kernel+libc+apps: Add mount and umount syscalls, libc wrappers, and utilities

apps/CMakeLists.txt

@@ -24,3 +24,5 @@ luna_app(uname.cpp uname)
 luna_app(base64.cpp base64)
 luna_app(login.cpp login)
 luna_app(ipc-test.cpp ipc-test)
+luna_app(mount.cpp mount)
+luna_app(umount.cpp umount)

apps/mount.cpp

@@ -0,0 +1,24 @@
+#include <os/ArgumentParser.h>
+#include <stdio.h>
+#include <sys/mount.h>
+
+Result<int> luna_main(int argc, char** argv)
+{
+    StringView target;
+    StringView fstype;
+
+    os::ArgumentParser parser;
+    parser.add_description("Mount a file system.");
+    parser.add_system_program_info("mount"_sv);
+    parser.add_positional_argument(target, "mountpoint"_sv, true);
+    parser.add_value_argument(fstype, 't', "type"_sv, "auto"_sv, "the file system type to use");
+    parser.parse(argc, argv);
+
+    if (mount(target.chars(), fstype.chars()) < 0)
+    {
+        perror("mount");
+        return 1;
+    }
+
+    return 0;
+}

apps/umount.cpp

@@ -0,0 +1,22 @@
+#include <os/ArgumentParser.h>
+#include <stdio.h>
+#include <sys/mount.h>
+
+Result<int> luna_main(int argc, char** argv)
+{
+    StringView target;
+
+    os::ArgumentParser parser;
+    parser.add_description("Unmount a file system.");
+    parser.add_system_program_info("umount"_sv);
+    parser.add_positional_argument(target, "mountpoint"_sv, true);
+    parser.parse(argc, argv);
+
+    if (umount(target.chars()) < 0)
+    {
+        perror("umount");
+        return 1;
+    }
+
+    return 0;
+}

kernel/CMakeLists.txt

@@ -38,6 +38,7 @@ set(SOURCES
     src/sys/chdir.cpp
     src/sys/link.cpp
     src/sys/uname.cpp
+    src/sys/mount.cpp
     src/fs/VFS.cpp
     src/fs/Pipe.cpp
     src/fs/Mount.cpp

kernel/src/sys/exec.cpp

@@ -88,7 +88,11 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
     {
         auto& descriptor = current->fd_table[i];
         if (!descriptor.has_value()) continue;
-        if (descriptor->flags & O_CLOEXEC) descriptor = {};
+        if (descriptor->flags & O_CLOEXEC)
+        {
+            descriptor->inode->fs()->remove_handle();
+            descriptor = {};
+        }
     }
 
     MMU::delete_userspace_page_directory(current->directory);
@@ -132,7 +136,11 @@ Result<u64> sys_fork(Registers* regs, SyscallArgs)
     thread->current_directory_path = move(current_directory_path);
     thread->parent = current;
 
-    for (int i = 0; i < FD_MAX; i++) { thread->fd_table[i] = current->fd_table[i]; }
+    for (int i = 0; i < FD_MAX; i++)
+    {
+        thread->fd_table[i] = current->fd_table[i];
+        if (current->fd_table[i].has_value()) current->fd_table[i]->inode->fs()->add_handle();
+    }
 
     image->apply(thread);
 

kernel/src/sys/mount.cpp

@@ -0,0 +1,34 @@
+#include "fs/VFS.h"
+#include "fs/tmpfs/FileSystem.h"
+#include "memory/MemoryManager.h"
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+
+Result<u64> sys_mount(Registers*, SyscallArgs args)
+{
+    auto target = TRY(MemoryManager::strdup_from_user(args[0]));
+    auto fstype = TRY(MemoryManager::strdup_from_user(args[1]));
+
+    auto* current = Scheduler::current();
+    if (current->auth.euid != 0) return err(EPERM);
+
+    // Right now we only support one file system.
+    if (fstype.view() != "tmpfs") return err(ENODEV);
+
+    auto fs = TRY(TmpFS::FileSystem::create());
+    TRY(VFS::mount(target.chars(), fs, current->auth, current->current_directory));
+
+    return 0;
+}
+
+Result<u64> sys_umount(Registers*, SyscallArgs args)
+{
+    auto target = TRY(MemoryManager::strdup_from_user(args[0]));
+
+    auto* current = Scheduler::current();
+    if (current->auth.euid != 0) return err(EPERM);
+
+    TRY(VFS::umount(target.chars(), current->auth, current->current_directory));
+
+    return 0;
+}

kernel/src/sys/open.cpp

@@ -72,6 +72,8 @@ Result<u64> sys_openat(Registers*, SyscallArgs args)
 
     kinfoln("openat: opening file %s from dirfd %d, flags %d, mode %#o = fd %d", path.chars(), dirfd, flags, mode, fd);
 
