[dev.link] cmd/link: remove some dependence on *Link

In an effort to make relocation application thread-safe remove another
dependence on context.

Change-Id: Ic53ea122cce72117fcebe56e386b710755f6eb68
Reviewed-on: https://go-review.googlesource.com/c/go/+/220838
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

src/cmd/link/internal/ld/data.go

@@ -100,7 +100,7 @@ func trampoline(ctxt *Link, s *sym.Symbol) {
 		if Symaddr(r.Sym) == 0 && (r.Sym.Type != sym.SDYNIMPORT && r.Sym.Type != sym.SUNDEFEXT) {
 			if r.Sym.File != s.File {
 				if !isRuntimeDepPkg(s.File) || !isRuntimeDepPkg(r.Sym.File) {
-					ctxt.ErrorUnresolved(s, r)
+					ctxt.errorUnresolved(ctxt.Syms.ROLookup, s, r)
 				}
 				// runtime and its dependent packages may call to each other.
 				// they are fine, as they will be laid down together.
@@ -167,7 +167,7 @@ func relocsym(ctxt *Link, target *Target, s *sym.Symbol) {
 					continue
 				}
 			} else {
-				ctxt.ErrorUnresolved(s, r)
+				ctxt.errorUnresolved(ctxt.Syms.ROLookup, s, r)
 				continue
 			}
 		}
@@ -335,7 +335,7 @@ func relocsym(ctxt *Link, target *Target, s *sym.Symbol) {
 				// symbol which isn't in .data. However, as .text has the
 				// same address once loaded, this is possible.
 				if s.Sect.Seg == &Segdata {
-					Xcoffadddynrel(ctxt, s, r)
+					Xcoffadddynrel(target, s, r)
 				}
 			}
 

src/cmd/link/internal/ld/errors.go

@@ -0,0 +1,61 @@
+// Copyright 2020 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 ld
+
+import (
+	"cmd/internal/obj"
+	"cmd/link/internal/sym"
+	"sync"
+)
+
+type unresolvedSymKey struct {
+	from *sym.Symbol // Symbol that referenced unresolved "to"
+	to   *sym.Symbol // Unresolved symbol referenced by "from"
+}
+
+// ErrorReporter is used to make error reporting thread safe.
+type ErrorReporter struct {
+	unresOnce  sync.Once
+	unresSyms  map[unresolvedSymKey]bool
+	unresMutex sync.Mutex
+}
+
+type roLookup func(name string, v int) *sym.Symbol
+
+// errorUnresolved prints unresolved symbol error for r.Sym that is referenced from s.
+func (reporter *ErrorReporter) errorUnresolved(lookup roLookup, s *sym.Symbol, r *sym.Reloc) {
+	reporter.unresOnce.Do(func() { reporter.unresSyms = make(map[unresolvedSymKey]bool) })
+
+	k := unresolvedSymKey{from: s, to: r.Sym}
+	reporter.unresMutex.Lock()
+	defer reporter.unresMutex.Unlock()
+	if !reporter.unresSyms[k] {
+		reporter.unresSyms[k] = true
+
+		// Try to find symbol under another ABI.
+		var reqABI, haveABI obj.ABI
+		haveABI = ^obj.ABI(0)
+		reqABI, ok := sym.VersionToABI(int(r.Sym.Version))
+		if ok {
+			for abi := obj.ABI(0); abi < obj.ABICount; abi++ {
+				v := sym.ABIToVersion(abi)
+				if v == -1 {
+					continue
+				}
+				if rs := lookup(r.Sym.Name, v); rs != nil && rs.Type != sym.Sxxx {
+					haveABI = abi
+				}
+			}
+		}
+
+		// Give a special error message for main symbol (see #24809).
+		if r.Sym.Name == "main.main" {
+			Errorf(s, "function main is undeclared in the main package")
+		} else if haveABI != ^obj.ABI(0) {
+			Errorf(s, "relocation target %s not defined for %s (but is defined for %s)", r.Sym.Name, reqABI, haveABI)
+		} else {
+			Errorf(s, "relocation target %s not defined", r.Sym.Name)
+		}
+	}
+}

src/cmd/link/internal/ld/link.go

@@ -32,7 +32,6 @@ package ld
 
 import (
 	"bufio"
-	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
 	"cmd/link/internal/loader"
@@ -52,6 +51,7 @@ type Shlib struct {
 // or for reading that input into the linker.
 type Link struct {
 	Target
+	ErrorReporter
 	Out *OutBuf
 
