Subject: [PATCH v2 19/28] arm64/sve: ptrace and ELF coredump support

From: [email-masked] (Alex Bennée)
Date: Thu, 14 Sep 2017 13:57:08 +0100

Dave Martin <[email-masked]> writes:

> This patch defines and implements a new regset NT_ARM_SVE, which
> describes a thread's SVE register state.  This allows a debugger to
> manipulate the SVE state, as well as being included in ELF
> coredumps for post-mortem debugging.
>
> Because the regset size and layout are dependent on the thread's
> current vector length, it is not possible to define a C struct to
> describe the regset contents as is done for existing regsets.
> Instead, and for the same reasons, NT_ARM_SVE is based on the
> freeform variable-layout approach used for the SVE signal frame.
>
> Additionally, to reduce debug overhead when debugging threads that
> might or might not have live SVE register state, NT_ARM_SVE may be
> presented in one of two different formats: the old struct
> user_fpsimd_state format is embedded for describing the state of a
> thread with no live SVE state, whereas a new variable-layout
> structure is embedded for describing live SVE state.  This avoids a
> debugger needing to poll NT_PRFPREG in addition to NT_ARM_SVE, and
> allows existing userspace code to handle the non-SVE case without
> too much modification.
>
> For this to work, NT_ARM_SVE is defined with a fixed-format header
> of type struct user_sve_header, which the recipient can use to
> figure out the content, size and layout of the reset of the regset.
> Accessor macros are defined to allow the vector-length-dependent
> parts of the regset to be manipulated.
>
> Signed-off-by: Alan Hayward <[email-masked]>
> Signed-off-by: Dave Martin <[email-masked]>
> Cc: Alex Benn?e <[email-masked]>
>
> ---
>
> Changes since v1
> ----------------
>
> Other changes related to Alex Benn?e's comments:
>
> * Migrate to SVE_VQ_BYTES instead of magic numbers.
>
> Requested by Alex Benn?e:
>
> * Thin out BUG_ON()s:
> Redundant BUG_ON()s and ones that just check invariants are removed.
> Important sanity-checks are migrated to WARN_ON()s, with some
> minimal best-effort patch-up code.
>
> Other:
>
> * [ABI fix] Bail out with -EIO if attempting to set the
> SVE regs for an unsupported VL, instead of misparsing the regset data.
>
> * Replace some in-kernel open-coded arithmetic with ALIGN()/
> DIV_ROUND_UP().
> ---
>  arch/arm64/include/asm/fpsimd.h      |  13 +-
>  arch/arm64/include/uapi/asm/ptrace.h | 135 ++++++++++++++++++
>  arch/arm64/kernel/fpsimd.c           |  40 +++++-
>  arch/arm64/kernel/ptrace.c           | 270 +++++++++++++++++++++++++++++++++--
>  include/uapi/linux/elf.h             |   1 +
>  5 files changed, 449 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
> index 6c22624..2723cca 100644
> --- a/arch/arm64/include/asm/fpsimd.h
> +++ b/arch/arm64/include/asm/fpsimd.h
> @@ -38,13 +38,16 @@ struct fpsimd_state {
>  			__uint128_t vregs[32];
>  			u32 fpsr;
>  			u32 fpcr;
> +			/*
> +			 * For ptrace compatibility, pad to next 128-bit
> +			 * boundary here if extending this struct.
