proc: use CPUID to determine maximum size of XSAVE area (#2256)

the maximum size of the Xsave area was previously hardcoded but the
CPUID instruction can be used to determine its maximum size.

pkg/proc/amd64util/xsave.go

+package amd64util
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+
+	"github.com/go-delve/delve/pkg/proc"
+)
+
+// AMD64Xstate represents amd64 XSAVE area. See Section 13.1 (and
+// following) of Intel® 64 and IA-32 Architectures Software Developer’s
+// Manual, Volume 1: Basic Architecture.
+type AMD64Xstate struct {
+	AMD64PtraceFpRegs
+	Xsave       []byte // raw xsave area
+	AvxState    bool   // contains AVX state
+	YmmSpace    [256]byte
+	Avx512State bool // contains AVX512 state
+	ZmmSpace    [512]byte
+}
+
+// AMD64PtraceFpRegs tracks user_fpregs_struct in /usr/include/x86_64-linux-gnu/sys/user.h
+type AMD64PtraceFpRegs struct {
+	Cwd      uint16
+	Swd      uint16
+	Ftw      uint16
+	Fop      uint16
+	Rip      uint64
+	Rdp      uint64
+	Mxcsr    uint32
+	MxcrMask uint32
+	StSpace  [32]uint32
+	XmmSpace [256]byte
+	Padding  [24]uint32
+}
+
+// Decode decodes an XSAVE area to a list of name/value pairs of registers.
+func (xsave *AMD64Xstate) Decode() []proc.Register {
+	var regs []proc.Register
+	// x87 registers
+	regs = proc.AppendUint64Register(regs, "CW", uint64(xsave.Cwd))
+	regs = proc.AppendUint64Register(regs, "SW", uint64(xsave.Swd))
+	regs = proc.AppendUint64Register(regs, "TW", uint64(xsave.Ftw))
+	regs = proc.AppendUint64Register(regs, "FOP", uint64(xsave.Fop))
+	regs = proc.AppendUint64Register(regs, "FIP", xsave.Rip)
+	regs = proc.AppendUint64Register(regs, "FDP", xsave.Rdp)
+
+	for i := 0; i < len(xsave.StSpace); i += 4 {
+		var buf bytes.Buffer
+		binary.Write(&buf, binary.LittleEndian, uint64(xsave.StSpace[i+1])<<32|uint64(xsave.StSpace[i]))
+		binary.Write(&buf, binary.LittleEndian, uint16(xsave.StSpace[i+2]))
+		regs = proc.AppendBytesRegister(regs, fmt.Sprintf("ST(%d)", i/4), buf.Bytes())
+	}
+
+	// SSE registers
+	regs = proc.AppendUint64Register(regs, "MXCSR", uint64(xsave.Mxcsr))
+	regs = proc.AppendUint64Register(regs, "MXCSR_MASK", uint64(xsave.MxcrMask))
+
+	for i := 0; i < len(xsave.XmmSpace); i += 16 {
+		n := i / 16
+		regs = proc.AppendBytesRegister(regs, fmt.Sprintf("XMM%d", n), xsave.XmmSpace[i:i+16])
+		if xsave.AvxState {
+			regs = proc.AppendBytesRegister(regs, fmt.Sprintf("YMM%d", n), xsave.YmmSpace[i:i+16])
+			if xsave.Avx512State {
+				regs = proc.AppendBytesRegister(regs, fmt.Sprintf("ZMM%d", n), xsave.ZmmSpace[n*32:(n+1)*32])
+			}
+		}
+	}
+
+	return regs
+}
+
+const (
+	_XSTATE_MAX_KNOWN_SIZE = 2969
+
+	_XSAVE_HEADER_START            = 512
+	_XSAVE_HEADER_LEN              = 64
+	_XSAVE_EXTENDED_REGION_START   = 576
+	_XSAVE_SSE_REGION_LEN          = 416
+	_XSAVE_AVX512_ZMM_REGION_START = 1152
+)
+
+// AMD64XstateRead reads a byte array containing an XSAVE area into regset.
+// If readLegacy is true regset.PtraceFpRegs will be filled with the
+// contents of the legacy region of the XSAVE area.
+// See Section 13.1 (and following) of Intel® 64 and IA-32 Architectures
+// Software Developer’s Manual, Volume 1: Basic Architecture.
+func AMD64XstateRead(xstateargs []byte, readLegacy bool, regset *AMD64Xstate) error {
+	if _XSAVE_HEADER_START+_XSAVE_HEADER_LEN >= len(xstateargs) {
+		return nil
+	}
+	if readLegacy {
+		rdr := bytes.NewReader(xstateargs[:_XSAVE_HEADER_START])
+		if err := binary.Read(rdr, binary.LittleEndian, &regset.AMD64PtraceFpRegs); err != nil {
+			return err
+		}
+	}
+	xsaveheader := xstateargs[_XSAVE_HEADER_START : _XSAVE_HEADER_START+_XSAVE_HEADER_LEN]
+	xstate_bv := binary.LittleEndian.Uint64(xsaveheader[0:8])
+	xcomp_bv := binary.LittleEndian.Uint64(xsaveheader[8:16])
+
+	if xcomp_bv&(1<<63) != 0 {
+		// compact format not supported
+		return nil
+	}
+
+	if xstate_bv&(1<<2) == 0 {
+		// AVX state not present
+		return nil
+	}
+
+	avxstate := xstateargs[_XSAVE_EXTENDED_REGION_START:]
+	regset.AvxState = true
+	copy(regset.YmmSpace[:], avxstate[:len(regset.YmmSpace)])
+
+	if xstate_bv&(1<<6) == 0 {
+		// AVX512 state not present
+		return nil
+	}
+
+	avx512state := xstateargs[_XSAVE_AVX512_ZMM_REGION_START:]
+	regset.Avx512State = true
+	copy(regset.ZmmSpace[:], avx512state[:len(regset.ZmmSpace)])
+
+	// TODO(aarzilli): if xstate_bv&(1<<7) is set then xstateargs[1664:2688]
+	// contains ZMM16 through ZMM31, those aren't just the higher 256bits, it's
+	// the full register so each is 64 bytes (512bits)
+
+	return nil
+}

