debug/elf: added MIPS ELF relocations

Change-Id: I05352749a852095baae2f67fd71ffcf5f727538d
Reviewed-on: https://go-review.googlesource.com/14453
Reviewed-by: Minux Ma <minux@golang.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/src/debug/elf/file.go b/src/debug/elf/file.go
index 40625435fd..3e766afe15 100644
--- a/src/debug/elf/file.go
+++ b/src/debug/elf/file.go
@@ -537,6 +537,8 @@ func (f *File) applyRelocations(dst []byte, rels []byte) error {
 		return f.applyRelocationsPPC(dst, rels)
 	case f.Class == ELFCLASS64 && f.Machine == EM_PPC64:
 		return f.applyRelocationsPPC64(dst, rels)
+	case f.Class == ELFCLASS64 && f.Machine == EM_MIPS:
+		return f.applyRelocationsMIPS64(dst, rels)
 	default:
 		return errors.New("applyRelocations: not implemented")
 	}
@@ -800,6 +802,58 @@ func (f *File) applyRelocationsPPC64(dst []byte, rels []byte) error {
 	return nil
 }
 
+func (f *File) applyRelocationsMIPS64(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)
+		var symNo uint64
+		var t R_MIPS
+		if f.ByteOrder == binary.BigEndian {
+			symNo = rela.Info >> 32
+			t = R_MIPS(rela.Info & 0xff)
+		} else {
+			symNo = rela.Info & 0xffffffff
+			t = R_MIPS(rela.Info >> 56)
+		}
+
+		if symNo == 0 || symNo > uint64(len(symbols)) {
+			continue
+		}
+		sym := &symbols[symNo-1]
+		if SymType(sym.Info&0xf) != STT_SECTION {
+			// We don't handle non-section relocations for now.
+			continue
+		}
+
+		switch t {
+		case R_MIPS_64:
+			if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
+				continue
+			}
+			f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], uint64(rela.Addend))
+		case R_MIPS_32:
+			if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
+				continue
+			}
+			f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], uint32(rela.Addend))
+		}
+	}
+
+	return nil
+}
+
 func (f *File) DWARF() (*dwarf.Data, error) {
 	// sectionData gets the data for s, checks its size, and
 	// applies any applicable relations.