Fix checking for page alignment

Author: simolus3

pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_android_test.dart

@@ -45,7 +45,8 @@ void main() {
           );
           await expectMachineArchitecture(libUri, target, OS.android);
           if (linkMode == DynamicLoadingBundled()) {
-            await expectPageSize(libUri, 16 * 1024);
+            final alignments = await loadAlignments(libUri);
+            expect(alignments, everyElement(16 * 1024));
           }
         });
       }
@@ -92,9 +93,12 @@ void main() {
       flags: ['-Wl,-z,max-page-size=$pageSize'],
     );
     if (Platform.isMacOS || Platform.isLinux) {
-      final address = await textSectionAddress(libUri);
-      expect(address, greaterThanOrEqualTo(pageSize));
-      expect(address, isNot(greaterThanOrEqualTo(pageSize * 4)));
+      final alignments = await loadAlignments(libUri);
+      expect(alignments, everyElement(greaterThanOrEqualTo(pageSize)));
+      expect(
+        alignments,
+        everyElement(isNot(greaterThanOrEqualTo(pageSize * 4))),
+      );
     }
   });
 }

pkgs/native_toolchain_c/test/helpers.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:ffi';
 import 'dart:io';
 
@@ -248,48 +249,26 @@ Future<RunProcessResult?> _runDumpbin(
   );
 }
 
-Future<int> textSectionAddress(Uri dylib) async {
-  if (Platform.isMacOS) {
-    // Find the line in the objdump output that looks like:
-    //  11 .text               00000046 00000000000045a0 TEXT
-    final result = await runProcess(
-      executable: Uri.file('objdump'),
-      arguments: ['--headers', dylib.toFilePath()],
-      logger: logger,
-    );
-    expect(result.exitCode, 0);
-    final textSection = result.stdout
-        .split('\n')
-        .firstWhere((e) => e.contains('.text'));
-    final parsed = textSection.split(' ').where((e) => e.isNotEmpty).toList();
-    expect(parsed[1], '.text');
-    expect(parsed[4], 'TEXT');
-    final vma = int.parse(parsed[3], radix: 16);
-    return vma;
-  }
-  if (Platform.isLinux) {
-    // Find the line in the readelf output that looks like:
-    // [11] .text             PROGBITS   00004328 000328 000064 00  AX  0   0  4
-    final result = await readelf(dylib.toFilePath(), 'S');
-    final textSection = result
-        .split('\n')
-        .firstWhere((e) => e.contains('.text'));
-    final parsed = textSection.split(' ').where((e) => e.isNotEmpty).toList();
-    expect(parsed[1], '.text');
-    expect(parsed[2], 'PROGBITS');
-    final addr = int.parse(parsed[3], radix: 16);
-    return addr;
-  }
-  throw UnimplementedError();
-}
+Future<List<int>> loadAlignments(Uri dylib) async {
+  // https://cs.android.com/android/platform/superproject/main/+/main:system/extras/tools/check_elf_alignment.sh;l=99
+  final result = await runProcess(
+    executable: Uri.file('objdump'),
+    arguments: ['-p', dylib.toFilePath()],
+    logger: logger,
+  );
+  expect(result.exitCode, 0);
 
-Future<void> expectPageSize(Uri dylib, int pageSize) async {
-  if (Platform.isMacOS || Platform.isLinux) {
-    // If page size is 16kb, the `.text` section address should be
-    // above 0x4000. With smaller page sizes it's above 0x1000.
-    final vma = await textSectionAddress(dylib);
-    expect(vma, greaterThanOrEqualTo(pageSize));
-  }
+  // Parse alignment from lines that look like this:
+  // LOAD off    <...> vaddr <...> paddr <...> align 2**12
+  final alignmentRegex = RegExp(r'align 2\*\*(\d+)');
+  return const LineSplitter()
+      .convert(result.stdout)
+      .where((e) => e.contains('LOAD'))
+      .map((line) {
+        final exponent = int.parse(alignmentRegex.firstMatch(line)!.group(1)!);
+        return 1 << exponent;
+      })
+      .toList();
 }
 
 int defaultMacOSVersion = 13;