runtime/pprof: add memory mapping info for Windows

Fixes #43296

Change-Id: Ib277c2e82c95f71a7a9b7fe1b22215ead7a54a88
Reviewed-on: https://go-review.googlesource.com/c/go/+/416975
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Than McIntosh <thanm@google.com>

5 files changed, 157 insertions, 19 deletions

diff --git a/src/runtime/pprof/pe.go b/src/runtime/pprof/pe.go
new file mode 100644
index 0000000000..41054585e9
--- /dev/null
+++ b/src/runtime/pprof/pe.go
@@ -0,0 +1,19 @@
+// Copyright 2022 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 pprof
+
+import "os"
+
+// peBuildID returns a best effort unique ID for the named executable.
+//
+// It would be wasteful to calculate the hash of the whole file,
+// instead use the binary name and the last modified time for the buildid.
+func peBuildID(file string) string {
+	s, err := os.Stat(file)
+	if err != nil {
+		return file
+	}
+	return file + s.ModTime().String()
+}
diff --git a/src/runtime/pprof/proto.go b/src/runtime/pprof/proto.go
index 085027cd98..9c82925165 100644
--- a/src/runtime/pprof/proto.go
+++ b/src/runtime/pprof/proto.go
@@ -10,7 +10,6 @@ import (
 	"fmt"
 	"internal/abi"
 	"io"
-	"os"
 	"runtime"
 	"strconv"
 	"strings"
@@ -46,10 +45,11 @@ type profileBuilder struct {
 
 type memMap struct {
 	// initialized as reading mapping
-	start         uintptr
-	end           uintptr
-	offset        uint64
-	file, buildID string
+	start   uintptr // Address at which the binary (or DLL) is loaded into memory.
+	end     uintptr // The limit of the address range occupied by this mapping.
+	offset  uint64  // Offset in the binary that corresponds to the first mapped address.
+	file    string  // The object this entry is loaded from.
+	buildID string  // A string that uniquely identifies a particular program version with high probability.
 
 	funcs symbolizeFlag
 	fake  bool // map entry was faked; /proc/self/maps wasn't available
@@ -640,20 +640,6 @@ func (b *profileBuilder) emitLocation() uint64 {
 	return id
 }
 
-// readMapping reads /proc/self/maps and writes mappings to b.pb.
-// It saves the address ranges of the mappings in b.mem for use
-// when emitting locations.
-func (b *profileBuilder) readMapping() {
-	data, _ := os.ReadFile("/proc/self/maps")
-	parseProcSelfMaps(data, b.addMapping)
-	if len(b.mem) == 0 { // pprof expects a map entry, so fake one.
-		b.addMappingEntry(0, 0, 0, "", "", true)
-		// TODO(hyangah): make addMapping return *memMap or
-		// take a memMap struct, and get rid of addMappingEntry
-		// that takes a bunch of positional arguments.
-	}
-}
-
 var space = []byte(" ")
 var newline = []byte("\n")
 
