From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9748BCA1002 for ; Thu, 4 Sep 2025 04:01:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=SUn1s3KASxz+/KODD5Z3C24H3E3cqWXBuJWl5gHGZ/0=; b=tbBE5BAAY0wx8G4BNkizr6VnSw 5b4ZYBW5TFjTJixeBEZKYItGp90LZOWo6/GXP7wrGHMD06mA08leqxkoAnmeKHIXn0XgpA+Sinuh9 yXU/wZByTU5SHWsDYpf0jsSs75R80IB0gE97Y8MByBP+Ktz3GjV/DqpRa2YVEs9W7RTksgpekS1DI 2n6myhLIL1pqkE/fof/oWHoz5co1bZytKZqLK+WrgRQnskmyzLptEirSff3NhwTUY+MBYISbUdvNT la0Lp3/rkgYQDG5ktymSToObVNxijgDf/Km1IsOKBwg8QTH06paJmMguDpmFPvGVOGtyByBsesJtc ea623y5w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uu19d-00000008pcA-3JF8; Thu, 04 Sep 2025 04:00:57 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uu0w7-00000008lR8-0LAD for linux-arm-kernel@lists.infradead.org; Thu, 04 Sep 2025 03:47:00 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 0EF3E44CB2; Thu, 4 Sep 2025 03:46:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC035C4CEF9; Thu, 4 Sep 2025 03:46:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756957616; bh=fAYAUBGJzo8b71uhoB5b/MGQo+Cci4aVf5GCY6U9+Og=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MQ1wii6xQtLMVMyBk31+A/kBaQZrsWcYyRslt3wRiqrIgJwSD/vMPaXxjHvlXQ70q woTlgLahuOMaNldVXWLhxv2VMw2yg/a+mZCFThs/9eKCSPvWWRfFrEOFKQtQiGkT8z sktrp+AQAN1Pdu004OOJa/HLhNZSkHtv9w1bXPvGVrCtnMgPiKUnBGz3Xmyr8+3RmF 5LJR8DZfAIL+HlnYDABwGlNeuiP5F6UhvbusAD7TJS/CpsANxCtcciMaUcy11PtthN xsT3PWpg8CJApz2ug6Z9Qhf11n7EK75u9A1C8Y5jXxW5j90q3cig/joCyV0pxelZI3 12GobLSRdOnrg== From: Kees Cook To: Peter Zijlstra Cc: Kees Cook , Nathan Chancellor , Vegard Nossum , Miguel Ojeda , Linus Walleij , Jeff Johnson , Randy Dunlap , David Woodhouse , "Russell King (Oracle)" , Nick Desaulniers , Bill Wendling , Justin Stitt , Marco Elver , Przemek Kitszel , Ramon de C Valle , Jonathan Corbet , "Paul E. McKenney" , Nicolas Schier , Masahiro Yamada , Arnd Bergmann , Krzysztof Kozlowski , Sami Tolvanen , Mark Rutland , linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2 5/9] x86/cfi: Add "debug" option to "cfi=" bootparam Date: Wed, 3 Sep 2025 20:46:44 -0700 Message-Id: <20250904034656.3670313-5-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250904033217.it.414-kees@kernel.org> References: <20250904033217.it.414-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4249; i=kees@kernel.org; h=from:subject; bh=fAYAUBGJzo8b71uhoB5b/MGQo+Cci4aVf5GCY6U9+Og=; b=owGbwMvMwCVmps19z/KJym7G02pJDBk7OYuNvPgOPD79OO+JnXXRp6Xu8nwx71xY93EVlCf3x 6bxXNvQUcrCIMbFICumyBJk5x7n4vG2Pdx9riLMHFYmkCEMXJwCMJGpYgy/2VR2/91myqOcFp/c 6yV1dvuyNcnb3k/h3Mb8pmgBG98MTYZ/Vv2fVK7qNr275O/OvuS9daCF9u2IlUJSrJ9OcjL0z+V mAwA= X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250903_204659_230850_252BD149 X-CRM114-Status: GOOD ( 16.