pkg/proc/amd64util/xsave_amd64.go

+package amd64util
+
+import (
+	"sync"
+)
+
+var xstateMaxSize int
+var loadXstateMaxSizeOnce sync.Once
+
+func cpuid(axIn, cxIn uint32) (axOut, bxOut, cxOut, dxOut uint32)
+
+func AMD64XstateMaxSize() int {
+	loadXstateMaxSizeOnce.Do(func() {
+		// See Intel 64 and IA-32 Architecture Software Developer's Manual, Vol. 1
+		// chapter 13.2 and Vol. 2A CPUID instruction for a description of all the
+		// magic constants.
+
+		_, _, cx, _ := cpuid(0x01, 0x00)
+
+		if cx&(1<<26) == 0 { // Vol. 2A, Table 3-10, XSAVE enabled bit check
+			// XSAVE not supported by this processor
+			xstateMaxSize = _XSTATE_MAX_KNOWN_SIZE
+			return
+		}
+
+		_, _, cx, _ = cpuid(0x0d, 0x00) // processor extended state enumeration main leaf
+		xstateMaxSize = int(cx)
+	})
+	return xstateMaxSize
+}

pkg/proc/amd64util/xsave_amd64.s

+TEXT ·cpuid(SB),$0-24
+	MOVL axIn+0(FP), AX
+	MOVL cxIn+4(FP), CX
+	CPUID
+	MOVL AX, axOut+8(FP)
+	MOVL BX, bxOut+12(FP)
+	MOVL CX, cxOut+16(FP)
+	MOVL DX, dxOut+20(FP)
+	RET

pkg/proc/amd64util/xsave_other.go

+//+build !amd64
+
+package amd64util
+
+func AMD64XstateMaxSize() int {
+	return _XSTATE_MAX_KNOWN_SIZE
+}

pkg/proc/core/linux_core.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/go-delve/delve/pkg/proc"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 	"github.com/go-delve/delve/pkg/proc/linutil"
 )
 
