From patchwork Tue May 25 15:14:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 12279211 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23304C2B9F8 for ; Tue, 25 May 2021 15:18:15 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id DBA2A6113B for ; Tue, 25 May 2021 15:18:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DBA2A6113B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bYkNGNlU98B9TARc27JwySJwbAnNHWuGF8a93pfkm8g=; b=vuRbeHxvacm0R4 HmVifAET8nMP5gvcmohCZsNqwbQ8c+C5Zptw1ICkJnF/NYOpcnhpxccNh0an2G+sxZhY8QbU7mab/ CZQnyxIEx1z6kPOzvYwBWRxw4CV0AaReSE7Yucfxx9UmHuKuhQ9iE1tCsNYedSXtvZ7XB3o+f1Vhl 27WpT4MopeHmsi0lX+FAW9iiSqo3ENt6lg7UlM+Ke0i1kg5G56xGsTpKIYhGNGFSYI10GVV7mMPmD AzQDDmXlnW/cFNHAlY8djaIEvyxqUIQjba+gYQ22Y0HQcEWIqaq84UgNPnZw0uzYYvwDv7M10YBuo KRGFo6fhOtx/gk0vGtKw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1llYn1-005tuX-G5; Tue, 25 May 2021 15:16:15 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1llYmF-005tXu-MU for linux-arm-kernel@lists.infradead.org; Tue, 25 May 2021 15:15:29 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1536C6141C; Tue, 25 May 2021 15:15:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621955727; bh=D1ZUCC3t4rqEiio5pZbDL/BbJagMpdBEJf9mcoEZS24=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DsK5CODEnyJbLuxsaSlEHUYANoGva9QrhRJ5owW5psbdWAVPoVbYGRfm/aEzKaWu7 k+9QS8bqrpnJQxt8JrFKgnpFLCJwfJzmggPLbYyMrlhvtpTIVgswop+Gt+WGgQpe+P DukJKtZoijSbzbFOugW9gFjf2FlQ7KijyUvq0wf5hMFf0wZkSfLL4D/gj9HXWRXvqQ 0KR1MOh2r/Oyd+TggptGb9VwbkYMA1Sa3QFFesujMZ9xFSWq3JUDn2UDlzWsuZjgeb rGFrSGjN29klv48KVMxBChIJVQBfB7otQ2rycZayro7Y6nibqmhb5OS/drl3S684nV dqtWMGd9yQiKQ== From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , "Rafael J. Wysocki" , Dietmar Eggemann , Daniel Bristot de Oliveira , kernel-team@android.com Subject: [PATCH v7 03/22] arm64: Allow mismatched 32-bit EL0 support Date: Tue, 25 May 2021 16:14:13 +0100 Message-Id: <20210525151432.16875-4-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210525151432.16875-1-will@kernel.org> References: <20210525151432.16875-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210525_081527_834145_52B3475F X-CRM114-Status: GOOD ( 22.70 ) 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 When confronted with a mixture of CPUs, some of which support 32-bit applications and others which don't, we quite sensibly treat the system as 64-bit only for userspace and prevent execve() of 32-bit binaries. Unfortunately, some crazy folks have decided to build systems like this with the intention of running 32-bit applications, so relax our sanitisation logic to continue to advertise 32-bit support to userspace on these systems and track the real 32-bit capable cores in a cpumask instead. For now, the default behaviour remains but will be tied to a command-line option in a later patch. Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/include/asm/cpufeature.h | 8 +- arch/arm64/kernel/cpufeature.c | 114 ++++++++++++++++++++++++---- arch/arm64/tools/cpucaps | 3 +- 3 files changed, 110 insertions(+), 15 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 338840c00e8e..603bf4160cd6 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -630,9 +630,15 @@ static inline bool cpu_supports_mixed_endian_el0(void) return id_aa64mmfr0_mixed_endian_el0(read_cpuid(ID_AA64MMFR0_EL1)); } +const struct cpumask *system_32bit_el0_cpumask(void); +DECLARE_STATIC_KEY_FALSE(arm64_mismatched_32bit_el0); + static inline bool system_supports_32bit_el0(void) { - return