feat(sandbox): add --gdb option to aumatically connect to GDB

This adds a sandbox option to setup GDB automatically and open it in a
new tmux window. This makes it easier to use GDB with firecracker using
common tooling.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

tests/framework/microvm_helpers.py

@@ -7,6 +7,7 @@
 import os
 import platform
 import subprocess
+import tempfile
 from pathlib import Path
 
 
@@ -245,3 +246,30 @@ def trace_cmd_guest(self, fns, cmd, port=4321):
             f"trace-cmd record -N {host_ip}:{port} -p function {' '.join(fns)} {cmd}"
         )
         return list(Path(".").glob("trace.*.dat"))
+
+    def tmux_gdb(self):
+        """Run GDB on a new tmux window"""
+        chroot_gdb_socket = Path(self.vm.jailer.chroot_path(), self.vm.gdb_socket)
+
+        with tempfile.NamedTemporaryFile(
+            mode="w", suffix=".gdb", delete=False, prefix="fc_gdb_"
+        ) as f:
+            f.write(
+                f"""
+                target remote {chroot_gdb_socket}
+                directory resources/linux
+                hbreak start_kernel
+                continue
+            """
+            )
+            gdb_script = f.name
+
+        self.tmux_neww(
+            f"""
+            until [ -S {chroot_gdb_socket} ]; do
+                echo 'waiting for {chroot_gdb_socket}';
+                sleep 1;
+            done;
+            gdb {self.vm.kernel_file} -x {gdb_script}
+            """
+        )

tools/sandbox.py

@@ -10,11 +10,13 @@
 
 import argparse
 import json
+import platform
 import re
 from pathlib import Path
 
+import host_tools.cargo_build as build_tools
 from framework.artifacts import disks, kernels
-from framework.defs import DEFAULT_BINARY_DIR
+from framework.defs import DEFAULT_BINARY_DIR, LOCAL_BUILD_PATH
 from framework.microvm import MicroVMFactory
 
 kernels = list(kernels("vmlinux-*"))
@@ -58,12 +60,31 @@ def parse_byte_size(param):
 parser.add_argument("--rootfs-size", type=parse_byte_size, default=1 * 2**30)  # 1GB
 parser.add_argument("--binary-dir", help="Path to the firecracker binaries")
 parser.add_argument("--cpu-template-path", help="CPU template to use", type=Path)
+parser.add_argument(
+    "--debug", action="store_true", default=False, help="Use debug kernel"
+)
+parser.add_argument(
+    "--gdb", action="store_true", default=False, help="Connect to Firecracker guest GDB"
+)
 args = parser.parse_args()
 print(args)
 
 binary_dir = None
 if args.binary_dir:
     binary_dir = Path(args.binary_dir).resolve()
+elif args.gdb:
+    # Build Firecracker with GDB feature if needed
+    print("Building Firecracker with GDB feature...")
+    machine = platform.machine()
+    target = f"{machine}-unknown-linux-musl"
+    build_dir = LOCAL_BUILD_PATH / "gdb"
+    build_tools.cargo(
+        "build",
+        f"--features gdb --target {target} --all",
+        env={"CARGO_TARGET_DIR": build_dir},
+    )
+    print("Build complete!")
+    binary_dir = build_dir / target / "debug"
 else:
     binary_dir = DEFAULT_BINARY_DIR
 
@@ -72,28 +93,26 @@ def parse_byte_size(param):
     cpu_template = json.loads(args.cpu_template_path.read_text())
 vmfcty = MicroVMFactory(binary_dir)
 
-print(f"uvm with kernel {args.kernel} ...")
-uvm = vmfcty.build(args.kernel, args.rootfs)
+if args.debug or args.gdb:
+    kernel = args.kernel.parent / "debug" / args.kernel.name
+else:
+    kernel = args.kernel
+
+print(f"uvm with kernel {kernel} ...")
+uvm = vmfcty.build(kernel, args.rootfs)
 uvm.help.enable_console()
 uvm.help.resize_disk(uvm.rootfs_file, args.rootfs_size)
-uvm.spawn(log_show_level=True)
+uvm.spawn(log_show_level=True, validate_api=False)
 uvm.help.print_log()
 uvm.add_net_iface()
 uvm.basic_config(vcpu_count=args.vcpus, mem_size_mib=args.guest_mem_size // 2**20)
 if cpu_template is not None:
     uvm.api.cpu_config.put(**cpu_template)
     print(cpu_template)
+
+if args.gdb:
+    uvm.enable_gdb()
+    uvm.help.tmux_gdb()
+
 uvm.start()
 uvm.get_all_metrics()
-
-kernel_dbg_dir = args.kernel.parent / "debug"
-kernel_dbg = kernel_dbg_dir / args.kernel.name
-print(f"uvm2 with kernel {kernel_dbg} ...")
-uvm2 = vmfcty.build(kernel_dbg, args.rootfs)
-uvm2.spawn()
-uvm2.add_net_iface()
-uvm2.basic_config(vcpu_count=args.vcpus, mem_size_mib=args.guest_mem_size // 2**20)
-uvm2.start()
-# trace-cmd needs this (DNS resolution?)
-uvm2.help.enable_ip_forwarding()
-files = uvm2.help.trace_cmd_guest(["-l", "read_msr"], cmd="sleep 5")