From: Dave Martin <Dave.Martin@arm.com> To: linux-arm-kernel@lists.infradead.org Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>, Marc Zyngier <Marc.Zyngier@arm.com>, Alan Hayward <alan.hayward@arm.com>, Christoffer Dall <christoffer.dall@linaro.org>, linux-arch@vger.kernel.org, libc-alpha@sourceware.org, Florian Weimer <fweimer@redhat.com>, Joseph Myers <joseph@codesourcery.com>, Szabolcs Nagy <szabolcs.nagy@arm.com>, Torvald Riegel <triegel@redhat.com>, gdb@sourceware.org, Yao Qi <qiyaoltc@gmail.com> Subject: [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control Date: Thu, 12 Jan 2017 11:26:06 +0000 [thread overview] Message-ID: <1484220369-23970-8-git-send-email-Dave.Martin@arm.com> (raw) In-Reply-To: <1484220369-23970-1-git-send-email-Dave.Martin@arm.com> Currently the vector length is inherited across both fork() and exec(). Inheritance across fork() is desirable both for creating a copy of a process (traditional fork) or creating a thread (where we want all threads to share the same VL by default). Inheritance across exec() is less desirable, because of the ABI impact of large vector lengths on the size of the signal frame -- when running a new binary, there is no guarantee that the new binary is compatible with these ABI changes. This flag makes the vector length non-inherited by default. Instead, the vector length is reset to a system default value, unless the THREAD_VL_INHERIT flag has been set for the thread. THREAD_VL_INHERIT is currently sticky: i.e., if set, it gets inherited too. This behaviour may be refined in future if it is not flexible enough. Signed-off-by: Dave Martin <Dave.Martin@arm.com> --- arch/arm64/include/asm/processor.h | 7 +++++++ arch/arm64/kernel/fpsimd.c | 33 ++++++++++++++++++++++++++------- include/uapi/linux/prctl.h | 5 +++++ 3 files changed, 38 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 96eada9..45ef11d 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -27,6 +27,7 @@ #ifdef __KERNEL__ +#include <linux/prctl.h> #include <linux/string.h> #include <asm/alternative.h> @@ -84,11 +85,17 @@ struct thread_struct { #endif struct fpsimd_state fpsimd_state; u16 sve_vl; /* SVE vector length */ + u16 sve_flags; /* SVE related flags */ unsigned long fault_address; /* fault info */ unsigned long fault_code; /* ESR_EL1 value */ struct debug_info debug; /* debugging */ }; +/* Flags for sve_flags (intentionally defined to match the prctl flags) */ + +/* Inherit sve_vl and sve_flags across execve(): */ +#define THREAD_VL_INHERIT PR_SVE_SET_VL_INHERIT + #ifdef CONFIG_COMPAT #define task_user_tls(t) \ ({ \ diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 32caca3..f010a1c 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -292,12 +292,15 @@ void fpsimd_flush_thread(void) * User tasks must have a valid vector length set, but tasks * forked early (e.g., init) may not have one yet. * By now, we will know what the hardware supports, so set the - * task vector length if it doesn't have one: + * task vector length to default if doesn't have one, or if + * the thread wasn't configured to inherit SVE configuration: */ - if (!current->thread.sve_vl) { + if (!current->thread.sve_vl || + !(current->thread.sve_flags & THREAD_VL_INHERIT)) { BUG_ON(!sve_vl_valid(sve_max_vl)); current->thread.sve_vl = sve_max_vl; + current->thread.sve_flags = 0; } } @@ -506,10 +509,10 @@ int sve_set_vector_length(struct task_struct *task, */ if (!(flags & PR_SVE_SET_VL_THREAD) && get_nr_threads(task) != 1) return -EINVAL; - flags &= ~(unsigned long)PR_SVE_SET_VL_THREAD; - if (flags) - return -EINVAL; /* No other flags defined yet */ + + if (flags & ~(unsigned long)PR_SVE_SET_VL_INHERIT) + return -EINVAL; if (!sve_vl_valid(vl)) return -EINVAL; @@ -542,11 +545,27 @@ int sve_set_vector_length(struct task_struct *task, task->thread.sve_vl = vl; + /* The THREAD_VL_* flag encodings match the relevant PR_* flags: */ + task->thread.sve_flags = flags; + fpsimd_flush_task_state(task); return 0; } +/* + * Encode the current vector length and flags for return. + * This is only required for prctl(): ptrace has separate fields + */ +static int sve_prctl_status(struct task_struct const *task) +{ + int ret = task->thread.sve_vl; + + ret |= task->thread.sve_vl << 16; + + return ret; +} + /* PR_SVE_SET_VL */ int sve_set_task_vl(struct task_struct *task, unsigned long vector_length, unsigned long flags) @@ -565,7 +584,7 @@ int sve_set_task_vl(struct task_struct *task, if (ret) return ret; - return task->thread.sve_vl; + return sve_prctl_status(task); } /* PR_SVE_GET_VL */ @@ -574,7 +593,7 @@ int sve_get_task_vl(struct task_struct *task) if (!