Separate static allocator from payload function interpositions

1 files changed, 173 insertions, 0 deletions

diff --git a/src/main.cc b/src/main.cc
new file mode 100644
index 0000000..8b6ca23
--- /dev/null
+++ b/src/main.cc
@@ -0,0 +1,173 @@
+#include "actual.h"
+
+#include "utility/io.h"
+#include "utility/logger.h"
+
+#include "tracking/path_matcher.h"
+#include "tracking/change_tracker.h"
+
+// `true`  signals the interposed functions to execute tracking logic
+// `false` signals the interposed functions to do plain forwarding
+static bool enabled = false;
+
+static std::unique_ptr<utility::FileDescriptorGuard> fd_guard;
+static std::unique_ptr<utility::Logger>              logger;
+static std::unique_ptr<tracking::PathMatcher>        matcher;
+static std::unique_ptr<tracking::ChangeTracker>      tracker;
+
+void initialize() __attribute__ ((constructor));
+void initialize() {
+	if ( getenv("CHANGE_LOG_TARGET") != NULL ) {
+		fd_guard = std::make_unique<utility::FileDescriptorGuard>(
+			getenv("CHANGE_LOG_TARGET")
+		);
+		logger   = std::make_unique<utility::Logger>(*fd_guard);
+	} else {
+		logger   = std::make_unique<utility::Logger>(STDERR_FILENO);
+	}
+
+	if ( getenv("CHANGE_LOG_DIFF_CMD") != NULL ) {
+		tracker = std::make_unique<tracking::ChangeTracker>(
+			logger.get(), getenv("CHANGE_LOG_DIFF_CMD")
+		);
+	} else {
+		tracker = std::make_unique<tracking::ChangeTracker>(logger.get());
+	}
+
+	if ( getenv("CHANGE_LOG_IGNORE_PATTERN_PATH") != NULL ) {
+		matcher = std::make_unique<tracking::PathMatcher>(
+			getenv("CHANGE_LOG_IGNORE_PATTERN_PATH")
+		);
+	} else {
+		matcher = std::make_unique<tracking::PathMatcher>();
+	}
+
+	// tracking is only enabled when everything is initialized as both
+	// the actual tracking and the decision if a event should be tracked
+	// depend on `logger` and `tracker` being fully instantiated.
+	// In most cases this library will work correctly without delayed
+	// activation but e.g. `nvim` crashes as it performs tracked syscalls
+	// before `init` has been called.
+	enabled = true;
+}
+
+inline void track_write(const int fd) {
+	if ( enabled && fd != *fd_guard && utility::is_regular_file(fd) ) {
+		const auto path = utility::get_file_path(fd);
+
+		if ( !matcher->isMatching(path) ) {
+			tracker->track(path);
+		}
+	}
+}
+
+inline void track_rename(
+	const std::string& old_path, const std::string& new_path) {
+	if ( enabled ) {
+		if ( !matcher->isMatching(old_path) ) {
+			tracker->track(old_path);
+
+			if ( !matcher->isMatching(new_path) ) {
+				logger->append("renamed '", old_path, "' to '", new_path, "'");
+			}
+		}
+	}
+}
+
+inline void track_remove(const std::string& path) {
+	if ( enabled && utility::is_regular_file(path.c_str()) ) {
+		if ( !matcher->isMatching(path) ) {
+			logger->append("removed '", path, "'");
+		}
+	}
+}
+
+ssize_t write(int fd, const void* buffer, size_t count) {
+	static actual::ptr<ssize_t, int, const void*, size_t> actual_write{};
+
+	if ( !actual_write ) {
+		actual_write = actual::get_ptr<decltype(actual_write)>("write");
+	}
+
+	track_write(fd);
+
+	return actual_write(fd, buffer, count);
+}
+
+ssize_t writev(int fd, const iovec* iov, int iovcnt) {
+	static actual::ptr<ssize_t, int, const iovec*, int> actual_writev{};
+
+	if ( !actual_writev ) {
+		actual_writev = actual::get_ptr<decltype(actual_writev)>("writev");
+	}
+
+	track_write(fd);
+
+	return actual_writev(fd, iov, iovcnt);
+}
+
+void* mmap(void* addr, size_t length, int prot, int flags, int fd, off_t offset) {
+	static actual::ptr<void*, void*, size_t, int, int, int, off_t> actual_mmap{};
+
+	if ( !actual_mmap ) {
+		actual_mmap = actual::get_ptr<decltype(actual_mmap)>("mmap");
+	}
+
+	if ( prot & PROT_WRITE ) {
+		track_write(fd);
+	}
+
+	return actual_mmap(addr, length, prot, flags, fd, offset);
+}
+
+int rename(const char* old_path, const char* new_path) {
+	static actual::ptr<int, const char*, const char*> actual_rename{};
+
+	if ( !actual_rename ) {
+		actual_rename = actual::get_ptr<decltype(actual_rename)>("rename");
+	}
+
+	track_rename(old_path, new_path);
+
+	return actual_rename(old_path, new_path);
+}
+
+int rmdir(const char* path) {
+	static actual::ptr<int, const char*> actual_rmdir{};
+
+	if ( !actual_rmdir ) {
+		actual_rmdir = actual::get_ptr<decltype(actual_rmdir)>("rmdir");
+	}
+
+	track_remove(path);
+
+	return actual_rmdir(path);
+}
+
+int unlink(const char* path) {
+	static actual::ptr<int, const char*> actual_unlink{};
+
+	if ( !actual_unlink ) {
+		actual_unlink = actual::get_ptr<decltype(actual_unlink)>("unlink");
+	}
+
+	track_remove(path);
+
+	return actual_unlink(path);
+}
+
+int unlinkat(int dirfd, const char* path, int flags) {
+	static actual::ptr<int, int, const char*, int> actual_unlinkat{};
+
+	if ( !actual_unlinkat ) {
+		actual_unlinkat = actual::get_ptr<decltype(actual_unlinkat)>("unlinkat");
+	}
+
+	if ( dirfd == AT_FDCWD ) {
+		track_remove(path);
+	} else {
+		track_remove(utility::get_file_path(dirfd) + path);
+	}
+
+	return actual_unlinkat(dirfd, path, flags);
+}