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/fs/VFS.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <luna/SharedPtr.h>
+#include <luna/StaticString.h>
 #include <sys/types.h>
 
 namespace VFS
@@ -12,6 +13,14 @@ namespace VFS
     };
 
     class FileSystem;
+    class Inode;
+
+    struct DirectoryEntry
+    {
+      public:
+        SharedPtr<Inode> inode;
+        StaticString<128> name;
+    };
 
     class Inode
     {
@@ -19,6 +28,8 @@ namespace VFS
         // Directory-specific methods
         virtual Result<SharedPtr<Inode>> find(const char* name) const = 0;
 
+        virtual Option<DirectoryEntry> get(usize index) const = 0;
+
         virtual Result<SharedPtr<Inode>> create_file(const char* name) = 0;
 
         virtual Result<SharedPtr<Inode>> create_subdirectory(const char* name) = 0;
@@ -60,6 +71,11 @@ namespace VFS
             return err(ENOTDIR);
         }
 
+        Option<DirectoryEntry> get(usize) const override
+        {
+            return {};
+        }
+
         Result<SharedPtr<Inode>> create_file(const char*) override
         {
             return err(ENOTDIR);
@@ -96,6 +112,11 @@ namespace VFS
             return err(ENOTDIR);
         }
 
+        Option<DirectoryEntry> get(usize) const override
+        {
+            return {};
+        }
+
         Result<SharedPtr<Inode>> create_file(const char*) override
         {
             return err(ENOTDIR);

kernel/src/fs/tmpfs/FileSystem.cpp

@@ -63,9 +63,18 @@ namespace TmpFS
         return err(ENOENT);
     }
 
+    Option<VFS::DirectoryEntry> DirInode::get(usize index) const
+    {
+        if (index >= m_entries.size()) return {};
+
+        return m_entries[index];
+    }
+
     Result<void> DirInode::add_entry(SharedPtr<VFS::Inode> inode, const char* name)
     {
-        Entry entry { inode, name };
+        if (find(name).has_value()) return err(EEXIST);
+
+        VFS::DirectoryEntry entry { inode, name };
 
         TRY(m_entries.try_append(move(entry)));
 
@@ -74,8 +83,6 @@ namespace TmpFS
 
     Result<SharedPtr<VFS::Inode>> DirInode::create_file(const char* name)
     {
-        if (find(name).has_value()) return err(EEXIST);
-
         auto inode = TRY(m_fs->create_file_inode());
 
         TRY(add_entry(inode, name));
@@ -85,8 +92,6 @@ namespace TmpFS
 
     Result<SharedPtr<VFS::Inode>> DirInode::create_subdirectory(const char* name)
     {
-        if (find(name).has_value()) return err(EEXIST);
-
         auto inode = TRY(m_fs->create_dir_inode(m_self));
 
         TRY(add_entry(inode, name));

kernel/src/fs/tmpfs/FileSystem.h

@@ -185,6 +185,7 @@ namespace TmpFS
         }
 
         Result<SharedPtr<VFS::Inode>> find(const char* name) const override;
+        Option<VFS::DirectoryEntry> get(usize index) const override;
 
         Result<usize> read(u8*, usize, usize) const override
         {
@@ -251,12 +252,6 @@ namespace TmpFS
 
         SharedPtr<VFS::Inode> m_self;
 
-        struct Entry
-        {
-            SharedPtr<VFS::Inode> inode;
-            StaticString<128> name;
-        };
-
-        Vector<Entry> m_entries;
+        Vector<VFS::DirectoryEntry> m_entries;
     };
 }

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;
+}

kernel/src/sys/mknod.cpp

@@ -24,8 +24,6 @@ Result<u64> sys_mknod(Registers*, SyscallArgs args)
 
     auto parent = TRY(VFS::resolve_path(dirname.chars()));
 
-    if (parent->find(basename.chars()).has_value()) return err(EEXIST);
-
     auto inode = TRY(parent->fs().create_device_inode(maj, min));
     TRY(parent->add_entry(inode, basename.chars()));
 

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
 {