Fix thread/process ID reading from linux core files

[labath]

Summary

This also adds a basic smoke test for linux core file reading. I'm checking in the core files as
well, so that the tests can run on all platforms. With some tricks I was able to produce
reasonably-sized core files (~40K).

This fixes the first part of pr26322.

[zturner]

Good to see we have a way to generate reasonably sized core files on other platforms as well.

lldb/trunk/packages/Python/lldbsuite/test/functionalities/postmortem/linux-core/TestLinuxCore.py

+"""
+Test basics of linux core file debugging.
+"""
+
+from __future__ import print_function
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class LinuxCoreTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @skipIf(bugnumber="llvm.org/pr26947")
+    @no_debug_info_test
+    def test_i386(self):
+        """Test that lldb can read the process information from an i386 linux core file."""
+        self.do_test("i386", 32306)
+
+    @no_debug_info_test
+    def test_x86_64(self):
+        """Test that lldb can read the process information from an x86_64 linux core file."""
+        self.do_test("x86_64", 32259)
+
+    def do_test(self, arch, pid):
+        target = self.dbg.CreateTarget(arch + ".out")
+        process = target.LoadCore(arch + ".core")
+        self.assertTrue(process, PROCESS_IS_VALID)
+        self.assertEqual(process.GetNumThreads(), 1)
+        self.assertEqual(process.GetProcessID(), pid)
+
+        thread = process.GetSelectedThread()
+        self.assertTrue(thread)
+        self.assertEqual(thread.GetThreadID(), pid)
+        backtrace = ["bar", "foo", "_start"]
+        self.assertEqual(thread.GetNumFrames(), len(backtrace))
+        for i in range(len(backtrace)):
+            frame = thread.GetFrameAtIndex(i)
+            self.assertTrue(frame)
+            self.assertEqual(frame.GetFunctionName(), backtrace[i])
+            self.assertEqual(frame.GetLineEntry().GetLine(),
+                    line_number("main.c", "Frame " + backtrace[i]))
+            self.assertEqual(frame.FindVariable("F").GetValueAsUnsigned(), ord(backtrace[i][0]))

lldb/trunk/packages/Python/lldbsuite/test/functionalities/postmortem/linux-core/main.c

+static void bar(char *boom)
+{
+    char F = 'b';
+    *boom = 47; // Frame bar
+}
+
+static void foo(char *boom, void (*boomer)(char *))
+{
+    char F = 'f';
+    boomer(boom); // Frame foo
+}
+
+void _start(void)
+{
+    char F = '_';
+    foo(0, bar); // Frame _start
+}

lldb/trunk/packages/Python/lldbsuite/test/functionalities/postmortem/linux-core/make-core.sh

+#! /bin/bash
+
+set -e -x
+
+if grep -q '^|' </proc/sys/kernel/core_pattern; then
+    cat <<EOF
+Your system uses a crash report tool ($(cat /proc/sys/kernel/core_pattern)). Core files
+will not be generated.  Please reset /proc/sys/kernel/core_pattern (requires root
+privileges) to enable core generation.
+EOF
+    exit 1
+fi
+
+ulimit -c 1000
+real_limit=$(ulimit -c)
+if [ $real_limit -lt 100 ]; then
+    cat <<EOF
+Unable to increase the core file limit. Core file may be truncated!
+To fix this, increase HARD core file limit (ulimit -H -c 1000). This may require root
+privileges.
+EOF
+fi
+
+${CC:-cc} -nostdlib -static -g $CFLAGS main.c -o a.out
+
+cat <<EOF
+Executable file is in a.out.
+Core file will be saved according to pattern $(cat /proc/sys/kernel/core_pattern).
+EOF
+
+ulimit -s 8 # Decrease stack size to 8k => smaller core files.
+exec ./a.out

lldb/trunk/source/Plugins/Process/elf-core/ProcessElfCore.cpp

while (offset < segment_header->p_filesz)
         else if (note.n_name == "CORE")
         {
             switch (note.n_type)
             {
                 case NT_PRSTATUS:
                     have_prstatus = true;
                     prstatus.Parse(note_data, arch);
                     thread_data->signo = prstatus.pr_cursig;
+                    thread_data->tid = prstatus.pr_pid;
                     header_size = ELFLinuxPrStatus::GetSize(arch);
                     len = note_data.GetByteSize() - header_size;
                     thread_data->gpregset = DataExtractor(note_data, header_size, len);
-                    // FIXME: Obtain actual tid on Linux
-                    thread_data->tid = m_thread_data.size();
                     break;
                 case NT_FPREGSET:
                     thread_data->fpregset = note_data;
                     break;
                 case NT_PRPSINFO:
                     have_prpsinfo = true;
                     prpsinfo.Parse(note_data, arch);
                     thread_data->name = prpsinfo.pr_fname;
+                    SetID(prpsinfo.pr_pid);
                     break;
                 case NT_AUXV:
                     m_auxv = DataExtractor(note_data);
                     break;
                 case NT_FILE:
                     {
                         m_nt_file_entries.clear();
                         lldb::offset_t offset = 0;