diff options
Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r-- | arch/x86/kernel/alternative.c | 108 |
1 files changed, 90 insertions, 18 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 5007c3ffe96f..d374cb3cf024 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -115,6 +115,7 @@ static void __init_or_module add_nops(void *insns, unsigned int len) } extern s32 __retpoline_sites[], __retpoline_sites_end[]; +extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[]; extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; extern s32 __smp_locks[], __smp_locks_end[]; void text_poke_early(void *addr, const void *opcode, size_t len); @@ -389,7 +390,7 @@ static int emit_indirect(int op, int reg, u8 *bytes) * * CALL *%\reg * - * It also tries to inline spectre_v2=retpoline,amd when size permits. + * It also tries to inline spectre_v2=retpoline,lfence when size permits. */ static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes) { @@ -407,7 +408,7 @@ static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes) BUG_ON(reg == 4); if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) && - !cpu_feature_enabled(X86_FEATURE_RETPOLINE_AMD)) + !cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) return -1; op = insn->opcode.bytes[0]; @@ -438,9 +439,9 @@ static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes) } /* - * For RETPOLINE_AMD: prepend the indirect CALL/JMP with an LFENCE. + * For RETPOLINE_LFENCE: prepend the indirect CALL/JMP with an LFENCE. */ - if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_AMD)) { + if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) { bytes[i++] = 0x0f; bytes[i++] = 0xae; bytes[i++] = 0xe8; /* LFENCE */ @@ -512,6 +513,42 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { } #endif /* CONFIG_RETPOLINE && CONFIG_STACK_VALIDATION */ +#ifdef CONFIG_X86_KERNEL_IBT + +/* + * Generated by: objtool --ibt + */ +void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) +{ + s32 *s; + + for (s = start; s < end; s++) { + u32 endbr, poison = gen_endbr_poison(); + void *addr = (void *)s + *s; + + if (WARN_ON_ONCE(get_kernel_nofault(endbr, addr))) + continue; + + if (WARN_ON_ONCE(!is_endbr(endbr))) + continue; + + DPRINTK("ENDBR at: %pS (%px)", addr, addr); + + /* + * When we have IBT, the lack of ENDBR will trigger #CP + */ + DUMP_BYTES(((u8*)addr), 4, "%px: orig: ", addr); + DUMP_BYTES(((u8*)&poison), 4, "%px: repl: ", addr); + text_poke_early(addr, &poison, 4); + } +} + +#else + +void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) { } + +#endif /* CONFIG_X86_KERNEL_IBT */ + #ifdef CONFIG_SMP static void alternatives_smp_lock(const s32 *start, const s32 *end, u8 *text, u8 *text_end) @@ -713,34 +750,39 @@ asm ( " .pushsection .init.text, \"ax\", @progbits\n" " .type int3_magic, @function\n" "int3_magic:\n" + ANNOTATE_NOENDBR " movl $1, (%" _ASM_ARG1 ")\n" ASM_RET " .size int3_magic, .-int3_magic\n" " .popsection\n" ); -extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */ +extern void int3_selftest_ip(void); /* defined in asm below */ static int __init int3_exception_notify(struct notifier_block *self, unsigned long val, void *data) { + unsigned long selftest = (unsigned long)&int3_selftest_ip; struct die_args *args = data; struct pt_regs *regs = args->regs; + OPTIMIZER_HIDE_VAR(selftest); + if (!regs || user_mode(regs)) return NOTIFY_DONE; if (val != DIE_INT3) return NOTIFY_DONE; - if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip) + if (regs->ip - INT3_INSN_SIZE != selftest) return NOTIFY_DONE; int3_emulate_call(regs, (unsigned long)&int3_magic); return NOTIFY_STOP; } -static void __init int3_selftest(void) +/* Must be noinline to ensure uniqueness of int3_selftest_ip. */ +static noinline void __init int3_selftest(void) { static __initdata struct notifier_block int3_exception_nb = { .notifier_call = int3_exception_notify, @@ -753,18 +795,12 @@ static void __init int3_selftest(void) /* * Basically: int3_magic(&val); but really complicated :-) * - * Stick the address of the INT3 instruction into int3_selftest_ip, - * then trigger the INT3, padded with NOPs to match a CALL instruction - * length. + * INT3 padded with NOP to CALL_INSN_SIZE. The int3_exception_nb + * notifier above will emulate CALL for us. */ - asm volatile ("1: int3; nop; nop; nop; nop\n\t" - ".pushsection .init.data,\"aw\"\n\t" - ".align " __ASM_SEL(4, 8) "\n\t" - ".type int3_selftest_ip, @object\n\t" - ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t" - "int3_selftest_ip:\n\t" - __ASM_SEL(.long, .quad) " 1b\n\t" - ".popsection\n\t" + asm volatile ("int3_selftest_ip:\n\t" + ANNOTATE_NOENDBR + " int3; nop; nop; nop; nop\n\t" : ASM_CALL_CONSTRAINT : __ASM_SEL_RAW(a, D) (&val) : "memory"); @@ -831,6 +867,8 @@ void __init alternative_instructions(void) */ apply_alternatives(__alt_instructions, __alt_instructions_end); + apply_ibt_endbr(__ibt_endbr_seal, __ibt_endbr_seal_end); + #ifdef CONFIG_SMP /* Patch to UP if other cpus not imminent. */ if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) { @@ -1102,6 +1140,40 @@ void *text_poke_kgdb(void *addr, const void *opcode, size_t len) return __text_poke(addr, opcode, len); } +/** + * text_poke_copy - Copy instructions into (an unused part of) RX memory + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy, could be more than 2x PAGE_SIZE + * + * Not safe against concurrent execution; useful for JITs to dump + * new code blocks into unused regions of RX memory. Can be used in + * conjunction with synchronize_rcu_tasks() to wait for existing + * execution to quiesce after having made sure no existing functions + * pointers are live. + */ +void *text_poke_copy(void *addr, const void *opcode, size_t len) +{ + unsigned long start = (unsigned long)addr; + size_t patched = 0; + + if (WARN_ON_ONCE(core_kernel_text(start))) + return NULL; + + mutex_lock(&text_mutex); + while (patched < len) { + unsigned long ptr = start + patched; + size_t s; + + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); + + __text_poke((void *)ptr, opcode + patched, s); + patched += s; + } + mutex_unlock(&text_mutex); + return addr; +} + static void do_sync_core(void *info) { sync_core(); |