@@ -73,7 +74,7 @@ func linuxThreadsFromNotes(p *process, notes []*note, machineType elf.Machine) p
 		case _NT_X86_XSTATE:
 			if machineType == _EM_X86_64 {
 				if lastThreadAMD != nil {
-					lastThreadAMD.regs.Fpregs = note.Desc.(*linutil.AMD64Xstate).Decode()
+					lastThreadAMD.regs.Fpregs = note.Desc.(*amd64util.AMD64Xstate).Decode()
 				}
 			}
 		case elf.NT_PRPSINFO:
@@ -279,8 +280,8 @@ func readNote(r io.ReadSeeker, machineType elf.Machine) (*note, error) {
 		note.Desc = data
 	case _NT_X86_XSTATE:
 		if machineType == _EM_X86_64 {
-			var fpregs linutil.AMD64Xstate
-			if err := linutil.AMD64XstateRead(desc, true, &fpregs); err != nil {
+			var fpregs amd64util.AMD64Xstate
+			if err := amd64util.AMD64XstateRead(desc, true, &fpregs); err != nil {
 				return nil, err
 			}
 			note.Desc = &fpregs

pkg/proc/fbsdutil/regs.go

@@ -4,7 +4,7 @@ import (
 	"golang.org/x/arch/x86/x86asm"
 
 	"github.com/go-delve/delve/pkg/proc"
-	"github.com/go-delve/delve/pkg/proc/linutil"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 )
 
 // AMD64Registers implements the proc.Registers interface for the native/freebsd
@@ -12,7 +12,7 @@ import (
 type AMD64Registers struct {
 	Regs     *AMD64PtraceRegs
 	Fpregs   []proc.Register
-	Fpregset *AMD64Xstate
+	Fpregset *amd64util.AMD64Xstate
 	Fsbase   uint64
 
 	loadFpRegs func(*AMD64Registers) error
@@ -323,7 +323,7 @@ func (r *AMD64Registers) Copy() (proc.Registers, error) {
 	}
 	var rr AMD64Registers
 	rr.Regs = &AMD64PtraceRegs{}
-	rr.Fpregset = &AMD64Xstate{}
+	rr.Fpregset = &amd64util.AMD64Xstate{}
 	*(rr.Regs) = *(r.Regs)
 	if r.Fpregset != nil {
 		*(rr.Fpregset) = *(r.Fpregset)
@@ -334,13 +334,3 @@ func (r *AMD64Registers) Copy() (proc.Registers, error) {
 	}
 	return &rr, nil
 }
-
-type AMD64Xstate linutil.AMD64Xstate
-
-func AMD64XstateRead(xstateargs []byte, readLegacy bool, regset *AMD64Xstate) error {
-	return linutil.AMD64XstateRead(xstateargs, readLegacy, (*linutil.AMD64Xstate)(regset))
-}
-
-func (xsave *AMD64Xstate) Decode() (regs []proc.Register) {
-	return (*linutil.AMD64Xstate).Decode((*linutil.AMD64Xstate)(xsave))
-}

pkg/proc/linutil/regs_amd64_arch.go

 package linutil
 
 import (
-	"bytes"
-	"encoding/binary"
-	"fmt"
-
 	"golang.org/x/arch/x86/x86asm"
 
 	"github.com/go-delve/delve/pkg/proc"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 )
 
 // AMD64Registers implements the proc.Registers interface for the native/linux
@@ -15,7 +12,7 @@ import (
 type AMD64Registers struct {
 	Regs     *AMD64PtraceRegs
 	Fpregs   []proc.Register
-	Fpregset *AMD64Xstate
+	Fpregset *amd64util.AMD64Xstate
 
