Kernel: Pass a parameter struct to mount()

This was the last remaining syscall that took a null-terminated string
and figured out how long it was by walking it in kernelspace *shudder*.

Kernel/Process.cpp

@@ -3575,28 +3575,35 @@ int Process::sys$reboot()
     return ESUCCESS;
 }
 
-int Process::sys$mount(const char* device_path, const char* mountpoint, const char* fstype)
+int Process::sys$mount(const Syscall::SC_mount_params* user_params)
 {
     if (!is_superuser())
         return -EPERM;
 
-    SmapDisabler disabler;
+    if (!validate_read_typed(user_params))
+        return -EFAULT;
+    Syscall::SC_mount_params params;
+    copy_from_user(&params, user_params);
 
-    if (!validate_read_str(device_path) || !validate_read_str(mountpoint) || !validate_read_str(fstype))
+    auto source = validate_and_copy_string_from_user(params.source);
+    auto target = validate_and_copy_string_from_user(params.target);
+    auto fs_type = validate_and_copy_string_from_user(params.fs_type);
+
+    if (source.is_null() || target.is_null() || fs_type.is_null())
         return -EFAULT;
 
-    dbg() << "mount " << fstype << ": device " << device_path << " @ " << mountpoint;
+    dbg() << "mount " << fs_type << ": source " << source << " @ " << target;
 
-    auto custody_or_error = VFS::the().resolve_path(mountpoint, current_directory());
+    auto custody_or_error = VFS::the().resolve_path(target, current_directory());
     if (custody_or_error.is_error())
         return custody_or_error.error();
 
-    auto& mountpoint_custody = custody_or_error.value();
+    auto& target_custody = custody_or_error.value();
 
-    RefPtr<FS> fs { nullptr };
+    RefPtr<FS> fs;
 
-    if (strcmp(fstype, "ext2") == 0 || strcmp(fstype, "Ext2FS") == 0) {
-        auto metadata_or_error = VFS::the().lookup_metadata(device_path, current_directory());
+    if (fs_type == "ext2" || fs_type == "Ext2FS") {
+        auto metadata_or_error = VFS::the().lookup_metadata(source, current_directory());
         if (metadata_or_error.is_error())
             return metadata_or_error.error();
 
@@ -3616,25 +3623,26 @@ int Process::sys$mount(const char* device_path, const char* mountpoint, const ch
 
         auto& disk_device = static_cast<DiskDevice&>(*device);
 
-        dbg() << "mount: attempting to mount device (" << major << "," << minor << ") on " << mountpoint;
+        dbg() << "mount: attempting to mount device (" << major << "," << minor << ") on " << target;
 
         fs = Ext2FS::create(disk_device);
-    } else if (strcmp(fstype, "proc") == 0 || strcmp(fstype, "ProcFS") == 0)
+    } else if (fs_type == "proc" || fs_type == "ProcFS") {
         fs = ProcFS::create();
-    else if (strcmp(fstype, "devpts") == 0 || strcmp(fstype, "DevPtsFS") == 0)
+    } else if (fs_type == "devpts" || fs_type == "DevPtsFS") {
         fs = DevPtsFS::create();
-    else if (strcmp(fstype, "tmp") == 0 || strcmp(fstype, "TmpFS") == 0)
+    } else if (fs_type == "tmp" || fs_type == "TmpFS") {
         fs = TmpFS::create();
-    else
-        return -ENODEV;
-
-    if (!fs->initialize()) {
-        dbg() << "mount: failed to initialize " << fstype << " filesystem on " << device_path;
+    } else {
         return -ENODEV;
     }
 
-    auto result = VFS::the().mount(fs.release_nonnull(), mountpoint_custody);
-    dbg() << "mount: successfully mounted " << device_path << " on " << mountpoint;
+    if (!fs->initialize()) {
+        dbg() << "mount: failed to initialize " << fs_type << " filesystem on " << source;
+        return -ENODEV;
+    }
+
+    auto result = VFS::the().mount(fs.release_nonnull(), target_custody);
+    dbg() << "mount: successfully mounted " << source << " on " << target;
     return result;
 }
 

Kernel/Process.h

@@ -179,7 +179,7 @@ public:
     int sys$unlink(const char* pathname, size_t path_length);
     int sys$symlink(const Syscall::SC_symlink_params*);
     int sys$rmdir(const char* pathname, size_t path_length);
-    int sys$mount(const char* device, const char* mountpoint, const char* fstype);
+    int sys$mount(const Syscall::SC_mount_params*);
     int sys$umount(const char* mountpoint, size_t mountpoint_length);
     int sys$chmod(const char* pathname, size_t path_length, mode_t);
     int sys$fchmod(int fd, mode_t);

Kernel/Syscall.h

@@ -355,6 +355,12 @@ struct SC_rename_params {
     StringArgument new_path;
 };
 
+struct SC_mount_params {
+    StringArgument source;
+    StringArgument target;
+    StringArgument fs_type;
+};
+
 void initialize();
 int sync();
 

Libraries/LibC/unistd.cpp

@@ -610,9 +610,14 @@ int reboot()
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-int mount(const char* device, const char* mountpoint, const char* fstype)
+int mount(const char* source, const char* target, const char* fs_type)
 {
-    int rc = syscall(SC_mount, device, mountpoint, fstype);
+    if (!source || !target || !fs_type) {
+        errno = EFAULT;
+        return -1;
+    }
+    Syscall::SC_mount_params params { { source, strlen(source) }, { target, strlen(target) }, { fs_type, strlen(fs_type) } };
+    int rc = syscall(SC_mount, &params);
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 

Libraries/LibC/unistd.h

@@ -111,7 +111,7 @@ int fchown(int fd, uid_t, gid_t);
 int ftruncate(int fd, off_t length);
 int halt();
 int reboot();
-int mount(const char* device, const char* mountpoint, const char* fstype);
+int mount(const char* source, const char* target, const char* fs_type);
 int umount(const char* mountpoint);
 
 enum {