From c44af2d4a23a30cb0930adfca9e56b3d1e04a35c Mon Sep 17 00:00:00 2001
From: Than McIntosh <thanm@google.com>
Date: Wed, 11 Mar 2020 11:18:00 -0400
Subject: [PATCH] [dev.link] cmd/internal/obj: add dump of aux symbols for -S=2

For compiler developers interested in seeing DWARF generation details,
this patch provides symbol "debug asm" dumps for DWARF aux symbols
when -S=2 is in effect.

Change-Id: I5a0b6b65ce7b708948cbbf23c6b0d279bd4f8d9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/223017
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/cmd/internal/obj/objfile.go  |  6 ++-
 src/cmd/internal/obj/objfile2.go | 30 ++++++++++++--
 src/cmd/internal/obj/sym.go      | 68 +++++++++++++++++++++++---------
 3 files changed, 81 insertions(+), 23 deletions(-)

diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index 4669e415cc..0f73e48b05 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -21,7 +21,11 @@ func WriteObjFile(ctxt *Link, bout *bio.Writer, pkgpath string) {
 }
 
 func (ctxt *Link) writeSymDebug(s *LSym) {
-	fmt.Fprintf(ctxt.Bso, "%s ", s.Name)
+	ctxt.writeSymDebugNamed(s, s.Name)
+}
+
+func (ctxt *Link) writeSymDebugNamed(s *LSym, name string) {
+	fmt.Fprintf(ctxt.Bso, "%s ", name)
 	if s.Type != 0 {
 		fmt.Fprintf(ctxt.Bso, "%v ", s.Type)
 	}
diff --git a/src/cmd/internal/obj/objfile2.go b/src/cmd/internal/obj/objfile2.go
index dc492733ac..9ccbcd5352 100644
--- a/src/cmd/internal/obj/objfile2.go
+++ b/src/cmd/internal/obj/objfile2.go
@@ -18,9 +18,8 @@ import (
 
 // Entry point of writing new object file.
 func WriteObjFile2(ctxt *Link, b *bio.Writer, pkgpath string) {
-	if ctxt.Debugasm > 0 {
-		ctxt.traverseSyms(traverseDefs, ctxt.writeSymDebug)
-	}
+
+	debugAsmEmit(ctxt)
 
 	genFuncInfoSyms(ctxt)
 
@@ -434,3 +433,28 @@ func genFuncInfoSyms(ctxt *Link) {
 	}
 	ctxt.defs = append(ctxt.defs, infosyms...)
 }
+
+// debugDumpAux is a dumper for selected aux symbols.
+func writeAuxSymDebug(ctxt *Link, par *LSym, aux *LSym) {
+	// Most aux symbols (ex: funcdata) are not interesting--
+	// pick out just the DWARF ones for now.
+	if aux.Type != objabi.SDWARFLOC &&
+		aux.Type != objabi.SDWARFINFO &&
+		aux.Type != objabi.SDWARFLINES &&
+		aux.Type != objabi.SDWARFRANGE {
+		return
+	}
+	ctxt.writeSymDebugNamed(aux, "aux for "+par.Name)
+}
+
+func debugAsmEmit(ctxt *Link) {
+	if ctxt.Debugasm > 0 {
+		ctxt.traverseSyms(traverseDefs, ctxt.writeSymDebug)
+		if ctxt.Debugasm > 1 {
+			fn := func(par *LSym, aux *LSym) {
+				writeAuxSymDebug(ctxt, par, aux)
+			}
+			ctxt.traverseAuxSyms(fn)
+		}
+	}
+}
diff --git a/src/cmd/internal/obj/sym.go b/src/cmd/internal/obj/sym.go
index e1e749db92..818d464c91 100644
--- a/src/cmd/internal/obj/sym.go
+++ b/src/cmd/internal/obj/sym.go
@@ -294,28 +294,58 @@ func (ctxt *Link) traverseSyms(flag traverseFlag, fn func(*LSym)) {
 					fn(s.Gotype)
 				}
 				if s.Type == objabi.STEXT {
-					pc := &s.Func.Pcln
-					for _, d := range pc.Funcdata {
-						if d != nil {
-							fn(d)
-						}
-					}
-					for _, f := range pc.File {
-						if fsym := ctxt.Lookup(f); fsym != nil {
-							fn(fsym)
-						}
-					}
-					for _, call := range pc.InlTree.nodes {
-						if call.Func != nil {
-							fn(call.Func)
-						}
-						f, _ := linkgetlineFromPos(ctxt, call.Pos)
-						if fsym := ctxt.Lookup(f); fsym != nil {
-							fn(fsym)
-						}
+					f := func(parent *LSym, aux *LSym) {
+						fn(aux)
 					}
+					ctxt.traverseFuncAux(s, f)
 				}
 			}
 		}
 	}
 }
+
+func (ctxt *Link) traverseFuncAux(fsym *LSym, fn func(parent *LSym, aux *LSym)) {
+	pc := &fsym.Func.Pcln
+	for _, d := range pc.Funcdata {
+		if d != nil {
+			fn(fsym, d)
+		}
+	}
+	for _, f := range pc.File {
+		if filesym := ctxt.Lookup(f); filesym != nil {
+			fn(fsym, filesym)
+		}
+	}
+	for _, call := range pc.InlTree.nodes {
+		if call.Func != nil {
+			fn(fsym, call.Func)
+		}
+		f, _ := linkgetlineFromPos(ctxt, call.Pos)
+		if filesym := ctxt.Lookup(f); filesym != nil {
+			fn(fsym, filesym)
+		}
+	}
+	dwsyms := []*LSym{fsym.Func.dwarfRangesSym, fsym.Func.dwarfLocSym}
+	for _, dws := range dwsyms {
+		if dws == nil || dws.Size == 0 {
+			continue
+		}
+		fn(fsym, dws)
+	}
+}
+
+// Traverse aux symbols, calling fn for each sym/aux pair.
+func (ctxt *Link) traverseAuxSyms(fn func(parent *LSym, aux *LSym)) {
+	lists := [][]*LSym{ctxt.Text, ctxt.Data, ctxt.ABIAliases}
+	for _, list := range lists {
+		for _, s := range list {
+			if s.Gotype != nil {
+				fn(s, s.Gotype)
+			}
+			if s.Type != objabi.STEXT {
+				continue
+			}
+			ctxt.traverseFuncAux(s, fn)
+		}
+	}
+}