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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
hifive-unleashed-5.1
Zhenzhong Duan 2018-11-02 01:45:41 -07:00 committed by Thomas Gleixner
parent 2e6e902d18
commit 4cd24de3a0
5 changed files with 10 additions and 13 deletions
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4
arch/x86/Kconfig
View File

@ -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

5
arch/x86/Makefile
View File

@ -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

10
arch/x86/include/asm/nospec-branch.h
View File

@ -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)

2
arch/x86/kernel/cpu/bugs.c
View File

@ -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)

2
scripts/Makefile.build
View File

@ -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