Merge branch 'junghee/entry-point0' into 'main'

Avoid generating `_start` symbol for entry-point 0 in shared libraries

Closes debloating/dykondo#42

See merge request rewriting/ddisasm!1207

CHANGELOG.md

@@ -28,6 +28,7 @@
 * Add alignment for x86-64 instructions that require explicitly aligned memory
   (e.g., some SIMD instructions)
 * Update capstone version from 4.0.1 to 5.0.1
+* Avoid generating `_start` symbol when the entry-point address is not a code block.
 
 # 1.8.0
 

src/datalog/binary/elf/symbolization.dl

@@ -136,7 +136,8 @@ start_function(EA):-
 start_function(Start_location):-
     binary_format("ELF"),
     !function_symbol(Start_location,"_start"),
-    entry_point(Start_location).
+    entry_point(Start_location),
+    code(Start_location).
 
 main_function(EA):-
     binary_format("ELF"),

tests/misc_test.py

@@ -995,5 +995,26 @@ def test_repeated_import(self):
             # so we don't check that here.
 
 
+class ZeroEntryPointTests(unittest.TestCase):
+    @unittest.skipUnless(
+        platform.system() == "Linux", "This test is linux only."
+    )
+    def test_zero_entry_point(self):
+        """
+        Test a shared library that has value 0 as its entry point.
+        We should not create an inferred symbol for `_start` for
+        entry-point 0 for shared libraries.
+        """
+
+        library = Path("ex.so")
+        with cd(ex_asm_dir / "ex_ifunc"):
+            self.assertTrue(compile("gcc", "g++", "-O0 --entry 0", []))
+            ir_library = disassemble(library).ir()
+            m = ir_library.modules[0]
+
+            # `_start` should not exist in the module.
+            self.assertEqual(len(list(m.symbols_named("_start"))), 0)
+
+
 if __name__ == "__main__":
     unittest.main()