vfs: fix seek, add fchmodat

kernel/filesystem/vfs.c

@@ -110,74 +110,39 @@ static off_t vfs_io_ops_seek(io_t *io, off_t offset, io_seek_whence_t whence)
 {
     file_t *file = container_of(io, file_t, io);
 
-    if (file_get_ops(file)->seek)
-        return file_get_ops(file)->seek(file, offset, whence); // use the filesystem's lseek if it exists
+    const file_ops_t *const ops = file_get_ops(file);
+    if (ops->seek)
+        return ops->seek(file, offset, whence); // use the filesystem's lseek if it exists
 
     spinlock_acquire(&file->offset_lock);
 
-    off_t ret = 0;
     switch (whence)
     {
         case IO_SEEK_SET:
         {
-            if (unlikely(offset < 0))
-            {
-                ret = 0;
-                break;
-            }
-
-            if ((size_t) offset > file->dentry->inode->size)
-                ret = file->dentry->inode->size; // beyond the end of the file
-            else
-                ret = offset;
-
-            file->offset = ret;
+            file->offset = MAX(offset, 0);
             break;
         }
         case IO_SEEK_CURRENT:
         {
-            if (offset < 0)
-            {
-                if (file->offset < (size_t) -offset)
-                    ret = 0; // before the beginning of the file
-                else
-                    ret = file->offset + offset;
-            }
-            else
-            {
-                if (file->offset + offset > file->dentry->inode->size)
-                    ret = file->dentry->inode->size; // beyond the end of the file
-                else
-                    ret = file->offset + offset;
-            }
-
-            file->offset = ret;
+            off_t new_offset = file->offset + offset;
+            new_offset = MAX(new_offset, 0);
+            file->offset = new_offset;
             break;
         }
         case IO_SEEK_END:
         {
-            if (offset < 0)
-            {
-                if (file->dentry->inode->size < (size_t) -offset)
-                    ret = 0; // before the beginning of the file
-                else
-                    ret = file->dentry->inode->size + offset;
-            }
-            else
-            {
-                // don't allow seeking past the end of the file, (yet)
-                pr_warn("vfs: seeking past the end of the file is not supported yet");
-            }
-
-            file->offset = ret;
+            off_t new_offset = file->dentry->inode->size + offset;
+            new_offset = MAX(new_offset, 0);
+            file->offset = new_offset;
             break;
         }
         case IO_SEEK_DATA: mos_warn("vfs: IO_SEEK_DATA is not supported"); break;
         case IO_SEEK_HOLE: mos_warn("vfs: IO_SEEK_HOLE is not supported"); break;
     };
 
     spinlock_release(&file->offset_lock);
-    return ret;
+    return file->offset;
 }
 
 static vmfault_result_t vfs_fault_handler(vmap_t *vmap, ptr_t fault_addr, pagefault_t *info)
@@ -553,7 +518,7 @@ long vfs_fstatat(fd_t fd, const char *path, file_stat_t *restrict statbuf, fstat
 
     pr_dinfo2(vfs, "vfs_fstatat(fd=%d, path='%s', stat=%p, flags=%x)", fd, path, (void *) statbuf, flags);
     dentry_t *basedir = path_is_absolute(path) ? root_dentry : dentry_from_fd(fd);
-    lastseg_resolve_flags_t resolve_flags = RESOLVE_EXPECT_FILE | RESOLVE_EXPECT_DIR | RESOLVE_EXPECT_EXIST;
+    lastseg_resolve_flags_t resolve_flags = RESOLVE_EXPECT_ANY_TYPE | RESOLVE_EXPECT_EXIST;
     if (flags & FSTATAT_NOFOLLOW)
         resolve_flags |= RESOLVE_SYMLINK_NOFOLLOW;
 
@@ -570,7 +535,7 @@ long vfs_fstatat(fd_t fd, const char *path, file_stat_t *restrict statbuf, fstat
 size_t vfs_readlinkat(fd_t dirfd, const char *path, char *buf, size_t size)
 {
     dentry_t *base = path_is_absolute(path) ? root_dentry : dentry_from_fd(dirfd);
-    dentry_t *dentry = dentry_get(base, root_dentry, path, RESOLVE_SYMLINK_NOFOLLOW | RESOLVE_EXPECT_EXIST);
+    dentry_t *dentry = dentry_get(base, root_dentry, path, RESOLVE_SYMLINK_NOFOLLOW | RESOLVE_EXPECT_EXIST | RESOLVE_EXPECT_FILE);
     if (IS_ERR(dentry))
         return PTR_ERR(dentry);
 
@@ -733,6 +698,20 @@ ssize_t vfs_getcwd(char *buf, size_t size)
     return dentry_path(cwd, root_dentry, buf, size);
 }
 
+long vfs_fchmodat(fd_t fd, const char *path, int perm, int flags)
+{
+    pr_dinfo2(vfs, "vfs_fchmodat(fd=%d, path='%s', perm=%o, flags=%x)", fd, path, perm, flags);
+    dentry_t *base = path_is_absolute(path) ? root_dentry : dentry_from_fd(fd);
+    dentry_t *dentry = dentry_get(base, root_dentry, path, RESOLVE_EXPECT_EXIST | RESOLVE_EXPECT_ANY_TYPE);
+    if (IS_ERR(dentry))
+        return PTR_ERR(dentry);
+
+    // TODO: check if the underlying filesystem supports chmod, and is not read-only
+    dentry->inode->perm = perm;
+    dentry_unref(dentry);
+    return 0;
+}
+
 // ! sysfs support
 
 static bool vfs_sysfs_filesystems(sysfs_file_t *f)

kernel/include/private/mos/filesystem/vfs.h

@@ -136,3 +136,14 @@ long vfs_chdir(const char *path);
  * @return ssize_t The size of the path, or 0 if the buffer was too small
  */
 ssize_t vfs_getcwd(char *buf, size_t size);
+
+/**
+ * @brief Change the permissions of a file
+ *
+ * @param fd The directory, or a file if FSTATAT_FILE is set
+ * @param path The path to the file
+ * @param perm The new permissions
+ * @param flags fstat_flags flags
+ * @return long 0 on success, or errno on failure
+ */
+long vfs_fchmodat(fd_t fd, const char *path, int perm, int flags);

kernel/ksyscall.c

@@ -622,3 +622,8 @@ DEFINE_SYSCALL(ssize_t, thread_getname)(tid_t tid, char *buf, size_t buflen)
     char *end = strncpy(buf, thread->name, buflen);
     return end - buf;
 }
+
+DEFINE_SYSCALL(long, vfs_fchmodat)(fd_t dirfd, const char *path, int mode, int flags)
+{
+    return vfs_fchmodat(dirfd, path, mode, flags);
+}

kernel/ksyscalls.json

@@ -457,6 +457,17 @@
             "name": "thread_getname",
             "return": "ssize_t",
             "arguments": [ { "type": "tid_t", "arg": "tid" }, { "type": "char *", "arg": "buf" }, { "type": "size_t", "arg": "buf_size" } ]
+        },
+        {
+            "number": 61,
+            "name": "vfs_fchmodat",
+            "return": "long",
+            "arguments": [
+                { "type": "fd_t", "arg": "dirfd" },
+                { "type": "const char *", "arg": "path" },
+                { "type": "int", "arg": "mode" },
+                { "type": "int", "arg": "flags" }
+            ]
         }
     ]
 }