cmd: add XCOFF objfile and adapt cmd/nm tests

This commit adds a new file format in cmd/internal/objfile for XCOFF.
It also adapts tests inside cmd/nm for AIX.

Updates: #25893

Change-Id: I1e55ea0b7f7d08a871343bee27d11e2d3baad254
Reviewed-on: https://go-review.googlesource.com/c/145397
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

2 files changed, 134 insertions, 0 deletions

diff --git a/src/cmd/internal/objfile/objfile.go b/src/cmd/internal/objfile/objfile.go
index 10307be072..41c5d9b9f5 100644
--- a/src/cmd/internal/objfile/objfile.go
+++ b/src/cmd/internal/objfile/objfile.go
@@ -61,6 +61,7 @@ var openers = []func(io.ReaderAt) (rawFile, error){
 	openMacho,
 	openPE,
 	openPlan9,
+	openXcoff,
 }
 
 // Open opens the named file.
diff --git a/src/cmd/internal/objfile/xcoff.go b/src/cmd/internal/objfile/xcoff.go
new file mode 100644
index 0000000000..c36b4362ba
--- /dev/null
+++ b/src/cmd/internal/objfile/xcoff.go
@@ -0,0 +1,133 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parsing of XCOFF executable (AIX)
+
+package objfile
+
+import (
+	"cmd/internal/xcoff"
+	"debug/dwarf"
+	"fmt"
+	"io"
+	"unicode"
+)
+
+type xcoffFile struct {
+	xcoff *xcoff.File
+}
+
+func openXcoff(r io.ReaderAt) (rawFile, error) {
+	f, err := xcoff.NewFile(r)
+	if err != nil {
+		return nil, err
+	}
+	return &xcoffFile{f}, nil
+}
+
+func (f *xcoffFile) symbols() ([]Sym, error) {
+	var syms []Sym
+	for _, s := range f.xcoff.Symbols {
+		const (
+			N_UNDEF = 0  // An undefined (extern) symbol
+			N_ABS   = -1 // An absolute symbol (e_value is a constant, not an address)
+			N_DEBUG = -2 // A debugging symbol
+		)
+		sym := Sym{Name: s.Name, Addr: s.Value, Code: '?'}
+
+		switch s.SectionNumber {
+		case N_UNDEF:
+			sym.Code = 'U'
+		case N_ABS:
+			sym.Code = 'C'
+		case N_DEBUG:
+			sym.Code = '?'
+		default:
+			if s.SectionNumber < 0 || len(f.xcoff.Sections) < int(s.SectionNumber) {
+				return nil, fmt.Errorf("invalid section number in symbol table")
+			}
+			sect := f.xcoff.Sections[s.SectionNumber-1]
+
+			// debug/xcoff returns an offset in the section not the actual address
+			sym.Addr += sect.VirtualAddress
+
+			if s.AuxCSect.SymbolType&0x3 == xcoff.XTY_LD {
+				// The size of a function is contained in the
+				// AUX_FCN entry
+				sym.Size = s.AuxFcn.Size
+			} else {
+				sym.Size = s.AuxCSect.Length
+			}
+
+			sym.Size = s.AuxCSect.Length
+
+			switch sect.Type {
+			case xcoff.STYP_TEXT:
+				if s.AuxCSect.StorageMappingClass == xcoff.XMC_RO {
+					sym.Code = 'R'
+				} else {
+					sym.Code = 'T'
+				}
+			case xcoff.STYP_DATA:
+				sym.Code = 'D'
+			case xcoff.STYP_BSS:
+				sym.Code = 'B'
+			}
+
+			if s.StorageClass == xcoff.C_HIDEXT {
+				// Local symbol
+				sym.Code = unicode.ToLower(sym.Code)
+			}
+
+		}
+		syms = append(syms, sym)
+	}
+
+	return syms, nil
+}
+
+func (f *xcoffFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+	if sect := f.xcoff.Section(".text"); sect != nil {
+		textStart = sect.VirtualAddress
+	}
+	if sect := f.xcoff.Section(".gosymtab"); sect != nil {
+		if symtab, err = sect.Data(); err != nil {
+			return 0, nil, nil, err
+		}
+	}
+	if sect := f.xcoff.Section(".gopclntab"); sect != nil {
+		if pclntab, err = sect.Data(); err != nil {
+			return 0, nil, nil, err
+		}
+	}
+	return textStart, symtab, pclntab, nil
+}
+
+func (f *xcoffFile) text() (textStart uint64, text []byte, err error) {
+	sect := f.xcoff.Section(".text")
+	if sect == nil {
+		return 0, nil, fmt.Errorf("text section not found")
+	}
+	textStart = sect.VirtualAddress
+	text, err = sect.Data()
+	return
+}
+
+func (f *xcoffFile) goarch() string {
+	switch f.xcoff.TargetMachine {
+	case xcoff.U802TOCMAGIC:
+		return "ppc"
+	case xcoff.U64_TOCMAGIC:
+		return "ppc64"
+	}
+	return ""
+}
+
+func (f *xcoffFile) loadAddress() (uint64, error) {
+	return 0, fmt.Errorf("unknown load address")
+}
+
+func (f *xcoffFile) dwarf() (*dwarf.Data, error) {
+	return f.xcoff.DWARF()
+}