Userspace: Add meminfo command that parses /proc/{pid}/meminfo

userspace/CMakeLists.txt

@@ -10,6 +10,7 @@ set(USERSPACE_PROJECTS
 	id
 	init
 	ls
+	meminfo
 	mmap-shared-test
 	poweroff
 	Shell

userspace/meminfo/CMakeLists.txt

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(meminfo CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(meminfo ${SOURCES})
+target_compile_options(meminfo PUBLIC -O2 -g)
+target_link_libraries(meminfo PUBLIC libc)
+
+add_custom_target(meminfo-install
+	COMMAND sudo cp ${CMAKE_CURRENT_BINARY_DIR}/meminfo ${BANAN_BIN}/
+	DEPENDS meminfo
+	USES_TERMINAL
+)

userspace/meminfo/main.cpp

@@ -0,0 +1,57 @@
+#include <ctype.h>
+#include <dirent.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, "/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
+		{
+			printf("process:\n");
+			printf("  pid:  %s\n", proc_ent->d_name);
+			printf("  vmem: %zu pages (%zu bytes)\n", meminfo.virt_pages, meminfo.page_size * meminfo.virt_pages);
+		}
+
+		close(fd);
+	}
+
+	closedir(proc);
+}