cpus_have_const_cap(ARM64_HAS_32BIT_EL0); + u64 pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); + + return static_branch_unlikely(&arm64_mismatched_32bit_el0) || + id_aa64pfr0_32bit_el0(pfr0); } static inline bool system_supports_4kb_granule(void) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index a4db25cd7122..4194a47de62d 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -107,6 +107,24 @@ DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE); bool arm64_use_ng_mappings = false; EXPORT_SYMBOL(arm64_use_ng_mappings); +/* + * Permit PER_LINUX32 and execve() of 32-bit binaries even if not all CPUs + * support it? + */ +static bool __read_mostly allow_mismatched_32bit_el0; + +/* + * Static branch enabled only if allow_mismatched_32bit_el0 is set and we have + * seen at least one CPU capable of 32-bit EL0. + */ +DEFINE_STATIC_KEY_FALSE(arm64_mismatched_32bit_el0); + +/* + * Mask of CPUs supporting 32-bit EL0. + * Only valid if arm64_mismatched_32bit_el0 is enabled. + */ +static cpumask_var_t cpu_32bit_el0_mask __cpumask_var_read_mostly; + /* * Flag to indicate if we have computed the system wide * capabilities based on the boot time active CPUs. This @@ -767,7 +785,7 @@ static void __init sort_ftr_regs(void) * Any bits that are not covered by an arm64_ftr_bits entry are considered * RES0 for the system-wide value, and must strictly match. */ -static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) +static void init_cpu_ftr_reg(u32 sys_reg, u64 new) { u64 val = 0; u64 strict_mask = ~0x0ULL; @@ -863,7 +881,7 @@ static void __init init_cpu_hwcaps_indirect_list(void) static void __init setup_boot_cpu_capabilities(void); -static void __init init_32bit_cpu_features(struct cpuinfo_32bit *info) +static void init_32bit_cpu_features(struct cpuinfo_32bit *info) { init_cpu_ftr_reg(SYS_ID_DFR0_EL1, info->reg_id_dfr0); init_cpu_ftr_reg(SYS_ID_DFR1_EL1, info->reg_id_dfr1); @@ -979,6 +997,22 @@ static void relax_cpu_ftr_reg(u32 sys_id, int field) WARN_ON(!ftrp->width); } +static void update_mismatched_32bit_el0_cpu_features(struct cpuinfo_arm64 *info, + struct cpuinfo_arm64 *boot) +{ + static bool boot_cpu_32bit_regs_overridden = false; + + if (!allow_mismatched_32bit_el0 || boot_cpu_32bit_regs_overridden) + return; + + if (id_aa64pfr0_32bit_el0(boot->reg_id_aa64pfr0)) + return; + + boot->aarch32 = info->aarch32; + init_32bit_cpu_features(&boot->aarch32); + boot_cpu_32bit_regs_overridden = true; +} + static int update_32bit_cpu_features(int cpu, struct cpuinfo_32bit *info, struct cpuinfo_32bit *boot) { @@ -1139,6 +1173,7 @@ void update_cpu_features(int cpu, * (e.g. SYS_ID_AA64PFR0_EL1), so we call it last. */ if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) { + update_mismatched_32bit_el0_cpu_features(info, boot); taint |= update_32bit_cpu_features(cpu, &info->aarch32, &boot->aarch32); } @@ -1251,6 +1286,28 @@ has_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope) return feature_matches(val, entry); } +const struct cpumask *system_32bit_el0_cpumask(void) +{ + if (!system_supports_32bit_el0()) + return cpu_none_mask; + + if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + return cpu_32bit_el0_mask; + + return cpu_possible_mask; +} + +static bool has_32bit_el0(const struct arm64_cpu_capabilities *entry, int scope) +{ + if (!has_cpuid_feature(entry, scope)) + return allow_mismatched_32bit_el0; + + if (scope == SCOPE_SYSTEM) + pr_info("detected: 32-bit EL0 Support\n"); + + return true; +} + static