(elf_hwcap & HWCAP_SVE)) return -EINVAL; - return task->thread.sve_vl; + return sve_prctl_status(task); } #endif /* CONFIG_ARM64_SVE */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index c55530b..cff6214 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -200,6 +200,11 @@ struct prctl_mm_map { /* arm64 Scalable Vector Extension controls */ #define PR_SVE_SET_VL 48 /* set task vector length */ # define PR_SVE_SET_VL_THREAD (1 << 1) /* set just this thread */ +# define PR_SVE_SET_VL_INHERIT (1 << 2) /* inherit across exec */ #define PR_SVE_GET_VL 49 /* get task vector length */ +/* Decode helpers for the return value from PR_SVE_GET_VL: */ +# define PR_SVE_GET_VL_LEN(ret) ((ret) & 0x3fff) /* vector length */ +# define PR_SVE_GET_VL_INHERIT (PR_SVE_SET_VL_INHERIT << 16) +/* For conveinence, PR_SVE_SET_VL returns the result in the same encoding */ #endif /* _LINUX_PRCTL_H */ -- 2.1.4
WARNING: multiple messages have this Message-ID (diff)
From: Dave.Martin@arm.com (Dave Martin) To: linux-arm-kernel@lists.infradead.org Subject: [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control Date: Thu, 12 Jan 2017 11:26:06 +0000 [thread overview] Message-ID: <1484220369-23970-8-git-send-email-Dave.Martin@arm.com> (raw) In-Reply-To: <1484220369-23970-1-git-send-email-Dave.Martin@arm.com> Currently the vector length is inherited across both fork() and exec(). Inheritance across fork() is desirable both for creating a copy of a process (traditional fork) or creating a thread (where we want all threads to share the same VL by default). Inheritance across exec() is less desirable, because of the ABI impact of large vector lengths on the size of the signal frame -- when running a new binary, there is no guarantee that the new binary is compatible with these ABI changes. This flag makes the vector length non-inherited by default. Instead, the vector length is reset to a system default value, unless the THREAD_VL_INHERIT flag has been set for the thread. THREAD_VL_INHERIT is currently sticky: i.e., if set, it gets inherited too. This behaviour may be refined in future if it is not flexible enough. Signed-off-by: Dave Martin <Dave.Martin@arm.com> --- arch/arm64/include/asm/processor.h | 7 +++++++ arch/arm64/kernel/fpsimd.c | 33 ++++++++++++++++++++++++++------- include/uapi/linux/prctl.h | 5 +++++ 3 files changed, 38 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 96eada9..45ef11d 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -27,6 +27,7 @@ #ifdef __KERNEL__ +#include <linux/prctl.h> #include <linux/string.h> #include <asm/alternative.h> @@ -84,11 +85,17 @@ struct thread_struct { #endif struct fpsimd_state fpsimd_state; u16 sve_vl; /* SVE vector length */ + u16 sve_flags; /* SVE related flags */ unsigned long fault_address; /* fault info */ unsigned long fault_code; /* ESR_EL1 value */ struct debug_info debug; /* debugging */ }; +/* Flags for sve_flags (intentionally defined to match the prctl flags) */ + +/* Inherit sve_vl and sve_flags across execve(): */ +#define THREAD_VL_INHERIT PR_SVE_SET_VL_INHERIT + #ifdef CONFIG_COMPAT #define task_user_tls(t) \ ({ \ diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 32caca3..f010a1c 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -292,12 +292,15 @@ void fpsimd_flush_thread(void) * User tasks must have a valid vector length set, but tasks * forked early (e.g., init) may not have one yet. * By now, we will know what the hardware supports, so set the - * task vector length if it doesn't have one: + * task vector length to default if doesn't have one, or if + * the thread wasn't configured to inherit SVE configuration: */ - if (!current->thread.sve_vl) { + if (!current->thread.sve_vl || + !(current->thread.sve_flags & THREAD_VL_INHERIT)) { BUG_ON(!sve_vl_valid(sve_max_vl)); current->thread.sve_vl = sve_max_vl; + current->thread.sve_flags = 0; } } @@ -506,10 +509,10 @@ int sve_set_vector_length(struct task_struct *task, */ if (!