kernel: Add a getdents() syscall

kernel/CMakeLists.txt

@@ -33,6 +33,7 @@ set(SOURCES
     src/sys/mkdir.cpp
     src/sys/mknod.cpp
     src/sys/waitpid.cpp
+    src/sys/getdents.cpp
     src/fs/VFS.cpp
     src/fs/tmpfs/FileSystem.cpp
     src/fs/devices/DeviceRegistry.cpp

kernel/src/sys/getdents.cpp

@@ -0,0 +1,40 @@
+#include "fs/VFS.h"
+#include "memory/MemoryManager.h"
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+#include <bits/getdents.h>
+
+Result<u64> sys_getdents(Registers*, SyscallArgs args)
+{
+    int fd = (int)args[0];
+    luna_dirent* ent = (luna_dirent*)args[1];
+    usize count = (usize)args[2];
+
+    Thread* current = Scheduler::current();
+
+    auto& descriptor = *TRY(current->resolve_fd(fd));
+
+    if (descriptor.inode->type() != VFS::InodeType::Directory) return err(ENOTDIR);
+
+    usize nwrite = 0;
+    while (nwrite < count)
+    {
+        auto maybe_entry = descriptor.inode->get(descriptor.offset);
+        if (!maybe_entry.has_value()) break;
+
+        descriptor.offset++;
+
+        auto entry = maybe_entry.release_value();
+
+        luna_dirent kent;
+        kent.inode = entry.inode->inode_number();
+        strlcpy(kent.name, entry.name.chars(), entry.name.length() + 1);
+
+        if (!MemoryManager::copy_to_user_typed(ent, &kent)) return err(EFAULT);
+
+        ent++;
+        nwrite++;
+    }
+
+    return nwrite;
+}

libc/include/bits/getdents.h

@@ -0,0 +1,14 @@
+/* bits/getdents.h: Definitions used for the getdents() system call. */
+
+#ifndef _BITS_GETDENTS_H
+#define _BITS_GETDENTS_H
+
+#include <sys/types.h>
+
+typedef struct
+{
+    ino_t inode;
+    char name[129];
+} luna_dirent;
+
+#endif

libc/include/sys/types.h

@@ -15,6 +15,7 @@ typedef __u16_t mode_t;
 typedef __u64_t useconds_t;
 typedef __i64_t off_t;
 typedef __u64_t dev_t;
+typedef __u64_t ino_t;
 
 typedef off_t fpos_t;
 

libluna/include/luna/Syscall.h

@@ -2,7 +2,7 @@
 
 #define enumerate_syscalls(_e)                                                                                         \
     _e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(open) _e(close) _e(read) _e(getpid) _e(write)         \
-        _e(lseek) _e(mkdir) _e(exec) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl)
+        _e(lseek) _e(mkdir) _e(exec) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl) _e(getdents)
 
 enum Syscalls
 {