Userspace: Implement barebones sudo

This doesn't do any password checking or anything. Just sets uid and
gid before execvp()

userspace/CMakeLists.txt

@@ -22,6 +22,7 @@ set(USERSPACE_PROJECTS
 	sleep
 	snake
 	stat
+	sudo
 	sync
 	tee
 	test

userspace/sudo/CMakeLists.txt

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(sudo CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(sudo ${SOURCES})
+target_compile_options(sudo PUBLIC -O2 -g)
+target_link_libraries(sudo PUBLIC libc)
+
+add_custom_target(sudo-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/sudo ${BANAN_BIN}/
+	COMMAND /bin/chmod u+s ${BANAN_BIN}/sudo
+	DEPENDS sudo
+)

userspace/sudo/main.cpp

@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int usage(char* argv0, int ret)
+{
+	FILE* fp = (ret == 0) ? stdout : stderr;
+	fprintf(fp, "usage: %s COMMAND [ARGUMENTS]\n", argv0);
+	return ret;
+}
+
+int main(int argc, char** argv)
+{
+	if (argc < 2)
+		return usage(argv[0], 1);
+	
+	if (setuid(0) == -1)
+	{
+		perror("setuid");
+		return 1;
+	}
+	if (setgid(0) == -1)
+	{
+		perror("setgid");
+		return 1;
+	}
+
+	execvp(argv[1], argv + 1);
+
+	perror("execv");
+	return 1;
+}