(flags & PR_SVE_SET_VL_THREAD) && get_nr_threads(task) != 1) return -EINVAL; - flags &= ~(unsigned long)PR_SVE_SET_VL_THREAD; - if (flags) - return -EINVAL; /* No other flags defined yet */ + + if (flags & ~(unsigned long)PR_SVE_SET_VL_INHERIT) + return -EINVAL; if (!sve_vl_valid(vl)) return -EINVAL; @@ -542,11 +545,27 @@ int sve_set_vector_length(struct task_struct *task, task->thread.sve_vl = vl; + /* The THREAD_VL_* flag encodings match the relevant PR_* flags: */ + task->thread.sve_flags = flags; + fpsimd_flush_task_state(task); return 0; } +/* + * Encode the current vector length and flags for return. + * This is only required for prctl(): ptrace has separate fields + */ +static int sve_prctl_status(struct task_struct const *task) +{ + int ret = task->thread.sve_vl; + + ret |= task->thread.sve_vl << 16; + + return ret; +} + /* PR_SVE_SET_VL */ int sve_set_task_vl(struct task_struct *task, unsigned long vector_length, unsigned long flags) @@ -565,7 +584,7 @@ int sve_set_task_vl(struct task_struct *task, if (ret) return ret; - return task->thread.sve_vl; + return sve_prctl_status(task); } /* PR_SVE_GET_VL */ @@ -574,7 +593,7 @@ int sve_get_task_vl(struct task_struct *task) if (!(elf_hwcap & HWCAP_SVE)) return -EINVAL; - return task->thread.sve_vl; + return sve_prctl_status(task); } #endif /* CONFIG_ARM64_SVE */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index c55530b..cff6214 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -200,6 +200,11 @@ struct prctl_mm_map { /* arm64 Scalable Vector Extension controls */ #define PR_SVE_SET_VL 48 /* set task vector length */ # define PR_SVE_SET_VL_THREAD (1 << 1) /* set just this thread */ +# define PR_SVE_SET_VL_INHERIT (1 << 2) /* inherit across exec */ #define PR_SVE_GET_VL 49 /* get task vector length */ +/* Decode helpers for the return value from PR_SVE_GET_VL: */ +# define PR_SVE_GET_VL_LEN(ret) ((ret) & 0x3fff) /* vector length */ +# define PR_SVE_GET_VL_INHERIT (PR_SVE_SET_VL_INHERIT << 16) +/* For conveinence, PR_SVE_SET_VL returns the result in the same encoding */ #endif /* _LINUX_PRCTL_H */ -- 2.1.4
next prev parent reply other threads:[~2017-01-12 11:27 UTC|newest] Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-01-12 11:25 [RFC PATCH 00/10] arm64/sve: Add userspace vector length control API Dave Martin 2017-01-12 11:25 ` Dave Martin 2017-01-12 11:25 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 01/10] prctl: Add skeleton for PR_SVE_{SET,GET}_VL controls Dave Martin 2017-01-12 11:26 ` [RFC PATCH 01/10] prctl: Add skeleton for PR_SVE_{SET, GET}_VL controls Dave Martin 2017-01-12 11:26 ` [RFC PATCH 02/10] arm64/sve: Track vector length for each task Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 03/10] arm64/sve: Set CPU vector length to match current task Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 04/10] arm64/sve: Factor out clearing of tasks' SVE regs Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 05/10] arm64/sve: Wire up vector length control prctl() calls Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 06/10] arm64/sve: Disallow VL setting for individual threads by default Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-16 11:34 ` Yao Qi 2017-01-16 11:34 ` Yao Qi 2017-01-16 12:23 ` Dave Martin 2017-01-16 12:23 ` Dave Martin 2017-01-12 11:26 ` Dave Martin [this message] 2017-01-12 11:26 ` [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control Dave Martin 2017-01-16 12:27 ` Yao Qi 2017-01-16 12:27 ` Yao Qi 2017-01-16 13:34 ` Dave Martin 2017-01-16 13:34 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 08/10] arm64/sve: ptrace: Wire up vector length control and reporting Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-16 12:20 ` Yao Qi 2017-01-16 12:20 ` Yao Qi 2017-01-16 13:32 ` Dave Martin 2017-01-16 13:32 ` Dave Martin 2017-01-16 15:11 ` Yao Qi 2017-01-16 15:11 ` Yao Qi 2017-01-16 15:47 ` Pedro Alves 2017-01-16 15:47 ` Pedro Alves 2017-01-16 16:31 ` Dave Martin 2017-01-16 16:31 ` Dave Martin 2017-01-17 10:03 ` Dave Martin 2017-01-17 10:03 ` Dave Martin 2017-01-17 13:31 ` Alan Hayward 2017-01-17 13:31 ` Alan Hayward 2017-01-19 17:11 ` Dave Martin 2017-01-19 17:11 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 09/10] arm64/sve: Enable default vector length control via procfs Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` [RFC PATCH 10/10] Revert "arm64/sve: Limit vector length to 512 bits by default" Dave Martin 2017-01-12 11:26 ` Dave Martin 2017-01-12 11:26 ` Dave Martin
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