From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9D01E2F12CA; Thu, 18 Dec 2025 08:13:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045582; cv=none; b=hDau27GV0cQy4OvvBD9KADD7WU2c8kZTzQVSpqr1gt/cxyFEpEOJ2JqXA9Zby417ou9Pa8oHpQ5remIIQFuHg4NaTkLikPNO2z6+I+FzkRNurzoMmirLNRr2ecTEfcXQa126iFsTmMefZVaSFLUIoPyacl32HnTAk0D8Sjvl4ZA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045582; c=relaxed/simple; bh=kPQRcvC7WfSPYhzJwayZjYIsAWbvmKAaCwsniNqkt7c=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=knadrPfPwmm+b6SqAJE/+lz07RedjR+JcgkgF71jkzfvzrC6RhVncY6PIGM6foBFJOZYWBaIryvNZZfWcMNYADQF39hKMTpwLo01HBGGEnxGWwQaij3uwF3e5S/ykRZCWV0UkRX01kkhJCw7prDfGONryvmuis/KUJc4nDcp+T4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jNDEIbmn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jNDEIbmn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BD54C113D0; Thu, 18 Dec 2025 08:12:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045581; bh=kPQRcvC7WfSPYhzJwayZjYIsAWbvmKAaCwsniNqkt7c=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=jNDEIbmnWGZ5xe3caj5iK+JefJd+0K9WJ0bqjEItqZ4Ax3S0/Eg2yFSr6jzcgq3fV YH9fRSNsJWYoRbDLfTTSgiLAbWWtht3osjPIBiAYw7eg73SugwJjc/SJgIPV5uls+M R542E98nqWG9yc/POXovJQgzTW/EqoxK4UEtAkq77EDAeFQT5Ae5zZSHZ5sRMzRG2X YUpXCnyNqVst12jP//HtBJ7kNhWgbvUmfRmCmEMx1z5T228Te/lsV2d0N/aqiWLw5s b9ksT/6RHrcVd1eEu88Ao91fEYdI3joX6OJbfigDFozqQ8Y0L/7lwQ96m6FdeYmISc LqwdNEntYSB+A== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:06 +0000 Subject: [PATCH v23 1/8] arm64/gcs: Return a success value from gcs_alloc_thread_stack() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-1-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=3646; i=broonie@kernel.org; h=from:subject:message-id; bh=kPQRcvC7WfSPYhzJwayZjYIsAWbvmKAaCwsniNqkt7c=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBpQ7d6whj/pB24OzdyEDg6QA3mhXAv8CI8+PPID LWorYWSy7SJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCaUO3egAKCRAk1otyXVSH 0Ne+B/9cF0EEL56snz9RmBIdM0oxWpZPDSNILdtEK+P5nmEYgGm/jQns2le1ZJ+/0thlA+eK4jh aORotdpZGq1RP79sUogPG/m7fxL8dIs1El8JuNC8krTB9AtFBonCAw63OicRxDZcxL6my91lrZe TG7UsuDnCty01bhOrEZHJ6Twf0EylaKtcniaY26KkluIIGVg4m9eD3yRVml90Z+6E/A8YuvhgtM bpiwhtOhCaF4DPLfs4xJTSXmWK47k6lRs2APCVq/xK0tS0AUdoI3YvpOkTadVF6t63fqIuOOtMd x+dR0KqBxj4zFxMehkOFEopVJ6US0GpzDk2cf2hAXU8d3Zkb X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Currently as a result of templating from x86 code gcs_alloc_thread_stack() returns a pointer as an unsigned int however on arm64 we don't actually use this pointer value as anything other than a pass/fail flag. Simplify the interface to just return an int with 0 on success and a negative error code on failure. Acked-by: Deepak Gupta Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- arch/arm64/include/asm/gcs.h | 8 ++++---- arch/arm64/kernel/process.c | 8 ++++---- arch/arm64/mm/gcs.c | 8 ++++---- 3 files changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h index 8fa0707069e8..534ea5ae9281 100644 --- a/arch/arm64/include/asm/gcs.h +++ b/arch/arm64/include/asm/gcs.h @@ -64,8 +64,8 @@ static inline bool task_gcs_el0_enabled(struct task_struc= t *task) void gcs_set_el0_mode(struct task_struct *task); void gcs_free(struct task_struct *task); void gcs_preserve_current_state(void); -unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args); +int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args); =20 static inline int gcs_check_locked(struct task_struct *task, unsigned long new_val) @@ -171,8 +171,8 @@ static inline void put_user_gcs(unsigned long val, unsi= gned long __user *addr, int *err) { } static inline void push_user_gcs(unsigned long val, int *err) { } =20 -static inline unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args) +static inline int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { return -ENOTSUPP; } diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index fba7ca102a8c..4dadc70df16b 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -299,7 +299,7 @@ static void flush_gcs(void) static int copy_thread_gcs(struct task_struct *p, const struct kernel_clone_args *args) { - unsigned long gcs; + int ret; =20 if (!system_supports_gcs()) return 0; @@ -310,9 +310,9 @@ static int copy_thread_gcs(struct task_struct *p, p->thread.gcs_el0_mode =3D current->thread.gcs_el0_mode; p->thread.gcs_el0_locked =3D current->thread.gcs_el0_locked; =20 - gcs =3D gcs_alloc_thread_stack(p, args); - if (IS_ERR_VALUE(gcs)) - return PTR_ERR((void *)gcs); + ret =3D gcs_alloc_thread_stack(p, args); + if (ret !=3D 0) + return ret; =20 return 0; } diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 6e93f78de79b..3abcbf9adb5c 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -38,8 +38,8 @@ static unsigned long gcs_size(unsigned long size) return max(PAGE_SIZE, size); } =20 -unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args) +int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { unsigned long addr, size; =20 @@ -59,13 +59,13 @@ unsigned long gcs_alloc_thread_stack(struct task_struct= *tsk, size =3D gcs_size(size); addr =3D alloc_gcs(0, size); if (IS_ERR_VALUE(addr)) - return addr; + return PTR_ERR((void *)addr); =20 tsk->thread.gcs_base =3D addr; tsk->thread.gcs_size =3D size; tsk->thread.gcspr_el0 =3D addr + size - sizeof(u64); =20 - return addr; + return 0; } =20 SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size= , unsigned int, flags) --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5272A2F25FD; Thu, 18 Dec 2025 08:13:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045588; cv=none; b=kh5yvZLnwiYrutb5Xq3PzcIA9sieS9Qo1CPpij+PbylERLphh4NvpSaceRwNRgf7yfZ1pklGb/DCw7AKg7+Nq+73VRfCW/E8W6PaiaRwEhpTEiogNqxGVxp7Wl1ugW2bb7Js7I+xE9ChaI7iHHvQU3t9V4SiuUxoprXOUzJZw0k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045588; c=relaxed/simple; bh=YllyAUQhoh+CFHaQ0RGYDGwfzXhe4WlNB73hILnrir0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=EHGvlj1+GFkUcWaABVQRXhrlnHijShYMw7FKUzZj71HX2WeTgJPBtbtbYjmGc2C2Eg8O7SPNdGvYiCw6hfwz6V70pBHWMMzJupVhsk9h9OSCyX3LOgV/IjLwuovMv7BKH5fR1YZa/C8JGWhFnGDMAlpzbTAaIvINnvxFOMmE+Ws= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WHQzHhm4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WHQzHhm4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 968AFC4CEFB; Thu, 18 Dec 2025 08:13:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045587; bh=YllyAUQhoh+CFHaQ0RGYDGwfzXhe4WlNB73hILnrir0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=WHQzHhm4DBTavlRmWFQWKiZDi+4x630wN4LmXaF0Lu41Akrko/SBDMidfk5ykOBYC 0wBfMGD8O8yJX2PnapoS8bxe2zhr/F444GZ+9SPIrBlykkg5DnorG718OcJjwnjRVj e5v5He9weMvgrB+9fyj0l+l34NmcFT7Nqw04n4JgNp13sXU0HcpePHI6Cs4uVRxTkf XbUtdKmskwERnaHtOPm1cxPEkqchAK0awIEgcYb5hFyg8oUWfO30i1UW4e73nfSwbw Mr1xB1ppGNyR5hhdlom6lr5B5YQKRUcKwFnZr4sdpM/u9bnJkp439PkDD5w8r3taJZ V9CBI7VJljPPQ== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:07 +0000 Subject: [PATCH v23 2/8] Documentation: userspace-api: Add shadow stack API documentation Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-2-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=3303; i=broonie@kernel.org; h=from:subject:message-id; bh=YllyAUQhoh+CFHaQ0RGYDGwfzXhe4WlNB73hILnrir0=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBpQ7d709A1tQDvPHAcxOWwzShzZwNk9FFDtIrZu