cmd/link: add new loading package for XCOFF files

This commit adds the new package cmd/link/internal/loadxcoff.

It also adds a new symbol kind in cmd/link/internal/sym package, which
aims to represent TOC entries for XCOFF files.

cmd/dist is updated to add this new package and cmd/internal/xcoff during
the bootstrap.

Updates: #25893

Change-Id: I42b6578cf0ba4cc28ad4aa98122a91ab1d1bbf6e
Reviewed-on: https://go-review.googlesource.com/c/138728
Run-TryBot: Tobias Klauser <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: Clément Chigot

src/cmd/dist/buildtool.go

@@ -74,6 +74,7 @@ var bootstrapDirs = []string{
 	"cmd/link/internal/loadelf",
 	"cmd/link/internal/loadmacho",
 	"cmd/link/internal/loadpe",
+	"cmd/link/internal/loadxcoff",
 	"cmd/link/internal/mips",
 	"cmd/link/internal/mips64",
 	"cmd/link/internal/objfile",

src/cmd/link/internal/loadxcoff/ldxcoff.go

@@ -0,0 +1,225 @@
+// 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.
+
+// Package loadxcoff implements a XCOFF file reader.
+package loadxcoff
+
+import (
+	"cmd/internal/bio"
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
+	"cmd/internal/xcoff"
+	"cmd/link/internal/sym"
+	"errors"
+	"fmt"
+)
+
+// ldSection is an XCOFF section with its symbols.
+type ldSection struct {
+	xcoff.Section
+	sym *sym.Symbol
+}
+
+// TODO(brainman): maybe just add ReadAt method to bio.Reader instead of creating xcoffBiobuf
+
+// xcoffBiobuf makes bio.Reader look like io.ReaderAt.
+type xcoffBiobuf bio.Reader
+
+func (f *xcoffBiobuf) ReadAt(p []byte, off int64) (int, error) {
+	ret := ((*bio.Reader)(f)).Seek(off, 0)
+	if ret < 0 {
+		return 0, errors.New("fail to seek")
+	}
+	n, err := f.Read(p)
+	if err != nil {
+		return 0, err
+	}
+	return n, nil
+}
+
+// Load loads the Xcoff file pn from f.
+// Symbols are written into syms, and a slice of the text symbols is returned.
+func Load(arch *sys.Arch, syms *sym.Symbols, input *bio.Reader, pkg string, length int64, pn string) (textp []*sym.Symbol, err error) {
+	errorf := func(str string, args ...interface{}) ([]*sym.Symbol, error) {
+		return nil, fmt.Errorf("loadxcoff: %v: %v", pn, fmt.Sprintf(str, args...))
+	}
+	localSymVersion := syms.IncVersion()
+
+	var ldSections []*ldSection
+
+	f, err := xcoff.NewFile((*xcoffBiobuf)(input))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	for _, sect := range f.Sections {
+		//only text, data and bss section
+		if sect.Type < xcoff.STYP_TEXT || sect.Type > xcoff.STYP_BSS {
+			continue
+		}
+		lds := new(ldSection)
+		lds.Section = *sect
+		name := fmt.Sprintf("%s(%s)", pkg, lds.Name)
+		s := syms.Lookup(name, localSymVersion)
+
+		switch lds.Type {
+		default:
+			return errorf("unrecognized section type 0x%x", lds.Type)
+		case xcoff.STYP_TEXT:
+			s.Type = sym.STEXT
+		case xcoff.STYP_DATA:
+			s.Type = sym.SNOPTRDATA
+		case xcoff.STYP_BSS:
+			s.Type = sym.SNOPTRBSS
+		}
+
+		s.Size = int64(lds.Size)
+		if s.Type != sym.SNOPTRBSS {
+			data, err := lds.Section.Data()
+			if err != nil {
+				return nil, err
+			}
+			s.P = data
+		}
+
+		lds.sym = s
+		ldSections = append(ldSections, lds)
+	}
+
+	// sx = symbol from file
+	// s = symbol for syms
+	for _, sx := range f.Symbols {
+		// get symbol type
+		stype, errmsg := getSymbolType(f, sx)
+		if errmsg != "" {
+			return errorf("error reading symbol %s: %s", sx.Name, errmsg)
+		}
+		if stype == sym.Sxxx {
+			continue
+		}
+
+		s := syms.Lookup(sx.Name, 0)
+
+		// Text symbol
+		if s.Type == sym.STEXT {
+			if s.Attr.OnList() {
+				return errorf("symbol %s listed multiple times", s.Name)
+			}
+			s.Attr |= sym.AttrOnList
+			textp = append(textp, s)
+		}
+	}
+
