Fix debug builds.

This change also adds instructions for using a debugger with syscall tests.

Fixes #9039

PiperOrigin-RevId: 563576842

g3doc/user_guide/debugging.md

@@ -65,7 +65,7 @@ Install a runsc with debug symbols (you can also use the
 [nightly release](../install/#nightly)):
 
 ```bash
-make dev BAZEL_OPTIONS="-c dbg"
+make dev BAZEL_OPTIONS="-c dbg --define gotags=debug"
 ```
 
 Start the container you want to debug using the runsc runtime with debug
@@ -94,6 +94,32 @@ In a different window connect to nginx to trigger the breakpoint:
 curl http://localhost:8080/
 ```
 
+It's also easy to attach a debugger to one of the predefined syscall tests when
+you're working on specific gVisor features. With the `delay-for-debugger` flag
+you can pause the test runner before execution so that you can attach the
+sandbox process to a debugger. Here is an example:
+
+```bash
+ make test BAZEL_OPTIONS="-c dbg --define gotags=debug" \
+ OPTIONS="--test_arg=--delay-for-debugger=5m --test_output=streamed" \
+ TARGETS=//test/syscalls:mount_test_runsc_systrap
+```
+
+The `delay-for-debugger=5m` flag means the test runner will pause for 5 minutes
+before running the test. To attach to the sandbox process, you can run the
+following in a separate window.
+
+```bash
+dlv attach $(ps aux | grep -m 1 -e 'runsc-sandbox' | awk '{print $2}')
+```
+
+Once you've attached to the process and set a breakpoint, you can signal the
+test to start by running the following in another separate window.
+
+```bash
+kill -SIGUSR1 $(ps aux | grep -m 1 -e 'bash.*test/syscalls' | awk '{print $2}')
+```
+
 ## Profiling
 
 `runsc` integrates with Go profiling tools and gives you easy commands to

runsc/boot/platforms/BUILD

@@ -13,6 +13,7 @@ exempt_go_library(
     srcs = [
         "platforms.go",
         "platforms_darwin.go",
+        "platforms_debug.go",
     ],
     # Nothing needs to be stateified, and stateify has trouble when select is
     # used to choose deps.

runsc/boot/platforms/platforms.go

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build linux
-// +build linux
+//go:build linux && !debug
+// +build linux,!debug
 
 // Package platforms imports all available platform packages.
 package platforms

runsc/boot/platforms/platforms_debug.go

@@ -0,0 +1,28 @@
+// Copyright 2023 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.
+
+//go:build linux && debug
+// +build linux,debug
+
+package platforms
+
+import (
+	// Import platforms that runsc might use.
+
+	// The KVM platform is not included because it's incompatible with debug
+	// builds. Unoptimized functions grow the stack too much and fail the nosplit
+	// check.
+	_ "gvisor.dev/gvisor/pkg/sentry/platform/ptrace"
+	_ "gvisor.dev/gvisor/pkg/sentry/platform/systrap"
+)

test/runner/main.go

@@ -332,10 +332,17 @@ func runRunsc(tc *gtest.TestCase, spec *specs.Spec) error {
 		if err != nil {
 			return fmt.Errorf("could not read pid file: %v", err)
 		}
-		log.Infof("Sandbox process ID is %s. You can attach to it from a debugger of your choice.", sandboxPidBytes)
-		log.Infof("For example, with Delve you can call: $ dlv attach %s", sandboxPidBytes)
-		log.Infof("The test will automatically start after %s.", *waitForPid)
-		log.Infof("You may also signal the test process to start the test immediately: $ kill -SIGUSR1 %d", os.Getpid())
+		msg := `
+
+		Sandbox is running. You can now attach to it from a debugger of your choice.
+		For example, with Delve you can call: $ dlv attach %s.
+		The test will automatically start after %s.
+		You may also signal the test process to start the test immediately: $ kill -SIGUSR1 %d.
+
+		If you're running a test using Make/docker, you'll have to obtain the runsc and test PIDs manually.
+		To attach run: $ dlv attach $(ps aux | grep -m 1 -e 'runsc-sandbox' | awk '{print $2}')
+		To signal the test process run: $ kill -SIGUSR1 $(ps aux | grep -m 1 -e 'bash.*test/syscalls' | awk '{print $2}')`
+		log.Infof(msg, sandboxPidBytes, *waitForPid, os.Getpid())
 
 		sigCh := make(chan os.Signal, 1)
 		signal.Notify(sigCh, unix.SIGUSR1)

tools/bazeldefs/go.bzl

@@ -57,7 +57,11 @@ def go_binary(name, static = False, pure = False, x_defs = None, **kwargs):
         kwargs["pure"] = "on"
     gc_goopts = select({
         "//conditions:default": kwargs.pop("gc_goopts", []),
-        "//tools:debug": kwargs.pop("gc_goopts", []) + ["-all=-N -l"],
+        "//tools:debug": kwargs.pop("gc_goopts", []) + ["-N", "-l"],
+    })
+    kwargs["gotags"] = select({
+        "//conditions:default": kwargs.pop("gotags", []),
+        "//tools:debug": kwargs.pop("gotags", []) + ["debug"],
     })
     _go_binary(
         name = name,