Messages in this thread Patch in this message | | | Date | Fri, 29 Apr 2022 13:36:44 -0700 | Subject | [RFC PATCH 21/21] x86: Add support for CONFIG_CFI_CLANG | From | Sami Tolvanen <> |
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Add CONFIG_CFI_CLANG error handling and allow the config to be selected on x86_64.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- arch/x86/Kconfig | 1 + arch/x86/include/asm/linkage.h | 7 ++++++ arch/x86/kernel/traps.c | 39 +++++++++++++++++++++++++++++++++- 3 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index b0142e01002e..01db5c5c4dde 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -108,6 +108,7 @@ config X86 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096 + select ARCH_SUPPORTS_CFI_CLANG if X86_64 select ARCH_SUPPORTS_LTO_CLANG select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_USE_BUILTIN_BSWAP diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h index 85865f1645bd..d20acf5ebae3 100644 --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -25,6 +25,13 @@ #define RET ret #endif +#ifdef CONFIG_CFI_CLANG +#define __CFI_TYPE(name) \ + .fill 10, 1, 0x90 ASM_NL \ + .4byte __kcfi_typeid_##name ASM_NL \ + .fill 2, 1, 0xcc +#endif + #else /* __ASSEMBLY__ */ #ifdef CONFIG_SLS diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 1563fb995005..b9e46e6ed83b 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -40,6 +40,7 @@ #include <linux/hardirq.h> #include <linux/atomic.h> #include <linux/ioasid.h> +#include <linux/cfi.h> #include <asm/stacktrace.h> #include <asm/processor.h> @@ -295,6 +296,41 @@ static inline void handle_invalid_op(struct pt_regs *regs) ILL_ILLOPN, error_get_trap_addr(regs)); } +#ifdef CONFIG_CFI_CLANG +void *arch_get_cfi_target(unsigned long addr, struct pt_regs *regs) +{ + char buffer[MAX_INSN_SIZE]; + int offset; + struct insn insn; + unsigned long *target; + + /* + * The expected CFI check instruction sequence: + * cmpl <id>, -6(%reg) ; 7 bytes + * je .Ltmp1 ; 2 bytes + * ud2 ; <- addr + * .Ltmp1: + * + * Therefore, the target address is in a register that we can + * decode from the cmpl instruction. + */ + if (copy_from_kernel_nofault(buffer, (void *)addr - 9, MAX_INSN_SIZE)) + return NULL; + if (insn_decode(&insn, buffer, MAX_INSN_SIZE, INSN_MODE_64)) + return NULL; + if (insn.opcode.value != 0x81) + return NULL; + + offset = insn_get_modrm_rm_off(&insn, regs); + if (offset < 0) + return NULL; + + target = (void *)regs + offset; + + return (void *)*target; +} +#endif + static noinstr bool handle_bug(struct pt_regs *regs) { bool handled = false; @@ -312,7 +348,8 @@ static noinstr bool handle_bug(struct pt_regs *regs) */ if (regs->flags & X86_EFLAGS_IF) raw_local_irq_enable(); - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN) { + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || + report_cfi(regs->ip, regs) == BUG_TRAP_TYPE_WARN) { regs->ip += LEN_UD2; handled = true; } -- 2.36.0.464.gb9c8b46e94-goog
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