+	// Read relocations
+	for _, sect := range ldSections {
+		// TODO(aix): Dwarf section relocation if needed
+		if sect.Type != xcoff.STYP_TEXT && sect.Type != xcoff.STYP_DATA {
+			continue
+		}
+		rs := make([]sym.Reloc, sect.Nreloc)
+		for i, rx := range sect.Relocs {
+			r := &rs[i]
+
+			r.Sym = syms.Lookup(rx.Symbol.Name, 0)
+			if uint64(int32(rx.VirtualAddress)) != rx.VirtualAddress {
+				return errorf("virtual address of a relocation is too big: 0x%x", rx.VirtualAddress)
+			}
+			r.Off = int32(rx.VirtualAddress)
+			switch rx.Type {
+			default:
+				return errorf("section %s: unknown relocation of type 0x%x", sect.Name, rx.Type)
+			case xcoff.R_POS:
+				// Reloc the address of r.Sym
+				// Length should be 64
+				if rx.Length != 64 {
+					return errorf("section %s: relocation R_POS has length different from 64: %d", sect.Name, rx.Length)
+				}
+				r.Siz = 8
+				r.Type = objabi.R_CONST
+				r.Add = int64(rx.Symbol.Value)
+
+			case xcoff.R_RBR:
+				r.Siz = 4
+				r.Type = objabi.R_CALLPOWER
+				r.Add = 0 //
+
+			}
+		}
+		s := sect.sym
+		s.R = rs
+		s.R = s.R[:sect.Nreloc]
+	}
+	return textp, nil
+
+}
+
+// Convert symbol xcoff type to sym.SymKind
+// Returns nil if this shouldn't be added into syms (like .file or .dw symbols )
+func getSymbolType(f *xcoff.File, s *xcoff.Symbol) (stype sym.SymKind, err string) {
+	// .file symbol
+	if s.SectionNumber == -2 {
+		if s.StorageClass == xcoff.C_FILE {
+			return sym.Sxxx, ""
+		}
+		return sym.Sxxx, "unrecognised StorageClass for sectionNumber = -2"
+	}
+
+	// extern symbols
+	// TODO(aix)
+	if s.SectionNumber == 0 {
+		return sym.Sxxx, ""
+	}
+
+	sectType := f.Sections[s.SectionNumber-1].SectionHeader.Type
+	switch sectType {
+	default:
+		return sym.Sxxx, fmt.Sprintf("getSymbolType for Section type 0x%x not implemented", sectType)
+	case xcoff.STYP_DWARF, xcoff.STYP_DEBUG:
+		return sym.Sxxx, ""
+	case xcoff.STYP_DATA, xcoff.STYP_BSS, xcoff.STYP_TEXT:
+	}
+
+	switch s.StorageClass {
+	default:
+		return sym.Sxxx, fmt.Sprintf("getSymbolType for Storage class 0x%x not implemented", s.StorageClass)
+	case xcoff.C_HIDEXT, xcoff.C_EXT, xcoff.C_WEAKEXT:
+		switch s.AuxCSect.StorageMappingClass {
+		default:
+			return sym.Sxxx, fmt.Sprintf("getSymbolType for Storage class 0x%x and Storage Map 0x%x not implemented", s.StorageClass, s.AuxCSect.StorageMappingClass)
+
+		// Program Code
+		case xcoff.XMC_PR:
+			if sectType == xcoff.STYP_TEXT {
+				return sym.STEXT, ""
+			}
+			return sym.Sxxx, fmt.Sprintf("unrecognised Section Type 0x%x for Storage Class 0x%x with Storage Map XMC_PR", sectType, s.StorageClass)
+
+		// Read/Write Data
+		case xcoff.XMC_RW:
+			if sectType == xcoff.STYP_DATA {
+				return sym.SDATA, ""
+			}
+			if sectType == xcoff.STYP_BSS {
+				return sym.SBSS, ""
+			}
+			return sym.Sxxx, fmt.Sprintf("unrecognised Section Type 0x%x for Storage Class 0x%x with Storage Map XMC_RW", sectType, s.StorageClass)
+
+		// Function descriptor
+		case xcoff.XMC_DS:
+			if sectType == xcoff.STYP_DATA {
+				return sym.SDATA, ""
+			}
+			return sym.Sxxx, fmt.Sprintf("unrecognised Section Type 0x%x for Storage Class 0x%x with Storage Map XMC_DS", sectType, s.StorageClass)
+
+		// TOC anchor and TOC entry
+		case xcoff.XMC_TC0, xcoff.XMC_TE:
+			if sectType == xcoff.STYP_DATA {
+				return sym.SXCOFFTOC, ""
+			}
+			return sym.Sxxx, fmt.Sprintf("unrecognised Section Type 0x%x for Storage Class 0x%x with Storage Map XMC_DS", sectType, s.StorageClass)
+
+		}
+	}
+}

src/cmd/link/internal/sym/symkind.go

@@ -92,6 +92,7 @@ const (
 	SBSS
 	SNOPTRBSS
 	STLSBSS
+	SXCOFFTOC
 	SXREF
 	SMACHOSYMSTR
 	SMACHOSYMTAB