> +			 */
>  		};
>  	};
>  	/* the id of the last cpu to have restored this state */
>  	unsigned int cpu;
>  };
>
> -
>  #if defined(__KERNEL__) && defined(CONFIG_COMPAT)
>  /* Masks for extracting the FPSR and FPCR from the FPSCR */
>  #define VFP_FPSCR_STAT_MASK	0xf800009f
> @@ -89,6 +92,10 @@ extern void sve_alloc(struct task_struct *task);
>  extern void fpsimd_release_thread(struct task_struct *task);
>  extern void fpsimd_dup_sve(struct task_struct *dst,
>  			   struct task_struct const *src);
> +extern void fpsimd_sync_to_sve(struct task_struct *task);
> +extern void sve_sync_to_fpsimd(struct task_struct *task);
> +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);
>
> @@ -103,6 +110,10 @@ static void __maybe_unused sve_alloc(struct task_struct *task) { }
>  static void __maybe_unused fpsimd_release_thread(struct task_struct *task) { }
>  static void __maybe_unused fpsimd_dup_sve(struct task_struct *dst,
>  					  struct task_struct const *src) { }
> +static void __maybe_unused sve_sync_to_fpsimd(struct task_struct *task) { }
> +static void __maybe_unused sve_sync_from_fpsimd_zeropad(
> +	struct task_struct *task) { }
> +
>  static void __maybe_unused sve_init_vq_map(void) { }
>  static void __maybe_unused sve_update_vq_map(void) { }
>  static int __maybe_unused sve_verify_vq_map(void) { return 0; }
> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
> index d1ff83d..1915ab0 100644
> --- a/arch/arm64/include/uapi/asm/ptrace.h
> +++ b/arch/arm64/include/uapi/asm/ptrace.h
> @@ -22,6 +22,7 @@
>  #include <linux/types.h>
>
>  #include <asm/hwcap.h>
> +#include <asm/sigcontext.h>
>
>
>  /*
> @@ -63,6 +64,8 @@
>
>  #ifndef __ASSEMBLY__
>
> +#include <linux/prctl.h>
> +
>  /*
>   * User structures for general purpose, floating point and debug registers.
>   */
> @@ -90,6 +93,138 @@ struct user_hwdebug_state {
>  	}		dbg_regs[16];
>  };
>
> +/* SVE/FP/SIMD state (NT_ARM_SVE) */
> +
> +struct user_sve_header {
> +	__u32 size; /* total meaningful regset content in bytes */
> +	__u32 max_size; /* maxmium possible size for this thread */
> +	__u16 vl; /* current vector length */
> +	__u16 max_vl; /* maximum possible vector length */
> +	__u16 flags;
> +	__u16 __reserved;
> +};
> +
> +/* Definitions for user_sve_header.flags: */
> +#define SVE_PT_REGS_MASK		(1 << 0)
> +
> +/* Flags: must be kept in sync with prctl interface in
> <linux/ptrace.h> */

Which flags? We base some on PR_foo flags but we seem to shift them
anyway so where is the requirement for them to match from?

> +#define SVE_PT_REGS_FPSIMD		0
> +#define SVE_PT_REGS_SVE			SVE_PT_REGS_MASK
> +
> +#define SVE_PT_VL_INHERIT		(PR_SVE_VL_INHERIT >> 16)
> +#define SVE_PT_VL_ONEXEC		(PR_SVE_SET_VL_ONEXEC >> 16)
> +
> +
> +/*
> + * The remainder of the SVE state follows struct user_sve_header.  The
> + * total size of the SVE state (including header) depends on the
> + * metadata in the header:  SVE_PT_SIZE(vq, flags) gives the total size
> + * of the state in bytes, including the header.
> + *
> + * Refer to <asm/sigcontext.h> for details of how to pass the correct
> + * "vq" argument to these macros.
> + */
> +
> +/* Offset from the start of struct user_sve_header to the register data */
> +#define SVE_PT_REGS_OFFSET					\
> +	((sizeof(struct sve_context) + (SVE_VQ_BYTES - 1))	\
> +		/ SVE_VQ_BYTES * SVE_VQ_BYTES)
> +
> +/*
> + * The register data content and layout depends on the value of the
> + * flags field.
> + */
> +
> +/*
> + * (flags & SVE_PT_REGS_MASK) == SVE_PT_REGS_FPSIMD case:
> + *
> + * The payload starts at offset SVE_PT_FPSIMD_OFFSET, and is of type
> + * struct user_fpsimd_state.  Additional data might be appended in the
> + * future: use SVE_PT_FPSIMD_SIZE(vq, flags) to compute the total size.
> + * SVE_PT_FPSIMD_SIZE(vq, flags) will never be less than
> + * sizeof(struct user_fpsimd_state).
