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[23.128.96.34]) by mx.google.com with ESMTPS id w23-20020a639357000000b00563e6fd0bf6si9806811pgm.792.2023.09.19.08.47.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Sep 2023 08:47:13 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.34 as permitted sender) client-ip=23.128.96.34; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=Qru0T7E8; dkim=neutral (no key) header.i=@linutronix.de; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.34 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by howler.vger.email (Postfix) with ESMTP id 99F24829F649; Tue, 19 Sep 2023 02:54:18 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at howler.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231792AbjISJyL (ORCPT + 26 others); Tue, 19 Sep 2023 05:54:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231687AbjISJxX (ORCPT ); Tue, 19 Sep 2023 05:53:23 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1A6D197; Tue, 19 Sep 2023 02:53:14 -0700 (PDT) Date: Tue, 19 Sep 2023 09:53:10 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1695117190; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lVOz8dN+IJEG2rC2ATXW5loVa6WqCbRIaF/8UV+BGrQ=; b=Qru0T7E8q96qzJsyN8KLarweBSKE4YyUM5jXSGY+89CK5o5v+tCwaiW+Z+R8edIq4l34IH QYczHj/lKb3ASsH0oV8c8qX1SYAiyNwZVZNA3rAFENFQvBQ/8bzJyVReUcQXBURTcPhsAm 2sxfgR/4psJyyzOmJ8CCDEwmLsLX6mcAACoASHpl01Im+buIgfRKcqwD0XZ336KiElLlj4 4EIge1gW5+9SksH2FaFDSKzdXqdHlN23RJ+GpvPRI9TtIqPZLHu3d8aGyeboi6whJVD6Xq oDfDnRU50xtjbO9oS0uTDDFeAfxdi++VNVVJbZU/AFgpV4EBNQrGNf/gEzNsLg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1695117190; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lVOz8dN+IJEG2rC2ATXW5loVa6WqCbRIaF/8UV+BGrQ=; b=vmXS5JzDGp9GDGkDTADVaZs8LGJIqv27Zs4E+kdZTJp4emCN7qZrxB37UanN1Hcn7Abdq6 BD4J0AqxwU4A90DA== From: "tip-bot2 for Josh Poimboeuf" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/bugs] x86/srso: Disentangle rethunk-dependent options Cc: Josh Poimboeuf , Ingo Molnar , "Borislav Petkov (AMD)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org> References: <2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org> MIME-Version: 1.0 Message-ID: <169511719012.27769.9275356413798164492.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Tue, 19 Sep 2023 02:54:18 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777481477812681172 X-GMAIL-MSGID: 1777481477812681172 The following commit has been merged into the x86/bugs branch of tip: Commit-ID: 8976895617cd0d212f90cb55557ec735db632b96 Gitweb: https://git.kernel.org/tip/8976895617cd0d212f90cb55557ec735db632b96 Author: Josh Poimboeuf AuthorDate: Mon, 04 Sep 2023 22:05:00 -07:00 Committer: Ingo Molnar CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00 x86/srso: Disentangle rethunk-dependent options CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all tangled up. De-spaghettify the code a bit. Some of the rethunk-related code has been shuffled around within the '.text..__x86.return_thunk' section, but otherwise there are no functional changes. srso_alias_untrain_ret() and srso_alias_safe_ret() ((which are very address-sensitive) haven't moved. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Acked-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org --- arch/x86/include/asm/nospec-branch.h | 25 ++-- arch/x86/kernel/cpu/bugs.c | 5 +- arch/x86/kernel/vmlinux.lds.S | 7 +- arch/x86/lib/retpoline.S | 157 ++++++++++++++------------ 4 files changed, 109 insertions(+), 85 deletions(-) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 6c14fd1..51e3f1a 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -289,19 +289,17 @@ * where we have a stack but before any RET instruction. */ .macro UNTRAIN_RET -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) +#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ - __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH + __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH #endif .endm .macro UNTRAIN_RET_VM -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) +#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ @@ -311,8 +309,7 @@ .endm .macro UNTRAIN_RET_FROM_CALL -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) +#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ @@ -348,6 +345,20 @@ extern void __x86_return_thunk(void); static inline void __x86_return_thunk(void) {} #endif +#ifdef CONFIG_CPU_UNRET_ENTRY +extern void retbleed_return_thunk(void); +#else +static inline void retbleed_return_thunk(void) {} +#endif + +#ifdef CONFIG_CPU_SRSO +extern void srso_return_thunk(void); +extern void srso_alias_return_thunk(void); +#else +static inline void srso_return_thunk(void) {} +static inline void srso_alias_return_thunk(void) {} +#endif + extern void retbleed_return_thunk(void); extern void srso_return_thunk(void); extern void srso_alias_return_thunk(void); diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6b443f0..9731e81 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd); static DEFINE_MUTEX(spec_ctrl_mutex); -void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk; +void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk; /* Update SPEC_CTRL MSR and its cached copy unconditionally */ static void update_spec_ctrl(u64 val) @@ -1041,8 +1041,7 @@ do_cmd_auto: setup_force_cpu_cap(X86_FEATURE_RETHUNK); setup_force_cpu_cap(X86_FEATURE_UNRET); - if (IS_ENABLED(CONFIG_RETHUNK)) - x86_return_thunk = retbleed_return_thunk; + x86_return_thunk = retbleed_return_thunk; if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index f15fb71..54a5596 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -139,10 +139,7 @@ SECTIONS STATIC_CALL_TEXT ALIGN_ENTRY_TEXT_BEGIN -#ifdef CONFIG_CPU_SRSO *(.text..__x86.rethunk_untrain) -#endif - ENTRY_TEXT #ifdef CONFIG_CPU_SRSO @@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store); "fixed_percpu_data is not at start of per-cpu area"); #endif -#ifdef CONFIG_RETHUNK +#ifdef CONFIG_CPU_UNRET_ENTRY . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned"); -. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned"); #endif #ifdef CONFIG_CPU_SRSO +. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned"); /* * GNU ld cannot do XOR until 2.41. * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1 diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index a40ba18..8ba79d2 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -126,12 +126,13 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) #include #undef GEN #endif -/* - * This function name is magical and is used by -mfunction-return=thunk-extern - * for the compiler to generate JMPs to it. - */ + #ifdef CONFIG_RETHUNK + .section .text..__x86.return_thunk + +#ifdef CONFIG_CPU_SRSO + /* * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at * special addresses: @@ -147,9 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) * * As a result, srso_alias_safe_ret() becomes a safe return. */ -#ifdef CONFIG_CPU_SRSO - .section .text..__x86.rethunk_untrain - + .pushsection .text..__x86.rethunk_untrain SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) UNWIND_HINT_FUNC ANNOTATE_NOENDBR @@ -157,17 +156,9 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) lfence jmp srso_alias_return_thunk SYM_FUNC_END(srso_alias_untrain_ret) + .popsection - .section .text..__x86.rethunk_safe -#else -/* dummy definition for alternatives */ -SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) - ANNOTATE_UNRET_SAFE - ret - int3 -SYM_FUNC_END(srso_alias_untrain_ret) -#endif - + .pushsection .text..