From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8DA101C5496; Mon, 25 Aug 2025 03:34:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756092878; cv=none; b=FUXARrhMe7EVmHL4Yt9UOHCKFdpWsQRi6h14nvYLF8LtlW5Ton0D/qVjBEe3RD1SpyIzD0CsCzLTB4XbtBgf7hwjFCPdG/IAEgDxI2dDjHJYjE+lvQROsic6zKJejVgAD1k98vtPkmJwVfoUvj2DmmEywXooLTCTzCl/D+pUx94= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756092878; c=relaxed/simple; bh=HQ1D+tm6U/2Iz5bWZlC9enB6ulnn3ioXax8Z0NIkJmI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AsQGeKsRdzrg+CODyPhRkxBJvEyy10g9TbwxCEfZW24EafM2hnsm47sL6aCiNxvgPpwe2RH6lftJ8XrrY7bOK/zhlMr+zL3zkoRRWVUlHmzDsXxlYTOGEzBwvjpHBmMzEmE8UzYvRfgPk9B8thOBgtiOW9Y7Bug6NT4ZOSb24qk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 599A52A9A; Sun, 24 Aug 2025 20:34:26 -0700 (PDT) Received: from u200865.usa.arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 711103F63F; Sun, 24 Aug 2025 20:34:33 -0700 (PDT) From: Jeremy Linton To: linux-trace-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org, mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, thiago.bauermann@linaro.org, broonie@kernel.org, yury.khrustalev@arm.com, kristina.martsenko@arm.com, liaochang1@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jeremy Linton Subject: [PATCH v7 3/7] arm64: uaccess: Add additional userspace GCS accessors Date: Sun, 24 Aug 2025 22:34:17 -0500 Message-ID: <20250825033421.463669-4-jeremy.linton@arm.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250825033421.463669-1-jeremy.linton@arm.com> References: <20250825033421.463669-1-jeremy.linton@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Uprobes need more advanced read, push, and pop userspace GCS functionality. Implement those features using the existing gcsstr() and copy_from_user(). Its important to note that GCS pages can be read by normal instructions, but the hardware validates that pages used by GCS specific operations, have a GCS privilege set. We aren't validating this in load_user_gcs because it requires stabilizing the VMA over the read which may fault. Signed-off-by: Jeremy Linton Reviewed-by: Catalin Marinas Reviewed-by: Mark Brown --- arch/arm64/include/asm/gcs.h | 54 ++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h index 10c68d3e6e30..97801543380e 100644 --- a/arch/arm64/include/asm/gcs.h +++ b/arch/arm64/include/asm/gcs.h @@ -116,6 +116,47 @@ static inline void put_user_gcs(unsigned long val, unsigned long __user *addr, uaccess_ttbr0_disable(); } +static inline void push_user_gcs(unsigned long val, int *err) +{ + u64 gcspr = read_sysreg_s(SYS_GCSPR_EL0); + + gcspr -= sizeof(u64); + put_user_gcs(val, (unsigned long __user *)gcspr, err); + if (!*err) + write_sysreg_s(gcspr, SYS_GCSPR_EL0); +} + +/* + * Unlike put/push_user_gcs() above, get/pop_user_gsc() doesn't + * validate the GCS permission is set on the page being read. This + * differs from how the hardware works when it consumes data stored at + * GCSPR. Callers should ensure this is acceptable. + */ +static inline u64 get_user_gcs(unsigned long __user *addr, int *err) +{ + unsigned long ret; + u64 load = 0; + + /* Ensure previous GCS operation are visible before we read the page */ + gcsb_dsync(); + ret = copy_from_user(&load, addr, sizeof(load)); + if (ret != 0) + *err = ret; + return load; +} + +static inline u64 pop_user_gcs(int *err) +{ + u64 gcspr = read_sysreg_s(SYS_GCSPR_EL0); + u64 read_val; + + read_val = get_user_gcs((unsigned long __user *)gcspr, err); + if (!*err) + write_sysreg_s(gcspr + sizeof(u64), SYS_GCSPR_EL0); + + return read_val; +} + #else static inline bool task_gcs_el0_enabled(struct task_struct *task) @@ -126,6 +167,10 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task) static inline void gcs_set_el0_mode(struct task_struct *task) { } static inline void gcs_free(struct task_struct *task) { } static inline void gcs_preserve_current_state(void) { } +static inline void put_user_gcs(unsigned long val, unsigned long __user *addr, + int *err) { } +static inline void push_user_gcs(unsigned long val, int *err) { } + static inline unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, const struct kernel_clone_args *args) { @@ -136,6 +181,15 @@ static inline int gcs_check_locked(struct task_struct *task, { return 0; } +static inline u64 get_user_gcs(unsigned long __user *addr, int *err) +{ + *err = -EFAULT; + return 0; +} +static inline u64 pop_user_gcs(int *err) +{ + return 0; +} #endif -- 2.50.1