> + */
> +
> +#define SVE_PT_FPSIMD_OFFSET		SVE_PT_REGS_OFFSET
> +
> +#define SVE_PT_FPSIMD_SIZE(vq, flags)	(sizeof(struct user_fpsimd_state))
> +
> +/*
> + * (flags & SVE_PT_REGS_MASK) == SVE_PT_REGS_SVE case:
> + *
> + * The payload starts at offset SVE_PT_SVE_OFFSET, and is of size
> + * SVE_PT_SVE_SIZE(vq, flags).
> + *
> + * Additional macros describe the contents and layout of the payload.
> + * For each, SVE_PT_SVE_x_OFFSET(args) is the start offset relative to
> + * the start of struct user_sve_header, and SVE_PT_SVE_x_SIZE(args) is
> + * the size in bytes:
> + *
> + *	x	type				description
> + *	-	----				-----------
> + *	ZREGS		\
> + *	ZREG		|
> + *	PREGS		| refer to <asm/sigcontext.h>
> + *	PREG		|
> + *	FFR		/
> + *
> + *	FPSR	uint32_t			FPSR
> + *	FPCR	uint32_t			FPCR
> + *
> + * Additional data might be appended in the future.
> + */
> +
> +#define SVE_PT_SVE_ZREG_SIZE(vq)	SVE_SIG_ZREG_SIZE(vq)
> +#define SVE_PT_SVE_PREG_SIZE(vq)	SVE_SIG_PREG_SIZE(vq)
> +#define SVE_PT_SVE_FFR_SIZE(vq)		SVE_SIG_FFR_SIZE(vq)
> +#define SVE_PT_SVE_FPSR_SIZE		sizeof(__u32)
> +#define SVE_PT_SVE_FPCR_SIZE		sizeof(__u32)
> +
> +#define __SVE_SIG_TO_PT(offset) \
> +	((offset) - SVE_SIG_REGS_OFFSET + SVE_PT_REGS_OFFSET)
> +
> +#define SVE_PT_SVE_OFFSET		SVE_PT_REGS_OFFSET
> +
> +#define SVE_PT_SVE_ZREGS_OFFSET \
> +	__SVE_SIG_TO_PT(SVE_SIG_ZREGS_OFFSET)
> +#define SVE_PT_SVE_ZREG_OFFSET(vq, n) \
> +	__SVE_SIG_TO_PT(SVE_SIG_ZREG_OFFSET(vq, n))
> +#define SVE_PT_SVE_ZREGS_SIZE(vq) \
> +	(SVE_PT_SVE_ZREG_OFFSET(vq, SVE_NUM_ZREGS) - SVE_PT_SVE_ZREGS_OFFSET)
> +
> +#define SVE_PT_SVE_PREGS_OFFSET(vq) \
> +	__SVE_SIG_TO_PT(SVE_SIG_PREGS_OFFSET(vq))
> +#define SVE_PT_SVE_PREG_OFFSET(vq, n) \
> +	__SVE_SIG_TO_PT(SVE_SIG_PREG_OFFSET(vq, n))
> +#define SVE_PT_SVE_PREGS_SIZE(vq) \
> +	(SVE_PT_SVE_PREG_OFFSET(vq, SVE_NUM_PREGS) - \
> +		SVE_PT_SVE_PREGS_OFFSET(vq))
> +
> +#define SVE_PT_SVE_FFR_OFFSET(vq) \
> +	__SVE_SIG_TO_PT(SVE_SIG_FFR_OFFSET(vq))
> +
> +#define SVE_PT_SVE_FPSR_OFFSET(vq)				\
> +	((SVE_PT_SVE_FFR_OFFSET(vq) + SVE_PT_SVE_FFR_SIZE(vq) +	\
> +			(SVE_VQ_BYTES - 1))			\
> +		/ SVE_VQ_BYTES * SVE_VQ_BYTES)
> +#define SVE_PT_SVE_FPCR_OFFSET(vq) \
> +	(SVE_PT_SVE_FPSR_OFFSET(vq) + SVE_PT_SVE_FPSR_SIZE)
> +
> +/*
> + * Any future extension appended after FPCR must be aligned to the next
> + * 128-bit boundary.
