commit 218f7fb68e219884f6eec9714afb4da691450bc5
author Josh Gao <jmgao@google.com> Fri Oct 07 16:42:05 2016 -0700
committer Josh Gao <jmgao@google.com> Fri Oct 07 18:04:05 2016 -0700
tree d827db4962558790212b5aeb74e72e8b384ebd38
parent 4a8b178c97ccc388a9c94663dfd7e1c614ffba64

debuggerd: report crashes even when out of file descriptors.

Use nasty clone hacks to let us close random file descriptors to be
able to connect to debuggerd when the fd table is full.

Bug: http://b/32013594
Test: crasher exhaustfd-SIGSEGV
Change-Id: I47772e9a5994da4473bd935b105d9c36827c017a

debuggerd/debuggerd.cpp

diff --git a/debuggerd/debuggerd.cpp b/debuggerd/debuggerd.cpp
index a6d3d38..b8a62a5 100644
--- a/debuggerd/debuggerd.cpp
+++ b/debuggerd/debuggerd.cpp
@@ -69,6 +69,7 @@
   debugger_action_t action;
   pid_t pid, tid;
   uid_t uid, gid;
+  pid_t ignore_tid;
   uintptr_t abort_msg_address;
 };
 
@@ -215,6 +216,7 @@
 
   out_request->action = static_cast<debugger_action_t>(msg.action);
   out_request->tid = msg.tid;
+  out_request->ignore_tid = msg.ignore_tid;
   out_request->pid = cr.pid;
   out_request->uid = cr.uid;
   out_request->gid = cr.gid;
@@ -408,7 +410,7 @@
 }
 #endif
 
-static void ptrace_siblings(pid_t pid, pid_t main_tid, std::set<pid_t>& tids) {
+static void ptrace_siblings(pid_t pid, pid_t main_tid, pid_t ignore_tid, std::set<pid_t>& tids) {
   char task_path[64];
 
   snprintf(task_path, sizeof(task_path), "/proc/%d/task", pid);
@@ -434,7 +436,7 @@
       continue;
     }
 
-    if (tid == main_tid) {
+    if (tid == main_tid || tid == ignore_tid) {
       continue;
     }
 
@@ -583,7 +585,7 @@
 
   std::set<pid_t> siblings;
   if (!attach_gdb) {
-    ptrace_siblings(request.pid, request.tid, siblings);
+    ptrace_siblings(request.pid, request.tid, request.ignore_tid, siblings);
   }
 
   // Generate the backtrace map before dropping privileges.