NufA1tJlHuJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCaUO3ewAKCRAk1otyXVSH 0G8UB/9O4gZ95A0cMps/ntHozyVXD672yyohi8Ta43JFciX4dj21kOlVbwyVQFHG1VOsVmWNEip bLWddkSPjXoW48zyaYC3na9v+wWqtkY9IlunM4dRp4TZ7uxsJVUSNmXX6XzCLwwXJZqDQ5zBw7k FFuD6J0q2JrKpgfmDv7qe4oC2ial3RlZmFOFGy2YD4pTilhz953XbseUPe0PKRWEUMIEQVBUWJU BqfpMOmBk/0cBFq4dqpsnatzrsSpf+FDp42R/CXkoUIDoaDxnd+Pj0b4AZIjQM9fVWcPX+SePJL 2mPpTOt3q/U+gc/r6VexMe2lXuzYUcVlJCucymCpXzZXNp8O X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB There are a number of architectures with shadow stack features which we are presenting to userspace with as consistent an API as we can (though there are some architecture specifics). Especially given that there are some important considerations for userspace code interacting directly with the feature let's provide some documentation covering the common aspects. Reviewed-by: Catalin Marinas Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Acked-by: Yury Khrustalev Reviewed-by: Deepak Gupta Tested-by: Rick Edgecombe Signed-off-by: Mark Brown --- Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/shadow_stack.rst | 44 ++++++++++++++++++++++++= ++++ 2 files changed, 45 insertions(+) diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspac= e-api/index.rst index 8a61ac4c1bf1..64b0099ee161 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -63,6 +63,7 @@ Everything else ELF liveupdate netlink/index + shadow_stack sysfs-platform_profile vduse futex2 diff --git a/Documentation/userspace-api/shadow_stack.rst b/Documentation/u= serspace-api/shadow_stack.rst new file mode 100644 index 000000000000..42617d0470ba --- /dev/null +++ b/Documentation/userspace-api/shadow_stack.rst @@ -0,0 +1,44 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Shadow Stacks +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Introduction +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Several architectures have features which provide backward edge +control flow protection through a hardware maintained stack, only +writable by userspace through very limited operations. This feature +is referred to as shadow stacks on Linux, on x86 it is part of Intel +Control Enforcement Technology (CET), on arm64 it is Guarded Control +Stacks feature (FEAT_GCS) and for RISC-V it is the Zicfiss extension. +It is expected that this feature will normally be managed by the +system dynamic linker and libc in ways broadly transparent to +application code, this document covers interfaces and considerations. + + +Enabling +=3D=3D=3D=3D=3D=3D=3D=3D + +Shadow stacks default to disabled when a userspace process is +executed, they can be enabled for the current thread with a syscall: + + - For x86 the ARCH_SHSTK_ENABLE arch_prctl() + - For other architectures the PR_SET_SHADOW_STACK_ENABLE prctl() + +It is expected that this will normally be done by the dynamic linker. +Any new threads created by a thread with shadow stacks enabled will +themselves have shadow stacks enabled. + + +Enablement considerations +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D + +- Returning from the function that enables shadow stacks without first + disabling them will cause a shadow stack exception. This includes + any syscall wrapper or other library functions, the syscall will need + to be inlined. +- A lock feature allows userspace to prevent disabling of shadow stacks. +- Those that change the stack context like longjmp() or use of ucontext + changes on signal return will need support from libc. --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 996C22F0C6E; Thu, 18 Dec 2025 08:13:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045598; cv=none; b=W/or65mK4rV3dAm1n5SOqbnVmgLz+62/Y8yskbR+JgCMR4bsL0CFGmPjevYmEVQyzHl8wLKnAPyoXzECXw1Zn19x1qE5XKUnq4T0vCA3KkThzwDgbUTumg11YRST+Woa9CxjF/W+arOvkavqzeXB1je+rdEntC6UbfCB0yBf0Ek= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045598; c=relaxed/simple; bh=SjAVk2oZop8/vkcGWDGWGjLdjw/OJ5G4Yfu/zz8d2Tc=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=MFMkBAg6gmCrKEgiu1aFxq03gwQ1SBXgjTRkag9UP2zlFsCJE6/p85WgUN5bM64/t3wKqeWP7D2DDTfNqR/zNqdl5hgV5tmii2OcVea1N+Kx7ik/oj5dbK6Wlnq8NTn03IgYlxq4UZDdZPh6whO4mqwqwwJ+r0iPYsBEkoyp7Go= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QH5qOyDt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QH5qOyDt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BDCFC16AAE; Thu, 18 Dec 2025 08:13:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045597; bh=SjAVk2oZop8/vkcGWDGWGjLdjw/OJ5G4Yfu/zz8d2Tc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=QH5qOyDtiGdOtqpjHUsshXWuxqPD5gXjt4KguV88z3OvywOr6ebTvoIT8gSKRTMvf 34PggfbY7uVuOcYZ8bcX0jCXLBmpy7OaseYHrk1xofwb8t9U++aPRZxmaYE9yye1Z2 qgiwWGPCNfXP3Q64eI9U2RwLnqQ7UWzFdbJ98BuxCK9B/TThM/jYnIyYj7AX/InE9O d+dyPY6FiTHjazNSpqGdwl79Wp8zQWNizmBOGMKc1V7yXIjjbnzN3BqsEtpI4jwu5Z wdbEc+GDUwK6l2Ow5ZxIf6402jZ8I0dF1yHFZcDtHSRyujFHwwZX2lBGJTWJ7qfqGN KOuF06bcCHtZw== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:08 +0000 Subject: [PATCH v23 3/8] selftests: Provide helper header for shadow stack testing Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-3-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=4438; i=broonie@kernel.org; h=from:subject:message-id; bh=SjAVk2oZop8/vkcGWDGWGjLdjw/OJ5G4Yfu/zz8d2Tc=; b=owGbwMvMwMWocq27KDak/QLjabUkhkzn7dWaq5UWswmtVZ+YMLG3/nlpVkzZNsVwjzWXehYJd 5z/X9fQyWjMwsDIxSArpsiy9lnGqvRwia3zH81/BTOIlQlkCgMXpwBMpNubg6H532W3NuGN27xc 4oIzdM8ppgs4Tu4NNE0oVbTjvse7LNk322y/qFRtQ4psa8x+/1TmkvVWT3veKFUFeFRueji7d+b B7OPRzP5+58pLLRc+qdH/c0NEZqJS9w/tB547dv8TOPh9seAjg5enNkvcmMTH2toVl1u9xTwj5m gTf+n14x/E65+EvXP8WG+/UEdONdlxZ80arZSTOW//7Zy0IXT6ltSlZ5c2xbJFR2oquemdaAgoX 5c78cWJZr2dJx9PeJVdNe1ToXJ6ZVlZmuQq06eMM9teGIT+PlGd/63A+1Lhje1B071EdXoPlRod 9465uJw9ap/E6QnFzpnG4su/uISoBE7WdLPnmb3yWGUSAA== X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB While almost all users of shadow stacks should be relying on the dynamic linker and libc to enable the feature there are several low level test programs where it is useful to enable without any libc support, allowing testing without full system enablement. This low level testing is helpful during bringup of the support itself, and also in enabling coverage by automated testing without needing all system components in the target root filesystems to have enablement. Provide a header with helpers for this purpose, intended for use only by test programs directly exercising shadow stack interfaces. Reviewed-by: Rick Edgecombe Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Acked-by: Catalin Marinas Tested-by: Rick Edgecombe Signed-off-by: Mark Brown --- tools/testing/selftests/ksft_shstk.h | 98 ++++++++++++++++++++++++++++++++= ++++ 1 file changed, 98 insertions(+) diff --git a/tools/testing/selftests/ksft_shstk.h b/tools/testing/selftests= /ksft_shstk.h new file mode 100644 index 000000000000..fecf91218ea5 --- /dev/null +++ b/tools/testing/selftests/ksft_shstk.h @@ -0,0 +1,98 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Helpers for shadow stack enablement, this is intended to only be + * used by low level test programs directly exercising interfaces for + * working with shadow stacks. + * + * Copyright (C) 2024 ARM Ltd. + */ + +#ifndef __KSFT_SHSTK_H +#define __KSFT_SHSTK_H + +#include + +/* This is currently only defined for x86 */ +#ifndef