add load exec

Co-authored-by: thenotsoquietninja44-collab <thenotsoquietninja44@gmail.com>

src/loader/loadExec.cpp

@@ -0,0 +1,63 @@
+#include "emulator.h"
+
+#include "common/file.h"
+#include "common/logging/log.h"
+#include "kernel/fileSystem.h"
+#include "libs/errno.h"
+
+#include <cerrno>
+#include <cstring>
+#include <fstream>
+#include <string_view>
+#include <vector>
+
+#if KYTY_PLATFORM == KYTY_PLATFORM_LINUX
+#include <linux/close_range.h>
+#include <unistd.h>
+#endif
+
+namespace Emulator {
+
+int LoadExec(const char* path, const char* const argv[]) {
+	using namespace Libs::SystemService;
+	if (path == nullptr || !std::string_view(path).starts_with("/app0/") ||
+	    !Common::File::IsFileExisting(Libs::LibKernel::FileSystem::GetRealFilename(path))) {
+		return SYSTEM_SERVICE_ERROR_PARAMETER;
+	}
+#if KYTY_PLATFORM == KYTY_PLATFORM_LINUX
+	std::ifstream command("/proc/self/cmdline", std::ios::binary);
+	std::vector<std::string> arguments;
+	for (std::string argument; std::getline(command, argument, '\0') && argument != "--guest-exec";) {
+		arguments.push_back(std::move(argument));
+	}
+	if (arguments.empty()) {
+		return SYSTEM_SERVICE_ERROR_INTERNAL;
+	}
+	arguments.insert(arguments.end(), {"--guest-exec", path});
+	size_t bytes = 0;
+	for (size_t i = 0; argv != nullptr && argv[i] != nullptr; ++i) {
+		const auto size = strnlen(argv[i], 4096 - bytes) + 1;
+		if (size > 4096 - bytes) {
+			return SYSTEM_SERVICE_ERROR_PARAMETER;
+		}
+		bytes += size;
+		arguments.emplace_back(argv[i]);
+	}
+	std::vector<char*> host_argv;
+	for (auto& argument: arguments) {
+		host_argv.push_back(argument.data());
+	}
+	host_argv.push_back(nullptr);
+	LOGF("LoadExec: %s\n", path);
+	Log::Flush();
+	if (close_range(3, ~0u, CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC) == 0) {
+		execvp(host_argv[0], host_argv.data());
+	}
+	LOGF("LoadExec failed: %s\n", std::strerror(errno));
+	return SYSTEM_SERVICE_ERROR_INTERNAL;
+#else
+	return SYSTEM_SERVICE_ERROR_UNAVAILABLE;
+#endif
+}
+
+} // namespace Emulator