+    inode->fs()->add_handle();
+
     current->fd_table[fd] = FileDescriptor { inode, 0, flags & FLAGS_TO_KEEP };
 
     return (u64)fd;
@@ -88,6 +90,8 @@ Result<u64> sys_close(Registers*, SyscallArgs args)
 
     if (!descriptor.has_value()) return err(EBADF);
 
+    descriptor->inode->fs()->remove_handle();
+
     descriptor = {};
 
     return 0;

kernel/src/thread/Scheduler.cpp

@@ -182,6 +182,11 @@ namespace Scheduler
         {
             auto stack = thread->kernel_stack;
             MemoryManager::unmap_owned_and_free_vm(stack.bottom(), stack.bytes() / ARCH_PAGE_SIZE).release_value();
+
+            for (int i = 0; i < FD_MAX; i++)
+            {
+                if (thread->fd_table[i].has_value()) thread->fd_table[i]->inode->fs()->remove_handle();
+            }
         }
 
         if (!thread->is_kernel) MMU::delete_userspace_page_directory(thread->directory);

kernel/src/thread/Thread.cpp

@@ -66,22 +66,6 @@ Result<SharedPtr<VFS::Inode>> Thread::resolve_atfile(int dirfd, const String& pa
     return VFS::resolve_path(path.chars(), this->auth, descriptor->inode);
 }
 
-FileDescriptor::FileDescriptor(SharedPtr<VFS::Inode> _inode, usize _offset, int _flags)
-    : inode(_inode), offset(_offset), flags(_flags)
-{
-    inode->fs()->add_handle();
-}
-
-FileDescriptor::FileDescriptor(const FileDescriptor& f) : inode(f.inode), offset(f.offset), flags(f.flags)
-{
-    inode->fs()->add_handle();
-}
-
-FileDescriptor::~FileDescriptor()
-{
-    inode->fs()->remove_handle();
-}
-
 bool FileDescriptor::should_append()
 {
     return flags & O_APPEND;

kernel/src/thread/Thread.h

@@ -33,10 +33,6 @@ struct FileDescriptor
     usize offset { 0 };
     int flags { 0 };
 
-    FileDescriptor(SharedPtr<VFS::Inode> inode, usize offset, int flags);
-    FileDescriptor(const FileDescriptor& f);
-    ~FileDescriptor();
-
     bool should_append();
     bool should_block();
     bool is_writable();

libc/CMakeLists.txt

@@ -24,6 +24,7 @@ set(SOURCES
     src/sys/wait.cpp
     src/sys/ioctl.cpp
     src/sys/utsname.cpp
+    src/sys/mount.cpp
 )
 
 if(${LUNA_ARCH} STREQUAL "x86_64")

libc/include/sys/mount.h

@@ -0,0 +1,21 @@
+/* sys/mount.h: Virtual file system mounting operations. */
+
+#ifndef _SYS_MOUNT_H
+#define _SYS_MOUNT_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Mount a file system on target. */
+    int mount(const char* target, const char* fstype);
+
+    /* Unmount the file system mounted on target. */
+    int umount(const char* target);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

libc/src/sys/mount.cpp

@@ -0,0 +1,19 @@
+#include <bits/errno-return.h>
+#include <sys/mount.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+extern "C"
+{
+    int mount(const char* target, const char* fstype)
+    {
+        long rc = syscall(SYS_mount, target, fstype);
+        __errno_return(rc, int);
+    }
+
+    int umount(const char* target)
+    {
+        long rc = syscall(SYS_umount, target);
+        __errno_return(rc, int);
+    }
+}

libluna/include/luna/Syscall.h

@@ -4,7 +4,8 @@
     _e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(openat) _e(close) _e(read) _e(getpid) _e(write)       \
         _e(lseek) _e(mkdir) _e(execve) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl) _e(getdents) _e(getuid)    \
             _e(geteuid) _e(getgid) _e(getegid) _e(setuid) _e(setgid) _e(seteuid) _e(setegid) _e(fchmodat) _e(fchownat) \
-                _e(ioctl) _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname) _e(dup2) _e(pipe)
+                _e(ioctl) _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname) _e(dup2) _e(pipe)    \
+                    _e(mount) _e(umount)
 
 enum Syscalls
 {