read/write: A zero byte read or write is a no-op not an error

diff --git a/Kernel/syscall_fs.c b/Kernel/syscall_fs.c
index 78799a9..24a6265 100644 (file)
--- a/Kernel/syscall_fs.c
+++ b/Kernel/syscall_fs.c
@@ -426,6 +426,9 @@ arg_t _read(void)
        inoptr ino;
        uint8_t flag;
 
+       if (!nbytes)
+               return 0;
+
        if (!valaddr(buf, nbytes))
                return -1;
        /* Set up u_base, u_offset, ino; check permissions, file num. */
@@ -486,6 +489,9 @@ arg_t _write(void)
        inoptr ino;
        uint8_t flag;
 
+       if (!nbytes)
+               return 0;
+
        if (!valaddr(buf, nbytes))
                return -1;
        /* Set up u_base, u_offset, ino; check permissions, file num. */