proc: load more registers

Adds ability to load x87, SSE and AVX registers.

Fixes #666

proc/ptrace_linux.go

@@ -1,6 +1,7 @@
 package proc
 
 import (
+	"encoding/binary"
 	"syscall"
 	"unsafe"
 
@@ -49,3 +50,47 @@ func PtracePeekUser(tid int, off uintptr) (uintptr, error) {
 	}
 	return val, nil
 }
+
+// PtraceGetRegset returns floating point registers of the specified thread
+// using PTRACE.
+// 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 PtraceXsave, err error) {
+	_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETFPREGS, uintptr(tid), uintptr(0), uintptr(unsafe.Pointer(&regset.PtraceFpRegs)), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
+	}
+
+	var xstateargs [_X86_XSTATE_MAX_SIZE]byte
+	iov := sys.Iovec{Base: &xstateargs[0], Len: _X86_XSTATE_MAX_SIZE}
+	_, _, 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) {
+		return
+	} else {
+		err = nil
+	}
+
+	if _XSAVE_HEADER_START+_XSAVE_HEADER_LEN >= iov.Len {
+		return
+	}
+	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
+	}
+
+	if xstate_bv&(1<<2) == 0 {
+		// AVX state not present
+		return
+	}
+
+	avxstate := xstateargs[_XSAVE_EXTENDED_REGION_START:iov.Len]
+	regset.AvxState = true
+	copy(regset.YmmSpace[:], avxstate[:len(regset.YmmSpace)])
+
+	return
+}