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Commit 43d4da2c authored by Dave Martin's avatar Dave Martin Committed by Will Deacon
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arm64/sve: ptrace and ELF coredump support



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: default avatarAlan Hayward <alan.hayward@arm.com>
Signed-off-by: default avatarDave Martin <Dave.Martin@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: Okamoto Takayuki <tokamoto@jp.fujitsu.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent fdfa976c
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+11 −1
Original line number Diff line number Diff line
@@ -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
@@ -88,6 +91,10 @@ extern size_t sve_state_size(struct task_struct const *task);

extern void sve_alloc(struct task_struct *task);
extern void fpsimd_release_task(struct task_struct *task);
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);

@@ -104,6 +111,9 @@ extern void __init sve_setup(void);

static inline void sve_alloc(struct task_struct *task) { }
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 void sve_init_vq_map(void) { }
static inline void sve_update_vq_map(void) { }
static inline int sve_verify_vq_map(void) { return 0; }
+138 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@
#include <linux/types.h>

#include <asm/hwcap.h>
#include <asm/sigcontext.h>


/*
@@ -62,6 +63,8 @@

#ifndef __ASSEMBLY__

#include <linux/prctl.h>

/*
 * User structures for general purpose, floating point and debug registers.
 */
@@ -89,6 +92,141 @@ 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)

#define SVE_PT_REGS_FPSIMD		0
#define SVE_PT_REGS_SVE			SVE_PT_REGS_MASK

/*
 * Common SVE_PT_* flags:
 * These must be kept in sync with prctl interface in <linux/ptrace.h>
 */
#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 */
+60 −0
Original line number Diff line number Diff line
@@ -428,6 +428,66 @@ void sve_alloc(struct task_struct *task)
	BUG_ON(!task->thread.sve_state);
}


/*
 * Ensure that task->thread.sve_state is up to date with respect to
 * the user task, irrespective of when SVE is in use or not.
 *
 * This should only be called by ptrace.  task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 */
void fpsimd_sync_to_sve(struct task_struct *task)
{
	if (!test_tsk_thread_flag(task, TIF_SVE))
		fpsimd_to_sve(task);
}

/*
 * Ensure that task->thread.fpsimd_state is up to date with respect to
 * the user task, irrespective of whether SVE is in use or not.
 *
 * This should only be called by ptrace.  task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 */
void sve_sync_to_fpsimd(struct task_struct *task)
{
	if (test_tsk_thread_flag(task, TIF_SVE))
		sve_to_fpsimd(task);
}

/*
 * Ensure that task->thread.sve_state is up to date with respect to
 * the task->thread.fpsimd_state.
 *
 * This should only be called by ptrace to merge new FPSIMD register
 * values into a task for which SVE is currently active.
 * task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 * task->thread.fpsimd_state must already have been initialised with
 * the new FPSIMD register values to be merged in.
 */
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]));
}

int sve_set_vector_length(struct task_struct *task,
			  unsigned long vl, unsigned long flags)
{
+272 −8
Original line number Diff line number Diff line
@@ -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>
@@ -618,17 +620,56 @@ 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,
static int __fpr_get(struct task_struct *target,
		     const struct user_regset *regset,
		     unsigned int pos, unsigned int count,
		   void *kbuf, void __user *ubuf)
		     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,
		     unsigned int start_pos)
{
	int ret;
	struct user_fpsimd_state newstate;

	/*
	 * Ensure target->thread.fpsimd_state is up to date, so that a
	 * short copyin can't resurrect stale data.
	 */
	sve_sync_to_fpsimd(target);

	newstate = target->thread.fpsimd_state.user_fpsimd;

	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,
@@ -636,15 +677,14 @@ static int fpr_set(struct task_struct *target, const struct user_regset *regset,
		   const void *kbuf, const void __user *ubuf)
{
	int ret;
	struct user_fpsimd_state newstate =
		target->thread.fpsimd_state.user_fpsimd;

	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate, 0, -1);
	ret = __fpr_set(target, regset, pos, count, kbuf, ubuf, 0);
	if (ret)
		return ret;

	target->thread.fpsimd_state.user_fpsimd = newstate;
	sve_sync_from_fpsimd_zeropad(target);
	fpsimd_flush_task_state(target);

	return ret;
}

@@ -702,6 +742,215 @@ 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);

	header->max_vl = sve_max_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,
		((unsigned long)header.flags & ~SVE_PT_REGS_MASK) << 16);
	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) {
		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);

	/*
	 * Ensure target->thread.sve_state is up to date with target's
	 * FPSIMD regs, so that a short copyin leaves trailing registers
	 * unmodified.
	 */
	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 +960,9 @@ 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 +1020,18 @@ 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 = {
+1 −0
Original line number Diff line number Diff line
@@ -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 */