From: Peter Zijlstra peterz@infradead.org
[ Upstream commit e463a09af2f0677b9485a7e8e4e70b396b2ffb6f ]
Make use of an upcoming GCC feature to mitigate straight-line-speculation for x86:
https://gcc.gnu.org/g:53a643f8568067d7700a9f2facc8ba39974973d3 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952 https://bugs.llvm.org/show_bug.cgi?id=52323
It's built tested on x86_64-allyesconfig using GCC-12 and GCC-11.
Maintenance overhead of this should be fairly low due to objtool validation.
Size overhead of all these additional int3 instructions comes to:
text data bss dec hex filename 22267751 6933356 2011368 31212475 1dc43bb defconfig-build/vmlinux 22804126 6933356 1470696 31208178 1dc32f2 defconfig-build/vmlinux.sls
Or roughly 2.4% additional text.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Borislav Petkov bp@suse.de Link: https://lore.kernel.org/r/20211204134908.140103474@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/Kconfig | 12 ++++++++++++ arch/x86/Makefile | 4 ++++ arch/x86/include/asm/linkage.h | 10 ++++++++++ arch/x86/include/asm/static_call.h | 2 +- arch/x86/kernel/ftrace.c | 2 +- arch/x86/kernel/static_call.c | 5 +++-- arch/x86/lib/memmove_64.S | 2 +- arch/x86/lib/retpoline.S | 2 +- scripts/Makefile.build | 3 ++- scripts/link-vmlinux.sh | 3 +++ 10 files changed, 38 insertions(+), 7 deletions(-)
--- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -468,6 +468,18 @@ config RETPOLINE branches. Requires a compiler with -mindirect-branch=thunk-extern support for full protection. The kernel may run slower.
+config CC_HAS_SLS + def_bool $(cc-option,-mharden-sls=all) + +config SLS + bool "Mitigate Straight-Line-Speculation" + depends on CC_HAS_SLS && X86_64 + default n + help + Compile the kernel with straight-line-speculation options to guard + against straight line speculation. The kernel image might be slightly + larger. + config X86_CPU_RESCTRL bool "x86 CPU resource control support" depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD) --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -179,6 +179,10 @@ ifdef CONFIG_RETPOLINE endif endif
+ifdef CONFIG_SLS + KBUILD_CFLAGS += -mharden-sls=all +endif + KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
ifdef CONFIG_LTO_CLANG --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -18,9 +18,19 @@ #define __ALIGN_STR __stringify(__ALIGN) #endif
+#ifdef CONFIG_SLS +#define RET ret; int3 +#else +#define RET ret +#endif + #else /* __ASSEMBLY__ */
+#ifdef CONFIG_SLS +#define ASM_RET "ret; int3\n\t" +#else #define ASM_RET "ret\n\t" +#endif
#endif /* __ASSEMBLY__ */
--- a/arch/x86/include/asm/static_call.h +++ b/arch/x86/include/asm/static_call.h @@ -35,7 +35,7 @@ __ARCH_DEFINE_STATIC_CALL_TRAMP(name, ".byte 0xe9; .long " #func " - (. + 4)")
#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \ - __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; nop; nop; nop; nop") + __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; int3; nop; nop; nop")
#define ARCH_ADD_TRAMP_KEY(name) \ --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -308,7 +308,7 @@ union ftrace_op_code_union { } __attribute__((packed)); };
-#define RET_SIZE 1 +#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS)
static unsigned long create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -16,6 +16,8 @@ enum insn_type { */ static const u8 xor5rax[] = { 0x2e, 0x2e, 0x2e, 0x31, 0xc0 };
+static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc }; + static void __ref __static_call_transform(void *insn, enum insn_type type, void *func) { const void *emulate = NULL; @@ -41,8 +43,7 @@ static void __ref __static_call_transfor break;
case RET: - code = text_gen_insn(RET_INSN_OPCODE, insn, func); - size = RET_INSN_SIZE; + code = &retinsn; break; }
--- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -40,7 +40,7 @@ SYM_FUNC_START(__memmove) /* FSRM implies ERMS => no length checks, do the copy directly */ .Lmemmove_begin_forward: ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM - ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; RET", X86_FEATURE_ERMS + ALTERNATIVE "", __stringify(movq %rdx, %rcx; rep movsb; RET), X86_FEATURE_ERMS
/* * movsq instruction have many startup latency --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -34,7 +34,7 @@ SYM_FUNC_START(__x86_indirect_thunk_\reg
ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \ - __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE + __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg; int3), X86_FEATURE_RETPOLINE_LFENCE
SYM_FUNC_END(__x86_indirect_thunk_\reg)
--- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -232,7 +232,8 @@ objtool_args = \ $(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\ $(if $(CONFIG_RETPOLINE), --retpoline) \ $(if $(CONFIG_X86_SMAP), --uaccess) \ - $(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) + $(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) \ + $(if $(CONFIG_SLS), --sls)
ifndef CONFIG_LTO_CLANG
--- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -139,6 +139,9 @@ objtool_link() if [ -n "${CONFIG_X86_SMAP}" ]; then objtoolopt="${objtoolopt} --uaccess" fi + if [ -n "${CONFIG_SLS}" ]; then + objtoolopt="${objtoolopt} --sls" + fi info OBJTOOL ${1} tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1} fi