> + */
> +
> +#define SVE_PT_SVE_SIZE(vq, flags)					\
> +	((SVE_PT_SVE_FPCR_OFFSET(vq) + SVE_PT_SVE_FPCR_SIZE		\
> +			- SVE_PT_SVE_OFFSET + (SVE_VQ_BYTES - 1))	\
> +		/ SVE_VQ_BYTES * SVE_VQ_BYTES)
> +
> +#define SVE_PT_SIZE(vq, flags)						\
> +	 (((flags) & SVE_PT_REGS_MASK) == SVE_PT_REGS_SVE ?		\
> +		  SVE_PT_SVE_OFFSET + SVE_PT_SVE_SIZE(vq, flags)	\
> +		: SVE_PT_FPSIMD_OFFSET + SVE_PT_FPSIMD_SIZE(vq, flags))
> +
>  #endif /* __ASSEMBLY__ */
>
>  #endif /* _UAPI__ASM_PTRACE_H */
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index fff9fcf..361c019 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -303,6 +303,37 @@ void sve_alloc(struct task_struct *task)
>  	BUG_ON(!task->thread.sve_state);
>  }
>
> +void fpsimd_sync_to_sve(struct task_struct *task)
> +{
> +	if (!test_tsk_thread_flag(task, TIF_SVE))
> +		fpsimd_to_sve(task);
> +}
> +
> +void sve_sync_to_fpsimd(struct task_struct *task)
> +{
> +	if (test_tsk_thread_flag(task, TIF_SVE))
> +		sve_to_fpsimd(task);
> +}
> +
> +void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
> +{
> +	unsigned int vq;
> +	void *sst = task->thread.sve_state;
> +	struct fpsimd_state const *fst = &task->thread.fpsimd_state;
> +	unsigned int i;
> +
> +	if (!test_tsk_thread_flag(task, TIF_SVE))
> +		return;
> +
> +	vq = sve_vq_from_vl(task->thread.sve_vl);
> +
> +	memset(sst, 0, SVE_SIG_REGS_SIZE(vq));
> +
> +	for (i = 0; i < 32; ++i)
> +		memcpy(ZREG(sst, vq, i), &fst->vregs[i],
> +		       sizeof(fst->vregs[i]));
> +}
> +
>  /*
>   * Handle SVE state across fork():
>   *
> @@ -459,10 +490,17 @@ static void __init sve_efi_setup(void)
>  	 * This is evidence of a crippled system and we are returning void,
>  	 * so no attempt is made to handle this situation here.
>  	 */
> -	BUG_ON(!sve_vl_valid(sve_max_vl));
> +	if (!sve_vl_valid(sve_max_vl))
> +		goto fail;
> +
>  	efi_sve_state = __alloc_percpu(
>  		SVE_SIG_REGS_SIZE(sve_vq_from_vl(sve_max_vl)), SVE_VQ_BYTES);
>  	if (!efi_sve_state)
> +		goto fail;
> +
> +	return;
> +
> +fail:
>  		panic("Cannot allocate percpu memory for EFI SVE save/restore");
>  }
>
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 9cbb612..5ef4735b 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -32,6 +32,7 @@
>  #include <linux/security.h>
>  #include <linux/init.h>
>  #include <linux/signal.h>
> +#include <linux/string.h>
>  #include <linux/uaccess.h>
>  #include <linux/perf_event.h>
>  #include <linux/hw_breakpoint.h>
> @@ -40,6 +41,7 @@
>  #include <linux/elf.h>
>
>  #include <asm/compat.h>
> +#include <asm/cpufeature.h>
>  #include <asm/debug-monitors.h>
>  #include <asm/pgtable.h>
>  #include <asm/stacktrace.h>
> @@ -618,33 +620,66 @@ static int gpr_set(struct task_struct *target, const struct user_regset *regset,
