diff --git a/arch/x86/include/asm/cfi.h b/arch/x86/include/asm/cfi.h index c40b9ebc1fb4..ab3fbbd947ed 100644 --- a/arch/x86/include/asm/cfi.h +++ b/arch/x86/include/asm/cfi.h @@ -111,6 +111,12 @@ extern bhi_thunk __bhi_args_end[]; struct pt_regs; +#ifdef CONFIG_CALL_PADDING +#define CFI_OFFSET (CONFIG_FUNCTION_PADDING_CFI+5) +#else +#define CFI_OFFSET 5 +#endif + #ifdef CONFIG_CFI enum bug_trap_type handle_cfi_failure(struct pt_regs *regs); #define __bpfcall @@ -119,11 +125,9 @@ static inline int cfi_get_offset(void) { switch (cfi_mode) { case CFI_FINEIBT: - return 16; + return /* fineibt_prefix_size */ 16; case CFI_KCFI: - if (IS_ENABLED(CONFIG_CALL_PADDING)) - return 16; - return 5; + return CFI_OFFSET; default: return 0; } diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h index 9d38ae744a2e..a7294656ad90 100644 --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -68,7 +68,7 @@ * Depending on -fpatchable-function-entry=N,N usage (CONFIG_CALL_PADDING) the * CFI symbol layout changes. * - * Without CALL_THUNKS: + * Without CALL_PADDING: * * .align FUNCTION_ALIGNMENT * __cfi_##name: @@ -77,7 +77,7 @@ * .long __kcfi_typeid_##name * name: * - * With CALL_THUNKS: + * With CALL_PADDING: * * .align FUNCTION_ALIGNMENT * __cfi_##name: diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index a888ae0f01fb..e87da25d1236 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1182,7 +1182,7 @@ void __init_or_module noinline apply_seal_endbr(s32 *start, s32 *end) poison_endbr(addr); if (IS_ENABLED(CONFIG_FINEIBT)) - poison_cfi(addr - 16); + poison_cfi(addr - CFI_OFFSET); } } @@ -1389,6 +1389,8 @@ extern u8 fineibt_preamble_end[]; #define fineibt_preamble_ud 0x13 #define fineibt_preamble_hash 5 +#define fineibt_prefix_size (fineibt_preamble_size - ENDBR_INSN_SIZE) + /* * : * 0: b8 78 56 34 12 mov $0x12345678, %eax @@ -1634,7 +1636,7 @@ static int cfi_rewrite_preamble(s32 *start, s32 *end) * have determined there are no indirect calls to it and we * don't need no CFI either. */ - if (!is_endbr(addr + 16)) + if (!is_endbr(addr + CFI_OFFSET)) continue; hash = decode_preamble_hash(addr, &arity); @@ -1642,6 +1644,15 @@ static int cfi_rewrite_preamble(s32 *start, s32 *end) addr, addr, 5, addr)) return -EINVAL; + /* + * FineIBT relies on being at func-16, so if the preamble is + * actually larger than that, place it the tail end. + * + * NOTE: this is possible with things like DEBUG_CALL_THUNKS + * and DEBUG_FORCE_FUNCTION_ALIGN_64B. + */ + addr += CFI_OFFSET - fineibt_prefix_size; + text_poke_early(addr, fineibt_preamble_start, fineibt_preamble_size); WARN_ON(*(u32 *)(addr + fineibt_preamble_hash) != 0x12345678); text_poke_early(addr + fineibt_preamble_hash, &hash, 4); @@ -1664,10 +1675,10 @@ static void cfi_rewrite_endbr(s32 *start, s32 *end) for (s = start; s < end; s++) { void *addr = (void *)s + *s; - if (!exact_endbr(addr + 16)) + if (!exact_endbr(addr + CFI_OFFSET)) continue; - poison_endbr(addr + 16); + poison_endbr(addr + CFI_OFFSET); } } @@ -1772,7 +1783,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, if (FINEIBT_WARN(fineibt_preamble_size, 20) || FINEIBT_WARN(fineibt_preamble_bhi + fineibt_bhi1_size, 20) || FINEIBT_WARN(fineibt_caller_size, 14) || - FINEIBT_WARN(fineibt_paranoid_size, 20)) + FINEIBT_WARN(fineibt_paranoid_size, 20) || + WARN_ON_ONCE(CFI_OFFSET < fineibt_prefix_size)) return; if (cfi_mode == CFI_AUTO) { @@ -1885,6 +1897,11 @@ static void poison_cfi(void *addr) */ switch (cfi_mode) { case CFI_FINEIBT: + /* + * FineIBT preamble is at func-16. + */ + addr += CFI_OFFSET - fineibt_prefix_size; + /* * FineIBT prefix should start with an ENDBR. */ @@ -1923,8 +1940,6 @@ static void poison_cfi(void *addr) } } -#define fineibt_prefix_size (fineibt_preamble_size - ENDBR_INSN_SIZE) - /* * When regs->ip points to a 0xD6 byte in the FineIBT preamble, * return true and fill out target and type. diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 8f10080e6fe3..e9b78040d703 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -438,17 +438,8 @@ static void emit_kcfi(u8 **pprog, u32 hash) EMIT1_off32(0xb8, hash); /* movl $hash, %eax */ #ifdef CONFIG_CALL_PADDING - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); - EMIT1(0x90); + for (int i = 0; i < CONFIG_FUNCTION_PADDING_CFI; i++) + EMIT1(0x90); #endif EMIT_ENDBR();