Support stdlib analyzers with nogo.

This immediately revealed an escape analysis violation (!), where
the sync.Map was being used in a context that escapes were not
allowed. This is a relatively minor fix and is included.

PiperOrigin-RevId: 328611237

8 files changed, 503 insertions, 133 deletions

diff --git a/tools/nogo/BUILD b/tools/nogo/BUILD
index e1bfb9a2c..fb35c5ffd 100644
--- a/tools/nogo/BUILD
+++ b/tools/nogo/BUILD
@@ -1,7 +1,18 @@
 load("//tools:defs.bzl", "bzl_library", "go_library")
+load("//tools/nogo:defs.bzl", "nogo_dump_tool", "nogo_stdlib")
 
 package(licenses = ["notice"])
 
+nogo_dump_tool(
+    name = "dump_tool",
+    visibility = ["//visibility:public"],
+)
+
+nogo_stdlib(
+    name = "stdlib",
+    visibility = ["//visibility:public"],
+)
+
 go_library(
     name = "nogo",
     srcs = [
@@ -16,7 +27,7 @@ go_library(
     deps = [
         "//tools/checkescape",
         "//tools/checkunsafe",
-        "//tools/nogo/data",
+        "//tools/nogo/dump",
         "@org_golang_x_tools//go/analysis:go_tool_library",
         "@org_golang_x_tools//go/analysis/internal/facts:go_tool_library",
         "@org_golang_x_tools//go/analysis/passes/asmdecl:go_tool_library",
diff --git a/tools/nogo/build.go b/tools/nogo/build.go
index 433d13738..37947b5c3 100644
--- a/tools/nogo/build.go
+++ b/tools/nogo/build.go
@@ -31,10 +31,10 @@ var (
 )
 
 // findStdPkg needs to find the bundled standard library packages.
-func (i *importer) findStdPkg(path string) (io.ReadCloser, error) {
+func findStdPkg(GOOS, GOARCH, path string) (io.ReadCloser, error) {
 	if path == "C" {
 		// Cgo builds cannot be analyzed. Skip.
 		return nil, ErrSkip
 	}
-	return os.Open(fmt.Sprintf("external/go_sdk/pkg/%s_%s/%s.a", i.GOOS, i.GOARCH, path))
+	return os.Open(fmt.Sprintf("external/go_sdk/pkg/%s_%s/%s.a", GOOS, GOARCH, path))
 }
diff --git a/tools/nogo/config.go b/tools/nogo/config.go
index 6958fca69..451cd4a4c 100644
--- a/tools/nogo/config.go
+++ b/tools/nogo/config.go
@@ -84,6 +84,14 @@ var analyzerConfig = map[*analysis.Analyzer]matcher{
 		externalExcluded(
 			".*protobuf/.*.go",              // Bad conversions.
 			".*flate/huffman_bit_writer.go", // Bad conversion.
+
+			// Runtime internal violations.
+			".*reflect/value.go",
+			".*encoding/xml/xml.go",
+			".*runtime/pprof/internal/profile/proto.go",
+			".*fmt/scan.go",
+			".*go/types/conversions.go",
+			".*golang.org/x/net/dns/dnsmessage/message.go",
 		),
 	),
 	shadow.Analyzer:      disableMatches(),  // Disabled for now.
diff --git a/tools/nogo/data/data.go b/tools/nogo/data/data.go
deleted file mode 100644
index eb84d0d27..000000000
--- a/tools/nogo/data/data.go
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2019 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 data contains shared data for nogo analysis.
-//
-// This is used to break a dependency cycle.
-package data
-
-// Objdump is the dumped binary under analysis.
-var Objdump string
diff --git a/tools/nogo/defs.bzl b/tools/nogo/defs.bzl
index 5377620b0..963084d53 100644
--- a/tools/nogo/defs.bzl
+++ b/tools/nogo/defs.bzl
@@ -2,6 +2,103 @@
 
 load("//tools/bazeldefs:defs.bzl", "go_context", "go_importpath", "go_rule", "go_test_library")
 
