1// Copyright 2018 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Parsing of XCOFF executable (AIX)
6
7package objfile
8
9import (
10	"debug/dwarf"
11	"fmt"
12	"internal/xcoff"
13	"io"
14	"unicode"
15)
16
17type xcoffFile struct {
18	xcoff *xcoff.File
19}
20
21func openXcoff(r io.ReaderAt) (rawFile, error) {
22	f, err := xcoff.NewFile(r)
23	if err != nil {
24		return nil, err
25	}
26	return &xcoffFile{f}, nil
27}
28
29func (f *xcoffFile) symbols() ([]Sym, error) {
30	var syms []Sym
31	for _, s := range f.xcoff.Symbols {
32		const (
33			N_UNDEF = 0  // An undefined (extern) symbol
34			N_ABS   = -1 // An absolute symbol (e_value is a constant, not an address)
35			N_DEBUG = -2 // A debugging symbol
36		)
37		sym := Sym{Name: s.Name, Addr: s.Value, Code: '?'}
38
39		switch s.SectionNumber {
40		case N_UNDEF:
41			sym.Code = 'U'
42		case N_ABS:
43			sym.Code = 'C'
44		case N_DEBUG:
45			sym.Code = '?'
46		default:
47			if s.SectionNumber < 0 || len(f.xcoff.Sections) < int(s.SectionNumber) {
48				return nil, fmt.Errorf("invalid section number in symbol table")
49			}
50			sect := f.xcoff.Sections[s.SectionNumber-1]
51
52			// debug/xcoff returns an offset in the section not the actual address
53			sym.Addr += sect.VirtualAddress
54
55			if s.AuxCSect.SymbolType&0x3 == xcoff.XTY_LD {
56				// The size of a function is contained in the
57				// AUX_FCN entry
58				sym.Size = s.AuxFcn.Size
59			} else {
60				sym.Size = s.AuxCSect.Length
61			}
62
63			sym.Size = s.AuxCSect.Length
64
65			switch sect.Type {
66			case xcoff.STYP_TEXT:
67				if s.AuxCSect.StorageMappingClass == xcoff.XMC_RO {
68					sym.Code = 'R'
69				} else {
70					sym.Code = 'T'
71				}
72			case xcoff.STYP_DATA:
73				sym.Code = 'D'
74			case xcoff.STYP_BSS:
75				sym.Code = 'B'
76			}
77
78			if s.StorageClass == xcoff.C_HIDEXT {
79				// Local symbol
80				sym.Code = unicode.ToLower(sym.Code)
81			}
82
83		}
84		syms = append(syms, sym)
85	}
86
87	return syms, nil
88}
89
90func (f *xcoffFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
91	if sect := f.xcoff.Section(".text"); sect != nil {
92		textStart = sect.VirtualAddress
93	}
94	if pclntab, err = loadXCOFFTable(f.xcoff, "runtime.pclntab", "runtime.epclntab"); err != nil {
95		return 0, nil, nil, err
96	}
97	symtab, _ = loadXCOFFTable(f.xcoff, "runtime.symtab", "runtime.esymtab") // ignore error, this symbol is not useful anyway
98	return textStart, symtab, pclntab, nil
99}
100
101func (f *xcoffFile) text() (textStart uint64, text []byte, err error) {
102	sect := f.xcoff.Section(".text")
103	if sect == nil {
104		return 0, nil, fmt.Errorf("text section not found")
105	}
106	textStart = sect.VirtualAddress
107	text, err = sect.Data()
108	return
109}
110
111func findXCOFFSymbol(f *xcoff.File, name string) (*xcoff.Symbol, error) {
112	for _, s := range f.Symbols {
113		if s.Name != name {
114			continue
115		}
116		if s.SectionNumber <= 0 {
117			return nil, fmt.Errorf("symbol %s: invalid section number %d", name, s.SectionNumber)
118		}
119		if len(f.Sections) < int(s.SectionNumber) {
120			return nil, fmt.Errorf("symbol %s: section number %d is larger than max %d", name, s.SectionNumber, len(f.Sections))
121		}
122		return s, nil
123	}
124	return nil, fmt.Errorf("no %s symbol found", name)
125}
126
127func loadXCOFFTable(f *xcoff.File, sname, ename string) ([]byte, error) {
128	ssym, err := findXCOFFSymbol(f, sname)
129	if err != nil {
130		return nil, err
131	}
132	esym, err := findXCOFFSymbol(f, ename)
133	if err != nil {
134		return nil, err
135	}
136	if ssym.SectionNumber != esym.SectionNumber {
137		return nil, fmt.Errorf("%s and %s symbols must be in the same section", sname, ename)
138	}
139	sect := f.Sections[ssym.SectionNumber-1]
140	data, err := sect.Data()
141	if err != nil {
142		return nil, err
143	}
144	return data[ssym.Value:esym.Value], nil
145}
146
147func (f *xcoffFile) goarch() string {
148	switch f.xcoff.TargetMachine {
149	case xcoff.U802TOCMAGIC:
150		return "ppc"
151	case xcoff.U64_TOCMAGIC:
152		return "ppc64"
153	}
154	return ""
155}
156
157func (f *xcoffFile) loadAddress() (uint64, error) {
158	return 0, fmt.Errorf("unknown load address")
159}
160
161func (f *xcoffFile) dwarf() (*dwarf.Data, error) {
162	return f.xcoff.DWARF()
163}
164