Merge pull request containers#23487 from Luap99/ebpf

add epbf program to trace podman cleanup errors in CI

.cirrus.yml

@@ -401,6 +401,9 @@ bindings_task:
         server_log_artifacts:
             path: ./podman-server.log
             type: text/plain
+        cleanup_tracer_artifacts:
+            path: ./podman-cleanup-tracer.log
+            type: text/plain
         df_script: '$SCRIPT_BASE/logcollector.sh df'
         audit_log_script: '$SCRIPT_BASE/logcollector.sh audit'
         journal_script: '$SCRIPT_BASE/logcollector.sh journal'

.gitignore

@@ -57,3 +57,4 @@ contrib/win-installer/shasums
 contrib/win-installer/*.wixobj
 contrib/win-installer/*.wixpdb
 contrib/win-installer/*.log
+podman-cleanup-tracer.log*

contrib/cirrus/runner.sh

@@ -458,6 +458,15 @@ msg "************************************************************"
 ((${SETUP_ENVIRONMENT:-0})) || \
     die "Expecting setup_environment.sh to have completed successfully"
 
+if [[ "$UID" -eq 0 ]] && ((CONTAINER==0)); then
+    # start ebpf cleanup tracer (#23487)
+    msg "start ebpf cleanup tracer"
+    # replace zero bytes to make the log more readable
+    bpftrace $GOSRC/hack/podman_cleanup_tracer.bt |& \
+        tr '\0' ' ' >$GOSRC/podman-cleanup-tracer.log &
+    TRACER_PID=$!
+fi
+
 # shellcheck disable=SC2154
 if [[ "$PRIV_NAME" == "rootless" ]] && [[ "$UID" -eq 0 ]]; then
     # Remove /var/lib/cni, it is not required for rootless cni.
@@ -499,4 +508,9 @@ fi
 
 showrun $handler
 
+if [[ -n "$TRACER_PID" ]]; then
+    # ignore any error here
+    kill "$TRACER_PID" || true
+fi
+
 showrun echo "finished"

hack/podman_cleanup_tracer.bt

@@ -0,0 +1,151 @@
+#!/usr/bin/env bpftrace
+
+// Traces podman and conmon commands for there exit status and all process that
+// send signals to them. Also prints stderr for all podman container cleanup processes.
+// The goal is to be able to trace all podman cleanup errors, while there is an
+// option to log the errors to the syslog that only works of the process if the
+// process got there and not if it was killed before. This program here will trace
+// the exit status as well so we know even if it was killed by a signal.
+//
+// This is script uses https://github.com/bpftrace/bpftrace to compile this into
+// kernel ebpf.
+//
+// Usage: sudo ./podman_cleanup_tracer.bt
+// see below for output format
+
+BEGIN {
+    print("Output format is one of:");
+    print("exec   TIME PID PPID COMM ARGV(truncated)");
+    print("cmd    TIME PID PPID ARGV(full)");
+    print("exit   TIME PID PPID COMM EXIT_CODE EXIT_SIGNAL");
+    print("kill   TIME PID PPID COMM SIGNAL TPID RET");
+    print("stderr TIME PID PPID COMM OUTPUT");
+}
+
+// Trace all exec calls to find all podman + conmon processes, it will also catch
+// netavark and aardvark-dns as they have podman in the path as well but this is
+// good so we can see any errors there as well.
+tracepoint:syscalls:sys_enter_exec*
+/ strcontains(str(args.argv[0]),"podman") || strcontains(str(args.argv[0]), "conmon")  /
+{
+
+    // create entry in pid map so we can check the pid later
+    @pids[pid] = 1;
+
+    // Find the podman cleanup process spawned by conmon.
+    // I tried matching argv but there seems to be no way to iterate over it.
+    // In practise parent name conmon and argv0 podman should contain all the
+    // cleanup processes we care about.
+    if (comm == "conmon" && strcontains(str(args.argv[0]), "podman")) {
+        @cleanupPids[pid] = 1;
+    }
+
+    printf("%-6s %s %-8d %-8d %-12s ",
+        "exec",
+        strftime("%H:%M:%S.%f", nsecs),
+        pid,
+        curtask->real_parent->tgid,
+        comm
+    );
+
+    // Unfortunately this doesn't print the full argv0 as there is some limit,
+    // as such we use the /proc/<>/cmdline reading hack below on exec exit.
+    join(args->argv);
+}
+
+
+// Print the full cmdline
+tracepoint:syscalls:sys_exit_exec*
+/ @pids[pid] /
+{
+    printf("%-6s %s %-8d %-8d ",
+        "cmd",
+        strftime("%H:%M:%S.%f", nsecs),
+        pid,
+        curtask->real_parent->tgid
+    );
+    // This can fail to open the file it is done in user space and
+    // thus racy if the process exits quickly.
+    cat("/proc/%d/cmdline", pid);
+    print("");
+}
+
+
+// Trace all exits for the pids we matched above,
+// pid == tid is used to only match the main exit
+// and not all thread exits which we do not care about.
+tracepoint:sched:sched_process_exit
+/ @pids[pid] && pid == tid /
+{
+    printf("%-6s %s %-8d %-8d %-12s %d %d\n",
+        "exit",
+        strftime("%H:%M:%S.%f", nsecs),
+        pid,
+        curtask->real_parent->tgid,
+        comm,
+        curtask->exit_code >> 8,  // actual exit code
+        curtask->exit_code & 0xFF // signal number if killed
+    );
+
+    // process is done remove pid from map
+    delete(@pids[pid]);
+    delete(@cleanupPids[pid]);
+}
+
+// Trace all kill calls that target our pids.
+// This will not catch signals send via pidfd_send_signal because
+// I don't see a way to translate the pidfd to our target pids and
+// I don't want to log all send signals on the system.
+tracepoint:syscalls:sys_enter_kill
+/ @pids[args.pid] /
+{
+	@tpid[tid] = args.pid;
+	@tsig[tid] = args.sig;
+}
+
+tracepoint:syscalls:sys_exit_kill
+/ @tpid[tid] /
+{
+	printf("%-6s %s %-8d %-8d %-12s %d %-8d %d\n",
+        "kill",
+		strftime("%H:%M:%S.%f", nsecs),
+		pid,
+        curtask->real_parent->tgid,
+        comm,
+        @tsig[tid],
+        @tpid[tid],
+        args.ret
+    );
+	delete(@tpid[tid]);
+	delete(@tsig[tid]);
+}
+
+
+// Print anything written on stderr for the podman container cleanup process.
+tracepoint:syscalls:sys_enter_write
+/ @cleanupPids[pid] && args.fd == 2 /
+{
+    printf("%-6s %s %-8d %-8d %-12s",
+        "stderr",
+		strftime("%H:%M:%S.%f", nsecs),
+		pid,
+        curtask->real_parent->tgid,
+        comm
+    );
+
+    // String size limit is is 64 by default, this includes the 0 byte and when we
+    // hit the string limit it also adds "..." when using 63 so we use 63 as len here.
+    // While upstream fixed these low string limits (https://github.com/bpftrace/bpftrace/issues/305)
+    // it is not yet in older distro version we use so we cannot use that yet.
+    // Thus manually print several times.
+    $len = 62;
+    $offset = 62;
+    printf("%s", str(args.buf, $len));
+
+    unroll(10) {
+        if ((int64)args.count > $offset ) {
+            printf("%s", str(args.buf + $offset, $len));
+        }
+        $offset += $len
+    }
+}