>  /*
>   * TODO: update fp accessors for lazy context switching (sync/flush hwstate)
>   */
> -static int fpr_get(struct task_struct *target, const struct user_regset *regset,
> -		   unsigned int pos, unsigned int count,
> -		   void *kbuf, void __user *ubuf)
> +static int __fpr_get(struct task_struct *target,
> +		     const struct user_regset *regset,
> +		     unsigned int pos, unsigned int count,
> +		     void *kbuf, void __user *ubuf, unsigned int start_pos)
>  {
>  	struct user_fpsimd_state *uregs;
> +
> +	sve_sync_to_fpsimd(target);
> +
>  	uregs = &target->thread.fpsimd_state.user_fpsimd;
>
> +	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs,
> +				   start_pos, start_pos + sizeof(*uregs));
> +}
> +
> +static int fpr_get(struct task_struct *target, const struct user_regset *regset,
> +		   unsigned int pos, unsigned int count,
> +		   void *kbuf, void __user *ubuf)
> +{
>  	if (target == current)
>  		fpsimd_preserve_current_state();
>
> -	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs, 0, -1);
> +	return __fpr_get(target, regset, pos, count, kbuf, ubuf, 0);
>  }
>
> -static int fpr_set(struct task_struct *target, const struct user_regset *regset,
> -		   unsigned int pos, unsigned int count,
> -		   const void *kbuf, const void __user *ubuf)
> +static int __fpr_set(struct task_struct *target,
> +		     const struct user_regset *regset,
> +		     unsigned int pos, unsigned int count,
> +		     const void *kbuf, const void __user *ubuf,
> +		     unsigned int start_pos)
>  {
>  	int ret;
>  	struct user_fpsimd_state newstate =
>  		target->thread.fpsimd_state.user_fpsimd;
>
> -	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate, 0, -1);
> +	sve_sync_to_fpsimd(target);
> +
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate,
> +				 start_pos, start_pos + sizeof(newstate));
>  	if (ret)
>  		return ret;
>
>  	target->thread.fpsimd_state.user_fpsimd = newstate;
> +
> +	return ret;
> +}
> +
> +static int fpr_set(struct task_struct *target, const struct user_regset *regset,
> +		   unsigned int pos, unsigned int count,
> +		   const void *kbuf, const void __user *ubuf)
> +{
> +	int ret;
> +
> +	ret = __fpr_set(target, regset, pos, count, kbuf, ubuf, 0);
> +	if (ret)
> +		return ret;
> +
> +	sve_sync_from_fpsimd_zeropad(target);
>  	fpsimd_flush_task_state(target);
> +
>  	return ret;
>  }
>
> @@ -702,6 +737,210 @@ static int system_call_set(struct task_struct *target,
>  	return ret;
>  }
>
> +#ifdef CONFIG_ARM64_SVE
> +
> +static void sve_init_header_from_task(struct user_sve_header *header,
> +				      struct task_struct *target)
> +{
> +	unsigned int vq;
> +
> +	memset(header, 0, sizeof(*header));
> +
> +	header->flags = test_tsk_thread_flag(target, TIF_SVE) ?