diff --git a/src/runtime/pprof/proto_other.go b/src/runtime/pprof/proto_other.go
new file mode 100644
index 0000000000..4a7fe79501
--- /dev/null
+++ b/src/runtime/pprof/proto_other.go
@@ -0,0 +1,30 @@
+// Copyright 2022 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.
+
+//go:build !windows
+
+package pprof
+
+import (
+	"errors"
+	"os"
+)
+
+// readMapping reads /proc/self/maps and writes mappings to b.pb.
+// It saves the address ranges of the mappings in b.mem for use
+// when emitting locations.
+func (b *profileBuilder) readMapping() {
+	data, _ := os.ReadFile("/proc/self/maps")
+	parseProcSelfMaps(data, b.addMapping)
+	if len(b.mem) == 0 { // pprof expects a map entry, so fake one.
+		b.addMappingEntry(0, 0, 0, "", "", true)
+		// TODO(hyangah): make addMapping return *memMap or
+		// take a memMap struct, and get rid of addMappingEntry
+		// that takes a bunch of positional arguments.
+	}
+}
+
+func readMainModuleMapping() (start, end uint64, err error) {
+	return 0, 0, errors.New("not implemented")
+}
diff --git a/src/runtime/pprof/proto_test.go b/src/runtime/pprof/proto_test.go
index 84a051a536..797c6502b4 100644
--- a/src/runtime/pprof/proto_test.go
+++ b/src/runtime/pprof/proto_test.go
@@ -101,6 +101,36 @@ func testPCs(t *testing.T) (addr1, addr2 uint64, map1, map2 *profile.Mapping) {
 		addr2 = mprof.Mapping[1].Start
 		map2 = mprof.Mapping[1]
 		map2.BuildID, _ = elfBuildID(map2.File)
+	case "windows":
+		addr1 = uint64(abi.FuncPCABIInternal(f1))
+		addr2 = uint64(abi.FuncPCABIInternal(f2))
+
+		exe, err := os.Executable()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		start, end, err := readMainModuleMapping()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		map1 = &profile.Mapping{
+			ID:           1,
+			Start:        start,
+			Limit:        end,
+			File:         exe,
+			BuildID:      peBuildID(exe),
+			HasFunctions: true,
+		}
+		map2 = &profile.Mapping{
+			ID:           1,
+			Start:        start,
+			Limit:        end,
+			File:         exe,
+			BuildID:      peBuildID(exe),
+			HasFunctions: true,
+		}
 	case "js":
 		addr1 = uint64(abi.FuncPCABIInternal(f1))
 		addr2 = uint64(abi.FuncPCABIInternal(f2))
diff --git a/src/runtime/pprof/proto_windows.go b/src/runtime/pprof/proto_windows.go
new file mode 100644
index 0000000000..d5ae4a5eec
--- /dev/null
+++ b/src/runtime/pprof/proto_windows.go
@@ -0,0 +1,73 @@
+// Copyright 2022 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 pprof
+
+import (
+	"errors"
+	"internal/syscall/windows"
+	"syscall"
+)
+
+// readMapping adds memory mapping information to the profile.
+func (b *profileBuilder) readMapping() {
+	snap, err := createModuleSnapshot()
+	if err != nil {
+		// pprof expects a map entry, so fake one, when we haven't added anything yet.
+		b.addMappingEntry(0, 0, 0, "", "", true)
+		return
+	}
+	defer func() { _ = syscall.CloseHandle(snap) }()
+
+	var module windows.ModuleEntry32
+	module.Size = uint32(windows.SizeofModuleEntry32)
+	err = windows.Module32First(snap, &module)
+	if err != nil {
+		// pprof expects a map entry, so fake one, when we haven't added anything yet.
+		b.addMappingEntry(0, 0, 0, "", "", true)
+		return
+	}
+	for err == nil {
+		exe := syscall.UTF16ToString(module.ExePath[:])
+		b.addMappingEntry(
+			uint64(module.ModBaseAddr),
+			uint64(module.ModBaseAddr)+uint64(module.ModBaseSize),
+			0,
+			exe,
+			peBuildID(exe),
+			false,
+		)
+		err = windows.Module32Next(snap, &module)
+	}
+}
+
+func readMainModuleMapping() (start, end uint64, err error) {
+	snap, err := createModuleSnapshot()
+	if err != nil {
+		return 0, 0, err
+	}
+	defer func() { _ = syscall.CloseHandle(snap) }()
+
+	var module windows.ModuleEntry32
+	module.Size = uint32(windows.SizeofModuleEntry32)
+	err = windows.Module32First(snap, &module)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	return uint64(module.ModBaseAddr), uint64(module.ModBaseAddr) + uint64(module.ModBaseSize), nil
+}
+
+func createModuleSnapshot() (syscall.Handle, error) {
+	for {
+		snap, err := syscall.CreateToolhelp32Snapshot(windows.TH32CS_SNAPMODULE|windows.TH32CS_SNAPMODULE32, uint32(syscall.Getpid()))
+		var errno syscall.Errno
+		if err != nil && errors.As(err, &errno) && errno == windows.ERROR_BAD_LENGTH {
+			// When CreateToolhelp32Snapshot(SNAPMODULE|SNAPMODULE32, ...) fails
+			// with ERROR_BAD_LENGTH then it should be retried until it succeeds.
+			continue
+		}
+		return snap, err
+	}
+}