truncate(2)/ftruncate(2)

arch/amd64/syscall.c

@@ -53,6 +53,8 @@ void *syscall_table[256] = {
     [SYSCALL_NR_SELECT] =           sys_select,
     [SYSCALL_NR_DUP] =              sys_dup,
     [SYSCALL_NR_DUP2] =             sys_dup2,
+    [SYSCALL_NR_TRUNCATE] =         sys_truncate,
+    [SYSCALL_NR_FTRUNCATE] =        sys_ftruncate,
     [SYSCALL_NR_GETCWD] =           sys_getcwd,
     [SYSCALL_NR_CHDIR] =            sys_chdir,
     [SYSCALL_NR_MKDIRAT] =          sys_mkdirat,

fs/vfs_ops.c

@@ -542,6 +542,22 @@ int vfs_fstatat(struct vfs_ioctx *ctx, struct vnode *at, const char *path, struc
     return node->op->stat(node, st);
 }
 
+int vfs_ftruncate(struct vfs_ioctx *ctx, struct vnode *node, off_t length) {
+    _assert(ctx);
+    _assert(node);
+
+    if (node->type != VN_REG) {
+        kwarn("truncate() on non-file\n");
+        return -EPERM;
+    }
+
+    if (node->op && node->op->truncate) {
+        return node->op->truncate(node, length);
+    } else {
+        return -ENOSYS;
+    }
+}
+
 ssize_t vfs_write(struct vfs_ioctx *ctx, struct ofile *fd, const void *buf, size_t count) {
     struct vnode *node;
     ssize_t b;

include/fs/vfs.h

@@ -54,6 +54,7 @@ int vfs_mknod(struct vfs_ioctx *ctx, const char *path, mode_t mode, struct vnode
 int vfs_chmod(struct vfs_ioctx *ctx, const char *path, mode_t mode);
 int vfs_chown(struct vfs_ioctx *ctx, const char *path, uid_t uid, gid_t gid);
 int vfs_ioctl(struct vfs_ioctx *ctx, struct ofile *fd, unsigned int cmd, void *arg);
+int vfs_ftruncate(struct vfs_ioctx *ctx, struct vnode *node, off_t length);
 
 int vfs_faccessat(struct vfs_ioctx *ctx, struct vnode *at, const char *path, int accmode, int flags);
 int vfs_fstatat(struct vfs_ioctx *ctx, struct vnode *at, const char *path, struct stat *st, int flags);

include/sys/sys_file.h

@@ -4,6 +4,8 @@
 
 ssize_t sys_read(int fd, void *data, size_t lim);
 ssize_t sys_write(int fd, const void *data, size_t lim);
+int sys_ftruncate(int fd, off_t length);
+int sys_truncate(const char *filename, off_t length);
 int sys_creat(const char *pathname, int mode);
 int sys_mkdirat(int dfd, const char *pathname, int mode);
 int sys_unlinkat(int dfd, const char *pathname, int flags);

include/user/syscall.h

@@ -15,6 +15,8 @@
 #define SYSCALL_NR_SELECT           23
 #define SYSCALL_NR_DUP              32
 #define SYSCALL_NR_DUP2             33
+#define SYSCALL_NR_TRUNCATE         76
+#define SYSCALL_NR_FTRUNCATE        77
 #define SYSCALL_NR_GETCWD           79
 #define SYSCALL_NR_CHDIR            80
 #define SYSCALL_NR_MKDIRAT          83

sys/sys_file.c

@@ -105,6 +105,31 @@ int sys_unlinkat(int dfd, const char *pathname, int flags) {
     return vfs_unlinkat(get_ioctx(), at, pathname, flags);
 }
 
+int sys_truncate(const char *pathname, off_t length) {
+    userptr_check(pathname);
+    struct vnode *node;
+    struct vfs_ioctx *ioctx = get_ioctx();
+    int res;
+
+    if ((res = vfs_find(ioctx, ioctx->cwd_vnode, pathname, 0, &node)) != 0) {
+        return res;
+    }
+
+    return vfs_ftruncate(ioctx, node, length);
+}
+
+int sys_ftruncate(int fd, off_t length) {
+    struct ofile *of = get_fd(fd);
+    if (!of) {
+        return -EBADF;
+    }
+    if (of->flags & OF_SOCKET) {
+        kwarn("truncate() on socket\n");
+        return -EINVAL;
+    }
+    return vfs_ftruncate(get_ioctx(), of->file.vnode, length);
+}
+
 int sys_chdir(const char *filename) {
     userptr_check(filename);
     return vfs_setcwd(get_ioctx(), filename);