> +		SVE_PT_REGS_SVE : SVE_PT_REGS_FPSIMD;
> +	if (test_tsk_thread_flag(target, TIF_SVE_VL_INHERIT))
> +		header->flags |= SVE_PT_VL_INHERIT;
> +
> +	header->vl = target->thread.sve_vl;
> +	vq = sve_vq_from_vl(header->vl);
> +
> +	if (WARN_ON(!sve_vl_valid(sve_max_vl)))
> +		header->max_vl = header->vl;
> +
> +	header->size = SVE_PT_SIZE(vq, header->flags);
> +	header->max_size = SVE_PT_SIZE(sve_vq_from_vl(header->max_vl),
> +				      SVE_PT_REGS_SVE);
> +}
> +
> +static unsigned int sve_size_from_header(struct user_sve_header const *header)
> +{
> +	return ALIGN(header->size, SVE_VQ_BYTES);
> +}
> +
> +static unsigned int sve_get_size(struct task_struct *target,
> +				 const struct user_regset *regset)
> +{
> +	struct user_sve_header header;
> +
> +	if (!system_supports_sve())
> +		return 0;
> +
> +	sve_init_header_from_task(&header, target);
> +	return sve_size_from_header(&header);
> +}
> +
> +static int sve_get(struct task_struct *target,
> +		   const struct user_regset *regset,
> +		   unsigned int pos, unsigned int count,
> +		   void *kbuf, void __user *ubuf)
> +{
> +	int ret;
> +	struct user_sve_header header;
> +	unsigned int vq;
> +	unsigned long start, end;
> +
> +	if (!system_supports_sve())
> +		return -EINVAL;
> +
> +	/* Header */
> +	sve_init_header_from_task(&header, target);
> +	vq = sve_vq_from_vl(header.vl);
> +
> +	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &header,
> +				  0, sizeof(header));
> +	if (ret)
> +		return ret;
> +
> +	if (target == current)
> +		fpsimd_preserve_current_state();
> +
> +	/* Registers: FPSIMD-only case */
> +
> +	BUILD_BUG_ON(SVE_PT_FPSIMD_OFFSET != sizeof(header));
> +	if ((header.flags & SVE_PT_REGS_MASK) == SVE_PT_REGS_FPSIMD)
> +		return __fpr_get(target, regset, pos, count, kbuf, ubuf,
> +				 SVE_PT_FPSIMD_OFFSET);
> +
> +	/* Otherwise: full SVE case */
> +
> +	BUILD_BUG_ON(SVE_PT_SVE_OFFSET != sizeof(header));
> +	start = SVE_PT_SVE_OFFSET;
> +	end = SVE_PT_SVE_FFR_OFFSET(vq) + SVE_PT_SVE_FFR_SIZE(vq);
> +	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
> +				  target->thread.sve_state,
> +				  start, end);
> +	if (ret)
> +		return ret;
> +
> +	start = end;
> +	end = SVE_PT_SVE_FPSR_OFFSET(vq);
> +	ret = user_regset_copyout_zero(&pos, &count, &kbuf, &ubuf,
> +				       start, end);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Copy fpsr, and fpcr which must follow contiguously in
> +	 * struct fpsimd_state:
> +	 */
> +	start = end;
> +	end = SVE_PT_SVE_FPCR_OFFSET(vq) + SVE_PT_SVE_FPCR_SIZE;
> +	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
> +				  &target->thread.fpsimd_state.fpsr,
> +				  start, end);
> +	if (ret)
> +		return ret;
> +
> +	start = end;
> +	end = sve_size_from_header(&header);
> +	return user_regset_copyout_zero(&pos, &count, &kbuf, &ubuf,
> +					start, end);
> +}
> +
> +static int sve_set(struct task_struct *target,
> +		   const struct user_regset *regset,
> +		   unsigned int pos, unsigned int count,
> +		   const void *kbuf, const void __user *ubuf)
> +{
> +	int ret;
> +	struct user_sve_header header;
> +	unsigned int vq;
> +	unsigned long start, end;
> +
> +	if (!system_supports_sve())
> +		return -EINVAL;
> +
> +	/* Header */
> +	if (count < sizeof(header))
> +		return -EINVAL;
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &header,
> +				 0, sizeof(header));
> +	if (ret)
> +		goto out;
> +
> +	/*
> +	 * Apart from PT_SVE_REGS_MASK, all PT_SVE_* flags are consumed by
> +	 * sve_set_vector_length(), which will also validate them for us:
> +	 */
> +	ret = sve_set_vector_length(target, header.vl,
> +				    header.flags & ~SVE_PT_REGS_MASK);
> +	if (ret)
> +		goto out;
> +
> +	/* Actual VL set may be less than the user asked for: */
> +	vq = sve_vq_from_vl(target->thread.sve_vl);
> +
> +	/* Registers: FPSIMD-only case */
> +
> +	BUILD_BUG_ON(SVE_PT_FPSIMD_OFFSET != sizeof(header));
> +	if ((header.flags & SVE_PT_REGS_MASK) == SVE_PT_REGS_FPSIMD) {
> +		sve_sync_to_fpsimd(target);
> +
> +		ret = __fpr_set(target, regset, pos, count, kbuf, ubuf,
> +				SVE_PT_FPSIMD_OFFSET);
> +		clear_tsk_thread_flag(target, TIF_SVE);
> +		goto out;
> +	}
> +
> +	/* Otherwise: full SVE case */
> +
> +	/*
> +	 * If setting a different VL from the requested VL and there is
> +	 * register data, the data layout will be wrong: don't even
> +	 * try to set the registers in this case.
