1 files changed, 209 insertions, 0 deletions
diff --git a/src/debug/pe/symbol.go b/src/debug/pe/symbol.go
new file mode 100644
index 0000000..b1654f8
--- /dev/null
+++ b/src/debug/pe/symbol.go
@@ -0,0 +1,209 @@
+// Copyright 2016 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.
+
+package pe
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"internal/saferio"
+	"io"
+	"unsafe"
+)
+
+const COFFSymbolSize = 18
+
+// COFFSymbol represents single COFF symbol table record.
+type COFFSymbol struct {
+	Name               [8]uint8
+	Value              uint32
+	SectionNumber      int16
+	Type               uint16
+	StorageClass       uint8
+	NumberOfAuxSymbols uint8
+}
+
+// readCOFFSymbols reads in the symbol table for a PE file, returning
+// a slice of COFFSymbol objects. The PE format includes both primary
+// symbols (whose fields are described by COFFSymbol above) and
+// auxiliary symbols; all symbols are 18 bytes in size. The auxiliary
+// symbols for a given primary symbol are placed following it in the
+// array, e.g.
+//
+//	...
+//	k+0:  regular sym k
+//	k+1:    1st aux symbol for k
+//	k+2:    2nd aux symbol for k
+//	k+3:  regular sym k+3
+//	k+4:    1st aux symbol for k+3
+//	k+5:  regular sym k+5
+//	k+6:  regular sym k+6
+//
+// The PE format allows for several possible aux symbol formats. For
+// more info see:
+//
+//	https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#auxiliary-symbol-records
+//
+// At the moment this package only provides APIs for looking at
+// aux symbols of format 5 (associated with section definition symbols).
+func readCOFFSymbols(fh *FileHeader, r io.ReadSeeker) ([]COFFSymbol, error) {
+	if fh.PointerToSymbolTable == 0 {
+		return nil, nil
+	}
+	if fh.NumberOfSymbols <= 0 {
+		return nil, nil
+	}
+	_, err := r.Seek(int64(fh.PointerToSymbolTable), seekStart)
+	if err != nil {
+		return nil, fmt.Errorf("fail to seek to symbol table: %v", err)
+	}
+	c := saferio.SliceCap((*COFFSymbol)(nil), uint64(fh.NumberOfSymbols))
+	if c < 0 {
+		return nil, errors.New("too many symbols; file may be corrupt")
+	}
+	syms := make([]COFFSymbol, 0, c)
+	naux := 0
+	for k := uint32(0); k < fh.NumberOfSymbols; k++ {
+		var sym COFFSymbol
+		if naux == 0 {
+			// Read a primary symbol.
+			err = binary.Read(r, binary.LittleEndian, &sym)
+			if err != nil {
+				return nil, fmt.Errorf("fail to read symbol table: %v", err)
+			}
+			// Record how many auxiliary symbols it has.
+			naux = int(sym.NumberOfAuxSymbols)
+		} else {
+			// Read an aux symbol. At the moment we assume all
+			// aux symbols are format 5 (obviously this doesn't always
+			// hold; more cases will be needed below if more aux formats
+			// are supported in the future).
+			naux--
+			aux := (*COFFSymbolAuxFormat5)(unsafe.Pointer(&sym))
+			err = binary.Read(r, binary.LittleEndian, aux)
+			if err != nil {
+				return nil, fmt.Errorf("fail to read symbol table: %v", err)
+			}
+		}
+		syms = append(syms, sym)
+	}
+	if naux != 0 {
+		return nil, fmt.Errorf("fail to read symbol table: %d aux symbols unread", naux)
+	}
+	return syms, nil
+}
+
+// isSymNameOffset checks symbol name if it is encoded as offset into string table.
+func isSymNameOffset(name [8]byte) (bool, uint32) {
+	if name[0] == 0 && name[1] == 0 && name[2] == 0 && name[3] == 0 {
+		return true, binary.LittleEndian.Uint32(name[4:])
+	}
+	return false, 0
+}
+
+// FullName finds real name of symbol sym. Normally name is stored
+// in sym.Name, but if it is longer then 8 characters, it is stored
+// in COFF string table st instead.
