From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D52C211703 for ; Mon, 21 Aug 2023 20:04:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58030C433C8; Mon, 21 Aug 2023 20:04:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692648289; bh=aB3kEMDtCkTkPvotAwUWNN5+fRZCXq3IuE5i7s+0OTo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qKUSsIIuUtJiSnkvU8F0E+cll0khF0N1ov8G67+8lpypiT1ig6v4SAhUMAqNhDWeu l4biaBTFlohebD96w6gM0fOr16ekzhxKyO/OImQk6ABmclxX6YvmnW4kHCAz5LZZ1+ zFuTDy5yYCxaCKvZk6pZQ1UUgmijCYjr2hL7e14Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Peter Zijlstra (Intel)" , "Borislav Petkov (AMD)" Subject: [PATCH 6.4 121/234] x86/cpu: Cleanup the untrain mess Date: Mon, 21 Aug 2023 21:41:24 +0200 Message-ID: <20230821194134.172641025@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230821194128.754601642@linuxfoundation.org> References: <20230821194128.754601642@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Peter Zijlstra commit e7c25c441e9e0fa75b4c83e0b26306b702cfe90d upstream. Since there can only be one active return_thunk, there only needs be one (matching) untrain_ret. It fundamentally doesn't make sense to allow multiple untrain_ret at the same time. Fold all the 3 different untrain methods into a single (temporary) helper stub. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230814121149.042774962@infradead.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/nospec-branch.h | 19 +++++-------------- arch/x86/kernel/cpu/bugs.c | 1 + arch/x86/lib/retpoline.S | 7 +++++++ 3 files changed, 13 insertions(+), 14 deletions(-) --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -268,9 +268,9 @@ .endm #ifdef CONFIG_CPU_UNRET_ENTRY -#define CALL_ZEN_UNTRAIN_RET "call retbleed_untrain_ret" +#define CALL_UNTRAIN_RET "call entry_untrain_ret" #else -#define CALL_ZEN_UNTRAIN_RET "" +#define CALL_UNTRAIN_RET "" #endif /* @@ -289,15 +289,10 @@ defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ - CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \ + CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH #endif - -#ifdef CONFIG_CPU_SRSO - ALTERNATIVE_2 "", "call srso_untrain_ret", X86_FEATURE_SRSO, \ - "call srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS -#endif .endm .macro UNTRAIN_RET_FROM_CALL @@ -305,15 +300,10 @@ defined(CONFIG_CALL_DEPTH_TRACKING) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ - CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \ + CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH #endif - -#ifdef CONFIG_CPU_SRSO - ALTERNATIVE_2 "", "call srso_untrain_ret", X86_FEATURE_SRSO, \ - "call srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS -#endif .endm @@ -351,6 +341,7 @@ extern void retbleed_untrain_ret(void); extern void srso_untrain_ret(void); extern void srso_alias_untrain_ret(void); +extern void entry_untrain_ret(void); extern void entry_ibpb(void); extern void (*x86_return_thunk)(void); --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -2458,6 +2458,7 @@ static void __init srso_select_mitigatio * like ftrace, static_call, etc. */ setup_force_cpu_cap(X86_FEATURE_RETHUNK); + setup_force_cpu_cap(X86_FEATURE_UNRET); if (boot_cpu_data.x86 == 0x19) { setup_force_cpu_cap(X86_FEATURE_SRSO_ALIAS); --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -290,6 +290,13 @@ SYM_CODE_START(srso_return_thunk) ud2 SYM_CODE_END(srso_return_thunk) +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 +SYM_FUNC_END(entry_untrain_ret) +__EXPORT_THUNK(entry_untrain_ret) + SYM_CODE_START(__x86_return_thunk) UNWIND_HINT_FUNC ANNOTATE_NOENDBR