crash_dump: print the identity of tracers.
Instead of printing a useless "ptrace attach failed: strerror(EPERM)"
message, print the name and pid of a competing tracer when we fail to
attach because a process is already being ptraced.
Bug: http://b/31531918
Test: debuggerd_test32, debuggerd_test64 on aosp_angler
Test: strace -p `pidof surfaceflinger`; debuggerd -b surfaceflinger
Change-Id: Ifd3f80fe03de30ff38c0e0068560a7b12875f29d
diff --git a/debuggerd/crash_dump.cpp b/debuggerd/crash_dump.cpp
index 4b1e51d..cd1da50 100644
--- a/debuggerd/crash_dump.cpp
+++ b/debuggerd/crash_dump.cpp
@@ -79,9 +79,27 @@
return fstatat(pid_proc_fd, task_path.c_str(), &st, 0) == 0;
}
+static pid_t get_tracer(pid_t tracee) {
+ // Check to see if the thread is being ptraced by another process.
+ android::procinfo::ProcessInfo process_info;
+ if (android::procinfo::GetProcessInfo(tracee, &process_info)) {
+ return process_info.tracer;
+ }
+ return -1;
+}
+
// Attach to a thread, and verify that it's still a member of the given process
static bool ptrace_seize_thread(int pid_proc_fd, pid_t tid, std::string* error) {
if (ptrace(PTRACE_SEIZE, tid, 0, 0) != 0) {
+ if (errno == EPERM) {
+ pid_t tracer = get_tracer(tid);
+ if (tracer != -1) {
+ *error = StringPrintf("failed to attach to thread %d, already traced by %d (%s)", tid,
+ tracer, get_process_name(tracer).c_str());
+ return false;
+ }
+ }
+
*error = StringPrintf("failed to attach to thread %d: %s", tid, strerror(errno));
return false;
}