+func (sym *COFFSymbol) FullName(st StringTable) (string, error) {
+	if ok, offset := isSymNameOffset(sym.Name); ok {
+		return st.String(offset)
+	}
+	return cstring(sym.Name[:]), nil
+}
+
+func removeAuxSymbols(allsyms []COFFSymbol, st StringTable) ([]*Symbol, error) {
+	if len(allsyms) == 0 {
+		return nil, nil
+	}
+	syms := make([]*Symbol, 0)
+	aux := uint8(0)
+	for _, sym := range allsyms {
+		if aux > 0 {
+			aux--
+			continue
+		}
+		name, err := sym.FullName(st)
+		if err != nil {
+			return nil, err
+		}
+		aux = sym.NumberOfAuxSymbols
+		s := &Symbol{
+			Name:          name,
+			Value:         sym.Value,
+			SectionNumber: sym.SectionNumber,
+			Type:          sym.Type,
+			StorageClass:  sym.StorageClass,
+		}
+		syms = append(syms, s)
+	}
+	return syms, nil
+}
+
+// Symbol is similar to COFFSymbol with Name field replaced
+// by Go string. Symbol also does not have NumberOfAuxSymbols.
+type Symbol struct {
+	Name          string
+	Value         uint32
+	SectionNumber int16
+	Type          uint16
+	StorageClass  uint8
+}
+
+// COFFSymbolAuxFormat5 describes the expected form of an aux symbol
+// attached to a section definition symbol. The PE format defines a
+// number of different aux symbol formats: format 1 for function
+// definitions, format 2 for .be and .ef symbols, and so on. Format 5
+// holds extra info associated with a section definition, including
+// number of relocations + line numbers, as well as COMDAT info. See
+// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#auxiliary-format-5-section-definitions
+// for more on what's going on here.
+type COFFSymbolAuxFormat5 struct {
+	Size           uint32
+	NumRelocs      uint16
+	NumLineNumbers uint16
+	Checksum       uint32
+	SecNum         uint16
+	Selection      uint8
+	_              [3]uint8 // padding
+}
+
+// These constants make up the possible values for the 'Selection'
+// field in an AuxFormat5.
+const (
+	IMAGE_COMDAT_SELECT_NODUPLICATES = 1
+	IMAGE_COMDAT_SELECT_ANY          = 2
+	IMAGE_COMDAT_SELECT_SAME_SIZE    = 3
+	IMAGE_COMDAT_SELECT_EXACT_MATCH  = 4
+	IMAGE_COMDAT_SELECT_ASSOCIATIVE  = 5
+	IMAGE_COMDAT_SELECT_LARGEST      = 6
+)
+
+// COFFSymbolReadSectionDefAux returns a blob of axiliary information
+// (including COMDAT info) for a section definition symbol. Here 'idx'
+// is the index of a section symbol in the main COFFSymbol array for
+// the File. Return value is a pointer to the appropriate aux symbol
+// struct. For more info, see:
+//
+// auxiliary symbols: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#auxiliary-symbol-records
+// COMDAT sections: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#comdat-sections-object-only
+// auxiliary info for section definitions: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#auxiliary-format-5-section-definitions
+func (f *File) COFFSymbolReadSectionDefAux(idx int) (*COFFSymbolAuxFormat5, error) {
+	var rv *COFFSymbolAuxFormat5
+	if idx < 0 || idx >= len(f.COFFSymbols) {
+		return rv, fmt.Errorf("invalid symbol index")
+	}
+	pesym := &f.COFFSymbols[idx]
+	const IMAGE_SYM_CLASS_STATIC = 3
+	if pesym.StorageClass != uint8(IMAGE_SYM_CLASS_STATIC) {
+		return rv, fmt.Errorf("incorrect symbol storage class")
+	}
+	if pesym.NumberOfAuxSymbols == 0 || idx+1 >= len(f.COFFSymbols) {
+		return rv, fmt.Errorf("aux symbol unavailable")
+	}
+	// Locate and return a pointer to the successor aux symbol.
+	pesymn := &f.COFFSymbols[idx+1]
+	rv = (*COFFSymbolAuxFormat5)(unsafe.Pointer(pesymn))
+	return rv, nil
+}