cmd/link: on AIX generate export file for host linker

Change-Id: I6638cb0f9ed751c76a29cae62a93a923f18f14f3
Reviewed-on: https://go-review.googlesource.com/c/go/+/164005
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index e99c81aeb72fe3247f43eddfbfe9c6454759296b..44befc96372334e6f3039ebdf6c1815c1a19801a 100644 (file)
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1266,6 +1266,10 @@ func (ctxt *Link) hostlink() {
        if ctxt.IsELF {
                argv = append(argv, "-rdynamic")
        }
+       if ctxt.HeadType == objabi.Haix {
+               fileName := xcoffCreateExportFile(ctxt)
+               argv = append(argv, "-Wl,-bE:"+fileName)
+       }
 
        if strings.Contains(argv[0], "clang") {
                argv = append(argv, "-Qunused-arguments")

diff --git a/src/cmd/link/internal/ld/xcoff.go b/src/cmd/link/internal/ld/xcoff.go
index 30a27d2b1826d4651034894b5a551c806bc9ac37..ee375bfe03ce2c67b72fdf34c563b53eeba2afb7 100644 (file)
--- a/src/cmd/link/internal/ld/xcoff.go
+++ b/src/cmd/link/internal/ld/xcoff.go
@@ -9,7 +9,9 @@ import (
        "cmd/internal/objabi"
        "cmd/link/internal/sym"
        "encoding/binary"
+       "io/ioutil"
        "math/bits"
+       "path/filepath"
        "sort"
        "strings"
 )
@@ -771,7 +773,7 @@ func (f *xcoffFile) writeSymbolFunc(ctxt *Link, x *sym.Symbol) []xcoffSym {
 
        s := &XcoffSymEnt64{
                Nsclass: C_EXT,
-               Noffset: uint32(xfile.stringTable.add(x.Name)),
+               Noffset: uint32(xfile.stringTable.add(x.Extname())),
                Nvalue:  uint64(x.Value),
                Nscnum:  f.getXCOFFscnum(x.Sect),
                Ntype:   SYM_TYPE_FUNC,
@@ -1182,6 +1184,26 @@ func (ctxt *Link) doxcoff() {
                // Change main name to match __start code.
                main := ctxt.Syms.ROLookup("_main", 0)
                main.Name = ".main"
+
+               for _, s := range ctxt.Syms.Allsym {
+                       if !s.Attr.CgoExport() {
+                               continue
+                       }
+
+                       name := s.Extname()
+                       if s.Type == sym.STEXT {
+                               // On AIX, a exported function must have two symbols:
+                               // - a .text symbol which must start with a ".".
+                               // - a .data symbol which is a function descriptor.
+                               ctxt.Syms.Rename(s.Name, "."+name, 0, ctxt.Reachparent)
+
+                               desc := ctxt.Syms.Lookup(name, 0)
+                               desc.Type = sym.SNOPTRDATA
+                               desc.AddAddr(ctxt.Arch, s)
+                               desc.AddAddr(ctxt.Arch, toc)
+                               desc.AddUint64(ctxt.Arch, 0)
+                       }
+               }
        }
 }
 
@@ -1614,3 +1636,36 @@ func (f *xcoffFile) emitRelocations(ctxt *Link, fileoff int64) {
 
        // TODO(aix): DWARF relocations
 }
+
+// xcoffCreateExportFile creates a file with exported symbols for
+// -Wl,-bE option.
+// ld won't export symbols unless they are listed in an export file.
+func xcoffCreateExportFile(ctxt *Link) (fname string) {
+       fname = filepath.Join(*flagTmpdir, "export_file.exp")
+       var buf bytes.Buffer
+
+       for _, s := range ctxt.Syms.Allsym {
+               if !s.Attr.CgoExport() {
+                       continue
+               }
+               if !strings.HasPrefix(s.String(), "_cgoexp_") {
+                       continue
+               }
+
+               // Retrieve the name of the initial symbol
+               // exported by cgo.
+               // The corresponding Go symbol is:
+               // _cgoexp_hashcode_symname.
+               name := strings.SplitN(s.Extname(), "_", 4)[3]
+
+               buf.Write([]byte(name + "\n"))
+       }
+
+       err := ioutil.WriteFile(fname, buf.Bytes(), 0666)
+       if err != nil {
+               Errorf(nil, "WriteFile %s failed: %v", fname, err)
+       }
+
+       return fname
+
+}