 	loadFpRegs func(*AMD64Registers) error
 }
@@ -299,7 +296,7 @@ func (r *AMD64Registers) Copy() (proc.Registers, error) {
 	}
 	var rr AMD64Registers
 	rr.Regs = &AMD64PtraceRegs{}
-	rr.Fpregset = &AMD64Xstate{}
+	rr.Fpregset = &amd64util.AMD64Xstate{}
 	*(rr.Regs) = *(r.Regs)
 	if r.Fpregset != nil {
 		*(rr.Fpregset) = *(r.Fpregset)
@@ -310,122 +307,3 @@ func (r *AMD64Registers) Copy() (proc.Registers, error) {
 	}
 	return &rr, nil
 }
-
-// AMD64PtraceFpRegs tracks user_fpregs_struct in /usr/include/x86_64-linux-gnu/sys/user.h
-type AMD64PtraceFpRegs struct {
-	Cwd      uint16
-	Swd      uint16
-	Ftw      uint16
-	Fop      uint16
-	Rip      uint64
-	Rdp      uint64
-	Mxcsr    uint32
-	MxcrMask uint32
-	StSpace  [32]uint32
-	XmmSpace [256]byte
-	Padding  [24]uint32
-}
-
-// AMD64Xstate represents amd64 XSAVE area. See Section 13.1 (and
-// following) of Intel® 64 and IA-32 Architectures Software Developer’s
-// Manual, Volume 1: Basic Architecture.
-type AMD64Xstate struct {
-	AMD64PtraceFpRegs
-	Xsave       []byte // raw xsave area
-	AvxState    bool   // contains AVX state
-	YmmSpace    [256]byte
-	Avx512State bool // contains AVX512 state
-	ZmmSpace    [512]byte
-}
-
-// Decode decodes an XSAVE area to a list of name/value pairs of registers.
-func (xsave *AMD64Xstate) Decode() (regs []proc.Register) {
-	// x87 registers
-	regs = proc.AppendUint64Register(regs, "CW", uint64(xsave.Cwd))
-	regs = proc.AppendUint64Register(regs, "SW", uint64(xsave.Swd))
-	regs = proc.AppendUint64Register(regs, "TW", uint64(xsave.Ftw))
-	regs = proc.AppendUint64Register(regs, "FOP", uint64(xsave.Fop))
-	regs = proc.AppendUint64Register(regs, "FIP", xsave.Rip)
-	regs = proc.AppendUint64Register(regs, "FDP", xsave.Rdp)
-
-	for i := 0; i < len(xsave.StSpace); i += 4 {
-		var buf bytes.Buffer
-		binary.Write(&buf, binary.LittleEndian, uint64(xsave.StSpace[i+1])<<32|uint64(xsave.StSpace[i]))
-		binary.Write(&buf, binary.LittleEndian, uint16(xsave.StSpace[i+2]))
-		regs = proc.AppendBytesRegister(regs, fmt.Sprintf("ST(%d)", i/4), buf.Bytes())
-	}
-
-	// SSE registers
-	regs = proc.AppendUint64Register(regs, "MXCSR", uint64(xsave.Mxcsr))
-	regs = proc.AppendUint64Register(regs, "MXCSR_MASK", uint64(xsave.MxcrMask))
-
-	for i := 0; i < len(xsave.XmmSpace); i += 16 {
-		n := i / 16
-		regs = proc.AppendBytesRegister(regs, fmt.Sprintf("XMM%d", n), xsave.XmmSpace[i:i+16])
-		if xsave.AvxState {
-			regs = proc.AppendBytesRegister(regs, fmt.Sprintf("YMM%d", n), xsave.YmmSpace[i:i+16])
-			if xsave.Avx512State {
-				regs = proc.AppendBytesRegister(regs, fmt.Sprintf("ZMM%d", n), xsave.ZmmSpace[n*32:(n+1)*32])
-			}
-		}
-	}
-
-	return
-}
-
-const (
-	_XSAVE_HEADER_START            = 512
-	_XSAVE_HEADER_LEN              = 64
-	_XSAVE_EXTENDED_REGION_START   = 576
-	_XSAVE_SSE_REGION_LEN          = 416
-	_XSAVE_AVX512_ZMM_REGION_START = 1152
-)
-
-// LinuxX86XstateRead reads a byte array containing an XSAVE area into regset.
-// If readLegacy is true regset.PtraceFpRegs will be filled with the
-// contents of the legacy region of the XSAVE area.
-// See Section 13.1 (and following) of Intel® 64 and IA-32 Architectures
-// Software Developer’s Manual, Volume 1: Basic Architecture.
-func AMD64XstateRead(xstateargs []byte, readLegacy bool, regset *AMD64Xstate) error {
-	if _XSAVE_HEADER_START+_XSAVE_HEADER_LEN >= len(xstateargs) {
-		return nil
-	}
-	if readLegacy {
-		rdr := bytes.NewReader(xstateargs[:_XSAVE_HEADER_START])
-		if err := binary.Read(rdr, binary.LittleEndian, &regset.AMD64PtraceFpRegs); err != nil {
-			return err
-		}
-	}
-	xsaveheader := xstateargs[_XSAVE_HEADER_START : _XSAVE_HEADER_START+_XSAVE_HEADER_LEN]
-	xstate_bv := binary.LittleEndian.Uint64(xsaveheader[0:8])
-	xcomp_bv := binary.LittleEndian.Uint64(xsaveheader[8:16])
-
-	if xcomp_bv&(1<<63) != 0 {
-		// compact format not supported
-		return nil
-	}
-
-	if xstate_bv&(1<<2) == 0 {
-		// AVX state not present
-		return nil
-	}
-
-	avxstate := xstateargs[_XSAVE_EXTENDED_REGION_START:]
-	regset.AvxState = true
-	copy(regset.YmmSpace[:], avxstate[:len(regset.YmmSpace)])
-
-	if xstate_bv&(1<<6) == 0 {
-		// AVX512 state not present
-		return nil
-	}
-
-	avx512state := xstateargs[_XSAVE_AVX512_ZMM_REGION_START:]
-	regset.Avx512State = true
-	copy(regset.ZmmSpace[:], avx512state[:len(regset.ZmmSpace)])
-
-	// TODO(aarzilli): if xstate_bv&(1<<7) is set then xstateargs[1664:2688]
-	// contains ZMM16 through ZMM31, those aren't just the higher 256bits, it's
-	// the full register so each is 64 bytes (512bits)
-
-	return nil
-}

