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Merge "soong_ui path.go: improve comments." am: 55e0022fc0

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Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1502731

Change-Id: Id91fb286b18739f485b8b021c91bd548701c8694
This commit is contained in:
Jingwen Chen 2020-11-20 05:24:13 +00:00 committed by Automerger Merge Worker
commit e6f2194126
1 changed files with 46 additions and 5 deletions
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51
ui/build/path.go
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@ -29,6 +29,9 @@ import (
"android/soong/ui/metrics"
)
// parsePathDir returns the list of filenames of readable files in a directory.
// This does not recurse into subdirectories, and does not contain subdirectory
// names in the list.
func parsePathDir(dir string) []string {
f, err := os.Open(dir)
if err != nil {
@ -54,10 +57,12 @@ func parsePathDir(dir string) []string {
return ret
}
// A "lite" version of SetupPath used for dumpvars, or other places that need
// minimal overhead (but at the expense of logging). If tmpDir is empty, the
// default TMPDIR is used from config.
// SetupLitePath is the "lite" version of SetupPath used for dumpvars, or other
// places that does not need the full logging capabilities of path_interposer,
// wants the minimal performance overhead, and still get the benefits of $PATH
// hermeticity.
func SetupLitePath(ctx Context, config Config, tmpDir string) {
// Don't replace the path twice.
if config.pathReplaced {
return
}
@ -67,6 +72,7 @@ func SetupLitePath(ctx Context, config Config, tmpDir string) {
origPath, _ := config.Environment().Get("PATH")
// If tmpDir is empty, the default TMPDIR is used from config.
if tmpDir == "" {
tmpDir, _ = config.Environment().Get("TMPDIR")
}
@ -74,8 +80,10 @@ func SetupLitePath(ctx Context, config Config, tmpDir string) {
ensureEmptyDirectoriesExist(ctx, myPath)
os.Setenv("PATH", origPath)
// Iterate over the ACL configuration of host tools for this build.
for name, pathConfig := range paths.Configuration {
if !pathConfig.Symlink {
// Excludes 'Forbidden' and 'LinuxOnlyPrebuilt' PathConfigs.
continue
}
@ -88,6 +96,7 @@ func SetupLitePath(ctx Context, config Config, tmpDir string) {
continue
}
// Symlink allowed host tools into a directory for hermeticity.
err = os.Symlink(origExec, filepath.Join(myPath, name))
if err != nil {
ctx.Fatalln("Failed to create symlink:", err)
@ -96,14 +105,26 @@ func SetupLitePath(ctx Context, config Config, tmpDir string) {
myPath, _ = filepath.Abs(myPath)
// Set up the checked-in prebuilts path directory for the current host OS.
prebuiltsPath, _ := filepath.Abs("prebuilts/build-tools/path/" + runtime.GOOS + "-x86")
myPath = prebuiltsPath + string(os.PathListSeparator) + myPath
// Set $PATH to be the directories containing the host tool symlinks, and
// the prebuilts directory for the current host OS.
config.Environment().Set("PATH", myPath)
config.pathReplaced = true
}
// SetupPath uses the path_interposer to intercept calls to $PATH binaries, and
// communicates with the interposer to validate allowed $PATH binaries at
// runtime, using logs as a medium.
//
// This results in hermetic directories in $PATH containing only allowed host
// tools for the build, and replaces $PATH to contain *only* these directories,
// and enables an incremental restriction of tools allowed in the $PATH without
// breaking existing use cases.
func SetupPath(ctx Context, config Config) {
// Don't replace $PATH twice.
if config.pathReplaced {
return
}
@ -112,9 +133,11 @@ func SetupPath(ctx Context, config Config) {
defer ctx.EndTrace()
origPath, _ := config.Environment().Get("PATH")
// The directory containing symlinks from binaries in $PATH to the interposer.
myPath := filepath.Join(config.OutDir(), ".path")
interposer := myPath + "_interposer"
// Bootstrap the path_interposer Go binary with microfactory.
var cfg microfactory.Config
cfg.Map("android/soong", "build/soong")
cfg.TrimPath, _ = filepath.Abs(".")
@ -122,15 +145,20 @@ func SetupPath(ctx Context, config Config) {
ctx.Fatalln("Failed to build path interposer:", err)
}
// Save the original $PATH in a file.
if err := ioutil.WriteFile(interposer+"_origpath", []byte(origPath), 0777); err != nil {
ctx.Fatalln("Failed to write original path:", err)
}
// Communication with the path interposer works over log entries. Set up the
// listener channel for the log entries here.
entries, err := paths.LogListener(ctx.Context, interposer+"_log")
if err != nil {
ctx.Fatalln("Failed to listen for path logs:", err)
}
// Loop over all log entry listener channels to validate usage of only
// allowed PATH tools at runtime.
go func() {
for log := range entries {
curPid := os.Getpid()
@ -140,6 +168,8 @@ func SetupPath(ctx Context, config Config) {
break
}
}
// Compute the error message along with the process tree, including
// parents, for this log line.
procPrints := []string{
"See https://android.googlesource.com/platform/build/+/master/Changes.md#PATH_Tools for more information.",
}
@ -150,6 +180,7 @@ func SetupPath(ctx Context, config Config) {
}
}
// Validate usage against disallowed or missing PATH tools.
config := paths.GetConfig(log.Basename)
if config.Error {
ctx.Printf("Disallowed PATH tool %q used: %#v", log.Basename, log.Args)
@ -165,8 +196,10 @@ func SetupPath(ctx Context, config Config) {
}
}()
// Create the .path directory.
ensureEmptyDirectoriesExist(ctx, myPath)
// Compute the full list of binaries available in the original $PATH.
var execs []string
for _, pathEntry := range filepath.SplitList(origPath) {
if pathEntry == "" {
@ -185,8 +218,14 @@ func SetupPath(ctx Context, config Config) {
ctx.Fatalln("TEMPORARY_DISABLE_PATH_RESTRICTIONS was a temporary migration method, and is now obsolete.")
}
// Create symlinks from the path_interposer binary to all binaries for each
// directory in the original $PATH. This ensures that during the build,
// every call to a binary that's expected to be in the $PATH will be
// intercepted by the path_interposer binary, and validated with the
// LogEntry listener above at build time.
for _, name := range execs {
if !paths.GetConfig(name).Symlink {
// Ignore host tools that shouldn't be symlinked.
continue
}
@ -200,11 +239,13 @@ func SetupPath(ctx Context, config Config) {
myPath, _ = filepath.Abs(myPath)
// We put some prebuilts in $PATH, since it's infeasible to add dependencies for all of
// them.
// We put some prebuilts in $PATH, since it's infeasible to add dependencies
// for all of them.
prebuiltsPath, _ := filepath.Abs("prebuilts/build-tools/path/" + runtime.GOOS + "-x86")
myPath = prebuiltsPath + string(os.PathListSeparator) + myPath
// Replace the $PATH variable with the path_interposer symlinks, and
// checked-in prebuilts.
config.Environment().Set("PATH", myPath)
config.pathReplaced = true
}