+def _nogo_dump_tool_impl(ctx):
+    # Extract the Go context.
+    go_ctx = go_context(ctx)
+
+    # Construct the magic dump command.
+    #
+    # Note that in some cases, the input is being fed into the tool via stdin.
+    # Unfortunately, the Go objdump tool expects to see a seekable file [1], so
+    # we need the tool to handle this case by creating a temporary file.
+    #
+    # [1] https://github.com/golang/go/issues/41051
+    env_prefix = " ".join(["%s=%s" % (key, value) for (key, value) in go_ctx.env.items()])
+    dumper = ctx.actions.declare_file(ctx.label.name)
+    ctx.actions.write(dumper, "\n".join([
+        "#!/bin/bash",
+        "set -euo pipefail",
+        "if [[ $# -eq 0 ]]; then",
+        " T=$(mktemp -u -t libXXXXXX.a)",
+        " cat /dev/stdin > ${T}",
+        "else",
+        " T=$1;",
+        "fi",
+        "%s %s tool objdump ${T}" % (
+            env_prefix,
+            go_ctx.go.path,
+        ),
+        "if [[ $# -eq 0 ]]; then",
+        " rm -rf ${T}",
+        "fi",
+        "",
+    ]), is_executable = True)
+
+    # Include the full runfiles.
+    return [DefaultInfo(
+        runfiles = ctx.runfiles(files = go_ctx.runfiles.to_list()),
+        executable = dumper,
+    )]
+
+nogo_dump_tool = go_rule(
+    rule,
+    implementation = _nogo_dump_tool_impl,
+)
+
+# NogoStdlibInfo is the set of standard library facts.
+NogoStdlibInfo = provider(
+    "information for nogo analysis (standard library facts)",
+    fields = {
+        "facts": "serialized standard library facts",
+    },
+)
+
+def _nogo_stdlib_impl(ctx):
+    # Extract the Go context.
+    go_ctx = go_context(ctx)
+
+    # Build the standard library facts.
+    facts = ctx.actions.declare_file(ctx.label.name + ".facts")
+    config = struct(
+        Srcs = [f.path for f in go_ctx.stdlib_srcs],
+        GOOS = go_ctx.goos,
+        GOARCH = go_ctx.goarch,
+        Tags = go_ctx.tags,
+        FactOutput = facts.path,
+    )
+    config_file = ctx.actions.declare_file(ctx.label.name + ".cfg")
+    ctx.actions.write(config_file, config.to_json())
+    ctx.actions.run(
+        inputs = [config_file] + go_ctx.stdlib_srcs,
+        outputs = [facts],
+        tools = depset(go_ctx.runfiles.to_list() + ctx.files._dump_tool),
+        executable = ctx.files._nogo[0],
+        mnemonic = "GoStandardLibraryAnalysis",
+        progress_message = "Analyzing Go Standard Library",
+        arguments = go_ctx.nogo_args + [
+            "-dump_tool=%s" % ctx.files._dump_tool[0].path,
+            "-stdlib=%s" % config_file.path,
+        ],
+    )
+
+    # Return the stdlib facts as output.
+    return [NogoStdlibInfo(
+        facts = facts,
+    )]
+
+nogo_stdlib = go_rule(
+    rule,
+    implementation = _nogo_stdlib_impl,
+    attrs = {
+        "_nogo": attr.label(
+            default = "//tools/nogo/check:check",
+        ),
+        "_dump_tool": attr.label(
+            default = "//tools/nogo:dump_tool",
+        ),
+    },
+)
+
 # NogoInfo is the serialized set of package facts for a nogo analysis.
 #
 # Each go_library rule will generate a corresponding nogo rule, which will run
@@ -33,6 +130,9 @@ def _nogo_aspect_impl(target, ctx):
     else:
         return [NogoInfo()]
 
+    # Extract the Go context.
+    go_ctx = go_context(ctx)
+
     # If we're using the "library" attribute, then we need to aggregate the
     # original library sources and dependencies into this target to perform
     # proper type analysis.
@@ -45,10 +145,6 @@ def _nogo_aspect_impl(target, ctx):
             if hasattr(info, "deps"):
                 deps = deps + info.deps
 
-    # Construct the Go environment from the go_ctx.env dictionary.
-    go_ctx = go_context(ctx)
-    env_prefix = " ".join(["%s=%s" % (key, value) for (key, value) in go_ctx.env.items()])
-
     # Start with all target files and srcs as input.
     inputs = target.files.to_list() + srcs
 