pkg/proc/linutil/regs_i386_arch.go

 package linutil
 
 import (
-	"bytes"
-	"encoding/binary"
-	"fmt"
-	"github.com/go-delve/delve/pkg/proc"
 	"golang.org/x/arch/x86/x86asm"
+
+	"github.com/go-delve/delve/pkg/proc"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 )
 
 // I386Registers implements the proc.Registers interface for the native/linux
@@ -13,7 +12,7 @@ import (
 type I386Registers struct {
 	Regs     *I386PtraceRegs
 	Fpregs   []proc.Register
-	Fpregset *I386Xstate
+	Fpregset *amd64util.AMD64Xstate
 	Tls      uint64
 
 	loadFpRegs func(*I386Registers) error
@@ -199,7 +198,7 @@ func (r *I386Registers) Copy() (proc.Registers, error) {
 	}
 	var rr I386Registers
 	rr.Regs = &I386PtraceRegs{}
-	rr.Fpregset = &I386Xstate{}
+	rr.Fpregset = &amd64util.AMD64Xstate{}
 	*(rr.Regs) = *(r.Regs)
 	if r.Fpregset != nil {
 		*(rr.Fpregset) = *(r.Fpregset)
@@ -210,95 +209,3 @@ func (r *I386Registers) Copy() (proc.Registers, error) {
 	}
 	return &rr, nil
 }
-
-// I386PtraceFpRegs tracks user_fpregs_struct in /usr/include/x86_64-linux-gnu/sys/user.h
-type I386PtraceFpRegs struct {
-	Cwd      uint16
-	Swd      uint16
-	Ftw      uint16
-	Fop      uint16
-	Rip      uint64
-	Rdp      uint64
-	Mxcsr    uint32
-	MxcrMask uint32
-	StSpace  [32]uint32
-	XmmSpace [256]byte
-	Padding  [24]uint32
-}
-
-// I386Xstate represents amd64 XSAVE area. See Section 13.1 (and
-// following) of Intel® 64 and IA-32 Architectures Software Developer’s
-// Manual, Volume 1: Basic Architecture.
-type I386Xstate struct {
-	I386PtraceFpRegs
-	Xsave    []byte // raw xsave area
-	AvxState bool   // contains AVX state
-	YmmSpace [256]byte
-}
-
-// Decode decodes an XSAVE area to a list of name/value pairs of registers.
-func (xsave *I386Xstate) Decode() (regs []proc.Register) {
-	// x87 registers
-	regs = proc.AppendUint64Register(regs, "CW", uint64(xsave.Cwd))
-	regs = proc.AppendUint64Register(regs, "SW", uint64(xsave.Swd))
-	regs = proc.AppendUint64Register(regs, "TW", uint64(xsave.Ftw))
-	regs = proc.AppendUint64Register(regs, "FOP", uint64(xsave.Fop))
-	regs = proc.AppendUint64Register(regs, "FIP", uint64(xsave.Rip))
-	regs = proc.AppendUint64Register(regs, "FDP", uint64(xsave.Rdp))
-
-	for i := 0; i < len(xsave.StSpace); i += 4 {
-		var buf bytes.Buffer
-		binary.Write(&buf, binary.LittleEndian, uint64(xsave.StSpace[i+1])<<32|uint64(xsave.StSpace[i]))
-		binary.Write(&buf, binary.LittleEndian, uint16(xsave.StSpace[i+2]))
-		regs = proc.AppendBytesRegister(regs, fmt.Sprintf("ST(%d)", i/4), buf.Bytes())
-	}
-
-	// SSE registers
-	regs = proc.AppendUint64Register(regs, "MXCSR", uint64(xsave.Mxcsr))
-	regs = proc.AppendUint64Register(regs, "MXCSR_MASK", uint64(xsave.MxcrMask))
-
-	for i := 0; i < len(xsave.XmmSpace); i += 16 {
-		regs = proc.AppendBytesRegister(regs, fmt.Sprintf("XMM%d", i/16), xsave.XmmSpace[i:i+16])
-		if xsave.AvxState {
-			regs = proc.AppendBytesRegister(regs, fmt.Sprintf("YMM%d", i/16), xsave.YmmSpace[i:i+16])
-		}
-	}
-
-	return
-}
-
-// LinuxX86XstateRead reads a byte array containing an XSAVE area into regset.
-// If readLegacy is true regset.PtraceFpRegs will be filled with the
-// contents of the legacy region of the XSAVE area.
-// See Section 13.1 (and following) of Intel® 64 and IA-32 Architectures
-// Software Developer’s Manual, Volume 1: Basic Architecture.
-func I386XstateRead(xstateargs []byte, readLegacy bool, regset *I386Xstate) error {
-	if _XSAVE_HEADER_START+_XSAVE_HEADER_LEN >= len(xstateargs) {
-		return nil
-	}
-	if readLegacy {
-		rdr := bytes.NewReader(xstateargs[:_XSAVE_HEADER_START])
-		if err := binary.Read(rdr, binary.LittleEndian, &regset.I386PtraceFpRegs); err != nil {
-			return err
-		}
-	}
-	xsaveheader := xstateargs[_XSAVE_HEADER_START : _XSAVE_HEADER_START+_XSAVE_HEADER_LEN]
-	xstate_bv := binary.LittleEndian.Uint64(xsaveheader[0:8])
-	xcomp_bv := binary.LittleEndian.Uint64(xsaveheader[8:16])
-
-	if xcomp_bv&(1<<63) != 0 {
-		// compact format not supported
-		return nil
-	}
-
-	if xstate_bv&(1<<2) == 0 {
-		// AVX state not present
-		return nil
-	}
-
-	avxstate := xstateargs[_XSAVE_EXTENDED_REGION_START:]
-	regset.AvxState = true
-	copy(regset.YmmSpace[:], avxstate[:len(regset.YmmSpace)])
-
-	return nil
-}

