From 7582e22038a266444eb87bc07c372592ad647439 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Tue, 31 Oct 2017 15:51:08 +0000 Subject: arm64/sve: Backend logic for setting the vector length MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch implements the core logic for changing a task's vector length on request from userspace. This will be used by the ptrace and prctl frontends that are implemented in later patches. The SVE architecture permits, but does not require, implementations to support vector lengths that are not a power of two. To handle this, logic is added to check a requested vector length against a possibly sparse bitmap of available vector lengths at runtime, so that the best supported value can be chosen. Signed-off-by: Dave Martin Reviewed-by: Catalin Marinas Cc: Alex Bennée Signed-off-by: Will Deacon --- include/uapi/linux/prctl.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/uapi/linux/prctl.h') diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index a8d0759a9e40..1b64901ca6b3 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -197,4 +197,9 @@ struct prctl_mm_map { # define PR_CAP_AMBIENT_LOWER 3 # define PR_CAP_AMBIENT_CLEAR_ALL 4 +/* arm64 Scalable Vector Extension controls */ +# define PR_SVE_SET_VL_ONEXEC (1 << 18) /* defer effect until exec */ +# define PR_SVE_VL_LEN_MASK 0xffff +# define PR_SVE_VL_INHERIT (1 << 17) /* inherit across exec */ + #endif /* _LINUX_PRCTL_H */ -- cgit v1.2.3 From 2d2123bc7c7f843aa9db87720de159a049839862 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Tue, 31 Oct 2017 15:51:14 +0000 Subject: arm64/sve: Add prctl controls for userspace vector length management MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch adds two arm64-specific prctls, to permit userspace to control its vector length: * PR_SVE_SET_VL: set the thread's SVE vector length and vector length inheritance mode. * PR_SVE_GET_VL: get the same information. Although these prctls resemble instruction set features in the SVE architecture, they provide additional control: the vector length inheritance mode is Linux-specific and nothing to do with the architecture, and the architecture does not permit EL0 to set its own vector length directly. Both can be used in portable tools without requiring the use of SVE instructions. Signed-off-by: Dave Martin Reviewed-by: Catalin Marinas Cc: Alex Bennée [will: Fixed up prctl constants to avoid clash with PDEATHSIG] Signed-off-by: Will Deacon --- arch/arm64/include/asm/fpsimd.h | 14 +++++++++++ arch/arm64/include/asm/processor.h | 4 +++ arch/arm64/kernel/fpsimd.c | 50 ++++++++++++++++++++++++++++++++++++++ include/uapi/linux/prctl.h | 4 +++ kernel/sys.c | 12 +++++++++ 5 files changed, 84 insertions(+) (limited to 'include/uapi/linux/prctl.h') diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index d754e5a6949c..b868412c815c 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -17,6 +17,7 @@ #define __ASM_FP_H #include +#include #ifndef __ASSEMBLY__ @@ -98,6 +99,9 @@ extern void sve_sync_from_fpsimd_zeropad(struct task_struct *task); extern int sve_set_vector_length(struct task_struct *task, unsigned long vl, unsigned long flags); +extern int sve_set_current_vl(unsigned long arg); +extern int sve_get_current_vl(void); + /* * Probing and setup functions. * Calls to these functions must be serialised with one another. @@ -114,6 +118,16 @@ static inline void fpsimd_release_task(struct task_struct *task) { } static inline void sve_sync_to_fpsimd(struct task_struct *task) { } static inline void sve_sync_from_fpsimd_zeropad(struct task_struct *task) { } +static inline int sve_set_current_vl(unsigned long arg) +{ + return -EINVAL; +} + +static inline int sve_get_current_vl(void) +{ + return -EINVAL; +} + static inline void sve_init_vq_map(void) { } static inline void sve_update_vq_map(void) { } static inline int sve_verify_vq_map(void) { return 0; } diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index c6fddb005dc2..023cacb946c3 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -217,5 +217,9 @@ static inline void spin_lock_prefetch(const void *ptr) int cpu_enable_pan(void *__unused); int cpu_enable_cache_maint_trap(void *__unused); +/* Userspace interface for PR_SVE_{SET,GET}_VL prctl()s: */ +#define SVE_SET_VL(arg) sve_set_current_vl(arg) +#define SVE_GET_VL() sve_get_current_vl() + #endif /* __ASSEMBLY__ */ #endif /* __ASM_PROCESSOR_H */ diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index b82d44693b9d..fd3cfdd7f9be 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include #include @@ -558,6 +559,55 @@ out: return 0; } +/* + * Encode the current vector length and flags for return. + * This is only required for prctl(): ptrace has separate fields + * + * flags are as for sve_set_vector_length(). + */ +static int sve_prctl_status(unsigned long flags) +{ + int ret; + + if (flags & PR_SVE_SET_VL_ONEXEC) + ret = current->thread.sve_vl_onexec; + else + ret = current->thread.sve_vl; + + if (test_thread_flag(TIF_SVE_VL_INHERIT)) + ret |= PR_SVE_VL_INHERIT; + + return ret; +} + +/* PR_SVE_SET_VL */ +int sve_set_current_vl(unsigned long arg) +{ + unsigned long vl, flags; + int ret; + + vl = arg & PR_SVE_VL_LEN_MASK; + flags = arg & ~vl; + + if (!system_supports_sve()) + return -EINVAL; + + ret = sve_set_vector_length(current, vl, flags); + if (ret) + return ret; + + return sve_prctl_status(flags); +} + +/* PR_SVE_GET_VL */ +int sve_get_current_vl(void) +{ + if (!system_supports_sve()) + return -EINVAL; + + return sve_prctl_status(0); +} + /* * Bitmap for temporary storage of the per-CPU set of supported vector lengths * during secondary boot. diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 1b64901ca6b3..f60db5db6e8e 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -198,7 +198,11 @@ struct prctl_mm_map { # define PR_CAP_AMBIENT_CLEAR_ALL 4 /* arm64 Scalable Vector Extension controls */ +/* Flag values must be kept in sync with ptrace NT_ARM_SVE interface */ +#define PR_SVE_SET_VL 50 /* set task vector length */ # define PR_SVE_SET_VL_ONEXEC (1 << 18) /* defer effect until exec */ +#define PR_SVE_GET_VL 51 /* get task vector length */ +/* Bits common to PR_SVE_SET_VL and PR_SVE_GET_VL */ # define PR_SVE_VL_LEN_MASK 0xffff # define PR_SVE_VL_INHERIT (1 << 17) /* inherit across exec */ diff --git a/kernel/sys.c b/kernel/sys.c index 9aebc2935013..c541916b38c6 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -110,6 +110,12 @@ #ifndef SET_FP_MODE # define SET_FP_MODE(a,b) (-EINVAL) #endif +#ifndef SVE_SET_VL +# define SVE_SET_VL(a) (-EINVAL) +#endif +#ifndef SVE_GET_VL +# define SVE_GET_VL() (-EINVAL) +#endif /* * this is where the system-wide overflow UID and GID are defined, for @@ -2385,6 +2391,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_GET_FP_MODE: error = GET_FP_MODE(me); break; + case PR_SVE_SET_VL: + error = SVE_SET_VL(arg2); + break; + case PR_SVE_GET_VL: + error = SVE_GET_VL(); + break; default: error = -EINVAL; break; -- cgit v1.2.3