Nuke builtin_mbr.

Those architectures needing either MBR boot code (amd64, i386,
landisk) or special boot partitions (macppc, loongson) have long
used /usr/mdec/mbr to provide that information.

Other architectures should not blindly write i386/amd64 boot code
into the MBR.

Fail quickly if the desired default MBR file is missing.

Prompted by deraadt@, tweak from kettenis@.

diff --git a/sbin/fdisk/fdisk.c b/sbin/fdisk/fdisk.c
index 39e7bbf..24a056a 100644 (file)
--- a/sbin/fdisk/fdisk.c
+++ b/sbin/fdisk/fdisk.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: fdisk.c,v 1.138 2021/09/29 22:55:40 krw Exp $ */
+/*     $OpenBSD: fdisk.c,v 1.139 2021/10/13 13:18:57 krw Exp $ */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -43,14 +43,11 @@
 #define        INIT_MBRBOOTCODE        4
 
 #define        _PATH_MBR               _PATH_BOOTDIR "mbr"
-static unsigned char           builtin_mbr[] = {
-#include "mbrcode.h"
-};
 
 int                    y_flag;
 
 void                   parse_bootprt(const char *);
-void                   get_default_dmbr(const char *, struct dos_mbr *);
+void                   get_default_dmbr(const char *);
 
 static void
 usage(void)
@@ -68,11 +65,7 @@ int
 main(int argc, char *argv[])
 {
        struct mbr               mbr;
-#ifdef HAS_MBR
-       const char              *mbrfile = _PATH_MBR;
-#else
        const char              *mbrfile = NULL;
-#endif
        const char              *errstr;
        int                      ch;
        int                      e_flag = 0, init = 0;
@@ -163,7 +156,7 @@ main(int argc, char *argv[])
        if (pledge("stdio rpath wpath disklabel proc exec", NULL) == -1)
                err(1, "pledge");
 
-       get_default_dmbr(mbrfile, &default_dmbr);
+       get_default_dmbr(mbrfile);
 
        switch (init) {
        case INIT_GPT:
@@ -254,27 +247,29 @@ parse_bootprt(const char *arg)
 }
 
 void
-get_default_dmbr(const char *mbrfile, struct dos_mbr *dmbr)
+get_default_dmbr(const char *mbrfile)
 {
-       ssize_t                 len;
-       int                     fd;
-
-       if (mbrfile == NULL) {
-               memcpy(dmbr, builtin_mbr, sizeof(*dmbr));
-       } else {
-               fd = open(mbrfile, O_RDONLY);
-               if (fd == -1) {
-                       warn("%s", mbrfile);
-                       warnx("using builtin MBR");
-                       memcpy(dmbr, builtin_mbr, sizeof(*dmbr));
-               } else {
-                       len = read(fd, dmbr, sizeof(*dmbr));
-                       close(fd);
-                       if (len == -1)
-                               err(1, "Unable to read MBR from '%s'", mbrfile);
-                       else if (len != sizeof(*dmbr))
-                               errx(1, "Unable to read complete MBR from '%s'",
-                                   mbrfile);
-               }
-       }
+       struct dos_mbr          *dmbr = &default_dmbr;
+       ssize_t                  len, sz;
+       int                      fd;
+
+       if (mbrfile == NULL)
+#ifdef HAS_MBR
+               mbrfile = _PATH_MBR;
+#else
+               return;
+#endif
+
+       fd = open(mbrfile, O_RDONLY);
+       if (fd == -1)
+               err(1, "%s", mbrfile);
+
+       sz = sizeof(*dmbr);
+       len = read(fd, dmbr, sz);
+       close(fd);
+
+       if (len == -1)
+               err(1, "read('%s')", mbrfile);
+       else if (len != sz)
+               errx(1, "read('%s'): read %zd bytes of %zd", mbrfile, len, sz);
 }