pkg/proc/native/ptrace_freebsd.go

@@ -14,7 +14,7 @@ import (
 
 	sys "golang.org/x/sys/unix"
 
-	"github.com/go-delve/delve/pkg/proc/fbsdutil"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 )
 
 // ptraceAttach executes the sys.PtraceAttach call.
@@ -54,7 +54,7 @@ func ptraceGetLwpInfo(wpid int) (info sys.PtraceLwpInfoStruct, err error) {
 	return info, err
 }
 
-func ptraceGetRegset(id int) (regset fbsdutil.AMD64Xstate, err error) {
+func ptraceGetRegset(id int) (regset amd64util.AMD64Xstate, err error) {
 	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETFPREGS, uintptr(id), uintptr(unsafe.Pointer(&regset.AMD64PtraceFpRegs)), 0, 0, 0)
 	if err == syscall.Errno(0) || err == syscall.ENODEV {
 		var xsave_len C.size_t
@@ -62,7 +62,7 @@ func ptraceGetRegset(id int) (regset fbsdutil.AMD64Xstate, err error) {
 		defer C.free(unsafe.Pointer(xsave))
 		if xsave != nil {
 			xsave_sl := C.GoBytes(unsafe.Pointer(xsave), C.int(xsave_len))
-			err = fbsdutil.AMD64XstateRead(xsave_sl, false, &regset)
+			err = amd64util.AMD64XstateRead(xsave_sl, false, &regset)
 		}
 	}
 	return

pkg/proc/native/ptrace_linux_386.go

@@ -9,7 +9,7 @@ import (
 
 	sys "golang.org/x/sys/unix"
 
-	"github.com/go-delve/delve/pkg/proc/linutil"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 )
 
