kernel+libos+apps: Support block devices and disallow seeking character devices or pipes

apps/stat.cpp

@@ -1,5 +1,6 @@
 #include <os/ArgumentParser.h>
 #include <os/FileSystem.h>
+#include <os/Mode.h>
 #include <stdio.h>
 #include <sys/stat.h>
 
@@ -10,6 +11,7 @@ static const char* file_type(mode_t mode)
     case S_IFREG: return "regular file";
     case S_IFDIR: return "directory";
     case S_IFCHR: return "character special device";
+    case S_IFBLK: return "block special device";
     case S_IFLNK: return "symbolic link";
     case S_IFIFO: return "pipe";
     default: return "unknown file type";
@@ -31,10 +33,13 @@ Result<int> luna_main(int argc, char** argv)
     struct stat st;
     TRY(os::FileSystem::stat(path, st, follow_symlinks));
 
+    char buf[11];
+    os::format_mode(st.st_mode, buf);
+
     printf(" File: %s\n", path.chars());
     printf(" Size: %zu (%s)\n", st.st_size, file_type(st.st_mode));
     printf("Inode: %lu Links: %lu\n", st.st_ino, st.st_nlink);
-    printf(" Mode: %#o UID: %u GID: %u\n", st.st_mode & ~S_IFMT, st.st_uid, st.st_gid);
+    printf(" Mode: (%#o/%s) UID: %u GID: %u\n", st.st_mode & ~S_IFMT, buf, st.st_uid, st.st_gid);
 
     return 0;
 }

kernel/src/fs/VFS.cpp

@@ -168,6 +168,11 @@ namespace VFS
         return inode->mode() & S_ISGID;
     }
 
+    bool is_seekable(SharedPtr<Inode> inode)
+    {
+        return inode->type() != InodeType::FIFO && inode->type() != InodeType::CharacterDevice;
+    }
+
     Result<void> mount_root(SharedPtr<VFS::FileSystem> fs)
     {
         root_fs = fs;

kernel/src/fs/VFS.h

@@ -13,7 +13,8 @@ namespace VFS
     {
         RegularFile,
         Directory,
-        Device,
+        CharacterDevice,
+        BlockDevice,
         Symlink,
         FIFO,
     };
@@ -261,7 +262,7 @@ namespace VFS
 
         InodeType type() const override
         {
-            return InodeType::Device;
+            return InodeType::CharacterDevice;
         }
 
         virtual ~DeviceInode() = default;
@@ -285,6 +286,8 @@ namespace VFS
     bool is_setuid(SharedPtr<Inode> inode);
     bool is_setgid(SharedPtr<Inode> inode);
 
+    bool is_seekable(VFS::InodeType type);
+
     Inode& root_inode();
 
     Result<void> mount_root(SharedPtr<VFS::FileSystem> fs);

kernel/src/fs/devices/Device.h

@@ -18,6 +18,11 @@ class Device
         return 0;
     }
 
+    virtual bool is_block_device() const
+    {
+        return false;
+    }
+
     virtual bool blocking() const = 0;
 
     virtual ~Device() = default;

kernel/src/fs/tmpfs/FileSystem.h

@@ -243,6 +243,11 @@ namespace TmpFS
       public:
         DeviceInode() = default;
 
+        VFS::InodeType type() const override
+        {
+            return m_device->is_block_device() ? VFS::InodeType::BlockDevice : VFS::InodeType::CharacterDevice;
+        }
+
         void set_fs(FileSystem& fs, Badge<FileSystem>)
         {
             m_fs = &fs;

kernel/src/sys/file.cpp

@@ -33,7 +33,7 @@ Result<u64> sys_read(Registers*, SyscallArgs args)
 
     usize nread = TRY(descriptor.inode->read(buf, descriptor.offset, size));
 
-    descriptor.offset += nread;
+    if (VFS::is_seekable(descriptor.inode->type())) descriptor.offset += nread;
 
     return nread;
 }
@@ -52,11 +52,12 @@ Result<u64> sys_write(Registers*, SyscallArgs args)
 
     if (!descriptor.is_writable()) return err(EBADF);
 
-    if (descriptor.should_append()) descriptor.offset = descriptor.inode->size();
+    if (descriptor.should_append() && VFS::is_seekable(descriptor.inode->type()))
+        descriptor.offset = descriptor.inode->size();
 
     usize nwritten = TRY(descriptor.inode->write(buf, descriptor.offset, size));
 
-    descriptor.offset += nwritten;
+    if (VFS::is_seekable(descriptor.inode->type())) descriptor.offset += nwritten;
 
     return nwritten;
 }
@@ -71,6 +72,10 @@ Result<u64> sys_lseek(Registers*, SyscallArgs args)
 
     auto& descriptor = *TRY(current->resolve_fd(fd));
 
+    if (descriptor.inode->type() == VFS::InodeType::FIFO) return err(ESPIPE);
+
+    if (!VFS::is_seekable(descriptor.inode->type())) return descriptor.offset;
+
     off_t new_offset;
 
     switch (whence)

kernel/src/sys/stat.cpp

@@ -13,7 +13,8 @@ static mode_t make_mode(mode_t mode, VFS::InodeType type)
     {
     case VFS::InodeType::RegularFile: result |= S_IFREG; break;
     case VFS::InodeType::Directory: result |= S_IFDIR; break;
-    case VFS::InodeType::Device: result |= S_IFCHR; break;
+    case VFS::InodeType::CharacterDevice: result |= S_IFCHR; break;
+    case VFS::InodeType::BlockDevice: result |= S_IFBLK; break;
     case VFS::InodeType::Symlink: result |= S_IFLNK; break;
     case VFS::InodeType::FIFO: result |= S_IFIFO; break;
     default: break;

libc/include/bits/modes.h

@@ -7,6 +7,7 @@
 #define S_IFREG 000000
 #define S_IFLNK 010000
 #define S_IFIFO 020000
+#define S_IFBLK 030000
 #define S_IFDIR 040000
 #define S_IFCHR 050000
 
@@ -15,6 +16,7 @@
 #define S_ISREG(mode) __CHECK_TYPE(mode, S_IFREG)
 #define S_ISDIR(mode) __CHECK_TYPE(mode, S_IFDIR)
 #define S_ISCHR(mode) __CHECK_TYPE(mode, S_IFCHR)
+#define S_ISBLK(mode) __CHECK_TYPE(mode, S_IFBLK)
 #define S_ISLNK(mode) __CHECK_TYPE(mode, S_IFLNK)
 #define S_ISFIFO(mode) __CHECK_TYPE(mode, S_IFIFO)
 

libos/src/Mode.cpp

@@ -9,6 +9,7 @@ namespace os
         if (S_ISDIR(mode)) return 'd';
 
         if (S_ISCHR(mode)) return 'c';
+        if (S_ISBLK(mode)) return 'b';
         if (S_ISLNK(mode)) return 'l';
         if (S_ISFIFO(mode)) return 'p';