From 396a9b98bac38dce31085146f8c713fbe3c0c664 Mon Sep 17 00:00:00 2001
From: Jeremy Faller <jeremy@golang.org>
Date: Tue, 29 Oct 2019 10:52:20 -0400
Subject: [PATCH] [dev.link] cmd/link: fix macho host objects

Small updates to macho loader, fixing some misunderstandings I had about
using the new object file format.

Change-Id: I9224b01ca327e3a087ebfa36800bd6eef6abcc80
Reviewed-on: https://go-review.googlesource.com/c/go/+/204097
Reviewed-by: Cherry Zhang <cherryyz@google.com>
---
 src/cmd/link/internal/ld/config.go         |  2 +-
 src/cmd/link/internal/ld/lib.go            |  3 ++-
 src/cmd/link/internal/loader/loader.go     |  2 +-
 src/cmd/link/internal/loadmacho/ldmacho.go | 27 ++++++++--------------
 4 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/src/cmd/link/internal/ld/config.go b/src/cmd/link/internal/ld/config.go
index 43dc472230..0c571c30e7 100644
--- a/src/cmd/link/internal/ld/config.go
+++ b/src/cmd/link/internal/ld/config.go
@@ -168,7 +168,7 @@ func canLinkHostObj(ctxt *Link) bool {
 	if !*flagNewobj {
 		return true
 	}
-	return ctxt.IsELF
+	return ctxt.IsELF || objabi.GOOS == "darwin"
 }
 
 // mustLinkExternal reports whether the program being linked requires
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index e5e0f1e0dd..679d44e8dd 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1653,11 +1653,12 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 	if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
 		if *flagNewobj {
 			ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
-				err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.Syms, f, pkg, length, pn)
+				textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.Syms, f, pkg, length, pn)
 				if err != nil {
 					Errorf(nil, "%v", err)
 					return
 				}
+				ctxt.Textp = append(ctxt.Textp, textp...)
 			}
 			return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
 		} else {
diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index f0689032f3..0ce6f54ef7 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -511,7 +511,7 @@ func (l *Loader) OuterSym(i Sym) Sym {
 	return 0
 }
 
-// SubSym gets sub symbols for a previously loaded host object symbol.
+// SubSym gets the subsymbol for host object loaded symbols.
 func (l *Loader) SubSym(i Sym) Sym {
 	sym := l.Syms[i]
 	if sym != nil && sym.Sub != nil {
diff --git a/src/cmd/link/internal/loadmacho/ldmacho.go b/src/cmd/link/internal/loadmacho/ldmacho.go
index 18a0678af8..f21d4bd14f 100644
--- a/src/cmd/link/internal/loadmacho/ldmacho.go
+++ b/src/cmd/link/internal/loadmacho/ldmacho.go
@@ -424,31 +424,24 @@ func macholoadsym(m *ldMachoObj, symtab *ldMachoSymtab) int {
 	return 0
 }
 
-func Load(l *loader.Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) error {
-	lookup := func(name string, version int) *sym.Symbol {
-		// Check to see if we've already defined the symbol.
-		if i := l.Lookup(name, version); i != 0 {
-			return l.Syms[i]
-		}
-		// Not defined, let's make one.
-		if s := l.AddExtSym(name, version); s == 0 {
+func Load(l *loader.Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) ([]*sym.Symbol, error) {
+	newSym := func(name string, version int) *sym.Symbol {
+		i := l.Lookup(name, version)
+		if i != 0 {
+			return l.LoadSymbol(name, version, syms)
+		}
+		if i = l.AddExtSym(name, version); i == 0 {
 			panic("AddExtSym returned bad index")
-		} else if int(s) != len(l.Syms) {
-			panic("unexpected length of loaded symbols")
 		}
 		newSym := syms.Newsym(name, version)
-		l.Syms = append(l.Syms, newSym)
+		l.Syms[i] = newSym
 		return newSym
 	}
-	_, err := load(arch, syms.IncVersion(), lookup, f, pkg, length, pn)
-	return err
+	return load(arch, syms.IncVersion(), newSym, f, pkg, length, pn)
 }
 
 func LoadOld(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) (textp []*sym.Symbol, err error) {
-	lookup := func(name string, version int) *sym.Symbol {
-		return syms.Lookup(name, version)
-	}
-	return load(arch, syms.IncVersion(), lookup, f, pkg, length, pn)
+	return load(arch, syms.IncVersion(), syms.Lookup, f, pkg, length, pn)
 }
 
 // load the Mach-O file pn from f.
-- 
2.48.1