From 16b751b6c610ec2c5a913cb8a818e9239ee7da71 Mon Sep 17 00:00:00 2001
From: Adin Scannell <ascannell@google.com>
Date: Thu, 1 Jul 2021 15:05:28 -0700
Subject: Mix checklocks and atomic analyzers.

This change makes the checklocks analyzer considerable more powerful, adding:
* The ability to traverse complex structures, e.g. to have multiple nested
  fields as part of the annotation.
* The ability to resolve simple anonymous functions and closures, and perform
  lock analysis across these invocations. This does not apply to closures that
  are passed elsewhere, since it is not possible to know the context in which
  they might be invoked.
* The ability to annotate return values in addition to receivers and other
  parameters, with the same complex structures noted above.
* Ignoring locking semantics for "fresh" objects, i.e. objects that are
  allocated in the local frame (typically a new-style function).
* Sanity checking of locking state across block transitions and returns, to
  ensure that no unexpected locks are held.

Note that initially, most of these findings are excluded by a comprehensive
nogo.yaml. The findings that are included are fundamental lock violations.
The changes here should be relatively low risk, minor refactorings to either
include necessary annotations to simplify the code structure (in general
removing closures in favor of methods) so that the analyzer can be easily
track the lock state.

This change additional includes two changes to nogo itself:
* Sanity checking of all types to ensure that the binary and ast-derived
  types have a consistent objectpath, to prevent the bug above from occurring
  silently (and causing much confusion). This also requires a trick in
  order to ensure that serialized facts are consumable downstream. This can
  be removed with https://go-review.googlesource.com/c/tools/+/331789 merged.
* A minor refactoring to isolation the objdump settings in its own package.
  This was originally used to implement the sanity check above, but this
  information is now being passed another way. The minor refactor is preserved
  however, since it cleans up the code slightly and is minimal risk.

PiperOrigin-RevId: 382613300
---
 tools/nogo/objdump/BUILD      | 10 +++++
 tools/nogo/objdump/objdump.go | 96 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 tools/nogo/objdump/BUILD
 create mode 100644 tools/nogo/objdump/objdump.go

(limited to 'tools/nogo/objdump')

diff --git a/tools/nogo/objdump/BUILD b/tools/nogo/objdump/BUILD
new file mode 100644
index 000000000..da56efdf7
--- /dev/null
+++ b/tools/nogo/objdump/BUILD
@@ -0,0 +1,10 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "objdump",
+    srcs = ["objdump.go"],
+    nogo = False,
+    visibility = ["//tools:__subpackages__"],
+)
diff --git a/tools/nogo/objdump/objdump.go b/tools/nogo/objdump/objdump.go
new file mode 100644
index 000000000..48484abf3
--- /dev/null
+++ b/tools/nogo/objdump/objdump.go
@@ -0,0 +1,96 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package objdump is a wrapper around relevant objdump flags.
+package objdump
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+)
+
+var (
+	// Binary is the binary under analysis.
+	//
+	// See Reader, below.
+	binary = flag.String("binary", "", "binary under analysis")
+
+	// Reader is the input stream.
+	//
+	// This may be set instead of Binary.
+	Reader io.Reader
+
+	// objdumpTool is the tool used to dump a binary.
+	objdumpTool = flag.String("objdump_tool", "", "tool used to dump a binary")
+)
+
+// LoadRaw reads the raw object output.
+func LoadRaw(fn func(r io.Reader) error) error {
+	var r io.Reader
+	if *binary != "" {
+		f, err := os.Open(*binary)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		r = f
+	} else if Reader != nil {
+		r = Reader
+	} else {
+		// We have no input stream.
+		return fmt.Errorf("no binary or reader provided")
+	}
+	return fn(r)
+}
+
+// Load reads the objdump output.
+func Load(fn func(r io.Reader) error) error {
+	var (
+		args  []string
+		stdin io.Reader
+	)
+	if *binary != "" {
+		args = append(args, *binary)
+	} else if Reader != nil {
+		stdin = Reader
+	} else {
+		// We have no input stream or binary.
+		return fmt.Errorf("no binary or reader provided")
+	}
+
+	// Construct our command.
+	cmd := exec.Command(*objdumpTool, args...)
+	cmd.Stdin = stdin
+	cmd.Stderr = os.Stderr
+	out, err := cmd.StdoutPipe()
+	if err != nil {
+		return err
+	}
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	// Call the user hook.
+	userErr := fn(out)
+
+	// Wait for the dump to finish.
+	if err := cmd.Wait(); userErr == nil && err != nil {
+		return err
+	}
+
+	return userErr
+}
-- 
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