@@ -64,26 +160,7 @@ def _nogo_aspect_impl(target, ctx):
     else:
         # Use the raw binary for go_binary and go_test targets.
         target_objfile = binaries[0]
-    disasm_file = ctx.actions.declare_file(target.label.name + ".out")
-    dumper = ctx.actions.declare_file("%s-dumper" % ctx.label.name)
-    ctx.actions.write(dumper, "\n".join([
-        "#!/bin/bash",
-        "%s %s tool objdump %s > %s\n" % (
-            env_prefix,
-            go_ctx.go.path,
-            target_objfile.path,
-            disasm_file.path,
-        ),
-    ]), is_executable = True)
-    ctx.actions.run(
-        inputs = [target_objfile],
-        outputs = [disasm_file],
-        tools = go_ctx.runfiles,
-        mnemonic = "GoObjdump",
-        progress_message = "Objdump %s" % target.label,
-        executable = dumper,
-    )
-    inputs.append(disasm_file)
+    inputs.append(target_objfile)
 
     # Extract the importpath for this package.
     if ctx.rule.kind == "go_test":
@@ -96,25 +173,9 @@ def _nogo_aspect_impl(target, ctx):
     else:
         importpath = go_importpath(target)
 
-    # The nogo tool requires a configfile serialized in JSON format to do its
-    # work. This must line up with the nogo.Config fields.
-    facts = ctx.actions.declare_file(target.label.name + ".facts")
-    config = struct(
-        ImportPath = importpath,
-        GoFiles = [src.path for src in srcs if src.path.endswith(".go")],
-        NonGoFiles = [src.path for src in srcs if not src.path.endswith(".go")],
-        # Google's internal build system needs a bit more help to find std.
-        StdZip = go_ctx.std_zip.short_path if hasattr(go_ctx, "std_zip") else "",
-        GOOS = go_ctx.goos,
-        GOARCH = go_ctx.goarch,
-        Tags = go_ctx.tags,
-        FactMap = {},  # Constructed below.
-        ImportMap = {},  # Constructed below.
-        FactOutput = facts.path,
-        Objdump = disasm_file.path,
-    )
-
     # Collect all info from shadow dependencies.
+    fact_map = dict()
+    import_map = dict()
     for dep in deps:
         # There will be no file attribute set for all transitive dependencies
         # that are not go_library or go_binary rules, such as a proto rules.
@@ -129,27 +190,46 @@ def _nogo_aspect_impl(target, ctx):
         x_files = [f.path for f in info.binaries if f.path.endswith(".x")]
         if not len(x_files):
             x_files = [f.path for f in info.binaries if f.path.endswith(".a")]
-        config.ImportMap[info.importpath] = x_files[0]
-        config.FactMap[info.importpath] = info.facts.path
+        import_map[info.importpath] = x_files[0]
+        fact_map[info.importpath] = info.facts.path
 
         # Ensure the above are available as inputs.
         inputs.append(info.facts)
         inputs += info.binaries
 
-    # Write the configuration and run the tool.
+    # Add the standard library facts.
+    stdlib_facts = ctx.attr._nogo_stdlib[NogoStdlibInfo].facts
+    inputs.append(stdlib_facts)
+
+    # The nogo tool operates on a configuration serialized in JSON format.
+    facts = ctx.actions.declare_file(target.label.name + ".facts")
+    config = struct(
+        ImportPath = importpath,
+        GoFiles = [src.path for src in srcs if src.path.endswith(".go")],
+        NonGoFiles = [src.path for src in srcs if not src.path.endswith(".go")],
+        GOOS = go_ctx.goos,
+        GOARCH = go_ctx.goarch,
+        Tags = go_ctx.tags,
+        FactMap = fact_map,
+        ImportMap = import_map,
+        StdlibFacts = stdlib_facts.path,
+        FactOutput = facts.path,
+    )
     config_file = ctx.actions.declare_file(target.label.name + ".cfg")
     ctx.actions.write(config_file, config.to_json())
     inputs.append(config_file)
-
-    # Run the nogo tool itself.
     ctx.actions.run(
         inputs = inputs,
         outputs = [facts],
-        tools = go_ctx.runfiles,
+        tools = depset(go_ctx.runfiles.to_list() + ctx.files._dump_tool),
         executable = ctx.files._nogo[0],
         mnemonic = "GoStaticAnalysis",
         progress_message = "Analyzing %s" % target.label,
-        arguments = ["-config=%s" % config_file.path],
+        arguments = go_ctx.nogo_args + [
+            "-binary=%s" % target_objfile.path,
+            "-dump_tool=%s" % ctx.files._dump_tool[0].path,
+            "-package=%s" % config_file.path,
+        ],
     )
 
