Only mmap() on regular files; mmap() on /dev/stdin will happily map as

much as we ask for but only the first page will be usable. (We could get
the actual size with ioctl(FIONREAD) and mmap() that but it would need
to be done in the parent - I think just using read() is simpler.)

diff --git a/usr.bin/file/file.c b/usr.bin/file/file.c
index 406e64b..2d65e65 100644 (file)
--- a/usr.bin/file/file.c
+++ b/usr.bin/file/file.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: file.c,v 1.42 2015/05/29 11:59:01 nicm Exp $ */
+/* $OpenBSD: file.c,v 1.43 2015/05/29 12:33:41 nicm Exp $ */
 
 /*
  * Copyright (c) 2015 Nicholas Marriott <nicm@openbsd.org>
@@ -405,26 +405,28 @@ load_file(struct input_file *inf)
        size_t  used;
 
        inf->size = inf->msg->sb.st_size;
-       if (inf->size > FILE_READ_SIZE)
+       if (inf->size == 0 && S_ISREG(inf->msg->sb.st_mode))
+               return (0); /* empty file */
+       if (inf->size == 0 || inf->size > FILE_READ_SIZE)
                inf->size = FILE_READ_SIZE;
-       if (inf->size == 0) {
-               if (!S_ISREG(inf->msg->sb.st_mode))
-                       inf->size = FILE_READ_SIZE;
-               else
-                       return (0);
-       }
+
+       if (!S_ISREG(inf->msg->sb.st_mode))
+               goto try_read;
 
        inf->base = mmap(NULL, inf->size, PROT_READ, MAP_PRIVATE, inf->fd, 0);
-       if (inf->base == MAP_FAILED) {
-               inf->base = fill_buffer(inf->fd, inf->size, &used);
-               if (inf->base == NULL) {
-                       xasprintf(&inf->result, "cannot read '%s' (%s)",
-                           inf->path, strerror(errno));
-                       return (1);
-               }
-               inf->size = used;
-       } else
-               inf->mapped = 1;
+       if (inf->base == MAP_FAILED)
+               goto try_read;
+       inf->mapped = 1;
+       return (0);
+
+try_read:
+       inf->base = fill_buffer(inf->fd, inf->size, &used);
+       if (inf->base == NULL) {
+               xasprintf(&inf->result, "cannot read '%s' (%s)", inf->path,
+                   strerror(errno));
+               return (1);
+       }
+       inf->size = used;
        return (0);
 }