> +	 */
> +	if (count && vq != sve_vq_from_vl(header.vl)) {
> +		ret = -EIO;
> +		goto out;
> +	}
> +
> +	sve_alloc(target);
> +	fpsimd_sync_to_sve(target);
> +	set_tsk_thread_flag(target, TIF_SVE);
> +
> +	BUILD_BUG_ON(SVE_PT_SVE_OFFSET != sizeof(header));
> +	start = SVE_PT_SVE_OFFSET;
> +	end = SVE_PT_SVE_FFR_OFFSET(vq) + SVE_PT_SVE_FFR_SIZE(vq);
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
> +				 target->thread.sve_state,
> +				 start, end);
> +	if (ret)
> +		goto out;
> +
> +	start = end;
> +	end = SVE_PT_SVE_FPSR_OFFSET(vq);
> +	ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf,
> +					start, end);
> +	if (ret)
> +		goto out;
> +
> +	/*
> +	 * Copy fpsr, and fpcr which must follow contiguously in
> +	 * struct fpsimd_state:
> +	 */
> +	start = end;
> +	end = SVE_PT_SVE_FPCR_OFFSET(vq) + SVE_PT_SVE_FPCR_SIZE;
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
> +				 &target->thread.fpsimd_state.fpsr,
> +				 start, end);
> +
> +out:
> +	fpsimd_flush_task_state(target);
> +	return ret;
> +}
> +
> +#endif /* CONFIG_ARM64_SVE */
> +
>  enum aarch64_regset {
>  	REGSET_GPR,
>  	REGSET_FPR,
> @@ -711,6 +950,9 @@ enum aarch64_regset {
>  	REGSET_HW_WATCH,
>  #endif
>  	REGSET_SYSTEM_CALL,
> +#ifdef CONFIG_ARM64_SVE
> +	REGSET_SVE,
> +#endif
>  };
>
>  static const struct user_regset aarch64_regsets[] = {
> @@ -768,6 +1010,18 @@ static const struct user_regset aarch64_regsets[] = {
>  		.get = system_call_get,
>  		.set = system_call_set,
>  	},
> +#ifdef CONFIG_ARM64_SVE
> +	[REGSET_SVE] = { /* Scalable Vector Extension */
> +		.core_note_type = NT_ARM_SVE,
> +		.n = DIV_ROUND_UP(SVE_PT_SIZE(SVE_VQ_MAX, SVE_PT_REGS_SVE),
> +				  SVE_VQ_BYTES),
> +		.size = SVE_VQ_BYTES,
> +		.align = SVE_VQ_BYTES,
> +		.get = sve_get,
> +		.set = sve_set,
> +		.get_size = sve_get_size,
> +	},
> +#endif
>  };
>
>  static const struct user_regset_view user_aarch64_view = {
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index b5280db..735b8f4 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -416,6 +416,7 @@ typedef struct elf64_shdr {
>  #define NT_ARM_HW_BREAK	0x402		/* ARM hardware breakpoint registers */
>  #define NT_ARM_HW_WATCH	0x403		/* ARM hardware watchpoint registers */
>  #define NT_ARM_SYSTEM_CALL	0x404	/* ARM system call number */
> +#define NT_ARM_SVE	0x405		/* ARM Scalable Vector Extension registers */
>  #define NT_METAG_CBUF	0x500		/* Metag catch buffer registers */
>  #define NT_METAG_RPIPE	0x501		/* Metag read pipeline state */
>  #define NT_METAG_TLS	0x502		/* Metag TLS pointer */

Otherwise:

Reviewed-by: Alex Benn?e <[email-masked]>

--
Alex Benn?e