     # Return the package facts as output.
@@ -172,7 +252,12 @@ nogo_aspect = go_rule(
     attrs = {
         "_nogo": attr.label(
             default = "//tools/nogo/check:check",
-            allow_single_file = True,
+        ),
+        "_nogo_stdlib": attr.label(
+            default = "//tools/nogo:stdlib",
+        ),
+        "_dump_tool": attr.label(
+            default = "//tools/nogo:dump_tool",
         ),
     },
 )
diff --git a/tools/nogo/data/BUILD b/tools/nogo/dump/BUILD
index b7564cc44..dfa29d651 100644
--- a/tools/nogo/data/BUILD
+++ b/tools/nogo/dump/BUILD
@@ -3,8 +3,8 @@ load("//tools:defs.bzl", "go_library")
 package(licenses = ["notice"])
 
 go_library(
-    name = "data",
-    srcs = ["data.go"],
+    name = "dump",
+    srcs = ["dump.go"],
     nogo = False,
     visibility = ["//tools:__subpackages__"],
 )
diff --git a/tools/nogo/dump/dump.go b/tools/nogo/dump/dump.go
new file mode 100644
index 000000000..f06567e0f
--- /dev/null
+++ b/tools/nogo/dump/dump.go
@@ -0,0 +1,78 @@
+// Copyright 2019 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 dump contains data dump tools.
+//
+// The interface used by the package corresponds to the tool generated by the
+// nogo_dump_tool rule.
+//
+// This package is separate in order to avoid a dependency cycle.
+package dump
+
+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
+
+	// Tool is the tool used to dump a binary.
+	tool = flag.String("dump_tool", "", "tool used to dump a binary")
+)
+
+// Command returns a command that will emit the dumped object on stdout.
+//
+// You must call Wait on the resulting command.
+func Command() (*exec.Cmd, io.Reader, error) {
+	var (
+		args  []string
+		stdin io.Reader
+	)
+	if *binary != "" {
+		args = append(args, *binary)
+		*binary = "" // Clear.
+	} else if Reader != nil {
+		stdin = Reader
+		Reader = nil // Clear.
+	} else {
+		// We have no input stream or binary.
+		return nil, nil, fmt.Errorf("no binary or reader provided!")
+	}
+
+	// Construct our command.
+	cmd := exec.Command(*tool, args...)
+	cmd.Stdin = stdin
+	cmd.Stderr = os.Stderr
+	out, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, nil, err
+	}
+	if err := cmd.Start(); err != nil {
+		return nil, nil, err
+	}
+
+	return cmd, out, err
+}
diff --git a/tools/nogo/nogo.go b/tools/nogo/nogo.go
index ea1e97076..e44f32d4c 100644
--- a/tools/nogo/nogo.go
+++ b/tools/nogo/nogo.go
@@ -32,51 +32,97 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"path"
 	"path/filepath"
 	"reflect"
+	"strings"
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/internal/facts"
 	"golang.org/x/tools/go/gcexportdata"
-	"gvisor.dev/gvisor/tools/nogo/data"
+	"gvisor.dev/gvisor/tools/nogo/dump"
 )
 
-// pkgConfig is serialized as the configuration.
+// stdlibConfig is serialized as the configuration.
 //
-// This contains everything required for the analysis.
-type pkgConfig struct {
-	ImportPath string
-	GoFiles    []string
-	NonGoFiles []string
-	Tags       []string
+// This contains everything required for stdlib analysis.
+type stdlibConfig struct {
+	Srcs       []string
 	GOOS       string
 	GOARCH     string
-	ImportMap  map[string]string
-	FactMap    map[string]string
+	Tags       []string
 	FactOutput string
-	Objdump    string
-	StdZip     string
 }
 
