forked from Minki/linux
x86: Add straight-line-speculation mitigation
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
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@ -472,6 +472,18 @@ config RETPOLINE
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branches. Requires a compiler with -mindirect-branch=thunk-extern
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support for full protection. The kernel may run slower.
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config CC_HAS_SLS
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def_bool $(cc-option,-mharden-sls=all)
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config SLS
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bool "Mitigate Straight-Line-Speculation"
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depends on CC_HAS_SLS && X86_64
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default n
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help
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Compile the kernel with straight-line-speculation options to guard
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against straight line speculation. The kernel image might be slightly
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larger.
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config X86_CPU_RESCTRL
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bool "x86 CPU resource control support"
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depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
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@ -191,6 +191,10 @@ ifdef CONFIG_RETPOLINE
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endif
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endif
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ifdef CONFIG_SLS
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KBUILD_CFLAGS += -mharden-sls=all
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endif
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KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
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ifdef CONFIG_LTO_CLANG
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@ -18,9 +18,19 @@
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#define __ALIGN_STR __stringify(__ALIGN)
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#endif
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#ifdef CONFIG_SLS
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#define RET ret; int3
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#else
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#define RET ret
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#endif
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#else /* __ASSEMBLY__ */
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#ifdef CONFIG_SLS
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#define ASM_RET "ret; int3\n\t"
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#else
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#define ASM_RET "ret\n\t"
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#endif
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#endif /* __ASSEMBLY__ */
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@ -36,7 +36,7 @@
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__ARCH_DEFINE_STATIC_CALL_TRAMP(name, ".byte 0xe9; .long " #func " - (. + 4)")
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#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \
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__ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; nop; nop; nop; nop")
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__ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; int3; nop; nop; nop")
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#define ARCH_ADD_TRAMP_KEY(name) \
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@ -303,7 +303,7 @@ union ftrace_op_code_union {
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} __attribute__((packed));
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};
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#define RET_SIZE 1
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#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS)
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static unsigned long
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create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
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@ -17,6 +17,8 @@ enum insn_type {
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*/
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static const u8 xor5rax[] = { 0x66, 0x66, 0x48, 0x31, 0xc0 };
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static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc };
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static void __ref __static_call_transform(void *insn, enum insn_type type, void *func)
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{
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const void *emulate = NULL;
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@ -42,8 +44,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void
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break;
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case RET:
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code = text_gen_insn(RET_INSN_OPCODE, insn, func);
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size = RET_INSN_SIZE;
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code = &retinsn;
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break;
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}
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@ -40,7 +40,7 @@ SYM_FUNC_START(__memmove)
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/* FSRM implies ERMS => no length checks, do the copy directly */
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.Lmemmove_begin_forward:
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ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM
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ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; RET", X86_FEATURE_ERMS
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ALTERNATIVE "", __stringify(movq %rdx, %rcx; rep movsb; RET), X86_FEATURE_ERMS
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/*
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* movsq instruction have many startup latency
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@ -34,7 +34,7 @@ SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
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ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
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__stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \
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__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD
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__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg; int3), X86_FEATURE_RETPOLINE_AMD
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.endm
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@ -234,7 +234,8 @@ objtool_args = \
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$(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\
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$(if $(CONFIG_RETPOLINE), --retpoline) \
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$(if $(CONFIG_X86_SMAP), --uaccess) \
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$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)
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$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) \
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$(if $(CONFIG_SLS), --sls)
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cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
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cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
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@ -139,6 +139,9 @@ objtool_link()
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if [ -n "${CONFIG_X86_SMAP}" ]; then
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objtoolopt="${objtoolopt} --uaccess"
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fi
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if [ -n "${CONFIG_SLS}" ]; then
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objtoolopt="${objtoolopt} --sls"
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fi
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info OBJTOOL ${1}
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tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
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fi
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