VFS/LibC: Create ftruncate function and corresponding syscall and libc implementation

Previously this function was only used for shared memory region created
by shm_open because I was lazy. Now exists for all files.

5 files changed, 45 insertions, 28 deletions

diff --git a/fs/ext2.c b/fs/ext2.c
index 98ef2c7..14bcfcb 100644
--- a/fs/ext2.c
+++ b/fs/ext2.c
@@ -505,7 +505,7 @@ vfs_inode_t *ext2_open(const char *path) {
                           1 /*is_open*/, NULL /*internal_object*/, file_size,
                           ext2_open, ext2_create_file, ext2_read, ext2_write,
                           ext2_close, ext2_create_directory,
-                          NULL /*get_vm_object*/);
+                          NULL /*get_vm_object*/, NULL/*truncate*/);
 }
 
 uint64_t end_of_last_entry_position(int dir_inode, uint64_t *entry_offset,
@@ -697,7 +697,7 @@ vfs_inode_t *ext2_mount(void) {
                           0 /*can_write*/, 0 /*is_open*/,
                           NULL /*internal_object*/, 0 /*file_size*/, ext2_open,
                           ext2_create_file, ext2_read, ext2_write, ext2_close,
-                          ext2_create_directory, NULL /*get_vm_object*/);
+                          ext2_create_directory, NULL /*get_vm_object*/, NULL/*truncate*/);
 }
 
 void parse_superblock(void) {
diff --git a/fs/shm.c b/fs/shm.c
index 8668c9a..4d5f2ab 100644
--- a/fs/shm.c
+++ b/fs/shm.c
@@ -47,6 +47,19 @@ vfs_vm_object_t *shm_get_vm_object(uint64_t length, uint64_t offset,
   return p;
 }
 
+int shm_ftruncate(vfs_fd_t *fd, size_t length) {
+  vfs_vm_object_t *p = fd->inode->internal_object;
+  p->size = length;
+  p->virtual_object = ksbrk(length);
+  int n = (uintptr_t)align_page((void *)(uint32_t)length) / 0x1000;
+  p->object = kmalloc(sizeof(void *) * n);
+  for (int i = 0; i < n; i++)
+    p->object[i] =
+        (void *)(get_page(p->virtual_object + (i * 0x1000), NULL, 0, 0)->frame *
+                 0x1000);
+  return 0;
+}
+
 int shm_open(const char *name, int oflag, mode_t mode) {
   // Try to find or create a new shared memory object.
   vfs_vm_object_t *internal_object =
@@ -60,11 +73,11 @@ int shm_open(const char *name, int oflag, mode_t mode) {
     hashmap_add_entry(shared_memory_objects, name, internal_object, NULL, 0);
   }
 
-  vfs_inode_t *inode =
-      vfs_create_inode(0 /*inode_num*/, 0 /*type*/, 1 /*has_data*/,
-                       1 /*can_write*/, 1 /*is_open*/, internal_object,
-                       0 /*file_size*/, NULL /*open*/, NULL /*create_file*/,
-                       shm_read, shm_write, NULL /*close*/, NULL/*create_directory*/, shm_get_vm_object);
+  vfs_inode_t *inode = vfs_create_inode(
+      0 /*inode_num*/, 0 /*type*/, 1 /*has_data*/, 1 /*can_write*/,
+      1 /*is_open*/, internal_object, 0 /*file_size*/, NULL /*open*/,
+      NULL /*create_file*/, shm_read, shm_write, NULL /*close*/,
+      NULL /*create_directory*/, shm_get_vm_object, shm_ftruncate);
 
   vfs_fd_t *fd_ptr;
   int fd = vfs_create_fd(oflag, mode, inode, &fd_ptr);
@@ -79,20 +92,3 @@ int shm_unlink(const char *name) {
   (void)name;
   return 0;
 }
-
-int ftruncate(int fildes, uint64_t length) {
-  kprintf("ftruncate: %d\n", length);
-  vfs_fd_t *fd = get_current_task()->file_descriptors[fildes];
-  if (!fd)
-    return -EBADF;
-  vfs_vm_object_t *p = fd->inode->internal_object;
-  p->size = length;
-  p->virtual_object = ksbrk(length);
-  int n = (uintptr_t)align_page((void *)(uint32_t)length) / 0x1000;
-  p->object = kmalloc(sizeof(void *) * n);
-  for (int i = 0; i < n; i++)
-    p->object[i] =
-        (void *)(get_page(p->virtual_object + (i * 0x1000), NULL, 0, 0)->frame *
-                 0x1000);
-  return 0;
-}
diff --git a/fs/tmpfs.c b/fs/tmpfs.c
index 575ab0c..a9a3c1f 100644
--- a/fs/tmpfs.c
+++ b/fs/tmpfs.c
@@ -48,7 +48,7 @@ void dual_pipe(int fd[2]) {
         0 /*inode_num*/, 0 /*type*/, has_data, can_write, is_open,
         internal_object, 0 /*file_size*/, NULL /*open*/, NULL /*create_file*/,
         tmp_read, tmp_write, tmp_close, NULL /*create_directory*/,
-        NULL /*get_vm_object*/);
+        NULL /*get_vm_object*/, NULL /*truncate*/);
     assert(inode);
 
