tests: Test debuginfo through debuglink and build-id sections

This commit introduces support for tests of the new debuglink and
build-id debuginfo resolution functionality. The tests build a
dummy.c file with a debuglink section, and again with a build-id
section, and make sure that the symbol resolution code can locate
the debug information correctly (in the binary's directory for
debuglink, and in /usr/lib/debug/.build-id for the build-id).

tests/python/CMakeLists.txt

@@ -36,6 +36,8 @@ add_test(NAME py_test_trace4 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_trace4 sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_trace4.py)
 add_test(NAME py_test_probe_count WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_probe_count sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_probe_count.py)
+add_test(NAME py_test_debuginfo WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+  COMMAND ${TEST_WRAPPER} py_test_debuginfo sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_debuginfo.py)
 add_test(NAME py_test_brb WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_brb_c sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_brb.py test_brb.c)
 add_test(NAME py_test_brb2 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
@@ -60,6 +62,5 @@ add_test(NAME py_test_utils WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_test_utils sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_utils.py)
 add_test(NAME py_test_percpu WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_test_percpu sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_percpu.py)
-
 add_test(NAME py_test_dump_func WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_dump_func simple ${CMAKE_CURRENT_SOURCE_DIR}/test_dump_func.py)

tests/python/dummy.c

+#include <unistd.h>
+#include <stdio.h>
+
+static __attribute__((noinline)) int some_function(int x, int y) {
+	volatile int z = x + y;
+	return z;
+}
+
+int main() {
+	printf("%p\n", &some_function);
+	fflush(stdout);
+	printf("result = %d\n", some_function(42, 11));
+	sleep(1000);
+	return 0;
+}

tests/python/test_debuginfo.py

+#!/usr/bin/env python
+# Copyright (c) Sasha Goldshtein
+# Licensed under the Apache License, Version 2.0 (the "License")
+
+import os
+import subprocess
+from bcc import SymbolCache
+from unittest import main, TestCase
+
+class Harness(TestCase):
+    def setUp(self):
+        self.build_command()
+        subprocess.check_output('objcopy --only-keep-debug dummy dummy.debug'
+                                .split())
+        self.debug_command()
+        subprocess.check_output('strip dummy'.split())
+        self.process = subprocess.Popen('./dummy', stdout=subprocess.PIPE)
+        # The process prints out the address of some symbol, which we then
+        # try to resolve in the test.
+        self.addr = int(self.process.stdout.readline().strip(), 16)
+        self.syms = SymbolCache(self.process.pid)
+
+    def tearDown(self):
+        self.process.kill()
+
+    def resolve_addr(self):
+        sym, offset, module = self.syms.resolve(self.addr)
+        self.assertEqual(sym, 'some_function')
+        self.assertEqual(offset, 0)
+        self.assertTrue(module[-5:] == 'dummy')
+
+    def resolve_name(self):
+        script_dir = os.path.dirname(os.path.realpath(__file__))
+        addr = self.syms.resolve_name(os.path.join(script_dir, 'dummy'),
+                                      'some_function')
+        self.assertEqual(addr, self.addr)
+        pass
+
+class TestDebuglink(Harness):
+    def build_command(self):
+        subprocess.check_output('gcc -o dummy dummy.c'.split())
+
+    def debug_command(self):
+        subprocess.check_output('objcopy --add-gnu-debuglink=dummy.debug dummy'
+                                .split())
+
+    def tearDown(self):
+        subprocess.check_output('rm dummy dummy.debug'.split())
+
+    def test_resolve_addr(self):
+        self.resolve_addr()
+
+    def test_resolve_name(self):
+        self.resolve_name()
+
+class TestBuildid(Harness):
+    def build_command(self):
+        subprocess.check_output(('gcc -o dummy -Xlinker ' + \
+               '--build-id=0x123456789abcdef0123456789abcdef012345678 dummy.c')
+               .split())
+
+    def debug_command(self):
+        subprocess.check_output('mkdir -p /usr/lib/debug/.build-id/12'.split())
+        subprocess.check_output(('mv dummy.debug /usr/lib/debug/.build-id' + \
+            '/12/3456789abcdef0123456789abcdef012345678.debug').split())
+
+    def tearDown(self):
+        subprocess.check_output('rm dummy'.split())
+        subprocess.check_output(('rm /usr/lib/debug/.build-id/12' +
+            '/3456789abcdef0123456789abcdef012345678.debug').split())
+
+    def test_resolve_name(self):
+        self.resolve_addr()
+
+    def test_resolve_addr(self):
+        self.resolve_name()
+
+if __name__ == "__main__":
+    main()