cmd/objdump, cmd/pprof: factor disassembly into cmd/internal/objfile

Moving so that new Go 1.4 pprof can use it.

The old 'GNU objdump workalike' mode for 'go tool objdump'
is now gone, as are the tests for that mode. It was used only
by pre-Go 1.4 pprof. You can still specify an address range on
the command line; you just get the same output format as
you do when dumping the entire binary (without an address
limitation).

LGTM=r
R=r
CC=golang-codereviews, iant
https://golang.org/cl/167320043

1 files changed, 38 insertions, 3 deletions

diff --git a/src/cmd/pprof/pprof.go b/src/cmd/pprof/pprof.go
index 89a5bb7d22..44f4f6cb72 100644
--- a/src/cmd/pprof/pprof.go
+++ b/src/cmd/pprof/pprof.go
@@ -11,6 +11,7 @@ import (
 	"os"
 	"regexp"
 	"strings"
+	"sync"
 
 	"cmd/internal/objfile"
 	"cmd/pprof/internal/commands"
@@ -100,7 +101,10 @@ func (flags) ExtraUsage() string {
 
 // objTool implements plugin.ObjTool using Go libraries
 // (instead of invoking GNU binutils).
-type objTool struct{}
+type objTool struct {
+	mu          sync.Mutex
+	disasmCache map[string]*objfile.Disasm
+}
 
 func (*objTool) Open(name string, start uint64) (plugin.ObjFile, error) {
 	of, err := objfile.Open(name)
@@ -119,8 +123,39 @@ func (*objTool) Demangle(names []string) (map[string]string, error) {
 	return make(map[string]string), nil
 }
 
-func (*objTool) Disasm(file string, start, end uint64) ([]plugin.Inst, error) {
-	return nil, fmt.Errorf("disassembly not supported")
+func (t *objTool) Disasm(file string, start, end uint64) ([]plugin.Inst, error) {
+	d, err := t.cachedDisasm(file)
+	if err != nil {
+		return nil, err
+	}
+	var asm []plugin.Inst
+	d.Decode(start, end, func(pc, size uint64, file string, line int, text string) {
+		asm = append(asm, plugin.Inst{Addr: pc, File: file, Line: line, Text: text})
+	})
+	return asm, nil
+}
+
+func (t *objTool) cachedDisasm(file string) (*objfile.Disasm, error) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.disasmCache == nil {
+		t.disasmCache = make(map[string]*objfile.Disasm)
+	}
+	d := t.disasmCache[file]
+	if d != nil {
+		return d, nil
+	}
+	f, err := objfile.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	d, err = f.Disasm()
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+	t.disasmCache[file] = d
+	return d, nil
 }
 
 func (*objTool) SetConfig(config string) {