 // ptraceGetRegset returns floating point registers of the specified thread
@@ -17,15 +17,15 @@ import (
 // See i386_linux_fetch_inferior_registers in gdb/i386-linux-nat.c.html
 // and i386_supply_xsave in gdb/i386-tdep.c.html
 // and Section 13.1 (and following) of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1: Basic Architecture
-func ptraceGetRegset(tid int) (regset linutil.I386Xstate, err error) {
-	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETFPREGS, uintptr(tid), uintptr(0), uintptr(unsafe.Pointer(&regset.I386PtraceFpRegs)), 0, 0)
+func ptraceGetRegset(tid int) (regset amd64util.AMD64Xstate, err error) {
+	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETFPREGS, uintptr(tid), uintptr(0), uintptr(unsafe.Pointer(&regset.AMD64PtraceFpRegs)), 0, 0)
 	if err == syscall.Errno(0) || err == syscall.ENODEV {
 		// ignore ENODEV, it just means this CPU doesn't have X87 registers (??)
 		err = nil
 	}
 
-	var xstateargs [_X86_XSTATE_MAX_SIZE]byte
-	iov := sys.Iovec{Base: &xstateargs[0], Len: _X86_XSTATE_MAX_SIZE}
+	xstateargs := make([]byte, amd64util.AMD64XstateMaxSize())
+	iov := sys.Iovec{Base: &xstateargs[0], Len: uint32(len(xstateargs))}
 	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETREGSET, uintptr(tid), _NT_X86_XSTATE, uintptr(unsafe.Pointer(&iov)), 0, 0)
 	if err != syscall.Errno(0) {
 		if err == syscall.ENODEV || err == syscall.EIO {
@@ -39,7 +39,7 @@ func ptraceGetRegset(tid int) (regset linutil.I386Xstate, err error) {
 	}
 
 	regset.Xsave = xstateargs[:iov.Len]
-	err = linutil.I386XstateRead(regset.Xsave, false, &regset)
+	err = amd64util.AMD64XstateRead(regset.Xsave, false, &regset)
 	return
 }
 

pkg/proc/native/ptrace_linux_amd64.go

@@ -6,7 +6,7 @@ import (
 
 	sys "golang.org/x/sys/unix"
 
-	"github.com/go-delve/delve/pkg/proc/linutil"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 )
 
 // ptraceGetRegset returns floating point registers of the specified thread
@@ -14,15 +14,15 @@ import (
 // See amd64_linux_fetch_inferior_registers in gdb/amd64-linux-nat.c.html
 // and amd64_supply_xsave in gdb/amd64-tdep.c.html
 // and Section 13.1 (and following) of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1: Basic Architecture
-func ptraceGetRegset(tid int) (regset linutil.AMD64Xstate, err error) {
+func ptraceGetRegset(tid int) (regset amd64util.AMD64Xstate, err error) {
 	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETFPREGS, uintptr(tid), uintptr(0), uintptr(unsafe.Pointer(&regset.AMD64PtraceFpRegs)), 0, 0)
 	if err == syscall.Errno(0) || err == syscall.ENODEV {
 		// ignore ENODEV, it just means this CPU doesn't have X87 registers (??)
 		err = nil
 	}
 
-	var xstateargs [_X86_XSTATE_MAX_SIZE]byte
-	iov := sys.Iovec{Base: &xstateargs[0], Len: _X86_XSTATE_MAX_SIZE}
+	xstateargs := make([]byte, amd64util.AMD64XstateMaxSize())
+	iov := sys.Iovec{Base: &xstateargs[0], Len: uint64(len(xstateargs))}
 	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETREGSET, uintptr(tid), _NT_X86_XSTATE, uintptr(unsafe.Pointer(&iov)), 0, 0)
 	if err != syscall.Errno(0) {
 		if err == syscall.ENODEV || err == syscall.EIO {
@@ -36,6 +36,6 @@ func ptraceGetRegset(tid int) (regset linutil.AMD64Xstate, err error) {
 	}
 
 	regset.Xsave = xstateargs[:iov.Len]
-	err = linutil.AMD64XstateRead(regset.Xsave, false, &regset)
+	err = amd64util.AMD64XstateRead(regset.Xsave, false, &regset)
 	return
 }

pkg/proc/native/register_linux_386.go

@@ -69,15 +69,7 @@ func registers(thread *nativeThread) (proc.Registers, error) {
 	return r, nil
 }
 
