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 AFE5F11703 for ; Mon, 21 Aug 2023 19:58:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3158BC433C7; Mon, 21 Aug 2023 19:58:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692647889; bh=u/pao4YBnKqtDvOQjiCAh/ojzQMYfgEkexng0fR5Avg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ugaKI5KMGRkZA0wpxIli0bjSNs89s9r9wNqeXoJJX/O3MrY6Tkum1yjoTt+Z7SPgR x6gLkGZSd/bzQQRjWMomo79aKGvxdtSCPHLTdgjH9atNwP0k7PZcuPw4q/apELhTgJ YbGfjcCVs+YdVQuoXucZxr31FTt2ED4XyUZocRgA= 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 6.1 175/194] x86/alternative: Make custom return thunk unconditional Date: Mon, 21 Aug 2023 21:42:34 +0200 Message-ID: <20230821194130.411698652@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230821194122.695845670@linuxfoundation.org> References: <20230821194122.695845670@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 095b8303f3835c68ac4a8b6d754ca1c3b6230711 upstream. There is infrastructure to rewrite return thunks to point to any random thunk one desires, unwrap that from CALL_THUNKS, which up to now was the sole user of that. [ bp: Make the thunks visible on 32-bit and add ifdeffery for the 32-bit builds. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230814121148.775293785@infradead.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/nospec-branch.h | 5 +++++ arch/x86/kernel/cpu/bugs.c | 2 ++ 2 files changed, 7 insertions(+) --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -210,7 +210,12 @@ typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE]; extern retpoline_thunk_t __x86_indirect_thunk_array[]; +#ifdef CONFIG_RETHUNK extern void __x86_return_thunk(void); +#else +static inline void __x86_return_thunk(void) {} +#endif + extern void zen_untrain_ret(void); extern void srso_untrain_ret(void); extern void srso_untrain_ret_alias(void); --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -62,6 +62,8 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd); static DEFINE_MUTEX(spec_ctrl_mutex); +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) {