LibCoreDump+CrashDaemon: Compress coredumps

Most coredumps contain large amounts of consecutive null bytes and as
such are a prime candidate for compression.

This commit makes CrashDaemon compress files once the kernel finishes
emitting them, as well as adds the functionality needed in LibCoreDump
to then parse them.

Kernel/CoreDump.cpp

@@ -72,7 +72,7 @@ RefPtr<FileDescription> CoreDump::create_target_file(const Process& process, con
         return nullptr;
     }
     auto dump_directory_metadata = dump_directory.value()->inode().metadata();
-    if (dump_directory_metadata.uid != 0 || dump_directory_metadata.gid != 0 || dump_directory_metadata.mode != 040755) {
+    if (dump_directory_metadata.uid != 0 || dump_directory_metadata.gid != 0 || dump_directory_metadata.mode != 040777) {
         dbgln("Refusing to put core dump in sketchy directory '{}'", output_directory);
         return nullptr;
     }
@@ -329,7 +329,7 @@ KResult CoreDump::write()
     if (result.is_error())
         return result;
 
-    return m_fd->chmod(0400); // Make coredump file readable
+    return m_fd->chmod(0600); // Make coredump file read/writable
 }
 
 }

Userland/Applications/CrashReporter/main.cpp

@@ -30,6 +30,7 @@
 #include <AK/URL.h>
 #include <Applications/CrashReporter/CrashReporterWindowGML.h>
 #include <LibCore/ArgsParser.h>
+#include <LibCore/File.h>
 #include <LibCoreDump/Backtrace.h>
 #include <LibCoreDump/Reader.h>
 #include <LibDesktop/AppFile.h>
@@ -118,10 +119,12 @@ int main(int argc, char** argv)
     }
 
     const char* coredump_path = nullptr;
+    bool unlink_after_use = false;
 
     Core::ArgsParser args_parser;
     args_parser.set_general_help("Show information from an application crash coredump.");
     args_parser.add_positional_argument(coredump_path, "Coredump path", "coredump-path");
+    args_parser.add_option(unlink_after_use, "Delete the coredump after its parsed", "unlink", 0);
     args_parser.parse(argc, argv);
 
     Vector<TitleAndText> thread_backtraces;
@@ -155,6 +158,11 @@ int main(int argc, char** argv)
         termination_signal = coredump->process_termination_signal();
     }
 
+    if (unlink_after_use) {
+        if (Core::File::remove(coredump_path, Core::File::RecursionMode::Disallowed, false).is_error())
+            dbgln("Failed deleting coredump file");
+    }
+
     auto app = GUI::Application::construct(argc, argv);
 
     if (pledge("stdio recvfd sendfd accept rpath unix", nullptr) < 0) {

Userland/Libraries/LibCoreDump/CMakeLists.txt

@@ -4,4 +4,4 @@ set(SOURCES
 )
 
 serenity_lib(LibCoreDump coredump)
-target_link_libraries(LibCoreDump LibC LibCore LibDebug)
+target_link_libraries(LibCoreDump LibC LibCompress LibCore LibDebug)

Userland/Libraries/LibCoreDump/Reader.cpp

@@ -26,6 +26,7 @@
 
 #include <AK/JsonObject.h>
 #include <AK/JsonValue.h>
+#include <LibCompress/Gzip.h>
 #include <LibCoreDump/Reader.h>
 #include <signal_numbers.h>
 #include <string.h>
@@ -37,12 +38,12 @@ OwnPtr<Reader> Reader::create(const String& path)
     auto file_or_error = MappedFile::map(path);
     if (file_or_error.is_error())
         return {};
-    return adopt_own(*new Reader(file_or_error.release_value()));
+    return adopt_own(*new Reader(file_or_error.value()->bytes()));
 }
 
-Reader::Reader(NonnullRefPtr<MappedFile> coredump_file)
-    : m_coredump_file(move(coredump_file))
-    , m_coredump_image(m_coredump_file->bytes())
+Reader::Reader(ReadonlyBytes coredump_bytes)
+    : m_coredump_buffer(decompress_coredump(coredump_bytes))
+    , m_coredump_image(m_coredump_buffer.bytes())
 {
     size_t index = 0;
     m_coredump_image.for_each_program_header([this, &index](auto pheader) {
@@ -56,6 +57,16 @@ Reader::Reader(NonnullRefPtr<MappedFile> coredump_file)
     VERIFY(m_notes_segment_index != -1);
 }
 
+ByteBuffer Reader::decompress_coredump(const ReadonlyBytes& raw_coredump)
+{
+    if (!Compress::GzipDecompressor::is_likely_compressed(raw_coredump))
+        return ByteBuffer::copy(raw_coredump); // handle old format core dumps (uncompressed)
+    auto decompressed_coredump = Compress::GzipDecompressor::decompress_all(raw_coredump);
+    if (!decompressed_coredump.has_value())
+        return ByteBuffer::copy(raw_coredump); // if we didnt manage to decompress it, try and parse it as decompressed core dump
+    return decompressed_coredump.value();
+}
+
 Reader::~Reader()
 {
 }

