From nobody Wed Apr 8 04:48:38 2026 Received: from mail-244116.protonmail.ch (mail-244116.protonmail.ch [109.224.244.116]) (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 0E08A3C65FE for ; Tue, 10 Mar 2026 18:03:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=109.224.244.116 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773165810; cv=none; b=OAOGU7Xx4ZC3MwuiHNvGH4TFq/Jr2RW6vIFgXyXEJ6ej7R9D77o4e0pwykB2nFOCD5IGgF5nw0f9oYiF1zcfst/Oyf97RTnSgXtfhuE/4d9a0pnEimhapbgCkHvmqr0X71/mn6tBBYHJdhx29hW7E8TgBe2OPJk4XF4KOMEmTRo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773165810; c=relaxed/simple; bh=7493yfGHFyplGsqxRWRyEFKkUveZX0XaX+7e8ubZ3F4=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=K0soBZ8JrbvJJdUIS8WdINn2MPiLR7Sbg/35R1tvxW+gP/kAjA0P0uqlpwTmFSrVxMuVexdj4xgz0nlVT+Cgl/ZRHlirLUJmn9e4UU4onerUD9/mUyRMkRNNPLHI3IjlDEcJStlta2i+BIHB48wJ7DKgvVOdkfLqYICE69eIczU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=pm.me; spf=pass smtp.mailfrom=pm.me; dkim=pass (2048-bit key) header.d=pm.me header.i=@pm.me header.b=aXMqVj5w; arc=none smtp.client-ip=109.224.244.116 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=pm.me Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pm.me Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=pm.me header.i=@pm.me header.b="aXMqVj5w" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail3; t=1773165807; x=1773425007; bh=N9d3l2i9j8xp5Zk8ZHq5d3FCVTfuOM3D2E8hKPZ+/oQ=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: Feedback-ID:From:To:Cc:Date:Subject:Reply-To:Feedback-ID: Message-ID:BIMI-Selector; b=aXMqVj5wEfUE4KtZK1a8VBe0AlIlHlUoty9G5F1SSKz1XMiJQblsRzP6jrrw/lkFx gVO5me+8vJT0U29EhbfQDyAXcI1OZ9EiEUi0Zf6DFvojHG0ggon1WiCfUvS8SU5Rk2 uIyi7l01xImuoWpnHnTtpv6pTSSGkVr3C2kMssdNTDTjYt0LFgKWC6iQdLyX7wFpx6 n8uRGHtwFrHzHzIE573HemQJxYV3LqkSqMm9wWJVe3GwlOLspWpjOeKrX8iKjAOUBn nzpvkqTRdJV2chfEE7hD1SiZOYuM2gpOobIcO9BGiDEMWoT7giXOd3G047xCuQO+eK 0ByVR/dyCxLyA== Date: Tue, 10 Mar 2026 18:03:22 +0000 To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" From: Maciej Wieczor-Retman Cc: sohil.mehta@intel.com, m.wieczorretman@pm.me, Maciej Wieczor-Retman , linux-kernel@vger.kernel.org Subject: [PATCH v9 2/3] x86/cpu: Check if feature string is non-zero Message-ID: <6443812f9a8a43986f37341d0db5074a2019e80a.1773165421.git.m.wieczorretman@pm.me> In-Reply-To: References: Feedback-ID: 164464600:user:proton X-Pm-Message-ID: 39f6571751e5f535b86a8c3f82844928eacd07e2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Maciej Wieczor-Retman In filter_cpuid_features, x86_cap_flags[] is read, but it's not verified whether the string is non-zero which could lead to unwanted output. In two more places there are open coded paths that try to retrieve a feature string, and if there isn't one, the feature word and bit are returned instead. While correcting filter_cpuid_features() with a helper it's trivial to also clean up these open coded cases. Signed-off-by: Maciej Wieczor-Retman --- Changelog v9: - 16 -> X86_CAP_BUF_SIZE. - Add comment to the x86_cap_name(). Changelog v8: - Move x86_cap_name() declaration from linux/cpu.h to the arch/cpu.h. Include arch/cpu.h in the cpuid-deps.c file instead of linux/cpu.h. Changelog v7: - sizeof(buf) -> 16 - Rebase onto 7.01-rc1. Changelog v6: - Remove parts of the patch message that are redundant and just copy what's visible in the diff. - Redo the helper to use an external char buffer instead of a local static string. arch/x86/include/asm/cpu.h | 4 ++++ arch/x86/kernel/cpu/common.c | 30 +++++++++++++++++++++++++----- arch/x86/kernel/cpu/cpuid-deps.c | 23 +++++------------------ 3 files changed, 34 insertions(+), 23 deletions(-) diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index ad235dda1ded..93e8ad2786bf 