kernel: Implement lseek()

Signed-off-by: Ian Moffett <ian@osmora.org>

4 files changed, 67 insertions, 1 deletions

diff --git a/sys/include/sys/filedesc.h b/sys/include/sys/filedesc.h
index 70b297d..83c32ee 100644
--- a/sys/include/sys/filedesc.h
+++ b/sys/include/sys/filedesc.h
@@ -39,6 +39,10 @@
 #define O_WRONLY 0x00001
 #define O_RDWR   0x00002
 
+#define SEEK_SET    0
+#define SEEK_CUR    1
+#define SEEK_END    2
+
 struct proc;
 
 struct filedesc {
@@ -56,11 +60,12 @@ void fd_close_fdnum(struct proc *td, int fdno);
 ssize_t write(int fd, const void *buf, size_t count);
 int open(const char *pathname, int oflag);
 int read(int fd, void *buf, size_t count);
+off_t lseek(int fd, off_t offset, int whence);
 
 uint64_t sys_write(struct syscall_args *args);
 uint64_t sys_open(struct syscall_args *args);
 uint64_t sys_close(struct syscall_args *args);
 uint64_t sys_read(struct syscall_args *args);
+uint64_t sys_lseek(struct syscall_args *args);
 #endif
-
 #endif
diff --git a/sys/include/sys/syscall.h b/sys/include/sys/syscall.h
index ae2438f..8ebc2da 100644
--- a/sys/include/sys/syscall.h
+++ b/sys/include/sys/syscall.h
@@ -42,6 +42,7 @@ enum {
     SYS_open,
     SYS_close,
     SYS_read,
+    SYS_lseek,
     __MAX_SYSCALLS
 };
 
diff --git a/sys/kern/kern_filedesc.c b/sys/kern/kern_filedesc.c
index 63ffa98..6cdc1ee 100644
--- a/sys/kern/kern_filedesc.c
+++ b/sys/kern/kern_filedesc.c
@@ -339,6 +339,54 @@ read(int fd, void *buf, size_t count)
 }
 
 /*
+ * Reposition the file offset
+ *
+ * @fd: File descriptor.
+ * @offset: Offset for the reposition
+ * @whence: SEEK_SET, SEEK_CUR, or SEEK_END
+ *
+ * TODO: Implement SEEK_END
+ */
+off_t
+lseek(int fd, off_t offset, int whence)
+{
+    struct filedesc *fd_desc;
+    struct vattr vattr;
+
+    fd_desc = fd_from_fdnum(this_td(), fd);
+
+    if (fd_desc == NULL) {
+        return -EBADF;
+    }
+
+    if (vfs_getattr(fd_desc->vnode, &vattr) != 0) {
+        return -1;
+    }
+
+    switch (whence) {
+    case SEEK_SET:
+        if (offset > vattr.size)
+            return -ESPIPE;
+
+        fd_desc->offset = offset;
+        break;
+    case SEEK_CUR:
+        if ((fd_desc->offset + offset) > vattr.size)
+            return -ESPIPE;
+
+        fd_desc->offset += offset;
+        break;
+    case SEEK_END:
+        /* TODO */
+        break;
+    default:
+        return -EINVAL;
+    }
+
+    return fd_desc->offset;
+}
+
+/*
  * arg0: int fd
  * arg1: const void *buf
  * arg2: count
@@ -418,3 +466,14 @@ sys_read(struct syscall_args *args)
     }
     return bytes_read;
 }
+
+/*
+ * arg0: fd
+ * arg1: offset:
+ * arg2: whence
+ */
+uint64_t
+sys_lseek(struct syscall_args *args)
+{
+    return lseek(args->arg0, args->arg1, args->arg2);
+}
diff --git a/sys/kern/kern_syscall.c b/sys/kern/kern_syscall.c
index 0f45469..a630195 100644
--- a/sys/kern/kern_syscall.c
+++ b/sys/kern/kern_syscall.c
@@ -46,4 +46,5 @@ uint64_t(*g_syscall_table[__MAX_SYSCALLS])(struct syscall_args *args) = {
     sys_open,
     sys_close,
     sys_read,
+    sys_lseek,
 };