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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 Cc: Yu-cheng Yu Subject: [PATCH v12 25/26] x86/cet/shstk: Add arch_prctl functions for shadow stack Date: Fri, 18 Sep 2020 12:21:23 -0700 Message-Id: <20200918192125.25473-26-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200918192125.25473-1-yu-cheng.yu@intel.com> References: <20200918192125.25473-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 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 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 --- v12: - Remove ARCH_X86_CET_MMAP_SHSTK. v11: - Check input for invalid features. - Fix prctl_cet() return values. - Change ARCH_X86_CET_ALLOC_SHSTK to ARCH_X86_CET_MMAP_SHSTK to take MAP_32BIT, MAP_POPULATE as inputs. v10: - Verify CET is enabled before handling arch_prctl. - Change input parameters from unsigned long to u64, to make it clear they are 64-bit. arch/x86/include/asm/cet.h | 3 ++ arch/x86/include/uapi/asm/prctl.h | 4 ++ arch/x86/kernel/Makefile | 2 +- arch/x86/kernel/cet_prctl.c | 68 +++++++++++++++++++++++++ arch/x86/kernel/process.c | 6 +-- tools/arch/x86/include/uapi/asm/prctl.h | 4 ++ 6 files changed, 83 insertions(+), 4 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 7a416c8af791..1ebe82416196 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -14,9 +14,11 @@ struct sc_ext; struct cet_status { unsigned long shstk_base; unsigned long shstk_size; + unsigned int locked:1; }; #ifdef CONFIG_X86_INTEL_CET +int prctl_cet(int option, u64 arg2); int cet_setup_shstk(void); int cet_setup_thread_shstk(struct task_struct *p, unsigned long clone_flags); void cet_disable_shstk(void); @@ -25,6 +27,7 @@ int cet_verify_rstor_token(bool ia32, unsigned long ssp, unsigned long *new_ssp) void cet_restore_signal(struct sc_ext *sc); int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc); #else +static inline int prctl_cet(int option, u64 arg2) { return -EINVAL; } static inline int cet_setup_thread_shstk(struct task_struct *p, unsigned long clone_flags) { return 0; } static inline void cet_disable_shstk(void) {} 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 76f27f518266..97556e4204d6 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -145,7 +145,7 @@ obj-$(CONFIG_UNWINDER_ORC) += unwind_orc.o obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o -obj-$(CONFIG_X86_INTEL_CET) += cet.o +obj-$(CONFIG_X86_INTEL_CET) += cet.o 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..3e1d049e65c3 --- /dev/null +++ b/arch/x86/kernel/cet_prctl.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* See Documentation/x86/intel_cet.rst. */ + +static int copy_status_to_user(struct cet_status *cet, u64 arg2) +{ + u64 buf[3] = {0, 0, 0}; + + if (cet->shstk_size) { + buf[0] |= GNU_PROPERTY_X86_FEATURE_1_SHSTK; + buf[1] = (u64)cet->shstk_base; + buf[2] = (u64)cet->shstk_size; + } + + return copy_to_user((u64 __user *)arg2, buf, sizeof(buf)); +} + +int prctl_cet(int option, u64 arg2) +{ + struct cet_status *cet; + unsigned int features; + + /* + * GLIBC's ENOTSUPP == EOPNOTSUPP == 95, and it does not recognize + * the kernel's ENOTSUPP (524). So return EOPNOTSUPP here. + */ + if (!IS_ENABLED(CONFIG_X86_INTEL_CET)) + return -EOPNOTSUPP; + + cet = ¤t->thread.cet; + + if (option == ARCH_X86_CET_STATUS) + return copy_status_to_user(cet, arg2); + + if (!static_cpu_has(X86_FEATURE_SHSTK)) + return -EOPNOTSUPP; + + switch (option) { + case ARCH_X86_CET_DISABLE: + if (cet->locked) + return -EPERM; + + features = (unsigned int)arg2; + + if (features & GNU_PROPERTY_X86_FEATURE_1_INVAL) + return -EINVAL; + if (features & GNU_PROPERTY_X86_FEATURE_1_SHSTK) + cet_disable_shstk(); + return 0; + + case ARCH_X86_CET_LOCK: + cet->locked = 1; + return 0; + + default: + return -ENOSYS; + } +} diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 1d292d0cfe8a..bd773036ed6b 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -976,14 +976,14 @@ 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); } diff --git a/tools/arch/x86/include/uapi/asm/prctl.h b/tools/arch/x86/include/uapi/asm/prctl.h index 5a6aac9fa41f..9245bf629120 100644 --- a/tools/arch/x86/include/uapi/asm/prctl.h +++ b/tools/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 */