fix start of text for objdump

Author: psilva261

src/debug/plan9obj/file.go

@@ -145,7 +145,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
 	if _, err := r.ReadAt(magic[:], 0); err != nil {
 		return nil, err
 	}
-	_, err := parseMagic(magic[:])
+	m, err := parseMagic(magic[:])
 	if err != nil {
 		return nil, err
 	}
@@ -169,7 +169,11 @@ func NewFile(r io.ReaderAt) (*File, error) {
 			return nil, err
 		}
 		f.PtrSize = 8
-		f.LoadAddress = 0x200000
+		if m == MagicARM64 {
+			f.LoadAddress = 0x10000
+		} else {
+			f.LoadAddress = 0x200000
+		}
 		f.HdrSize += 8
 	}
 

src/debug/plan9obj/file_test.go

@@ -38,6 +38,17 @@ var fileTests = []fileTest{
 			{"pcsz", 0xca0, 0x7947},
 		},
 	},
+	{
+		"testdata/arm64-plan9-exec",
+		FileHeader{MagicARM64, 0x408, 0x1003c, 8, 0x10000, 40},
+		[]*SectionHeader{
+			{"text", 0x4a00, 0x28},
+			{"data", 0xaa0, 0x4a28},
+			{"syms", 0x294a, 0x54c8},
+			{"spsz", 0x0, 0x7e12},
+			{"pcsz", 0xa6c, 0x7e12},
+		},
+	},
 }
 
 func TestOpen(t *testing.T) {