BuildSystem: Cleanup userspace directory layout

userspace programs are now in userspace/programs
userspace tests are now in userspace/tests

This makes listing userspace projects much cleaner. Libraries were
already separated to their own directory, so other programs should also.

userspace/programs/meminfo/CMakeLists.txt

@@ -0,0 +1,8 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(meminfo ${SOURCES})
+banan_link_library(meminfo libc)
+
+install(TARGETS meminfo OPTIONAL)

userspace/programs/meminfo/main.cpp

@@ -0,0 +1,99 @@
+#include <ctype.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/banan-os.h>
+
+bool is_only_digits(const char* str)
+{
+	while (*str)
+		if (!isdigit(*str++))
+			return false;
+	return true;
+}
+
+int main()
+{
+	DIR* proc = opendir("/proc");
+	if (proc == nullptr)
+	{
+		perror("opendir");
+		return 1;
+	}
+
+	char path_buffer[128] {};
+	while (dirent* proc_ent = readdir(proc))
+	{
+		if (proc_ent->d_type != DT_DIR)
+			continue;
+		if (!is_only_digits(proc_ent->d_name))
+			continue;
+
+		{
+			strcpy(path_buffer, proc_ent->d_name);
+			strcat(path_buffer, "/cmdline");
+
+			int fd = openat(dirfd(proc), path_buffer, O_RDONLY);
+			if (fd == -1)
+			{
+				if (errno != EACCES)
+					perror("openat");
+				continue;
+			}
+
+			printf("process: ");
+
+			while (ssize_t nread = read(fd, path_buffer, sizeof(path_buffer) - 1))
+			{
+				if (nread < 0)
+				{
+					perror("read");
+					break;
+				}
+				for (int i = 0; i < nread; i++)
+					if (path_buffer[i] == '\0')
+						path_buffer[i] = ' ';
+
+				path_buffer[nread] = '\0';
+
+				int written = 0;
+				while (written < nread)
+					written += printf("%s ", path_buffer + written);
+			}
+
+			printf("\n");
+
+			close(fd);
+		}
+
+		printf("  pid:  %s\n", proc_ent->d_name);
+
+		{
+			strcpy(path_buffer, proc_ent->d_name);
+			strcat(path_buffer, "/meminfo");
+
+			int fd = openat(dirfd(proc), path_buffer, O_RDONLY);
+			if (fd == -1)
+			{
+				perror("openat");
+				continue;
+			}
+
+			proc_meminfo_t meminfo;
+			if (read(fd, &meminfo, sizeof(meminfo)) == -1)
+				perror("read");
+			else
+			{
+				size_t percent_times_100 = 10000 * meminfo.phys_pages / meminfo.virt_pages;
+				printf("  vmem: %zu pages (%zu bytes)\n", meminfo.virt_pages, meminfo.page_size * meminfo.virt_pages);
+				printf("  pmem: %zu pages (%zu bytes) %zu.%02zu%%\n", meminfo.phys_pages, meminfo.page_size * meminfo.phys_pages, percent_times_100 / 100, percent_times_100 % 100);
+			}
+
+			close(fd);
+		}
+	}
+
+	closedir(proc);
+}