crosvm: add debug labels to devices for improved SIGCHLD logs

Each device (Bus, Pci, Proxy, etc), gets a debug label associated with
it. When a child is spawned, the debug label for it is stored in
a map with the child's pid as the key. If a SIGCHLD is handled, this map
is used to print a more helpful message about exactly which child died.

BUG=None
TEST=run with sandboxing and a faulty child device
     check logs for message about child died
     the child should have a debug label

Change-Id: I61fbbee0a8e701249533a7a3a6a1ad48840f12e5
Reviewed-on: https://chromium-review.googlesource.com/1432835
Commit-Ready: Chih-Yang Hsia <paulhsia@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/devices/src/serial.rs b/devices/src/serial.rs
index 25911f9..b2a5651 100644
--- a/devices/src/serial.rs
+++ b/devices/src/serial.rs
@@ -185,6 +185,10 @@ impl Serial {
 }
 
 impl BusDevice for Serial {
+    fn debug_label(&self) -> String {
+        "serial".to_owned()
+    }
+
     fn write(&mut self, offset: u64, data: &[u8]) {
         if data.len() != 1 {
             return;