SHADOW_STACK_SET_TOKEN +#define SHADOW_STACK_SET_TOKEN (1ULL << 0) +#endif + +static bool shadow_stack_enabled; + +#ifdef __x86_64__ +#define ARCH_SHSTK_ENABLE 0x5001 +#define ARCH_SHSTK_SHSTK (1ULL << 0) + +#define ARCH_PRCTL(arg1, arg2) \ +({ \ + long _ret; \ + register long _num asm("eax") =3D __NR_arch_prctl; \ + register long _arg1 asm("rdi") =3D (long)(arg1); \ + register long _arg2 asm("rsi") =3D (long)(arg2); \ + \ + asm volatile ( \ + "syscall\n" \ + : "=3Da"(_ret) \ + : "r"(_arg1), "r"(_arg2), \ + "0"(_num) \ + : "rcx", "r11", "memory", "cc" \ + ); \ + _ret; \ +}) + +#define ENABLE_SHADOW_STACK +static __always_inline void enable_shadow_stack(void) +{ + int ret =3D ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK); + if (ret =3D=3D 0) + shadow_stack_enabled =3D true; +} + +#endif + +#ifdef __aarch64__ +#define PR_SET_SHADOW_STACK_STATUS 75 +# define PR_SHADOW_STACK_ENABLE (1UL << 0) + +#define my_syscall2(num, arg1, arg2) = \ +({ = \ + register long _num __asm__ ("x8") =3D (num); \ + register long _arg1 __asm__ ("x0") =3D (long)(arg1); \ + register long _arg2 __asm__ ("x1") =3D (long)(arg2); \ + register long _arg3 __asm__ ("x2") =3D 0; \ + register long _arg4 __asm__ ("x3") =3D 0; \ + register long _arg5 __asm__ ("x4") =3D 0; \ + \ + __asm__ volatile ( \ + "svc #0\n" \ + : "=3Dr"(_arg1) \ + : "r"(_arg1), "r"(_arg2), \ + "r"(_arg3), "r"(_arg4), \ + "r"(_arg5), "r"(_num) \ + : "memory", "cc" \ + ); \ + _arg1; \ +}) + +#define ENABLE_SHADOW_STACK +static __always_inline void enable_shadow_stack(void) +{ + int ret; + + ret =3D my_syscall2(__NR_prctl, PR_SET_SHADOW_STACK_STATUS, + PR_SHADOW_STACK_ENABLE); + if (ret =3D=3D 0) + shadow_stack_enabled =3D true; +} + +#endif + +#ifndef __NR_map_shadow_stack +#define __NR_map_shadow_stack 453 +#endif + +#ifndef ENABLE_SHADOW_STACK +static inline void enable_shadow_stack(void) { } +#endif + +#endif --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 AF75B3314D9; Thu, 18 Dec 2025 08:13:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045606; cv=none; b=EbFg02ggfH0P8pInn1jx/qr5Q/Jtic4MYJ1DkFAcN/zutA8bZDNCNSH7GmqZe5NJIPkCJKZ3tc7jwUEnVWnaOq610MKm3yrjYb5LSk0ptmVgl1s1lsDK/5qXCDb770yNatf0k+QrPQqYSjdPUkG4gGq9o/XbM+pkHeLbJnZuJww= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045606; c=relaxed/simple; bh=2dnm5SBFCMhzTgb+Mx+zi2f+4FvnpK5s9wA4+SsLu0A=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=iu2UXj67Q+LTu8iwYx0SBHqnDoHYJdRRgJaq4gEywKJnbU8kNcyOjx420tILqulqIXUPzXRB/fQJOaChHdMXgc1jNHsEmD/Pu6pnxBJgUtaIDxenMAqJlOqj7gfefIlEAApvtGEKquels82ylLBQ19xJZ4TFWZSd3FJ/2pgjsTk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Awl1M07U; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Awl1M07U" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8E90C4CEFB; Thu, 18 Dec 2025 08:13:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045606; bh=2dnm5SBFCMhzTgb+Mx+zi2f+4FvnpK5s9wA4+SsLu0A=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Awl1M07Uo8JAZj13kkNT2TAj7wO/puFEWO3Xdu0+eHLIDWz/2rCQ+/ujtBDYmOhM6 ptpg/fBwQgjPFW+zyoUd00YRLua+nPcmRq/bjUNt7UiKOy5/pNieCUwKvdhVbB64Nx JpMjvVKTv9ePlICewGzU5ovQAayOXike3tVec68mYbmijjbkd69t4feWTOKpdf49eA NLnZmfgHkFPd9iIj5rdfzG6ttCkF/XBh1v/ENjbPsmdTnJrVHnLaDCx6lWEsxZEWYf 3qdq6O6fdk86xP0U8NYELOtbtsMEJ3rejhlaCcejRoVWwLEDk2EvkSnUh5cHwGHnBJ RLJlSKkwAammw== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:09 +0000 Subject: [PATCH v23 4/8] fork: Add shadow stack support to clone3() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-4-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=16150; i=broonie@kernel.org; h=from:subject:message-id; bh=2dnm5SBFCMhzTgb+Mx+zi2f+4FvnpK5s9wA4+SsLu0A=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBpQ7d80VQQ0HpWAWLjzC0yD9TFNMQ8/XhdDIxkv jkOQtinGiWJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCaUO3fAAKCRAk1otyXVSH 0IviB/9WiSEKDBYPpiSnUD8uxG0/BT6iRmd3rs7Kq7z8+nwDR+xV7lBPJxzHQzWtorTiAnlJWLk gTxscx1kUuEo14DHoLAb+EKnPUq6js8628YwPm0c7t8shYav8fNR88Mj+BeNF1Tm7TUrnxIx8uc ELoXKL0bcYwEBFVMM5qFEjo+jZi3cZTuWgVMgombbPJ9/Z7wwLmsVnNEJ66jaDw3V/gBiA+yckz egHOCMzg3eBaaX/fYL9w5MYxXhxVLdP4BNgYXM/HcHWHe3fxdYw6Qvgxbkz7O61a+ZiG75FgH2j nmfFafKPGGjWEyHMWL6C0pjkuiYICbxF6K/cNu95uiHd9DF3 X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Unlike with the normal stack there is no API for configuring the shadow stack for a new thread, instead the kernel will dynamically allocate a new shadow stack with the same size as the normal stack. This appears to be due to the shadow stack series having been in development since before the more extensible clone3() was added rather than anything more deliberate. Add a parameter to clone3() specifying a shadow stack pointer to use for the new thread, this is inconsistent with the way we specify the normal stack but during review concerns were expressed about having to identify where the shadow stack pointer should be placed especially in cases where the shadow stack has been previously active. If no shadow stack is specified then the existing implicit allocation behaviour is maintained. If a shadow stack pointer is specified then it is required to have an architecture defined token placed on the stack, this will be consumed by the new task, the shadow stack is specified by pointing to this token. If no valid token is present then this will be reported with -EINVAL. This token prevents new threads being created pointing at the shadow stack of an existing running thread. On architectures with support for userspace pivoting of shadow stacks it is expected that the same format and placement of tokens will be used, this is the case for arm64 and x86. If the architecture does not support shadow stacks the shadow stack pointer must be not be specified, architectures that do support the feature are expected to enforce the same requirement on individual systems that lack shadow stack support. Update the existing arm64 and x86 implementations to pay attention to the newly added arguments, in order to maintain compatibility we use the existing behaviour if no shadow stack is specified. Since we are now using more fields from the kernel_clone_args we pass that into the shadow stack code rather than individual fields. Portions of the x86 architecture code were written by Rick Edgecombe. Acked-by: Yury Khrustalev Reviewed-by: Rick Edgecombe Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- arch/arm64/mm/gcs.c | 47 +++++++++++++++++++- arch/x86/include/asm/shstk.h | 11 +++-- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 53 ++++++++++++++++++++--- include/asm-generic/cacheflush.h | 11 +++++ include/linux/sched/task.h | 17 ++++++++ include/uapi/linux/sched.h | 9 ++-- kernel/fork.c | 93 ++++++++++++++++++++++++++++++++++--= ---- 8 files changed, 217 insertions(+), 26 deletions(-) diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 3abcbf9adb5c..fd1d5a6655de 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -43,8 +43,23 @@ int gcs_alloc_thread_stack(struct task_struct *tsk, { unsigned long addr, size; =20 - if (!system_supports_gcs()) + if (!system_supports_gcs()) { + if (args->shstk_token) + return -EINVAL; + return 0; + } + + /* + * If the user specified a GCS then use it, otherwise fall + * back to a default allocation strategy. Validation is done + * in arch_shstk_validate_clone(). + */ + if (args->shstk_token) { + tsk->thread.gcs_base =3D 0; + tsk->thread.gcs_size =3D 0; + return 0; + } =20 if (!task_gcs_el0_enabled(tsk)) return 0; @@ -68,6 +83,36 @@ int gcs_alloc_thread_stack(struct task_struct *tsk, return 0; } =20 +static bool gcs_consume_token(struct vm_area_struct *vma, struct page *pag= e, + unsigned long user_addr) +{ + u64 expected =3D GCS_CAP(user_addr); + u64 *token =3D page_address(page) + offset_in_page(user_addr); + + if (!cmpxchg_to_user_page(vma, page, user_addr, token, expected, 0)) + return false; + set_page_dirty_lock(page); + + return true; +} + +int arch_shstk_validate_clone(struct task_struct *tsk, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + unsigned long gcspr_el0; + int ret =3D 0; + + gcspr_el0 =3D args->shstk_token; + if (!gcs_consume_token(vma, page, gcspr_el0)) + return -EINVAL; + + tsk->thread.gcspr_el0 =3D gcspr_el0 + sizeof(u64); + + return ret; +} + SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size= , unsigned int, flags) { unsigned long alloc_size; diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h index fc7dcec58fd4..42a5f03a51e2 100644 --- a/arch/x86/include/asm/shstk.h +++ b/arch/x86/include/asm/shstk.h @@ -6,6 +6,7 @@ #include =20 struct task_struct; +struct kernel_clone_args; struct ksignal; =20 #ifdef CONFIG_X86_USER_SHADOW_STACK @@ -16,8 +17,8 @@ struct thread_shstk { =20 long shstk_prctl(struct task_struct *task, int option, unsigned long arg2); void reset_thread_features(void); -unsigned long shstk_alloc_thread_stack(struct task_struct *p, u64 clone_fl= ags, - unsigned long stack_size); +unsigned long shstk_alloc_thread_stack(struct task_struct *p, + const struct kernel_clone_args *args); void shstk_free(struct task_struct *p); int setup_signal_shadow_stack(struct ksignal *ksig); int restore_signal_shadow_stack(void); @@ -30,8 +31,10 @@ static inline long shstk_prctl(struct task_struct *task,= int option, unsigned long arg2) { return -EINVAL; } static inline void reset_thread_features(void) {} static inline unsigned long shstk_alloc_thread_stack(struct task_struct *p, - u64 clone_flags, - unsigned long stack_size) { return 0; } + const struct kernel_clone_args *args) +{ + return 0; +} static inline void shstk_free(struct task_struct *p) {} static inline int setup_signal_shadow_stack(struct ksignal *ksig) { return= 0; } static inline int restore_signal_shadow_stack(void) { return 0; } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 4c718f8adc59..449da29a9f92 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -219,7 +219,7 @@ int copy_thread(struct task_struct *p, const struct ker= nel_clone_args *args) * is disabled, new_ssp will remain 0, and fpu_clone() will know not to * update it. */ - new_ssp =3D shstk_alloc_thread_stack(p, clone_flags, args->stack_size); + new_ssp =3D shstk_alloc_thread_stack(p, args); if (IS_ERR_VALUE(new_ssp)) return PTR_ERR((void *)new_ssp); =20 diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 978232b6d48d..d66c866274d0 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -191,18 +191,61 @@ void reset_thread_features(void) current->thread.features_locked =3D 0; } =20 -unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, u64 clone_= flags, - unsigned long stack_size) +int arch_shstk_validate_clone(struct task_struct *t, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + void *maddr =3D page_address(page); + unsigned long token; + int offset; + u64 expected; + + /* + * kernel_clone_args() verification assures token address is 8 + * byte aligned. + */ + token =3D args->shstk_token; + expected =3D (token + SS_FRAME_SIZE) | BIT(0); + offset =3D offset_in_page(token); + + if (!cmpxchg_to_user_page(vma, page, token, (unsigned long *)(maddr + off= set), + expected, 0)) + return -EINVAL; + set_page_dirty_lock(page); + + return 0; +} + +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { struct thread_shstk *shstk =3D &tsk->thread.shstk; + u64 clone_flags =3D args->flags; unsigned long addr, size; =20 /* * If shadow stack is not enabled on the new thread, skip any - * switch to a new shadow stack. + * implicit switch to a new shadow stack and reject attempts to + * explicitly specify one. */ - if (!features_enabled(ARCH_SHSTK_SHSTK)) + if (!features_enabled(ARCH_SHSTK_SHSTK)) { + if (args->shstk_token) + return (unsigned long)ERR_PTR(-EINVAL); + return 0; + } + + /* + * If the user specified a shadow stack then use it, otherwise + * fall back to a default allocation strategy. Validation is + * done in arch_shstk_validate_clone(). + */ + if (args->shstk_token) { + shstk->base =3D 0; + shstk->size =3D 0; + return args->shstk_token + 8; + } =20 /* * For CLONE_VFORK the child will share the parents shadow stack. @@ -222,7 +265,7 @@ unsigned long shstk_alloc_thread_stack(struct task_stru= ct *tsk, u64 clone_flags, if (!(clone_flags & CLONE_VM)) return 0; =20 - size =3D adjust_shstk_size(stack_size); + size =3D adjust_shstk_size(args->stack_size); addr =3D alloc_shstk(0, size, 0, false); if (IS_ERR_VALUE(addr)) return addr; diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cachefl= ush.h index 7ee8a179d103..96cc0c7a5c90 100644 --- a/include/asm-generic/cacheflush.h +++ b/include/asm-generic/cacheflush.h @@ -124,4 +124,15 @@ static inline void flush_cache_vunmap(unsigned long st= art, unsigned long end) } while (0) #endif =20 +#ifndef cmpxchg_to_user_page +#define cmpxchg_to_user_page(vma, page, vaddr, ptr, old, new) \ +({ \ + bool ret; \ + \ + ret =3D try_cmpxchg(ptr, &old, new); \ + flush_icache_user_page(vma, page, vaddr, sizeof(*ptr)); \ + ret; \ +}) +#endif + #endif /* _ASM_GENERIC_CACHEFLUSH_H */ diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 525aa2a632b2..7f860edc58da 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -16,6 +16,7 @@ struct task_struct; struct rusage; union thread_union; struct css_set; +struct vm_area_struct; =20 /* All the bits taken by the old clone syscall. */ #define CLONE_LEGACY_FLAGS 0xffffffffULL @@ -44,6 +45,7 @@ struct kernel_clone_args { struct cgroup *cgrp; struct css_set *cset; unsigned int kill_seq; + unsigned long shstk_token; }; =20 /* @@ -225,4 +227,19 @@ static inline void task_unlock(struct task_struct *p) =20 DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_= T)) =20 +#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK +int arch_shstk_validate_clone(struct task_struct *p, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args); +#else +static inline int arch_shstk_validate_clone(struct task_struct *p, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + return 0; +} +#endif + #endif /* _LINUX_SCHED_TASK_H */ diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 359a14cc76a4..7e18e7b3df3a 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -84,6 +84,7 @@ * kernel's limit of nested PID namespaces. * @cgroup: If CLONE_INTO_CGROUP is specified set this to * a file descriptor for the cgroup. + * @shstk_token: Pointer to shadow stack token at top of stack. * * The structure is versioned by size and thus extensible. * New struct members must go at the end of the struct and @@ -101,12 +102,14 @@ struct clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; + __aligned_u64 shstk_token; }; #endif =20 -#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ -#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ -#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ +#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#define CLONE_ARGS_SIZE_VER3 96 /* sizeof fourth published struct */ =20 /* * Scheduling policies diff --git a/kernel/fork.c b/kernel/fork.c index b1f3915d5f8e..0d171e9055d6 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1955,6 +1955,51 @@ static bool need_futex_hash_allocate_default(u64 clo= ne_flags) return true; } =20 +static int shstk_validate_clone(struct task_struct *p, + struct kernel_clone_args *args) +{ + struct mm_struct *mm; + struct vm_area_struct *vma; + struct page *page; + unsigned long addr; + int ret; + + if (!IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK)) + return 0; + + if (!args->shstk_token) + return 0; + + mm =3D get_task_mm(p); + if (!mm) + return -EFAULT; + + mmap_read_lock(mm); + + addr =3D untagged_addr_remote(mm, args->shstk_token); + page =3D get_user_page_vma_remote(mm, addr, FOLL_FORCE | FOLL_WRITE, + &vma); + if (IS_ERR(page)) { + ret =3D -EFAULT; + goto out; + } + + if (!