     vfs_fd_t *fd_ptr;
@@ -77,7 +77,8 @@ void pipe(int fd[2]) {
     vfs_inode_t *inode = vfs_create_inode(
         0 /*inode_num*/, 0 /*type*/, has_data, can_write, is_open,
         internal_object, 0 /*file_size*/, NULL /*open*/, NULL /*create_file*/,
-        tmp_read, tmp_write, tmp_close, NULL/*create_directory*/, NULL /*get_vm_object*/);
+        tmp_read, tmp_write, tmp_close, NULL /*create_directory*/,
+        NULL /*get_vm_object*/, NULL/*truncate*/);
     assert(inode);
 
     vfs_fd_t *fd_ptr;
diff --git a/fs/vfs.c b/fs/vfs.c
index 5f61d89..0c616a2 100644
--- a/fs/vfs.c
+++ b/fs/vfs.c
@@ -32,7 +32,8 @@ vfs_inode_t *vfs_create_inode(
     void (*close)(vfs_fd_t *fd),
     int (*create_directory)(const char *path, int mode),
     vfs_vm_object_t *(*get_vm_object)(uint64_t length, uint64_t offset,
-                                      vfs_fd_t *fd)) {
+                                      vfs_fd_t *fd),
+    int (*truncate)(vfs_fd_t *fd, size_t length)) {
   vfs_inode_t *r = kmalloc(sizeof(inode_t));
   r->inode_num = inode_num;
   r->type = type;
@@ -48,6 +49,7 @@ vfs_inode_t *vfs_create_inode(
   r->close = close;
   r->create_directory = create_directory;
   r->get_vm_object = get_vm_object;
+  r->truncate = truncate;
   return r;
 }
 
@@ -291,6 +293,21 @@ int vfs_dup2(int org_fd, int new_fd) {
   return 1;
 }
 
+int vfs_ftruncate(int fd, size_t length) {
+  vfs_fd_t *fd_ptr = get_vfs_fd(fd);
+  if (!fd_ptr)
+    return -EBADF;
+  if (!(fd_ptr->flags & O_READ))
+    return -EINVAL;
+  vfs_inode_t *inode = fd_ptr->inode;
+  if (!inode)
+    return -EINVAL;
+  if (!inode->truncate)
+    return -EINVAL;
+
+  return inode->truncate(fd_ptr, length);
+}
+
 void vfs_mount(char *path, vfs_inode_t *local_root) {
   int len = strlen(path);
   mounts[num_mounts].path = kmalloc_eternal(len + 1);
diff --git a/fs/vfs.h b/fs/vfs.h
index b8a9984..f8a4b19 100644
--- a/fs/vfs.h
+++ b/fs/vfs.h
@@ -68,6 +68,7 @@ struct vfs_inode {
   int (*create_directory)(const char *path, int mode);
   vfs_vm_object_t *(*get_vm_object)(uint64_t length, uint64_t offset,
                                     vfs_fd_t *fd);
+  int (*truncate)(vfs_fd_t *fd, size_t length);
 };
 
 int vfs_close(int fd);
@@ -83,6 +84,7 @@ int vfs_dup2(int org_fd, int new_fd);
 vfs_inode_t *vfs_internal_open(const char *file);
 int vfs_mkdir(const char *path, int mode);
 int vfs_create_fd(int flags, int mode, vfs_inode_t *inode, vfs_fd_t **fd);
+int vfs_ftruncate(int fd, size_t length);
 vfs_inode_t *vfs_create_inode(
     int inode_num, int type, uint8_t has_data, uint8_t can_write,
     uint8_t is_open, void *internal_object, uint64_t file_size,
@@ -93,5 +95,6 @@ vfs_inode_t *vfs_create_inode(
     void (*close)(vfs_fd_t *fd),
     int (*create_directory)(const char *path, int mode),
     vfs_vm_object_t *(*get_vm_object)(uint64_t length, uint64_t offset,
-                                      vfs_fd_t *fd));
+                                      vfs_fd_t *fd),
+    int (*truncate)(vfs_fd_t *fd, size_t length));
 #endif