-// loadFacts finds and loads facts per FactMap.
-func (c *pkgConfig) loadFacts(path string) ([]byte, error) {
-	realPath, ok := c.FactMap[path]
-	if !ok {
-		return nil, nil // No facts available.
+// packageConfig is serialized as the configuration.
+//
+// This contains everything required for single package analysis.
+type packageConfig struct {
+	ImportPath  string
+	GoFiles     []string
+	NonGoFiles  []string
+	Tags        []string
+	GOOS        string
+	GOARCH      string
+	ImportMap   map[string]string
+	FactMap     map[string]string
+	FactOutput  string
+	StdlibFacts string
+}
+
+// loader is a fact-loader function.
+type loader func(string) ([]byte, error)
+
+// saver is a fact-saver function.
+type saver func([]byte) error
+
+// factLoader returns a function that loads facts.
+//
+// This resolves all standard library facts and imported package facts up
+// front. The returned loader function will never return an error, only
+// empty facts.
+//
+// This is done because all stdlib data is stored together, and we don't want
+// to load this data many times over.
+func (c *packageConfig) factLoader() (loader, error) {
+	allFacts := make(map[string][]byte)
+	if c.StdlibFacts != "" {
+		data, err := ioutil.ReadFile(c.StdlibFacts)
+		if err != nil {
+			return nil, fmt.Errorf("error loading stdlib facts from %q: %w", c.StdlibFacts, err)
+		}
+		var stdlibFacts map[string][]byte
+		if err := json.Unmarshal(data, &stdlibFacts); err != nil {
+			return nil, fmt.Errorf("error loading stdlib facts: %w", err)
+		}
+		for pkg, data := range stdlibFacts {
+			allFacts[pkg] = data
+		}
+	}
+	for pkg, file := range c.FactMap {
+		data, err := ioutil.ReadFile(file)
+		if err != nil {
+			return nil, fmt.Errorf("error loading %q: %w", file, err)
+		}
+		allFacts[pkg] = data
 	}
+	return func(path string) ([]byte, error) {
+		return allFacts[path], nil
+	}, nil
+}
 
-	// Read the files file.
-	data, err := ioutil.ReadFile(realPath)
-	if err != nil {
-		return nil, err
+// factSaver may be used directly as a saver.
+func (c *packageConfig) factSaver(factData []byte) error {
+	if c.FactOutput == "" {
+		return nil // Nothing to save.
 	}
-	return data, nil
+	return ioutil.WriteFile(c.FactOutput, factData, 0644)
 }
 
 // shouldInclude indicates whether the file should be included.
 //
 // NOTE: This does only basic parsing of tags.
-func (c *pkgConfig) shouldInclude(path string) (bool, error) {
+func (c *packageConfig) shouldInclude(path string) (bool, error) {
 	ctx := build.Default
 	ctx.GOOS = c.GOOS
 	ctx.GOARCH = c.GOARCH
@@ -90,10 +136,11 @@ func (c *pkgConfig) shouldInclude(path string) (bool, error) {
 // files, and the facts. Note that this importer implementation will always
 // pass when a given package is not available.
 type importer struct {
-	pkgConfig
-	fset    *token.FileSet
-	cache   map[string]*types.Package
-	lastErr error
+	*packageConfig
+	fset     *token.FileSet
+	cache    map[string]*types.Package
+	lastErr  error
+	callback func(string) error
 }
 
 // Import implements types.Importer.Import.
@@ -104,6 +151,17 @@ func (i *importer) Import(path string) (*types.Package, error) {
 		// analyzers are specifically looking for this.
 		return types.Unsafe, nil
 	}
+
+	// Call the internal callback. This is used to resolve loading order
+	// for the standard library. See checkStdlib.
+	if i.callback != nil {
+		if err := i.callback(path); err != nil {
+			i.lastErr = err
+			return nil, err
+		}
+	}
+
+	// Actually load the data.
 	realPath, ok := i.ImportMap[path]
 	var (
 		rc  io.ReadCloser
@@ -112,7 +170,7 @@ func (i *importer) Import(path string) (*types.Package, error) {
 	if !ok {
 		// Not found in the import path. Attempt to find the package
 		// via the standard library.
-		rc, err = i.findStdPkg(path)
+		rc, err = findStdPkg(i.GOOS, i.GOARCH, path)
 	} else {
 		// Open the file.
 		rc, err = os.Open(realPath)
@@ -135,6 +193,139 @@ func (i *importer) Import(path string) (*types.Package, error) {
 // ErrSkip indicates the package should be skipped.
 var ErrSkip = errors.New("skipped")
 