(vma->vm_flags & VM_SHADOW_STACK) || + !(vma->vm_flags & VM_WRITE)) { + ret =3D -EFAULT; + goto out_page; + } + + ret =3D arch_shstk_validate_clone(p, vma, page, args); + +out_page: + put_page(page); +out: + mmap_read_unlock(mm); + mmput(mm); + return ret; +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -2228,6 +2273,9 @@ __latent_entropy struct task_struct *copy_process( if (retval) goto bad_fork_cleanup_namespaces; retval =3D copy_thread(p, args); + if (retval) + goto bad_fork_cleanup_io; + retval =3D shstk_validate_clone(p, args); if (retval) goto bad_fork_cleanup_io; =20 @@ -2807,7 +2855,9 @@ static noinline int copy_clone_args_from_user(struct = kernel_clone_args *kargs, CLONE_ARGS_SIZE_VER1); BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=3D CLONE_ARGS_SIZE_VER2); - BUILD_BUG_ON(sizeof(struct clone_args) !=3D CLONE_ARGS_SIZE_VER2); + BUILD_BUG_ON(offsetofend(struct clone_args, shstk_token) !=3D + CLONE_ARGS_SIZE_VER3); + BUILD_BUG_ON(sizeof(struct clone_args) !=3D CLONE_ARGS_SIZE_VER3); =20 if (unlikely(usize > PAGE_SIZE)) return -E2BIG; @@ -2840,16 +2890,17 @@ static noinline int copy_clone_args_from_user(struc= t kernel_clone_args *kargs, return -EINVAL; =20 *kargs =3D (struct kernel_clone_args){ - .flags =3D args.flags, - .pidfd =3D u64_to_user_ptr(args.pidfd), - .child_tid =3D u64_to_user_ptr(args.child_tid), - .parent_tid =3D u64_to_user_ptr(args.parent_tid), - .exit_signal =3D args.exit_signal, - .stack =3D args.stack, - .stack_size =3D args.stack_size, - .tls =3D args.tls, - .set_tid_size =3D args.set_tid_size, - .cgroup =3D args.cgroup, + .flags =3D args.flags, + .pidfd =3D u64_to_user_ptr(args.pidfd), + .child_tid =3D u64_to_user_ptr(args.child_tid), + .parent_tid =3D u64_to_user_ptr(args.parent_tid), + .exit_signal =3D args.exit_signal, + .stack =3D args.stack, + .stack_size =3D args.stack_size, + .tls =3D args.tls, + .set_tid_size =3D args.set_tid_size, + .cgroup =3D args.cgroup, + .shstk_token =3D args.shstk_token, }; =20 if (args.set_tid && @@ -2890,6 +2941,24 @@ static inline bool clone3_stack_valid(struct kernel_= clone_args *kargs) return true; } =20 +/** + * clone3_shadow_stack_valid - check and prepare shadow stack + * @kargs: kernel clone args + * + * Verify that shadow stacks are only enabled if supported. + */ +static inline bool clone3_shadow_stack_valid(struct kernel_clone_args *kar= gs) +{ + if (!kargs->shstk_token) + return true; + + if (!IS_ALIGNED(kargs->shstk_token, sizeof(void *))) + return false; + + /* Fail if the kernel wasn't built with shadow stacks */ + return IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK); +} + static bool clone3_args_valid(struct kernel_clone_args *kargs) { /* Verify that no unknown flags are passed along. */ @@ -2912,7 +2981,7 @@ static bool clone3_args_valid(struct kernel_clone_arg= s *kargs) kargs->exit_signal) return false; =20 - if (!clone3_stack_valid(kargs)) + if (!clone3_stack_valid(kargs) || !clone3_shadow_stack_valid(kargs)) return false; =20 return true; --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2563E3328FA; Thu, 18 Dec 2025 08:13:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045613; cv=none; b=R1lWVBRnGn3VWf75Ulbr5f+1PRwhb86cF31rVcBTev5tKlfR0flwAra30OUcPXx/tI3R6x4BJ6DuyZ1QDrvcJ+8BlkqERQW+P8B7GY7P3yzcUuk4UPPT1Wtt7f4whUFel03VnXWQWJdlSTC1x2evZJnFskyAxh4PzQ5W4313hy4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045613; c=relaxed/simple; bh=p/HV5NAkkDiAEYyZwvxSSeBqc7NHv593vzQCAZgVHbg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Cy+lw4TZ7RxxG59UWPNz9bEacHGxXgSOd1hWF/EI+v0fzc56OrdID4pnfIvT70ZevAJ27fo2DPlDzuCs+Yp/Rvp/VQEIt/MIWFal2zlfWcSOHIpMUpu7PhQ5l/UDiDh/8L7uYip4Ai42s2ihoO5JZXaZ/agNknuitjernu689Do= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JRirV3Hm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JRirV3Hm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7E31C16AAE; Thu, 18 Dec 2025 08:13:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045612; bh=p/HV5NAkkDiAEYyZwvxSSeBqc7NHv593vzQCAZgVHbg=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=JRirV3Hm29C4eUeVBA8PiCi1dIazJYLZGa4/fMPh715BJJzjRxsEuo806PXIzyKRQ XM7rNmJzdwU2c8vkB1Ik5ol5YKkzVHo+5cMeaFw9QAxBJC1us2D14kOmK2gs6v3GBT bHNE1htSQpBttc8eZNfdOe6WmU5/LQkuax4h4vMuFZ218xnaEdyydiresqnE98HmaB g7TKKdM4lUW2kM8zw4ZT3Likx4a6eWNkb8lLFXT6dLBZ5gLoDGyRj1pbJ1Y1dJxdJV RXAQIx9k7o/vaB2W2mG19V91r3jkTQvBN+vmE6QODrg7pHzPcHut9x0TmOrZiDZyhO blJhIyqx1Qixw== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:10 +0000 Subject: [PATCH v23 5/8] selftests/clone3: Remove redundant flushes of output streams Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-5-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=1170; i=broonie@kernel.org; h=from:subject:message-id; bh=p/HV5NAkkDiAEYyZwvxSSeBqc7NHv593vzQCAZgVHbg=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBpQ7d9SDT0u5qV6dyQJiXLZWIbDp1RVQNiCMjDM PyMXHcbcguJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCaUO3fQAKCRAk1otyXVSH 0Gv2B/wKmkBlyQZoiw7flpJ77bHqHVOEboQlVL+wfZauhfIxd7dZygbbm2lDl4BaqOtUsOkjzOZ tSdhtLV6jtdEGE43lDgQj685rsO5wQFGSgTztumUN203g6nX1+VBPjBrNL4kdvOaOfCfqomJYZY iDS2C38+pt8PteqNP1zE9DWTY9XBR+kzUkfIB7NpCkxLdJDcsUQNcSG3lOajLLWORyu9DcTvEp+ CyaNBVcBtpqaf4w+V9ivt0UWjUv6FsUIuoi+qysNkBXbDQdBFKLrUtp2DvWtENilXzGxOh3c9p0 2UkwBGE8Ah0mrbTyF4XoumW8dgm3ZT9fy9ET/ihp8pBaVdD7 X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Since there were widespread issues with output not being flushed the kselftest framework was modified to explicitly set the output streams unbuffered in commit 58e2847ad2e6 ("selftests: line buffer test program's stdout") so there is no need to explicitly flush in the clone3 tests. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Tested-by: Rick Edgecombe Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3_selftests.