Fix lldb-gdbserver gdb-remote unit tests that require attaching to the inferior.

[tfiala]

Summary

Some Linux kernels have a ptrace security feature that prevents a ptracer from attaching to the inferior if the ptracer is not an ancestor in the process hierarchy. In the gdb-remote attach tests, the llgs is not a parent of the inferior, so kernels that protect against this are failing on the attach tests.

This change to the inferior test program checks if the inferior is running on Linux and has the relevant ptrace flags, and if so, first thing enables a ptracer that is not part of the parent hierarchy.

[tfiala]

I verified this on a stock ubuntu 14.04 x86_64 system. This fixes 4 of the 11 failing tests I see on a stock ubuntu 14.04 x86_64 system. I'm going to go ahead and check this in.

[tfiala]

This fixes the following test failures:

FAIL: LLDB (suite) :: TestGdbRemoteProcessInfo.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestGdbRemoteAttach.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestLldbGdbServer.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestGdbRemoteKill.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

Checked in here.

svn commit
Sending        test/tools/lldb-gdbserver/main.cpp
Transmitting file data .
Committed revision 220181.

[tfiala]

FWIW:

These are the test failures I still see on a stock Linux x86_64 system at TOT:

FAIL: LLDB (suite) :: TestCallStopAndContinue.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestDataFormatterStdVector.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestDataFormatterStdVBool.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestDataFormatterStdMap.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestDataFormatterSynthVal.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestReportData.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

FAIL: LLDB (suite) :: TestMemoryHistory.py (Linux vagrant 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64)

test/tools/lldb-gdbserver/main.cpp

 #include <sys/syscall.h>
 #endif
 
+#if defined(__linux__)
+#include <sys/prctl.h>
+#endif
+
 static const char *const RETVAL_PREFIX               = "retval:";
 static const char *const SLEEP_PREFIX                = "sleep:";
 static const char *const STDERR_PREFIX               = "stderr:";

 
 int main (int argc, char **argv)
 {
+#if defined(__linux__)
+    // Immediately enable any ptracer so that we can allow the stub attach
+    // operation to succeed.  Some Linux kernels are locked down so that
+    // only an ancestor can be a ptracer of a process.  This disables that
+    // restriction.  Without it, attach-related stub tests will fail.
+#if defined(PR_SET_PTRACER) && defined(PR_SET_PTRACER_ANY)
+    const int prctl_result = prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0);
+    static_cast<void> (prctl_result);
+#endif
+#endif
+
   std::vector<pthread_t> threads;
   std::unique_ptr<uint8_t[]> heap_array_up;
     int return_value = 0;