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Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang Cc: Yu-cheng Yu Subject: [PATCH v24 27/30] x86/cet/shstk: Add arch_prctl functions for shadow stack Date: Thu, 1 Apr 2021 15:11:01 -0700 Message-Id: <20210401221104.31584-28-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210401221104.31584-1-yu-cheng.yu@intel.com> References: <20210401221104.31584-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf19; identity=mailfrom; envelope-from=""; helo=mga03.intel.com; client-ip=134.134.136.65 X-HE-DKIM-Result: none/none X-HE-Tag: 1617315089-383457 X-Stat-Signature: r166cf4hyhzg76j753wt49arg347w9ss X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 85576E00010A Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf13; identity=mailfrom; envelope-from=""; helo=smtprelay.hostedemail.com; client-ip=216.40.44.177 X-HE-DKIM-Result: none/none X-HE-Tag: 1617315091-798559 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: arch_prctl(ARCH_X86_CET_STATUS, u64 *args) Get CET feature status. The parameter 'args' is a pointer to a user buffer. The kernel returns the following information: *args = shadow stack/IBT status *(args + 1) = shadow stack base address *(args + 2) = shadow stack size 32-bit binaries use the same interface, but only lower 32-bits of each item. arch_prctl(ARCH_X86_CET_DISABLE, unsigned int features) Disable CET features specified in 'features'. Return -EPERM if CET is locked. arch_prctl(ARCH_X86_CET_LOCK) Lock in CET features. Also change do_arch_prctl_common()'s parameter 'cpuid_enabled' to 'arg2', as it is now also passed to prctl_cet(). Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook --- v24: - Update #ifdef placement relating to shadow stack and ibt split. - Update function names. arch/x86/include/asm/cet.h | 7 ++++ arch/x86/include/uapi/asm/prctl.h | 4 +++ arch/x86/kernel/Makefile | 1 + arch/x86/kernel/cet_prctl.c | 60 +++++++++++++++++++++++++++++++ arch/x86/kernel/process.c | 6 ++-- 5 files changed, 75 insertions(+), 3 deletions(-) create mode 100644 arch/x86/kernel/cet_prctl.c diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index 5e66919bd2fe..26124820d46f 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -14,6 +14,7 @@ struct sc_ext; struct cet_status { unsigned long shstk_base; unsigned long shstk_size; + unsigned int locked:1; }; #ifdef CONFIG_X86_SHADOW_STACK @@ -40,6 +41,12 @@ static inline int shstk_check_rstor_token(bool ia32, unsigned long token_addr, unsigned long *new_ssp) { return 0; } #endif +#ifdef CONFIG_X86_CET +int prctl_cet(int option, u64 arg2); +#else +static inline int prctl_cet(int option, u64 arg2) { return -EINVAL; } +#endif + #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_CET_H */ diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 5a6aac9fa41f..9245bf629120 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -14,4 +14,8 @@ #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 +#define ARCH_X86_CET_STATUS 0x3001 +#define ARCH_X86_CET_DISABLE 0x3002 +#define ARCH_X86_CET_LOCK 0x3003 + #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 0f99b093f350..868cb3aac618 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -151,6 +151,7 @@ obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev-es.o obj-$(CONFIG_X86_SHADOW_STACK) += shstk.o +obj-$(CONFIG_X86_CET) += cet_prctl.o ### # 64 bit specific files diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c new file mode 100644 index 000000000000..5f0054177d2a --- /dev/null +++ b/arch/x86/kernel/cet_prctl.c @@ -0,0 +1,60 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* See Documentation/x86/intel_cet.rst. */ + +static int cet_copy_status_to_user(struct cet_status *cet, u64 __user *ubuf) +{ + u64 buf[3] = {}; + + if (cet->shstk_size) { + buf[0] |= GNU_PROPERTY_X86_FEATURE_1_SHSTK; + buf[1] = cet->shstk_base; + buf[2] = cet->shstk_size; + } + + return copy_to_user(ubuf, buf, sizeof(buf)); +} + +int prctl_cet(int option, u64 arg2) +{ + struct cet_status *cet; + + if (!cpu_feature_enabled(X86_FEATURE_CET)) + return -ENOTSUPP; + + cet = ¤t->thread.cet; + + if (option == ARCH_X86_CET_STATUS) + return cet_copy_status_to_user(cet, (u64 __user *)arg2); + + switch (option) { + case ARCH_X86_CET_DISABLE: + if (cet->locked) + return -EPERM; + + if (arg2 & ~GNU_PROPERTY_X86_FEATURE_1_VALID) + return -EINVAL; + if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK) + shstk_disable(); + return 0; + + case ARCH_X86_CET_LOCK: + if (arg2) + return -EINVAL; + cet->locked = 1; + return 0; + + default: + return -ENOSYS; + } +} diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index fa01e8679d01..315668a334fd 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -980,14 +980,14 @@ unsigned long get_wchan(struct task_struct *p) } long do_arch_prctl_common(struct task_struct *task, int option, - unsigned long cpuid_enabled) + unsigned long arg2) { switch (option) { case ARCH_GET_CPUID: return get_cpuid_mode(); case ARCH_SET_CPUID: - return set_cpuid_mode(task, cpuid_enabled); + return set_cpuid_mode(task, arg2); } - return -EINVAL; + return prctl_cet(option, arg2); }