| From foo@baz Wed Mar 9 04:10:24 PM CET 2022 |
| From: Zhenzhong Duan <zhenzhong.duan@oracle.com> |
| Date: Fri, 2 Nov 2018 01:45:41 -0700 |
| Subject: x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support |
| |
| From: Zhenzhong Duan <zhenzhong.duan@oracle.com> |
| |
| commit 4cd24de3a0980bf3100c9dcb08ef65ca7c31af48 upstream. |
| |
| 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 |
| [bwh: Backported to 4.9: |
| - Drop change to objtool options |
| - Adjust context, indentation] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/Kconfig | 4 ---- |
| arch/x86/Makefile | 5 +++-- |
| arch/x86/include/asm/nospec-branch.h | 10 ++++++---- |
| arch/x86/kernel/cpu/bugs.c | 2 +- |
| 4 files changed, 10 insertions(+), 11 deletions(-) |
| |
| --- a/arch/x86/Kconfig |
| +++ b/arch/x86/Kconfig |
| @@ -418,10 +418,6 @@ 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. |
| - |
| if X86_32 |
| config X86_EXTENDED_PLATFORM |
| bool "Support for extended (non-PC) x86 platforms" |
| --- a/arch/x86/Makefile |
| +++ b/arch/x86/Makefile |
| @@ -221,9 +221,10 @@ ifdef CONFIG_RETPOLINE |
| 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 += $(RETPOLINE_CFLAGS) -DRETPOLINE |
| + ifeq ($(RETPOLINE_CFLAGS),) |
| + $(error You are building kernel with non-retpoline compiler, please update your compiler.) |
| endif |
| + KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) |
| endif |
| |
| archscripts: scripts_basic |
| --- a/arch/x86/include/asm/nospec-branch.h |
| +++ b/arch/x86/include/asm/nospec-branch.h |
| @@ -164,11 +164,12 @@ |
| _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 \ |
| @@ -183,7 +184,7 @@ |
| 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 |
| @@ -213,6 +214,7 @@ |
| 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) |
| --- a/arch/x86/kernel/cpu/bugs.c |
| +++ b/arch/x86/kernel/cpu/bugs.c |
| @@ -812,7 +812,7 @@ static void __init spec_v2_print_cond(co |
| |
| static inline bool retp_compiler(void) |
| { |
| - return __is_defined(RETPOLINE); |
| + return __is_defined(CONFIG_RETPOLINE); |
| } |
| |
| static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) |