__x86.rethunk_safe SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE) lea 8(%_ASM_SP), %_ASM_SP UNWIND_HINT_FUNC @@ -182,8 +173,58 @@ SYM_CODE_START_NOALIGN(srso_alias_return_thunk) call srso_alias_safe_ret ud2 SYM_CODE_END(srso_alias_return_thunk) + .popsection + +/* + * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret() + * above. On kernel entry, srso_untrain_ret() is executed which is a + * + * movabs $0xccccc30824648d48,%rax + * + * and when the return thunk executes the inner label srso_safe_ret() + * later, it is a stack manipulation and a RET which is mispredicted and + * thus a "safe" one to use. + */ + .align 64 + .skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc +SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE) + ANNOTATE_NOENDBR + .byte 0x48, 0xb8 + +/* + * This forces the function return instruction to speculate into a trap + * (UD2 in srso_return_thunk() below). This RET will then mispredict + * and execution will continue at the return site read from the top of + * the stack. + */ +SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL) + lea 8(%_ASM_SP), %_ASM_SP + ret + int3 + int3 + /* end of movabs */ + lfence + call srso_safe_ret + ud2 +SYM_CODE_END(srso_safe_ret) +SYM_FUNC_END(srso_untrain_ret) + +SYM_CODE_START(srso_return_thunk) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR + call srso_safe_ret + ud2 +SYM_CODE_END(srso_return_thunk) + +#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret" +#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret" +#else /* !CONFIG_CPU_SRSO */ +#define JMP_SRSO_UNTRAIN_RET "ud2" +#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2" +#endif /* CONFIG_CPU_SRSO */ + +#ifdef CONFIG_CPU_UNRET_ENTRY - .section .text..__x86.return_thunk /* * Some generic notes on the untraining sequences: * @@ -263,64 +304,21 @@ SYM_CODE_END(retbleed_return_thunk) int3 SYM_FUNC_END(retbleed_untrain_ret) -/* - * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret() - * above. On kernel entry, srso_untrain_ret() is executed which is a - * - * movabs $0xccccc30824648d48,%rax - * - * and when the return thunk executes the inner label srso_safe_ret() - * later, it is a stack manipulation and a RET which is mispredicted and - * thus a "safe" one to use. - */ - .align 64 - .skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc -SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE) - ANNOTATE_NOENDBR - .byte 0x48, 0xb8 +#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret" +#else /* !CONFIG_CPU_UNRET_ENTRY */ +#define JMP_RETBLEED_UNTRAIN_RET "ud2" +#endif /* CONFIG_CPU_UNRET_ENTRY */ -/* - * This forces the function return instruction to speculate into a trap - * (UD2 in srso_return_thunk() below). This RET will then mispredict - * and execution will continue at the return site read from the top of - * the stack. - */ -SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL) - lea 8(%_ASM_SP), %_ASM_SP - ret - int3 - int3 - /* end of movabs */ - lfence - call srso_safe_ret - ud2 -SYM_CODE_END(srso_safe_ret) -SYM_FUNC_END(srso_untrain_ret) - -SYM_CODE_START(srso_return_thunk) - UNWIND_HINT_FUNC - ANNOTATE_NOENDBR - call srso_safe_ret - ud2 -SYM_CODE_END(srso_return_thunk) +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO) SYM_FUNC_START(entry_untrain_ret) - ALTERNATIVE_2 "jmp retbleed_untrain_ret", \ - "jmp srso_untrain_ret", X86_FEATURE_SRSO, \ - "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS + ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET, \ + JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO, \ + JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS SYM_FUNC_END(entry_untrain_ret) __EXPORT_THUNK(entry_untrain_ret) -SYM_CODE_START(__x86_return_thunk) - UNWIND_HINT_FUNC - ANNOTATE_NOENDBR - ANNOTATE_UNRET_SAFE - ret - int3 -SYM_CODE_END(__x86_return_thunk) -EXPORT_SYMBOL(__x86_return_thunk) - -#endif /* CONFIG_RETHUNK */ +#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */ #ifdef CONFIG_CALL_DEPTH_TRACKING @@ -355,3 +353,22 @@ SYM_FUNC_START(__x86_return_skl) SYM_FUNC_END(__x86_return_skl) #endif /* CONFIG_CALL_DEPTH_TRACKING */ + +/* + * This function name is magical and is used by -mfunction-return=thunk-extern + * for the compiler to generate JMPs to it. + * + * This code is only used during kernel boot or module init. All + * 'JMP __x86_return_thunk' sites are changed to something else by + * apply_returns(). + */ +SYM_CODE_START(__x86_return_thunk) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR + ANNOTATE_UNRET_SAFE + ret + int3 +SYM_CODE_END(__x86_return_thunk) +EXPORT_SYMBOL(__x86_return_thunk) + +#endif /* CONFIG_RETHUNK */