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/test= ing/selftests/clone3/clone3_selftests.h index a0593e8950f0..a7ab2f1cccda 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -35,8 +35,6 @@ struct __clone_args { =20 static pid_t sys_clone3(struct __clone_args *args, size_t size) { - fflush(stdout); - fflush(stderr); return syscall(__NR_clone3, args, size); } =20 --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3CA3A332918; Thu, 18 Dec 2025 08:13:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045619; cv=none; b=pWk9HadHWthr6AA/yrPHIaeg2TsMm7MCA1hypzqJPUWHY0R42WH/8sqx5EvtzicrYnCu8gmc2d2Fo+0C/6K5MReU3S7YzEpOk22EToto/9MiWDSUDWO6XQTsB52O9yD0c6lzJp3f+XBPU74PG14A3o7sSzFG9fcGBGyILg33pNE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045619; c=relaxed/simple; bh=d62mKnZ8KnVaUGN6V9Sf3vOPMwiSvjXfVmsMQG7U0Yg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=JpucoHMySLZU/GGCxGUdIBiMZh0FxQx/ojj1HRLX/HgR/fPb8+rvLx2cmZIMZPDGNC0ckrB+SyPfnhUEG0Dm+/unrgMcWifGAZZVd8g0Mz6Zf+11frTfoszg+RU9z4xJ7Vc6sw0McZ4Ovys7KESaffOkb7MTeQ092vFp/k7Co9c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ipntjqPS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ipntjqPS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B020C19422; Thu, 18 Dec 2025 08:13:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045619; bh=d62mKnZ8KnVaUGN6V9Sf3vOPMwiSvjXfVmsMQG7U0Yg=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=ipntjqPSASQDkkyaGqBYOZ3NCdBuysXrFQjx5/K2m0AU0faZ8KcY6ck6p5ZBAVYk2 nmMmpbbLOkWDtxKTuU4zaxFg0SkL+sOVbUELctRmEpWxnC3/E/Jt4xZM+dLoNdrPjS sf1isWMXvfWxdSrcdzHjkHLshJsqSuE4AZCqFcjRfb8VX5R9gj7an5fy6poOENeoy6 /F75zTZ9+aQV78oofoYrDGgAC6KYOSkVoeASeRt7p1PehYo0s8lDQzXP3lshOmdaIp DG+wP6BBVsfxwcV8n+yZWParV9aV9l22+9w1wapo5d3SysBKsTLh3vmgO+Qa6sZ8YT 2ZT5llQLlkRmg== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:11 +0000 Subject: [PATCH v23 6/8] selftests/clone3: Factor more of main loop into test_clone3() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-6-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=3987; i=broonie@kernel.org; h=from:subject:message-id; bh=d62mKnZ8KnVaUGN6V9Sf3vOPMwiSvjXfVmsMQG7U0Yg=; b=owGbwMvMwMWocq27KDak/QLjabUkhkzn7XVsm+eE7C4P9li78eRinj/z1nTxTLnupOko3LT7U NyyshLdTkZjFgZGLgZZMUWWtc8yVqWHS2yd/2j+K5hBrEwgUxi4OAVgIleWsv/39PlWzPLYQNRr 50X+pdGOXy/wr2fV+F/g0vy4mVdNe5m1nMMxhUvbjisayfTXsU4tEKzdF2603miLaK3os3a9gkD 9vomqq4ub/FwXJ17sVf8WU8G2pUzBuPOodB9bkiL/goTARIcF+9+L9rfcfX3hcP5cgS8v63IZ1p kW5guwvWE3Ovqt3Ckq4mihfuOlrqhPH649ik7Z7K8453vhf9ZimXOHzU+mH3cXOblW7532e//mA v+eK5f6BHsbNQ8vmuf0bGf5l0YZsztLfTKnrvcI7VIovtx2/6DAVx5hzogHDFfLX6z1lOll79jo nzp729qKiat69J9w/J5XuFVd6mWt4HXLooyOCfb9012MAQ== X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB In order to make it easier to add more configuration for the tests and more support for runtime detection of when tests can be run pass the structure describing the tests into test_clone3() rather than picking the arguments out of it and have that function do all the per-test work. No functional change. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Tested-by: Rick Edgecombe Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 77 ++++++++++++++++-------------= ---- 1 file changed, 37 insertions(+), 40 deletions(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selfte= sts/clone3/clone3.c index 289e0c7c1f09..8c852d022c55 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -30,6 +30,19 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, }; =20 +typedef bool (*filter_function)(void); +typedef size_t (*size_function)(void); + +struct test { + const char *name; + uint64_t flags; + size_t size; + size_function size_function; + int expected; + enum test_mode test_mode; + filter_function filter; +}; + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mo= de) { struct __clone_args args =3D { @@ -109,30 +122,40 @@ static int call_clone3(uint64_t flags, size_t size, e= num test_mode test_mode) return 0; } =20 -static bool test_clone3(uint64_t flags, size_t size, int expected, - enum test_mode test_mode) +static void test_clone3(const struct test *test) { + size_t size; int ret; =20 + if (test->filter && test->filter()) { + ksft_test_result_skip("%s\n", test->name); + return; + } + + if (test->size_function) + size =3D test->size_function(); + else + size =3D test->size; + + ksft_print_msg("Running test '%s'\n", test->name); + ksft_print_msg( "[%d] Trying clone3() with flags %#" PRIx64 " (size %zu)\n", - getpid(), flags, size); - ret =3D call_clone3(flags, size, test_mode); + getpid(), test->flags, size); + ret =3D call_clone3(test->flags, size, test->test_mode); ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n", - getpid(), ret, expected); - if (ret !=3D expected) { + getpid(), ret, test->expected); + if (ret !=3D test->expected) { ksft_print_msg( "[%d] Result (%d) is different than expected (%d)\n", - getpid(), ret, expected); - return false; + getpid(), ret, test->expected); + ksft_test_result_fail("%s\n", test->name); + return; } =20 - return true; + ksft_test_result_pass("%s\n", test->name); } =20 -typedef bool (*filter_function)(void); -typedef size_t (*size_function)(void); - static bool not_root(void) { if (getuid() !=3D 0) { @@ -160,16 +183,6 @@ static size_t page_size_plus_8(void) return getpagesize() + 8; } =20 -struct test { - const char *name; - uint64_t flags; - size_t size; - size_function size_function; - int expected; - enum test_mode test_mode; - filter_function filter; -}; - static const struct test tests[] =3D { { .name =3D "simple clone3()", @@ -319,24 +332,8 @@ int main(int argc, char *argv[]) ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); =20 - for (i =3D 0; i < ARRAY_SIZE(tests); i++) { - if (tests[i].filter && tests[i].filter()) { - ksft_test_result_skip("%s\n", tests[i].name); - continue; - } - - if (tests[i].size_function) - size =3D tests[i].size_function(); - else - size =3D tests[i].size; - - ksft_print_msg("Running test '%s'\n", tests[i].name); - - ksft_test_result(test_clone3(tests[i].flags, size, - tests[i].expected, - tests[i].test_mode), - "%s\n", tests[i].name); - } + for (i =3D 0; i < ARRAY_SIZE(tests); i++) + test_clone3(&tests[i]); =20 ksft_finished(); } --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EAFE12DE1E0; Thu, 18 Dec 2025 08:13:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045626; cv=none; b=pR6yibdKQKbUMfh/nntg2OIZcm2EFErZpyK5g2n6wCqGovIb1uUeTYKa19xTmn0NDP1jhAGAKUVRylGHSkkGNJ1keKCYKVk+mZlW3To/0A791mS3ozRWHLkl0ljvDMkENredV0Qi4czy9rFB3Bl8XiKxP2PNt1VS6MTD1WrsHDU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045626; c=relaxed/simple; bh=A1dmn1Lt5Sgv7peqK8b9pCFAystHjFcAgH6JkrDrGcE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TESh0fDpJQM3H+CGzKvxETvXiPUx5IAnpLWXgXThv8jU2VN8+a/4rgpWel+CbxD+gGuBOuigiqXchVI8huZbFW5kZ8fELXV2vcDQBKaUL64zQWIT4OHhnPoRWzsuTV919s7g3qFjzcIenpCLa59QFQw0fgwZoX/fa3cMJidhzh8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=a55ul0/i; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="a55ul0/i" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 817A5C113D0; Thu, 18 Dec 2025 08:13:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045625; bh=A1dmn1Lt5Sgv7peqK8b9pCFAystHjFcAgH6JkrDrGcE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=a55ul0/iKesGTk3btVfegJA7OlyQLzSiO5XN9QWiNTaZ0VVTWzLgVsRDxdXYkrRQN faWs8VydkBfKcV6JAd/5afTVkIdmCW4mfLA4WjlZMNFGG6VtAG6iy6Log7Rp/My7MY 2sdiu4Ejdf+9FixuoiI1V9icQMOJyYDyOQodzn8vthX9VsZ3cZIlF7eBInsHwnpHxk mye8MSpgILBNpUguNeFZ9EoPAePwh6D/F6zFmlbBOeKiNPibdjxde3RLUx+GF7NOp4 2EpLIdWdowlTb0I1C7ZHAftQv3qp7t3t0re+zMcdS5192QRvMRz1NzwuwRYOIuTb0C 8+CakaO7S+aVw== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:12 +0000 Subject: [PATCH v23 7/8] selftests/clone3: Allow tests to flag if -E2BIG is a valid error code Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-7-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=2131; i=broonie@kernel.org; h=from:subject:message-id; bh=A1dmn1Lt5Sgv7peqK8b9pCFAystHjFcAgH6JkrDrGcE=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBpQ7d/JSCYBDCqmM/wHVJTzJN5r0x+agtCQ3NX+ Jmk+wj0Ar6JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCaUO3fwAKCRAk1otyXVSH 0GafB/90LBIaRWKm1cl1IIoCA7eGSlx0BnYY9504ESUUdEYLHFKaSMwm4f6t9bLIWgfxdPgbmIG YZo/+PBCHWvXNxbWsU7uDeiYx6f5gFSm08QH1FPpFsX6jreTrVTW1pdcEW93+2cPHzjQb6JgC33 sgIYMwCR19X790qpYeIfXkAmugD6uhKhL0M9mF4C1y5o3Of1iceEkyuIqMxKNdX3K7fNGFiPSti NiwXQ5Zq9ZC/8MbyHX3EuzE5QcJAA6zv0w0ptIcGdLOtE8Y6IXOjsGTJKqlr65aCRarz7WfLT9h SyBdeEe7z1eYskN0gb2QrxMybNVqgv0zkCv8onhajppKfx9g X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB The clone_args structure is extensible, with the syscall passing in the length of the structure. Inside the kernel we use copy_struct_from_user() to read the struct but this has the unfortunate side effect of silently accepting some overrun in the structure size providing the extra data is all zeros. This means that we can't discover the clone3() features that the running kernel supports by simply probing with various struct sizes. We need to check this for the benefit of test systems which run newer kselftests on old kernels. Add a flag which can be set on a test to indicate that clone3() may return -E2BIG due to the use of newer struct versions. Currently no tests need this but it will become an issue for testing clone3() support for shadow stacks, the support for shadow stacks is already present on x86. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Tested-by: Rick Edgecombe Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selfte= sts/clone3/clone3.c index 8c852d022c55..932cc64e9ae4 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -39,6 +39,7 @@ struct test { size_t size; size_function size_function; int expected; + bool e2big_valid; enum test_mode test_mode; filter_function filter; }; @@ -146,6 +147,11 @@ static void test_clone3(const struct test *test) ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n", getpid(), ret, test->expected); if (ret !=3D test->expected) { + if (test->e2big_valid && ret =3D=3D -E2BIG) { + ksft_print_msg("Test reported -E2BIG\n"); + ksft_test_result_skip("%s\n", test->name); + return; + } ksft_print_msg( "[%d] Result (%d) is different than expected (%d)\n", getpid(), ret, test->expected); --=20 2.47.3 From nobody Thu Dec 18 21:45:20 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 F10C42DE1E0; Thu, 18 Dec 2025 08:13:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045632; cv=none; b=bswCm4nvqgW0kE7an4SGOoXKGbNw0Jplf/+S3XyRTKWccqnvYpCzh9ioZgEElT6RUZuL8PyPBo2HxqKjav/ywfE+vpBFiHn/VBCJkkZLm8LsbaFrVVATL4z0D2IaeUDELEHg80OucpbM5pHow9l0fiN/xjHMFYq0MLZ7k88soYg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766045632; c=relaxed/simple; bh=aA2zG1Qrocuod6XoXRd+TJqJEQq7bY75FiwjG0Iq/w0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=PtEATw9yBn/fAfenywtVgJHxSpWmNHlZjmJ6Wp1DTB/XdECXxsXR6hHhxtTGLPm+dvImY+sWouP+/OLoSBSixjRlQxfPzDw5MpendaRSi7eA+pi7srz8prBAjmECVECbnsbcg05t8GBigK/GfvyRZcc7I4zOCe4+2hkEK3ccVA4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RxduBvSz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RxduBvSz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D37E0C4CEFB; Thu, 18 Dec 2025 08:13:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766045631; bh=aA2zG1Qrocuod6XoXRd+TJqJEQq7bY75FiwjG0Iq/w0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=RxduBvSzxStdaU4nKGYWi2u4SE15njyLLdSkgZ2csnVJUmBYV9KoaT5taJ2tHuBBB Emg9k8NMWlqj96wOoHfA4UYfa/gfAyO4q22zuyqCPSgyvUXHLrYyRi/mlLVsqTNy8/ RVD7Kza5cMOQyF+qBKaokV0QqIiql743bZBO7M1iRmQFP0xkSLVyFkgvl4Tb84zH9Q rD1CNdLtwOOohl7oHyP1eHTXMNUmAht0HjHbIWYTYZpwV722eME4CxmOvQ8iKu7zqJ Dur/1zhKMzF0RW35uynMWJ+y+bn2LSXhOwk+G7MTN92BMoURVy5fGLFN01pCvzG+we dxuFBVG2lI//A== From: Mark Brown Date: Thu, 18 Dec 2025 08:10:13 +0000 Subject: [PATCH v23 8/8] selftests/clone3: Test shadow stack support Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251218-clone3-shadow-stack-v23-8-7cb318fbb385@kernel.org> References: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> In-Reply-To: <20251218-clone3-shadow-stack-v23-0-7cb318fbb385@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Andrew Morton , Yury Khrustalev , "H.J. Lu" , Adhemerval Zanella Netto , Wilco Dijkstra , CarlosO'Donell , Florian Weimer , Rich Felker , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=10203; i=broonie@kernel.org; h=from:subject:message-id; bh=aA2zG1Qrocuod6XoXRd+TJqJEQq7bY75FiwjG0Iq/w0=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBpQ7d/RDguygyeDPJuah6EoBC0ucBLFo/rRanAM P1Uk12WdrSJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCaUO3fwAKCRAk1otyXVSH 0B35B/9OqJeccaD8zjHVpLJxPIHQ7z5E0GGq0aUa8nVCxN7OR5YjFyKoUXugrl2FEKW2py46l9l ynQkQ4iG2/hd7R+hxVxfqMTQIG/ucOWd4xVu/LbzyRj2PLcmlD6NaKwsFuNbETWwSVQpxUzxk9+ GGt736DtzBwPO3af6f/fPXWxxBdsJHKKXVHFpzD7GBMvD+X5KAc9RBuq2uvf7wf7QtuHp76yjwn sO1w0PISNd1i2yRs623uikTQcAdBVInwnr2uLwgIqvDri7968ZRuY+oljnUwuOJNJSS8R0uSNPz 1lYEQHkEnCHYCKQDx47AAVjzAuG1gR8tSm/uDiePMuyb3h/m X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Add basic test coverage for specifying the shadow stack for a newly created thread via clone3(), including coverage of the newly extended argument structure. We check that a user specified shadow stack can be provided, and that invalid combinations of parameters are rejected. In order to facilitate testing on systems without userspace shadow stack support we manually enable shadow stacks on startup, this is architecture specific due to the use of an arch_prctl() on x86. Due to interactions with potential userspace locking of features we actually detect support for shadow stacks on the running system by attempting to allocate a shadow stack page during initialisation using map_shadow_stack(), warning if this succeeds when the enable failed. In order to allow testing of user configured shadow stacks on architectures with that feature we need to ensure that we do not return from the function where the clone3() syscall is called in the child process, doing so would trigger a shadow stack underflow. To do this we use inline assembly rather than the standard syscall wrapper to call clone3(). In order to avoid surprises we also use a syscall rather than the libc exit() function., this should be overly cautious. Acked-by: Shuah Khan Tested-by: Rick Edgecombe Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 143 ++++++++++++++++++= +++- tools/testing/selftests/clone3/clone3_selftests.h | 63 ++++++++++ 2 files changed, 205 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selfte= sts/clone3/clone3.c index 932cc64e9ae4..829f0d1268c8 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -3,6 +3,7 @@ /* Based on Christian Brauner's clone3() example */ =20 #define _GNU_SOURCE +#include #include #include #include @@ -11,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -19,8 +21,12 @@ #include =20 #include "kselftest.h" +#include "ksft_shstk.h" #include "clone3_selftests.h" =20 +static bool shadow_stack_supported; +static size_t max_supported_args_size; + enum test_mode { CLONE3_ARGS_NO_TEST, CLONE3_ARGS_ALL_0, @@ -28,6 +34,10 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, + CLONE3_ARGS_SHADOW_STACK, + CLONE3_ARGS_SHADOW_STACK_MISALIGNED, + CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, }; =20 typedef bool (*filter_function)(void); @@ -44,6 +54,44 @@ struct test { filter_function filter; }; =20 + +/* + * We check for shadow stack support by attempting to use + * map_shadow_stack() since features may have been locked by the + * dynamic linker resulting in spurious errors when we attempt to + * enable on startup. We warn if the enable failed. + */ +static void test_shadow_stack_supported(void) +{ + long ret; + + ret =3D syscall(__NR_map_shadow_stack, 0, getpagesize(), 0); + if (ret =3D=3D -1) { + ksft_print_msg("map_shadow_stack() not supported\n"); + } else if ((void *)ret =3D=3D MAP_FAILED) { + ksft_print_msg("Failed to map shadow stack\n"); + } else { + ksft_print_msg("Shadow stack supportd\n"); + shadow_stack_supported =3D true; + + if (!shadow_stack_enabled) + ksft_print_msg("Mapped but did not enable shadow stack\n"); + } +} + +static void *get_shadow_stack_page(unsigned long flags) +{ + unsigned long long page; + + page =3D syscall(__NR_map_shadow_stack, 0, getpagesize(), flags); + if ((void *)page =3D=3D MAP_FAILED) { + ksft_print_msg("map_shadow_stack() failed: %d\n", errno); + return 0; + } + + return (void *)page; +} + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mo= de) { struct __clone_args args =3D { @@ -57,6 +105,7 @@ static int call_clone3(uint64_t flags, size_t size, enum= test_mode test_mode) } args_ext; =20 pid_t pid =3D -1; + void *p; int status; =20 memset(&args_ext, 0, sizeof(args_ext)); @@ -89,6 +138,26 @@ static int call_clone3(uint64_t flags, size_t size, enu= m test_mode test_mode) case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG: args.exit_signal =3D 0x00000000000000f0ULL; break; + case CLONE3_ARGS_SHADOW_STACK: + p =3D get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + p +=3D getpagesize() - sizeof(void *); + args.shstk_token =3D (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_MISALIGNED: + p =3D get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + p +=3D getpagesize() - sizeof(void *) - 1; + args.shstk_token =3D (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY: + p =3D malloc(getpagesize()); + p +=3D getpagesize() - sizeof(void *); + args.shstk_token =3D (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NO_TOKEN: + p =3D get_shadow_stack_page(0); + p +=3D getpagesize() - sizeof(void *); + args.shstk_token =3D (unsigned long long)p; + break; } =20 memcpy(&args_ext.args, &args, sizeof(struct __clone_args)); @@ -102,7 +171,12 @@ static int call_clone3(uint64_t flags, size_t size, en= um test_mode test_mode) =20 if (pid =3D=3D 0) { ksft_print_msg("I am the child, my PID is %d\n", getpid()); - _exit(EXIT_SUCCESS); + /* + * Use a raw syscall to ensure we don't get issues + * with manually specified shadow stack and exit handlers. + */ + syscall(__NR_exit, EXIT_SUCCESS); + ksft_print_msg("CHILD FAILED TO EXIT PID is %d\n", getpid()); } =20 ksft_print_msg("I am the parent (%d). My child's pid is %d\n", @@ -184,6 +258,26 @@ static bool no_timenamespace(void) return true; } =20 +static bool have_shadow_stack(void) +{ + if (shadow_stack_supported) { + ksft_print_msg("Shadow stack supported\n"); + return true; + } + + return false; +} + +static bool no_shadow_stack(void) +{ + if (!shadow_stack_supported) { + ksft_print_msg("Shadow stack not supported\n"); + return true; + } + + return false; +} + static size_t page_size_plus_8(void) { return getpagesize() + 8; @@ -327,6 +421,50 @@ static const struct test tests[] =3D { .expected =3D -EINVAL, .test_mode =3D CLONE3_ARGS_NO_TEST, }, + { + .name =3D "Shadow stack on system with shadow stack", + .size =3D 0, + .expected =3D 0, + .e2big_valid =3D true, + .test_mode =3D CLONE3_ARGS_SHADOW_STACK, + .filter =3D no_shadow_stack, + }, + { + .name =3D "Shadow stack with misaligned address", + .flags =3D CLONE_VM, + .size =3D 0, + .expected =3D -EINVAL, + .e2big_valid =3D true, + .test_mode =3D CLONE3_ARGS_SHADOW_STACK_MISALIGNED, + .filter =3D no_shadow_stack, + }, + { + .name =3D "Shadow stack with normal memory", + .flags =3D CLONE_VM, + .size =3D 0, + .expected =3D -EFAULT, + .e2big_valid =3D true, + .test_mode =3D CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, + .filter =3D no_shadow_stack, + }, + { + .name =3D "Shadow stack with no token", + .flags =3D CLONE_VM, + .size =3D 0, + .expected =3D -EINVAL, + .e2big_valid =3D true, + .test_mode =3D CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + .filter =3D no_shadow_stack, + }, + { + .name =3D "Shadow stack on system without shadow stack", + .flags =3D CLONE_VM, + .size =3D 0, + .expected =3D -EFAULT, + .e2big_valid =3D true, + .test_mode =3D CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, + .filter =3D have_shadow_stack, + }, }; =20 int main(int argc, char *argv[]) @@ -334,9 +472,12 @@ int main(int argc, char *argv[]) size_t size; int i; =20 + enable_shadow_stack(); + ksft_print_header(); ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); + test_shadow_stack_supported(); =20 for (i =3D 0; i < ARRAY_SIZE(tests); i++) test_clone3(&tests[i]); diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/test= ing/selftests/clone3/clone3_selftests.h index a7ab2f1cccda..97d98d07fb78 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -31,12 +31,75 @@ struct __clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; +#ifndef CLONE_ARGS_SIZE_VER2 +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#endif + __aligned_u64 shstk_token; +#ifndef CLONE_ARGS_SIZE_VER3 +#define CLONE_ARGS_SIZE_VER3 96 /* sizeof fourth published struct */ +#endif }; =20 +/* + * For architectures with shadow stack support we need to be + * absolutely sure that the clone3() syscall will be inline and not a + * function call so we open code. + */ +#ifdef __x86_64__ +static __always_inline pid_t sys_clone3(struct __clone_args *args, size_t = size) +{ + register long _num __asm__ ("rax") =3D __NR_clone3; + register long _args __asm__ ("rdi") =3D (long)(args); + register long _size __asm__ ("rsi") =3D (long)(size); + long ret; + + __asm__ volatile ( + "syscall\n" + : "=3Da"(ret) + : "r"(_args), "r"(_size), + "0"(_num) + : "rcx", "r11", "memory", "cc" + ); + + if (ret < 0) { + errno =3D -ret; + return -1; + } + + return ret; +} +#elif defined(__aarch64__) +static __always_inline pid_t sys_clone3(struct __clone_args *args, size_t = size) +{ + register long _num __asm__ ("x8") =3D __NR_clone3; + register long _args __asm__ ("x0") =3D (long)(args); + register long _size __asm__ ("x1") =3D (long)(size); + register long arg2 __asm__ ("x2") =3D 0; + register long arg3 __asm__ ("x3") =3D 0; + register long arg4 __asm__ ("x4") =3D 0; + + __asm__ volatile ( + "svc #0\n" + : "=3Dr"(_args) + : "r"(_args), "r"(_size), + "r"(_num), "r"(arg2), + "r"(arg3), "r"(arg4) + : "memory", "cc" + ); + + if ((int)_args < 0) { + errno =3D -((int)_args); + return -1; + } + + return _args; +} +#else static pid_t sys_clone3(struct __clone_args *args, size_t size) { return syscall(__NR_clone3, args, size); } +#endif =20 static inline void test_clone3_supported(void) { --=20 2.47.3