am 02526d48: debuggerd: properly unblock signal handler.
* commit '02526d486803de153d03851f4d5f9be7c555e46c':
debuggerd: properly unblock signal handler.
diff --git a/debuggerd/debuggerd.c b/debuggerd/debuggerd.c
index 5fa4442..7a3e781 100644
--- a/debuggerd/debuggerd.c
+++ b/debuggerd/debuggerd.c
@@ -642,7 +642,7 @@
goto done;
}
- sprintf(buf,"/proc/%d/task/%d", cr.pid, tid);
+ snprintf(buf, sizeof buf, "/proc/%d/task/%d", cr.pid, tid);
if(stat(buf, &s)) {
LOG("tid %d does not exist in pid %d. ignoring debug request\n",
tid, cr.pid);
@@ -652,7 +652,19 @@
XLOG("BOOM: pid=%d uid=%d gid=%d tid=%d\n", cr.pid, cr.uid, cr.gid, tid);
+ /* Note that at this point, the target thread's signal handler
+ * is blocked in a read() call. This gives us the time to PTRACE_ATTACH
+ * to it before it has a chance to really fault.
+ *
+ * After the attach, the thread is stopped, and we write to the file
+ * descriptor to ensure that it will run as soon as we call PTRACE_CONT
+ * below. See details in bionic/libc/linker/debugger.c, in function
+ * debugger_signal_handler().
+ */
tid_attach_status = ptrace(PTRACE_ATTACH, tid, 0, 0);
+
+ TEMP_FAILURE_RETRY(write(fd, &tid, 1));
+
if(tid_attach_status < 0) {
LOG("ptrace attach failed: %s\n", strerror(errno));
goto done;