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add "debug" option for "cfi=" bootparam to get details on early CFI initialization steps so future Kees can find breakage easier. Signed-off-by: Kees Cook --- Cc: Peter Zijlstra --- .../admin-guide/kernel-parameters.txt | 1 + arch/x86/kernel/alternative.c | 23 +++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 8bbffbb334ab..c8337d0e6ba3 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -624,6 +624,7 @@ bhi: Enable register poisoning to stop speculation across FineIBT. (Disabled by default.) warn: Do not enforce CFI checking: warn only. + debug: Report CFI initialization details. cgroup_disable= [KNL] Disable a particular controller or optional feature Format: {name of the controller(s) or feature(s) to disable} diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index d8f4ac95b4df..b311e31a9056 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1177,6 +1177,7 @@ void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { } #endif enum cfi_mode cfi_mode __ro_after_init = __CFI_DEFAULT; +static bool cfi_debug __ro_after_init; #ifdef CONFIG_FINEIBT_BHI bool cfi_bhi __ro_after_init = false; @@ -1259,6 +1260,8 @@ static __init int cfi_parse_cmdline(char *str) } else if (!strcmp(str, "off")) { cfi_mode = CFI_OFF; cfi_rand = false; + } else if (!strcmp(str, "debug")) { + cfi_debug = true; } else if (!strcmp(str, "kcfi")) { cfi_mode = CFI_KCFI; } else if (!strcmp(str, "fineibt")) { @@ -1734,6 +1737,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, * rewrite them. This disables all CFI. If this succeeds but any of the * later stages fails, we're without CFI. */ + if (cfi_debug) + pr_info("CFI: disabling all indirect call checking\n"); ret = cfi_disable_callers(start_retpoline, end_retpoline); if (ret) goto err; @@ -1744,14 +1749,23 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, cfi_bpf_hash = cfi_rehash(cfi_bpf_hash); cfi_bpf_subprog_hash = cfi_rehash(cfi_bpf_subprog_hash); } + if (cfi_debug) + pr_info("CFI: cfi_seed: 0x%08x\n", cfi_seed); + if (cfi_debug) + pr_info("CFI: rehashing all preambles\n"); ret = cfi_rand_preamble(start_cfi, end_cfi); if (ret) goto err; + if (cfi_debug) + pr_info("CFI: rehashing all indirect calls\n"); ret = cfi_rand_callers(start_retpoline, end_retpoline); if (ret) goto err; + } else { + if (cfi_debug) + pr_info("CFI: rehashing disabled\n"); } switch (cfi_mode) { @@ -1761,6 +1775,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, return; case CFI_KCFI: + if (cfi_debug) + pr_info("CFI: enabling all indirect call checking\n"); ret = cfi_enable_callers(start_retpoline, end_retpoline); if (ret) goto err; @@ -1771,17 +1787,23 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, return; case CFI_FINEIBT: + if (cfi_debug) + pr_info("CFI: adding FineIBT to all preambles\n"); /* place the FineIBT preamble at func()-16 */ ret = cfi_rewrite_preamble(start_cfi, end_cfi); if (ret) goto err; /* rewrite the callers to target func()-16 */ + if (cfi_debug) + pr_info("CFI: rewriting indirect call sites to use FineIBT\n"); ret = cfi_rewrite_callers(start_retpoline, end_retpoline); if (ret) goto err; /* now that nobody targets func()+0, remove ENDBR there */ + if (cfi_debug) + pr_info("CFI: removing old endbr insns\n"); cfi_rewrite_endbr(start_cfi, end_cfi); if (builtin) { @@ -2324,6 +2346,7 @@ void __init alternative_instructions(void) __apply_fineibt(__retpoline_sites, __retpoline_sites_end, __cfi_sites, __cfi_sites_end, true); + cfi_debug = false; /* * Rewrite the retpolines, must be done before alternatives since -- 2.34.1