Kernel+LibC+Userland: Support mounting other kinds of filesystems

Author: https://github.com/bugaevc
Commit: https://github.com/SerenityOS/serenity/commit/425c356288d
Pull-request: https://github.com/SerenityOS/serenity/pull/456
Reviewed-by: https://github.com/awesomekling ✅

Kernel/Process.cpp

@@ -9,6 +9,9 @@
 #include <Kernel/Devices/NullDevice.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/Ext2FileSystem.h>
+#include <Kernel/FileSystem/ProcFS.h>
+#include <Kernel/FileSystem/DevPtsFS.h>
+#include <Kernel/FileSystem/TmpFS.h>
 #include <Kernel/FileSystem/FIFO.h>
 #include <Kernel/FileSystem/FileDescription.h>
 #include <Kernel/FileSystem/InodeWatcher.h>
@@ -2735,15 +2738,15 @@ int Process::sys$reboot()
     return ESUCCESS;
 }
 
-int Process::sys$mount(const char* device_path, const char* mountpoint)
+int Process::sys$mount(const char* device_path, const char* mountpoint, const char* fstype)
 {
     if (!is_superuser())
         return -EPERM;
 
-    if (!validate_read_str(device_path) || !validate_read_str(mountpoint))
+    if (!validate_read_str(device_path) || !validate_read_str(mountpoint) || !validate_read_str(fstype))
         return -EFAULT;
 
-    dbg() << "mount: device " << device_path << " @ " << mountpoint;
+    dbg() << "mount " << fstype << ": device " << device_path << " @ " << mountpoint;
 
     auto custody_or_error = VFS::the().resolve_path(mountpoint, current_directory());
     if (custody_or_error.is_error())
@@ -2751,37 +2754,47 @@ int Process::sys$mount(const char* device_path, const char* mountpoint)
 
     auto& mountpoint_custody = custody_or_error.value();
 
-    auto metadata_or_error = VFS::the().lookup_metadata(device_path, current_directory());
-    if (metadata_or_error.is_error())
-        return metadata_or_error.error();
+    RefPtr<FS> fs { nullptr };
 
-    auto major = metadata_or_error.value().major_device;
-    auto minor = metadata_or_error.value().minor_device;
+    if (strcmp(fstype, "ext2") == 0 || strcmp(fstype, "Ext2FS") == 0) {
+        auto metadata_or_error = VFS::the().lookup_metadata(device_path, current_directory());
+        if (metadata_or_error.is_error())
+            return metadata_or_error.error();
 
-    auto* device = VFS::the().get_device(major, minor);
-    if (!device) {
-        dbg() << "mount: device (" << major << "," << minor << ") not found";
+        auto major = metadata_or_error.value().major_device;
+        auto minor = metadata_or_error.value().minor_device;
+
+        auto* device = VFS::the().get_device(major, minor);
+        if (!device) {
+            dbg() << "mount: device (" << major << "," << minor << ") not found";
+            return -ENODEV;
+        }
+
+        if (!device->is_disk_device()) {
+            dbg() << "mount: device (" << major << "," << minor << ") is not a DiskDevice";
+            return -ENODEV;
+        }
+
+        auto& disk_device = static_cast<DiskDevice&>(*device);
+
+        dbg() << "mount: attempting to mount device (" << major << "," << minor << ") on " << mountpoint;
+
+        fs = Ext2FS::create(disk_device);
+    } else if (strcmp(fstype, "proc") == 0 || strcmp(fstype, "ProcFS") == 0)
+        fs = ProcFS::create();
+    else if (strcmp(fstype, "devpts") == 0 || strcmp(fstype, "DevPtsFS") == 0)
+        fs = DevPtsFS::create();
+    else if (strcmp(fstype, "tmp") == 0 || strcmp(fstype, "TmpFS") == 0)
+        fs = TmpFS::create();
+    else
+        return -ENODEV;
+
+    if (!fs->initialize()) {
+        dbg() << "mount: failed to initialize " << fstype << " filesystem on " << device_path;
         return -ENODEV;
     }
 