Userland/Libraries/LibCoreDump/Reader.h

@@ -70,7 +70,9 @@ public:
     HashMap<String, String> metadata() const;
 
 private:
-    Reader(NonnullRefPtr<MappedFile>);
+    Reader(ReadonlyBytes);
+
+    static ByteBuffer decompress_coredump(const ReadonlyBytes&);
 
     class NotesEntryIterator {
     public:
@@ -92,7 +94,7 @@ private:
     // as getters with the appropriate (non-JsonValue) types.
     const JsonObject process_info() const;
 
-    NonnullRefPtr<MappedFile> m_coredump_file;
+    ByteBuffer m_coredump_buffer;
     ELF::Image m_coredump_image;
     ssize_t m_notes_segment_index { -1 };
 };

Userland/Services/CrashDaemon/CMakeLists.txt

@@ -3,4 +3,4 @@ set(SOURCES
 )
 
 serenity_bin(CrashDaemon)
-target_link_libraries(CrashDaemon LibC LibCore LibCoreDump)
+target_link_libraries(CrashDaemon LibC LibCompress LibCore LibCoreDump)

Userland/Services/CrashDaemon/main.cpp

@@ -25,6 +25,9 @@
  */
 
 #include <AK/LexicalPath.h>
+#include <AK/MappedFile.h>
+#include <LibCompress/Gzip.h>
+#include <LibCore/File.h>
 #include <LibCore/FileWatcher.h>
 #include <LibCoreDump/Backtrace.h>
 #include <LibCoreDump/Reader.h>
@@ -49,6 +52,33 @@ static void wait_until_coredump_is_ready(const String& coredump_path)
     }
 }
 
+static bool compress_coredump(const String& coredump_path)
+{
+    auto file_or_error = MappedFile::map(coredump_path);
+    if (file_or_error.is_error()) {
+        dbgln("Could not open coredump '{}': {}", coredump_path, file_or_error.error());
+        return false;
+    }
+    auto coredump_file = file_or_error.value();
+    auto compressed_coredump = Compress::GzipCompressor::compress_all(coredump_file->bytes());
+    if (!compressed_coredump.has_value()) {
+        dbgln("Could not compress coredump '{}'", coredump_path);
+        return false;
+    }
+    auto output_path = String::formatted("{}.gz", coredump_path);
+    auto output_file_or_error = Core::File::open(output_path, Core::File::WriteOnly);
+    if (output_file_or_error.is_error()) {
+        dbgln("Could not open '{}' for writing: {}", output_path, output_file_or_error.error());
+        return false;
+    }
+    auto output_file = output_file_or_error.value();
+    if (!output_file->write(compressed_coredump.value().data(), compressed_coredump.value().size())) {
+        dbgln("Could not write compressed coredump '{}'", output_path);
+        return false;
+    }
+    return true;
+}
+
 static void print_backtrace(const String& coredump_path)
 {
     auto coredump = CoreDump::Reader::create(coredump_path);
@@ -70,10 +100,10 @@ static void print_backtrace(const String& coredump_path)
     });
 }
 
-static void launch_crash_reporter(const String& coredump_path)
+static void launch_crash_reporter(const String& coredump_path, bool unlink_after_use)
 {
     pid_t child;
-    const char* argv[] = { "CrashReporter", coredump_path.characters(), nullptr, nullptr };
+    const char* argv[] = { "CrashReporter", coredump_path.characters(), unlink_after_use ? "--unlink" : nullptr, nullptr, nullptr };
     if ((errno = posix_spawn(&child, "/bin/CrashReporter", nullptr, nullptr, const_cast<char**>(argv), environ))) {
         perror("posix_spawn");
     } else {
@@ -84,7 +114,7 @@ static void launch_crash_reporter(const String& coredump_path)
 
 int main()
 {
-    if (pledge("stdio rpath proc exec", nullptr) < 0) {
+    if (pledge("stdio rpath wpath cpath proc exec", nullptr) < 0) {
         perror("pledge");
         return 1;
     }
@@ -96,9 +126,12 @@ int main()
         if (event.value().type != Core::FileWatcherEvent::Type::ChildAdded)
             continue;
         auto coredump_path = event.value().child_path;
+        if (coredump_path.ends_with(".gz"))
+            continue; // stops compress_coredump from accidentally triggering us
         dbgln("New coredump file: {}", coredump_path);
         wait_until_coredump_is_ready(coredump_path);
+        auto compressed = compress_coredump(coredump_path);
         print_backtrace(coredump_path);
-        launch_crash_reporter(coredump_path);
+        launch_crash_reporter(coredump_path, compressed);
     }
 }

Userland/Services/SystemServer/main.cpp

@@ -185,7 +185,8 @@ static void create_tmp_coredump_directory()
 {
     dbgln("Creating /tmp/coredump directory");
     auto old_umask = umask(0);
-    auto rc = mkdir("/tmp/coredump", 0755);
+    // FIXME: the coredump directory should be made read-only once CrashDaemon is no longer responsible for compressing coredumps
+    auto rc = mkdir("/tmp/coredump", 0777);
     if (rc < 0) {
         perror("mkdir(/tmp/coredump)");
         VERIFY_NOT_REACHED();