+// checkStdlib checks the standard library.
+//
+// This constructs a synthetic package configuration for each library in the
+// standard library sources, and call checkPackage repeatedly.
+//
+// Note that not all parts of the source are expected to build. We skip obvious
+// test files, and cmd files, which should not be dependencies.
+func checkStdlib(config *stdlibConfig) ([]string, error) {
+	if len(config.Srcs) == 0 {
+		return nil, nil
+	}
+
+	// Ensure all paths are normalized.
+	for i := 0; i < len(config.Srcs); i++ {
+		config.Srcs[i] = path.Clean(config.Srcs[i])
+	}
+
+	// Calculate the root directory.
+	longestPrefix := path.Dir(config.Srcs[0])
+	for _, file := range config.Srcs[1:] {
+		for i := 0; i < len(file) && i < len(longestPrefix); i++ {
+			if file[i] != longestPrefix[i] {
+				// Truncate here; will stop the loop.
+				longestPrefix = longestPrefix[:i]
+				break
+			}
+		}
+	}
+	if len(longestPrefix) > 0 && longestPrefix[len(longestPrefix)-1] != '/' {
+		longestPrefix += "/"
+	}
+
+	// Aggregate all files by directory.
+	packages := make(map[string]*packageConfig)
+	for _, file := range config.Srcs {
+		d := path.Dir(file)
+		if len(longestPrefix) >= len(d) {
+			continue // Not a file.
+		}
+		pkg := path.Dir(file)[len(longestPrefix):]
+		// Skip cmd packages and obvious test files: see above.
+		if strings.HasPrefix(pkg, "cmd/") || strings.HasSuffix(file, "_test.go") {
+			continue
+		}
+		c, ok := packages[pkg]
+		if !ok {
+			c = &packageConfig{
+				ImportPath: pkg,
+				GOOS:       config.GOOS,
+				GOARCH:     config.GOARCH,
+				Tags:       config.Tags,
+			}
+			packages[pkg] = c
+		}
+		// Add the files appropriately. Note that they will be further
+		// filtered by architecture and build tags below, so this need
+		// not be done immediately.
+		if strings.HasSuffix(file, ".go") {
+			c.GoFiles = append(c.GoFiles, file)
+		} else {
+			c.NonGoFiles = append(c.NonGoFiles, file)
+		}
+	}
+
+	// Closure to check a single package.
+	allFindings := make([]string, 0)
+	stdlibFacts := make(map[string][]byte)
+	var checkOne func(pkg string) error // Recursive.
+	checkOne = func(pkg string) error {
+		// Is this already done?
+		if _, ok := stdlibFacts[pkg]; ok {
+			return nil
+		}
+
+		// Lookup the configuration.
+		config, ok := packages[pkg]
+		if !ok {
+			return nil // Not known.
+		}
+
+		// Find the binary package, and provide to objdump.
+		rc, err := findStdPkg(config.GOOS, config.GOARCH, pkg)
+		if err != nil {
+			// If there's no binary for this package, it is likely
+			// not built with the distribution. That's fine, we can
+			// just skip analysis.
+			return nil
+		}
+
+		// Provide the input.
+		oldReader := dump.Reader
+		dump.Reader = rc // For analysis.
+		defer func() {
+			rc.Close()
+			dump.Reader = oldReader // Restore.
+		}()
+
+		// Run the analysis.
+		findings, err := checkPackage(config, func(factData []byte) error {
+			stdlibFacts[pkg] = factData
+			return nil
+		}, checkOne)
+		if err != nil {
+			// If we can't analyze a package from the standard library,
+			// then we skip it. It will simply not have any findings.
+			return nil
+		}
+		allFindings = append(allFindings, findings...)
+		return nil
+	}
+
+	// Check all packages.
+	//
+	// Note that this may call checkOne recursively, so it's not guaranteed
+	// to evaluate in the order provided here. We do ensure however, that
+	// all packages are evaluated.
+	for pkg := range packages {
+		checkOne(pkg)
+	}
+
+	// Write out all findings.
+	factData, err := json.Marshal(stdlibFacts)
+	if err != nil {
+		return nil, fmt.Errorf("error saving stdlib facts: %w", err)
+	}
+	if err := ioutil.WriteFile(config.FactOutput, factData, 0644); err != nil {
+		return nil, fmt.Errorf("error saving findings to %q: %v", config.FactOutput, err)
+	}
+
+	// Return all findings.
+	return allFindings, nil
+}
+
 // checkPackage runs all analyzers.
 //
 // The implementation was adapted from [1], which was in turn adpated from [2].
@@ -143,11 +334,12 @@ var ErrSkip = errors.New("skipped")
 //
 // [1] bazelbuid/rules_go/tools/builders/nogo_main.go
 // [2] golang.org/x/tools/go/checker/internal/checker
-func checkPackage(config pkgConfig) ([]string, error) {
+func checkPackage(config *packageConfig, factSaver saver, importCallback func(string) error) ([]string, error) {
 	imp := &importer{
-		pkgConfig: config,
-		fset:      token.NewFileSet(),
-		cache:     make(map[string]*types.Package),
+		packageConfig: config,
+		fset:          token.NewFileSet(),
+		cache:         make(map[string]*types.Package),
+		callback:      importCallback,
 	}
 
