the syscall entry path,
- it is not entirely pointless.
-
config INTEL_RDT
bool "Intel Resource Director Technology support"
depends on X86 && CPU_SUP_INTEL
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 88398fdf8129..f5d7f4134524 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -220,9 +220,10 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
# Avoid indirect branches in kernel to deal with Spectre
ifdef CONFIG_RETPOLINE
-ifneq ($(RETPOLINE_CFLAGS),)
- KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+ $(error You are building kernel with non-retpoline compiler, please update your compiler.)
endif
+ KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
endif
archscripts: scripts_basic
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 80dc14422495..8b09cbb2d52c 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -162,11 +162,12 @@
_ASM_PTR " 999b\n\t" \
".popsection\n\t"
-#if defined(CONFIG_X86_64) && defined(RETPOLINE)
+#ifdef CONFIG_RETPOLINE
+#ifdef CONFIG_X86_64
/*
- * Since the inline asm uses the %V modifier which is only in newer GCC,
- * the 64-bit one is dependent on RETPOLINE not CONFIG_RETPOLINE.
+ * Inline asm uses the %V modifier which is only in newer GCC
+ * which is ensured when CONFIG_RETPOLINE is defined.
*/
# define CALL_NOSPEC \
ANNOTATE_NOSPEC_ALTERNATIVE \
@@ -181,7 +182,7 @@
X86_FEATURE_RETPOLINE_AMD)
# define THUNK_TARGET(addr) [thunk_target] "r" (addr)
-#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE)
+#else /* CONFIG_X86_32 */
/*
* For i386 we use the original ret-equivalent retpoline, because
* otherwise we'll run out of registers. We don't care about CET
@@ -211,6 +212,7 @@
X86_FEATURE_RETPOLINE_AMD)
# define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
+#endif
#else /* No retpoline for C / inline asm */
# define CALL_NOSPEC "call *%[thunk_target]\n"
# define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c37e66e493bf..d0108fb6e4dd 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -252,7 +252,7 @@ static void __init spec2_print_if_secure(const char *reason)
static inline bool retp_compiler(void)
{
- return __is_defined(RETPOLINE);
+ return __is_defined(CONFIG_RETPOLINE);
}
static inline bool match_option(const char *arg, int arglen, const char *opt)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a8e7ba9f73e8..6a6be9f440cf 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -236,10 +236,8 @@ ifdef CONFIG_GCOV_KERNEL
objtool_args += --no-unreachable
endif
ifdef CONFIG_RETPOLINE
-ifneq ($(RETPOLINE_CFLAGS),)
objtool_args += --retpoline
endif
-endif
ifdef CONFIG_MODVERSIONS