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -9,6 +9,8 @@ #include #include =20 +#define X86_CAP_BUF_SIZE 16 + #ifndef CONFIG_SMP #define cpu_physical_id(cpu) boot_cpu_physical_apicid #define cpu_acpi_id(cpu) 0 @@ -67,4 +69,6 @@ int intel_microcode_sanity_check(void *mc, bool print_err= , int hdr_type); =20 extern struct cpumask cpus_stop_mask; =20 +const char *x86_cap_name(unsigned int bit, char *buf); + #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 76339e988304..cfffbbda3d95 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -678,6 +678,7 @@ cpuid_dependent_features[] =3D { static void filter_cpuid_features(struct cpuinfo_x86 *c, bool warn) { const struct cpuid_dependent_feature *df; + char feature_buf[X86_CAP_BUF_SIZE]; =20 for (df =3D cpuid_dependent_features; df->feature; df++) { =20 @@ -700,7 +701,7 @@ static void filter_cpuid_features(struct cpuinfo_x86 *c= , bool warn) continue; =20 pr_warn("CPU: CPU feature %s disabled, no CPUID level 0x%x\n", - x86_cap_flags[df->feature], df->level); + x86_cap_name(df->feature, feature_buf), df->level); } } =20 @@ -1637,6 +1638,7 @@ static inline bool parse_set_clear_cpuid(char *arg, b= ool set) =20 while (arg) { bool found __maybe_unused =3D false; + char name_buf[X86_CAP_BUF_SIZE]; unsigned int bit; =20 opt =3D strsep(&arg, ","); @@ -1657,10 +1659,7 @@ static inline bool parse_set_clear_cpuid(char *arg, = bool set) setup_clear_cpu_cap(bit); } /* empty-string, i.e., ""-defined feature flags */ - if (!x86_cap_flags[bit]) - pr_cont(" %d:%d\n", bit >> 5, bit & 31); - else - pr_cont(" %s\n", x86_cap_flags[bit]); + pr_cont(" %s\n", x86_cap_name(bit, name_buf)); =20 taint++; } @@ -1983,6 +1982,27 @@ static void generic_identify(struct cpuinfo_x86 *c) #endif } =20 +/* + * Return the feature "name" if available, otherwise return the + * X86_FEATURE_* numerals to make it easier to identify the feature. + */ +const char *x86_cap_name(unsigned int bit, char *buf) +{ + unsigned int word =3D bit >> 5; + const char *name =3D NULL; + + if (likely(word < NCAPINTS)) + name =3D x86_cap_flags[bit]; + else if (likely(word < NCAPINTS + NBUGINTS)) + name =3D x86_bug_flags[bit - 32 * NCAPINTS]; + + if (name) + return name; + + snprintf(buf, X86_CAP_BUF_SIZE, "%u:%u", word, bit & 31); + return buf; +} + /* * This does the hard work of actually picking apart the CPU stuff... */ diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-d= eps.c index 146f6f8b0650..49fd45b5fbd6 100644 --- a/arch/x86/kernel/cpu/cpuid-deps.c +++ b/arch/x86/kernel/cpu/cpuid-deps.c @@ -2,6 +2,8 @@ #include #include #include + +#include #include =20 struct cpuid_dep { @@ -156,24 +158,9 @@ void setup_clear_cpu_cap(unsigned int feature) do_clear_cpu_cap(NULL, feature); } =20 -/* - * Return the feature "name" if available, otherwise return - * the X86_FEATURE_* numerals to make it easier to identify - * the feature. - */ -static const char *x86_feature_name(unsigned int feature, char *buf) -{ - if (x86_cap_flags[feature]) - return x86_cap_flags[feature]; - - snprintf(buf, 16, "%d*32+%2d", feature / 32, feature % 32); - - return buf; -} - void check_cpufeature_deps(struct cpuinfo_x86 *c) { - char feature_buf[16], depends_buf[16]; + char feature_buf[X86_CAP_BUF_SIZE], depends_buf[X86_CAP_BUF_SIZE]; const struct cpuid_dep *d; =20 for (d =3D cpuid_deps; d->feature; d++) { @@ -185,8 +172,8 @@ void check_cpufeature_deps(struct cpuinfo_x86 *c) */ pr_warn_once("x86 CPU feature dependency check failure: CPU%d has '%s' = enabled but '%s' disabled. Kernel might be fine, but no guarantees.\n", smp_processor_id(), - x86_feature_name(d->feature, feature_buf), - x86_feature_name(d->depends, depends_buf)); + x86_cap_name(d->feature, feature_buf), + x86_cap_name(d->depends, depends_buf)); } } } --=20 2.53.0