Meta: Implement checker for IPC magic number collisions

Author: https://github.com/BenWiederhake
Commit: https://github.com/SerenityOS/serenity/commit/585554a245f
Pull-request: https://github.com/SerenityOS/serenity/pull/10748
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/trflynn89

Meta/Lagom/Tools/CMakeLists.txt

@@ -11,5 +11,6 @@ function(lagom_tool tool)
     )
 endfunction()
 
-add_subdirectory(ConfigureComponents)
 add_subdirectory(CodeGenerators)
+add_subdirectory(ConfigureComponents)
+add_subdirectory(IPCMagicLinter)

Meta/Lagom/Tools/IPCMagicLinter/CMakeLists.txt

@@ -0,0 +1,5 @@
+set(SOURCES
+    main.cpp
+)
+
+lagom_tool(IPCMagicLinter)

Meta/Lagom/Tools/IPCMagicLinter/main.cpp

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/HashMap.h>
+#include <AK/StringView.h>
+#include <AK/Vector.h>
+#include <LibCore/File.h>
+
+// Exit code is bitwise-or of these values:
+static constexpr auto EXIT_COLLISION = 0x1;
+static constexpr auto EXIT_ERROR = 0x2;
+
+int main(int argc, char** argv)
+{
+    if (argc < 3) {
+        warnln("Usage: {} path/to/some.ipc path/to/other.ipc [more ipc files ...]", argv[0]);
+        return EXIT_ERROR;
+    }
+
+    // Read files, compute their hashes, ignore collisions for now.
+    HashMap<u32, Vector<String>> inverse_hashes;
+    bool had_errors = false;
+    for (int file_index = 1; file_index < argc; ++file_index) {
+        String filename(argv[file_index]);
+        auto file_or_error = Core::File::open(filename, Core::OpenMode::ReadOnly);
+        if (file_or_error.is_error()) {
+            warnln("Error: Cannot open '{}': {}", filename, file_or_error.error());
+            had_errors = true;
+            continue; // next file
+        }
+        auto file = file_or_error.value();
+        String endpoint_name;
+        while (true) {
+            String line = file->read_line();
+            if (file->error() != 0 || line.is_null())
+                break;
+            if (!line.starts_with("endpoint "sv))
+                continue;
+            auto line_endpoint_name = line.substring("endpoint "sv.length());
+            if (!endpoint_name.is_null()) {
+                // Note: If there are three or more endpoints defined in a file, these errors will look a bit wonky.
+                // However, that's fine, because it shouldn't happen in the first place.
+                warnln("Error: Multiple endpoints in file '{}': Found {} and {}", filename, file->error());
+                had_errors = true;
+                continue; // next line
+            }
+            endpoint_name = line_endpoint_name;
+        }
+        if (file->error() != 0) {
+            warnln("Error: Failed to read '{}': {}", filename, file->error());
+            had_errors = true;
+            continue; // next file
+        }
+        if (endpoint_name.is_null()) {
+            // If this happens, this file probably needs to parse the endpoint name more carefully.
+            warnln("Error: Could not detect endpoint name in file '{}'", filename);
+            had_errors = true;
+            continue; // next file
+        }
+        u32 hash = endpoint_name.hash();
+        auto& files_with_hash = inverse_hashes.ensure(hash);
+        files_with_hash.append(filename);
+    }
+
+    // Report any collisions
+    bool had_collisions = false;
+    for (auto const& specific_collisions : inverse_hashes) {
+        if (specific_collisions.value.size() <= 1)
+            continue;
+        outln("Collision: Multiple endpoints use the magic number {}:", specific_collisions.key);
+        for (auto const& colliding_file : specific_collisions.value) {
+            outln("- {}", colliding_file);
+        }
+        had_collisions = true;
+    }
+
+    outln("Checked {} files, saw {} distinct magic numbers.", argc - 1, inverse_hashes.size());
+    if (had_collisions)
+        outln("Consider giving your new service a different name.");
+
+    if (had_errors)
+        warnln("Some errors were encountered. There may be endpoints with colliding magic numbers.");
+
+    int exit_code = 0;
+    if (had_collisions)
+        exit_code |= EXIT_COLLISION;
+    if (had_errors)
+        exit_code |= EXIT_ERROR;
+    return exit_code;
+}