From nobody Thu Oct 2 20:46:42 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 6F5D0270551; Thu, 11 Sep 2025 07:34:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757576100; cv=none; b=R9E7ZxXGGTzZKvorB+pj9fXDrS11QgmJuRTVp7QRIrPzTQym5eL0XRfqYfWBZNV4lftrtfPDVQQfB+W27lH9mSXa9LiExy/tXKSeD3L0p0SJi7NkYJWBlW5LFAtUteb5xvFZDDSjoUbdTKHkFKBkwxJatKyP3BgCLOdJTlLtgQc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757576100; c=relaxed/simple; bh=nx6GuDLCEB5Imf9p8IVHjW3S7stvA5GaYrOEtB2WNj8=; h=Date:From:To:Subject:Cc:MIME-Version:Message-ID:Content-Type; b=MwL+SHvTEJMudIUzbjv1vf4gr2R+5FmzZixyaGpV+za3wfRFhUeJg4GbTNJIGmeRAe9SebCDDMT958sQ+Xa5J6fF6MYhT4BlHG94V6LjEbJ/HLPRbLagsOSv40fUcUgos9P9Cw1jabrxbh1QP+AWtqq/QroiPMHnJhgK2hxTkEc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=GZ+5C4rY; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=2IVeBLf5; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="GZ+5C4rY"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="2IVeBLf5" Date: Thu, 11 Sep 2025 07:34:55 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1757576096; 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; bh=5AxggaBUu2K5XN75Srxhaxw1mkxT4u3JcXNtDDrjvbo=; b=GZ+5C4rYwxnayIY3ie1EhwavMfn+2JlXCe+WVjzg//gHO1eWhaluUBnC41pgSzAPE7lzl5 Uecx9KWGq/c0M2GuvsvLi1e04Cj7im45dS0+OXXB4B0Z9jWoTrlM5q44l7yBHtB3UUwTev 7sqLGh1bGc+kpemq9VAzL/zd0sWgsgR23YBVarOewZ9nEVw+6vr8aWjlDnlb96aMjoY4+Y NwuJ4z8X3F7KTVudQIVeBK+YbsqgDeNMeCktxPv1mFSR06qdFhs7O2xPcsp1VBDGsCAa6Y S54zDipAXWOk0V6ytuLQuPrxFe/XigG6NWWa9mtVN4P9ibvUqv8FHfdywlZZ+g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1757576096; 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; bh=5AxggaBUu2K5XN75Srxhaxw1mkxT4u3JcXNtDDrjvbo=; b=2IVeBLf5K1sU75FGK8p6LpHw7zMtyoEtYEtT46T9YXWl8uQD6mdpdIEN6vLGOyBFQtt2mc SXTz0wlBr9v5mLBA== From: "tip-bot2 for Kees Cook" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/core] x86/cfi: Add "debug" option to "cfi=" bootparam Cc: Kees Cook , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <175757609542.709179.13938862888547182704.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the x86/core branch of tip: Commit-ID: 026211c40b055485b4c65c10d644a92864623225 Gitweb: https://git.kernel.org/tip/026211c40b055485b4c65c10d644a9286= 4623225 Author: Kees Cook AuthorDate: Wed, 03 Sep 2025 20:46:44 -07:00 Committer: Peter Zijlstra CommitterDate: Thu, 04 Sep 2025 21:59:08 +02:00 x86/cfi: Add "debug" option to "cfi=3D" bootparam Add "debug" option for "cfi=3D" bootparam to get details on early CFI initialization steps so future Kees can find breakage easier. Signed-off-by: Kees Cook Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250904034656.3670313-5-kees@kernel.org --- Documentation/admin-guide/kernel-parameters.txt | 1 +- arch/x86/kernel/alternative.c | 16 ++++++++++++++++- 2 files changed, 17 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 8bbffbb..c8337d0 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. =20 cgroup_disable=3D [KNL] Disable a particular controller or optional featu= re 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 d8f4ac9..7d4a992 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, s3= 2 *end) { } #endif =20 enum cfi_mode cfi_mode __ro_after_init =3D __CFI_DEFAULT; +static bool cfi_debug __ro_after_init; =20 #ifdef CONFIG_FINEIBT_BHI bool cfi_bhi __ro_after_init =3D false; @@ -1259,6 +1260,8 @@ static __init int cfi_parse_cmdline(char *str) } else if (!strcmp(str, "off")) { cfi_mode =3D CFI_OFF; cfi_rand =3D false; + } else if (!strcmp(str, "debug")) { + cfi_debug =3D true; } else if (!strcmp(str, "kcfi")) { cfi_mode =3D CFI_KCFI; } else if (!strcmp(str, "fineibt")) { @@ -1707,6 +1710,8 @@ static int cfi_rewrite_callers(s32 *start, s32 *end) return 0; } =20 +#define pr_cfi_debug(X...) if (cfi_debug) pr_info(X) + static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, s32 *start_cfi, s32 *end_cfi, bool builtin) { @@ -1734,6 +1739,7 @@ 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. */ + pr_cfi_debug("CFI: disabling all indirect call checking\n"); ret =3D cfi_disable_callers(start_retpoline, end_retpoline); if (ret) goto err; @@ -1744,14 +1750,19 @@ static void __apply_fineibt(s32 *start_retpoline, s= 32 *end_retpoline, cfi_bpf_hash =3D cfi_rehash(cfi_bpf_hash); cfi_bpf_subprog_hash =3D cfi_rehash(cfi_bpf_subprog_hash); } + pr_cfi_debug("CFI: cfi_seed: 0x%08x\n", cfi_seed); =20 + pr_cfi_debug("CFI: rehashing all preambles\n"); ret =3D cfi_rand_preamble(start_cfi, end_cfi); if (ret) goto err; =20 + pr_cfi_debug("CFI: rehashing all indirect calls\n"); ret =3D cfi_rand_callers(start_retpoline, end_retpoline); if (ret) goto err; + } else { + pr_cfi_debug("CFI: rehashing disabled\n"); } =20 switch (cfi_mode) { @@ -1761,6 +1772,7 @@ static void __apply_fineibt(s32 *start_retpoline, s32= *end_retpoline, return; =20 case CFI_KCFI: + pr_cfi_debug("CFI: re-enabling all indirect call checking\n"); ret =3D cfi_enable_callers(start_retpoline, end_retpoline); if (ret) goto err; @@ -1771,17 +1783,20 @@ static void __apply_fineibt(s32 *start_retpoline, s= 32 *end_retpoline, return; =20 case CFI_FINEIBT: + pr_cfi_debug("CFI: adding FineIBT to all preambles\n"); /* place the FineIBT preamble at func()-16 */ ret =3D cfi_rewrite_preamble(start_cfi, end_cfi); if (ret) goto err; =20 /* rewrite the callers to target func()-16 */ + pr_cfi_debug("CFI: rewriting indirect call sites to use FineIBT\n"); ret =3D cfi_rewrite_callers(start_retpoline, end_retpoline); if (ret) goto err; =20 /* now that nobody targets func()+0, remove ENDBR there */ + pr_cfi_debug("CFI: removing old endbr insns\n"); cfi_rewrite_endbr(start_cfi, end_cfi); =20 if (builtin) { @@ -2324,6 +2339,7 @@ void __init alternative_instructions(void) =20 __apply_fineibt(__retpoline_sites, __retpoline_sites_end, __cfi_sites, __cfi_sites_end, true); + cfi_debug =3D false; =20 /* * Rewrite the retpolines, must be done before alternatives since