-    if (!device->is_disk_device()) {
-        dbg() << "mount: device (" << major << "," << minor << ") is not a DiskDevice";
-        return -ENODEV;
-    }
-
-    auto& disk_device = static_cast<DiskDevice&>(*device);
-
-    dbg() << "mount: attempting to mount device (" << major << "," << minor << ") on " << mountpoint;
-
-    // We currently only support ext2. Sorry :^)
-    auto ext2fs = Ext2FS::create(disk_device);
-    if (!ext2fs->initialize()) {
-        dbg() << "mount: could not find ext2 filesystem on " << device_path;
-        return -ENODEV;
-    }
-
-    // Let's mount the volume now
-    auto result = VFS::the().mount(ext2fs, mountpoint_custody);
+    auto result = VFS::the().mount(fs.release_nonnull(), mountpoint_custody);
     dbg() << "mount: successfully mounted " << device_path << " on " << mountpoint;
     return result;
 }

Kernel/Process.h

@@ -186,7 +186,7 @@ public:
     int sys$unlink(const char* pathname);
     int sys$symlink(const char* target, const char* linkpath);
     int sys$rmdir(const char* pathname);
-    int sys$mount(const char* device, const char* mountpoint);
+    int sys$mount(const char* device, const char* mountpoint, const char* fstype);
     int sys$umount(const char* mountpoint);
     int sys$read_tsc(u32* lsw, u32* msw);
     int sys$chmod(const char* pathname, mode_t);

Kernel/Syscall.cpp

@@ -293,7 +293,7 @@ static u32 handle(RegisterDump& regs, u32 function, u32 arg1, u32 arg2, u32 arg3
         break;
     }
     case Syscall::SC_mount:
-        return current->process().sys$mount((const char*)arg1, (const char*)arg2);
+        return current->process().sys$mount((const char*)arg1, (const char*)arg2, (const char*)arg3);
     case Syscall::SC_reboot: {
         return current->process().sys$reboot();
     }

Libraries/LibC/unistd.cpp

@@ -551,9 +551,9 @@ int reboot()
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-int mount(const char* device, const char* mountpoint)
+int mount(const char* device, const char* mountpoint, const char* fstype)
 {
-    int rc = syscall(SC_mount, device, mountpoint);
+    int rc = syscall(SC_mount, device, mountpoint, fstype);
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 

Libraries/LibC/unistd.h

@@ -100,7 +100,7 @@ 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);
+int mount(const char* device, const char* mountpoint, const char* fstype);
 int umount(const char* mountpoint);
 
 enum {

Userland/mount.cpp

@@ -2,28 +2,27 @@
 #include <stdio.h>
 #include <unistd.h>
 
-// This version of 'mount' must have the following arguments
-// 'mount <device_path> <mount_point>
-// It can currently only mount _physical_ devices found in /dev
-//
-// Currently, it is only possible to mount ext2 devices. Sorry! :^)
 int main(int argc, char** argv)
 {
     CArgsParser args_parser("mount");
     args_parser.add_arg("devname", "device path");
     args_parser.add_arg("mountpoint", "mount point");
+    args_parser.add_arg("fstype", "file system type");
     CArgsParserResult args = args_parser.parse(argc, argv);
 
-    if (argc == 3) {
-        // Let's use lstat so we can convert devname into a major/minor device pair!
-        if (mount(argv[1], argv[2]) < 0) {
-            perror("mount");
-            return 1;
-        }
-    } else {
+    if (argc < 3 || argc > 4) {
         args_parser.print_usage();
         return 0;
     }
 
+    const char* devname = argv[1];
+    const char* mountpoint = argv[2];
+    const char* fstype = argc == 4 ? argv[3] : "ext2";
+
+    if (mount(devname, mountpoint, fstype) < 0) {
+        perror("mount");
+        return 1;
+    }
+
     return 0;
 }