bool has_useable_gicv3_cpuif(const struct arm64_cpu_capabilities *entry, int scope) { bool has_sre; @@ -1869,10 +1926,9 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .cpu_enable = cpu_copy_el2regs, }, { - .desc = "32-bit EL0 Support", - .capability = ARM64_HAS_32BIT_EL0, + .capability = ARM64_HAS_32BIT_EL0_DO_NOT_USE, .type = ARM64_CPUCAP_SYSTEM_FEATURE, - .matches = has_cpuid_feature, + .matches = has_32bit_el0, .sys_reg = SYS_ID_AA64PFR0_EL1, .sign = FTR_UNSIGNED, .field_pos = ID_AA64PFR0_EL0_SHIFT, @@ -2381,7 +2437,7 @@ static const struct arm64_cpu_capabilities compat_elf_hwcaps[] = { {}, }; -static void __init cap_set_elf_hwcap(const struct arm64_cpu_capabilities *cap) +static void cap_set_elf_hwcap(const struct arm64_cpu_capabilities *cap) { switch (cap->hwcap_type) { case CAP_HWCAP: @@ -2426,7 +2482,7 @@ static bool cpus_have_elf_hwcap(const struct arm64_cpu_capabilities *cap) return rc; } -static void __init setup_elf_hwcaps(const struct arm64_cpu_capabilities *hwcaps) +static void setup_elf_hwcaps(const struct arm64_cpu_capabilities *hwcaps) { /* We support emulation of accesses to CPU ID feature registers */ cpu_set_named_feature(CPUID); @@ -2601,7 +2657,7 @@ static void check_early_cpu_features(void) } static void -verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps) +__verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps) { for (; caps->matches; caps++) @@ -2612,6 +2668,14 @@ verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps) } } +static void verify_local_elf_hwcaps(void) +{ + __verify_local_elf_hwcaps(arm64_elf_hwcaps); + + if (id_aa64pfr0_32bit_el0(read_cpuid(ID_AA64PFR0_EL1))) + __verify_local_elf_hwcaps(compat_elf_hwcaps); +} + static void verify_sve_features(void) { u64 safe_zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1); @@ -2676,11 +2740,7 @@ static void verify_local_cpu_capabilities(void) * on all secondary CPUs. */ verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU); - - verify_local_elf_hwcaps(arm64_elf_hwcaps); - - if (system_supports_32bit_el0()) - verify_local_elf_hwcaps(compat_elf_hwcaps); + verify_local_elf_hwcaps(); if (system_supports_sve()) verify_sve_features(); @@ -2815,6 +2875,34 @@ void __init setup_cpu_features(void) ARCH_DMA_MINALIGN); } +static int enable_mismatched_32bit_el0(unsigned int cpu) +{ + struct cpuinfo_arm64 *info = &per_cpu(cpu_data, cpu); + bool cpu_32bit = id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0); + + if (cpu_32bit) { + cpumask_set_cpu(cpu, cpu_32bit_el0_mask); + static_branch_enable_cpuslocked(&arm64_mismatched_32bit_el0); + setup_elf_hwcaps(compat_elf_hwcaps); + } + + return 0; +} + +static int __init init_32bit_el0_mask(void) +{ + if (!allow_mismatched_32bit_el0) + return 0; + + if (!zalloc_cpumask_var(&cpu_32bit_el0_mask, GFP_KERNEL)) + return -ENOMEM; + + return cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, + "arm64/mismatched_32bit_el0:online", + enable_mismatched_32bit_el0, NULL); +} +subsys_initcall_sync(init_32bit_el0_mask); + static void __maybe_unused cpu_enable_cnp(struct arm64_cpu_capabilities const *cap) { cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps index 21fbdda7086e..49305c2e6dfd 100644 --- a/arch/arm64/tools/cpucaps +++ b/arch/arm64/tools/cpucaps @@ -3,7 +3,8 @@ # Internal CPU capabilities constants, keep this list sorted BTI -HAS_32BIT_EL0 +# Unreliable: use system_supports_32bit_el0() instead. +HAS_32BIT_EL0_DO_NOT_USE HAS_32BIT_EL1 HAS_ADDRESS_AUTH HAS_ADDRESS_AUTH_ARCH