debug/elf: add s390x relocations

Change-Id: I8440f69c7f99d65b2f69035c26b4a62104f22bd3
Reviewed-on: https://go-review.googlesource.com/20874
Reviewed-by: Minux Ma <minux@golang.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/src/debug/elf/file.go b/src/debug/elf/file.go
index 72796d535f..c28a964b73 100644
--- a/src/debug/elf/file.go
+++ b/src/debug/elf/file.go
@@ -596,6 +596,8 @@ func (f *File) applyRelocations(dst []byte, rels []byte) error {
 		return f.applyRelocationsPPC64(dst, rels)
 	case f.Class == ELFCLASS64 && f.Machine == EM_MIPS:
 		return f.applyRelocationsMIPS64(dst, rels)
+	case f.Class == ELFCLASS64 && f.Machine == EM_S390:
+		return f.applyRelocationss390x(dst, rels)
 	default:
 		return errors.New("applyRelocations: not implemented")
 	}
@@ -911,6 +913,55 @@ func (f *File) applyRelocationsMIPS64(dst []byte, rels []byte) error {
 	return nil
 }
 
+func (f *File) applyRelocationss390x(dst []byte, rels []byte) error {
+	// 24 is the size of Rela64.
+	if len(rels)%24 != 0 {
+		return errors.New("length of relocation section is not a multiple of 24")
+	}
+
+	symbols, _, err := f.getSymbols(SHT_SYMTAB)
+	if err != nil {
+		return err
+	}
+
+	b := bytes.NewReader(rels)
+	var rela Rela64
+
+	for b.Len() > 0 {
+		binary.Read(b, f.ByteOrder, &rela)
+		symNo := rela.Info >> 32
+		t := R_390(rela.Info & 0xffff)
+
+		if symNo == 0 || symNo > uint64(len(symbols)) {
+			continue
+		}
+		sym := &symbols[symNo-1]
+		switch SymType(sym.Info & 0xf) {
+		case STT_SECTION, STT_NOTYPE:
+			break
+		default:
+			continue
+		}
+
+		switch t {
+		case R_390_64:
+			if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
+				continue
+			}
+			val := sym.Value + uint64(rela.Addend)
+			f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val)
+		case R_390_32:
+			if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
+				continue
+			}
+			val := uint32(sym.Value) + uint32(rela.Addend)
+			f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val)
+		}
+	}
+
+	return nil
+}
+
 func (f *File) DWARF() (*dwarf.Data, error) {
 	// sectionData gets the data for s, checks its size, and
 	// applies any applicable relations.