 	// Load all source files.
@@ -184,14 +376,15 @@ func checkPackage(config pkgConfig) ([]string, error) {
 	}
 
 	// Load all package facts.
-	facts, err := facts.Decode(types, config.loadFacts)
+	loader, err := config.factLoader()
+	if err != nil {
+		return nil, fmt.Errorf("error loading facts: %w", err)
+	}
+	facts, err := facts.Decode(types, loader)
 	if err != nil {
 		return nil, fmt.Errorf("error decoding facts: %w", err)
 	}
 
-	// Set the binary global for use.
-	data.Objdump = config.Objdump
-
 	// Register fact types and establish dependencies between analyzers.
 	// The visit closure will execute recursively, and populate results
 	// will all required analysis results.
@@ -263,11 +456,9 @@ func checkPackage(config pkgConfig) ([]string, error) {
 	}
 
 	// Write the output file.
-	if config.FactOutput != "" {
-		factData := facts.Encode()
-		if err := ioutil.WriteFile(config.FactOutput, factData, 0644); err != nil {
-			return nil, fmt.Errorf("error: unable to open facts output %q: %v", config.FactOutput, err)
-		}
+	factData := facts.Encode()
+	if err := factSaver(factData); err != nil {
+		return nil, fmt.Errorf("error: unable to save facts: %v", err)
 	}
 
 	// Convert all diagnostics to strings.
@@ -284,38 +475,56 @@ func checkPackage(config pkgConfig) ([]string, error) {
 }
 
 var (
-	configFile = flag.String("config", "", "configuration file (in JSON format)")
+	packageFile = flag.String("package", "", "package configuration file (in JSON format)")
+	stdlibFile  = flag.String("stdlib", "", "stdlib configuration file (in JSON format)")
 )
 
-// Main is the entrypoint; it should be called directly from main.
-//
-// N.B. This package registers it's own flags.
-func Main() {
-	// Parse all flags.
-	flag.Parse()
-
+func loadConfig(file string, config interface{}) interface{} {
 	// Load the configuration.
-	f, err := os.Open(*configFile)
+	f, err := os.Open(file)
 	if err != nil {
-		log.Fatalf("unable to open configuration %q: %v", *configFile, err)
+		log.Fatalf("unable to open configuration %q: %v", file, err)
 	}
 	defer f.Close()
-	config := new(pkgConfig)
 	dec := json.NewDecoder(f)
 	dec.DisallowUnknownFields()
 	if err := dec.Decode(config); err != nil {
 		log.Fatalf("unable to decode configuration: %v", err)
 	}
+	return config
+}
 
-	// Process the package.
-	findings, err := checkPackage(*config)
+// Main is the entrypoint; it should be called directly from main.
+//
+// N.B. This package registers it's own flags.
+func Main() {
+	// Parse all flags.
+	flag.Parse()
+
+	var (
+		findings []string
+		err      error
+	)
+
+	// Check the configuration.
+	if *packageFile != "" && *stdlibFile != "" {
+		log.Fatalf("unable to perform stdlib and package analysis; provide only one!")
+	} else if *stdlibFile != "" {
+		c := loadConfig(*stdlibFile, new(stdlibConfig)).(*stdlibConfig)
+		findings, err = checkStdlib(c)
+	} else if *packageFile != "" {
+		c := loadConfig(*packageFile, new(packageConfig)).(*packageConfig)
+		findings, err = checkPackage(c, c.factSaver, nil)
+	} else {
+		log.Fatalf("please provide at least one of package or stdlib!")
+	}
+
+	// Handle findings & errors.
 	if err != nil {
 		log.Fatalf("error checking package: %v", err)
 	}
-
-	// No findings?
 	if len(findings) == 0 {
-		os.Exit(0)
+		return
 	}
 
 	// Print findings and exit with non-zero code.