 	Syms *sym.Symbols
@@ -81,10 +81,6 @@ type Link struct {
 
 	tramps []*sym.Symbol // trampolines
 
-	// unresolvedSymSet is a set of erroneous unresolved references.
-	// Used to avoid duplicated error messages.
-	unresolvedSymSet map[unresolvedSymKey]bool
-
 	// Used to implement field tracking.
 	Reachparent map[*sym.Symbol]*sym.Symbol
 
@@ -104,48 +100,6 @@ type cgodata struct {
 	directives [][]string
 }
 
-type unresolvedSymKey struct {
-	from *sym.Symbol // Symbol that referenced unresolved "to"
-	to   *sym.Symbol // Unresolved symbol referenced by "from"
-}
-
-// ErrorUnresolved prints unresolved symbol error for r.Sym that is referenced from s.
-func (ctxt *Link) ErrorUnresolved(s *sym.Symbol, r *sym.Reloc) {
-	if ctxt.unresolvedSymSet == nil {
-		ctxt.unresolvedSymSet = make(map[unresolvedSymKey]bool)
-	}
-
-	k := unresolvedSymKey{from: s, to: r.Sym}
-	if !ctxt.unresolvedSymSet[k] {
-		ctxt.unresolvedSymSet[k] = true
-
-		// Try to find symbol under another ABI.
-		var reqABI, haveABI obj.ABI
-		haveABI = ^obj.ABI(0)
-		reqABI, ok := sym.VersionToABI(int(r.Sym.Version))
-		if ok {
-			for abi := obj.ABI(0); abi < obj.ABICount; abi++ {
-				v := sym.ABIToVersion(abi)
-				if v == -1 {
-					continue
-				}
-				if rs := ctxt.Syms.ROLookup(r.Sym.Name, v); rs != nil && rs.Type != sym.Sxxx {
-					haveABI = abi
-				}
-			}
-		}
-
-		// Give a special error message for main symbol (see #24809).
-		if r.Sym.Name == "main.main" {
-			Errorf(s, "function main is undeclared in the main package")
-		} else if haveABI != ^obj.ABI(0) {
-			Errorf(s, "relocation target %s not defined for %s (but is defined for %s)", r.Sym.Name, reqABI, haveABI)
-		} else {
-			Errorf(s, "relocation target %s not defined", r.Sym.Name)
-		}
-	}
-}
-
 // The smallest possible offset from the hardware stack pointer to a local
 // variable on the stack. Architectures that use a link register save its value
 // on the stack in the function prologue and so always have a pointer between

src/cmd/link/internal/ld/xcoff.go

@@ -1096,8 +1096,8 @@ func (f *xcoffFile) adddynimpsym(ctxt *Link, s *sym.Symbol) {
 
 // Xcoffadddynrel adds a dynamic relocation in a XCOFF file.
 // This relocation will be made by the loader.
-func Xcoffadddynrel(ctxt *Link, s *sym.Symbol, r *sym.Reloc) bool {
-	if ctxt.LinkMode == LinkExternal {
+func Xcoffadddynrel(target *Target, s *sym.Symbol, r *sym.Reloc) bool {
+	if target.IsExternal() {
 		return true
 	}
 	if s.Type <= sym.SPCLNTAB {

src/cmd/link/internal/ppc64/asm.go

@@ -266,7 +266,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 	if ctxt.IsELF {
 		return addelfdynrel(ctxt, s, r)
 	} else if ctxt.HeadType == objabi.Haix {
-		return ld.Xcoffadddynrel(ctxt, s, r)
+		return ld.Xcoffadddynrel(&ctxt.Target, s, r)
 	}
 	return false
 }