-const (
-	_X86_XSTATE_MAX_SIZE = 2688
-	_NT_X86_XSTATE       = 0x202
-
-	_XSAVE_HEADER_START          = 512
-	_XSAVE_HEADER_LEN            = 64
-	_XSAVE_EXTENDED_REGION_START = 576
-	_XSAVE_SSE_REGION_LEN        = 416
-)
+const _NT_X86_XSTATE = 0x202
 
 func (thread *nativeThread) fpRegisters() (regs []proc.Register, fpregs linutil.I386Xstate, err error) {
 	thread.dbp.execPtraceFunc(func() { fpregs, err = ptraceGetRegset(thread.ID) })

pkg/proc/native/registers_freebsd_amd64.go

@@ -6,6 +6,7 @@ import (
 	sys "golang.org/x/sys/unix"
 
 	"github.com/go-delve/delve/pkg/proc"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 	"github.com/go-delve/delve/pkg/proc/fbsdutil"
 )
 
@@ -61,7 +62,7 @@ func registers(thread *nativeThread) (proc.Registers, error) {
 		return nil, err
 	}
 	r := fbsdutil.NewAMD64Registers(&regs, uint64(fsbase), func(r *fbsdutil.AMD64Registers) error {
-		var fpregset fbsdutil.AMD64Xstate
+		var fpregset amd64util.AMD64Xstate
 		var floatLoadError error
 		r.Fpregs, fpregset, floatLoadError = thread.fpRegisters()
 		r.Fpregset = &fpregset
@@ -70,17 +71,9 @@ func registers(thread *nativeThread) (proc.Registers, error) {
 	return r, nil
 }
 
-const (
-	_X86_XSTATE_MAX_SIZE = 2696
-	_NT_X86_XSTATE       = 0x202
+const _NT_X86_XSTATE = 0x202
 
-	_XSAVE_HEADER_START          = 512
-	_XSAVE_HEADER_LEN            = 64
-	_XSAVE_EXTENDED_REGION_START = 576
-	_XSAVE_SSE_REGION_LEN        = 416
-)
-
-func (thread *nativeThread) fpRegisters() (regs []proc.Register, fpregs fbsdutil.AMD64Xstate, err error) {
+func (thread *nativeThread) fpRegisters() (regs []proc.Register, fpregs amd64util.AMD64Xstate, err error) {
 	thread.dbp.execPtraceFunc(func() { fpregs, err = ptraceGetRegset(thread.ID) })
 	if err != nil {
 		err = fmt.Errorf("could not get floating point registers: %v", err.Error())

pkg/proc/native/registers_linux_amd64.go

@@ -6,6 +6,7 @@ import (
 	sys "golang.org/x/sys/unix"
 
 	"github.com/go-delve/delve/pkg/proc"
+	"github.com/go-delve/delve/pkg/proc/amd64util"
 	"github.com/go-delve/delve/pkg/proc/linutil"
 )
 
@@ -56,7 +57,7 @@ func registers(thread *nativeThread) (proc.Registers, error) {
 		return nil, err
 	}
 	r := linutil.NewAMD64Registers(&regs, func(r *linutil.AMD64Registers) error {
-		var fpregset linutil.AMD64Xstate
+		var fpregset amd64util.AMD64Xstate
 		var floatLoadError error
 		r.Fpregs, fpregset, floatLoadError = thread.fpRegisters()
 		r.Fpregset = &fpregset
@@ -65,17 +66,9 @@ func registers(thread *nativeThread) (proc.Registers, error) {
 	return r, nil
 }
 
-const (
-	_X86_XSTATE_MAX_SIZE = 2696
-	_NT_X86_XSTATE       = 0x202
+const _NT_X86_XSTATE = 0x202
 
-	_XSAVE_HEADER_START          = 512
-	_XSAVE_HEADER_LEN            = 64
-	_XSAVE_EXTENDED_REGION_START = 576
-	_XSAVE_SSE_REGION_LEN        = 416
-)
-
-func (thread *nativeThread) fpRegisters() (regs []proc.Register, fpregs linutil.AMD64Xstate, err error) {
+func (thread *nativeThread) fpRegisters() (regs []proc.Register, fpregs amd64util.AMD64Xstate, err error) {
 	thread.dbp.execPtraceFunc(func() { fpregs, err = ptraceGetRegset(thread.ID) })
 	regs = fpregs.Decode()
 	if err != nil {