Date: Mon, 14 Apr 1997 12:32:38 +0200 From: Martin Kammerhofer <dada@freepass.tu-graz.ac.at> To: FreeBSD-gnats-submit@freebsd.org Subject: kern/3288: addition of a -f (force) option to "write_mfs_in_kernel.c" Message-ID: <199704141032.MAA14186@freepass.tu-graz.ac.at> Resent-Message-ID: <199704141040.DAA02758@freefall.freebsd.org>
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>Number: 3288
>Category: kern
>Synopsis: addition of a -f (force) option to "write_mfs_in_kernel.c"
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Mon Apr 14 03:40:37 PDT 1997
>Last-Modified:
>Originator: Martin Kammerhofer
>Organization:
Graz University of Technology
>Release: FreeBSD 2.2.1-RELEASE i386
>Environment:
>Description:
I4m a FreeBSD user who (inspired by the handbooks chapter
FreeBSD internals/The FreeBSD Booting Process/Interesting combinations)
made myself custom bootfloppies.
During development the MFS inside the kernel changes frequently
and therefore altered MFS-images are written into the development
kernel.
Unfortunately the (undocumented) utility write_mfs_in_kernel allows
this only ONCE because there4s a check for all zeroes.
My proposed patch eliminates the need to relink the kernel every time
a (non-kernel) file is changed and therefore saves a lot of time.
>How-To-Repeat:
>Fix:
Index: write_mfs_in_kernel.c
--- /usr/src/release/write_mfs_in_kernel.c Tue Apr 25 05:45:18 1995
+++ mfs2kernel.c Thu Jan 16 16:29:58 1997
@@ -21,17 +22,33 @@
#include <sys/stat.h>
#include <ufs/ffs/fs.h>
+static int force = 0; /* don't check for zeros, may corrupt kernel */
+
+int
main(int argc, char **argv)
{
- unsigned char *buf_kernel, *buf_fs, *p,*q;
- int fd_kernel, fd_fs;
+ unsigned char *buf_kernel, *buf_fs, *p,*q, *prog;
+ int fd_kernel, fd_fs, ch, errs=0;
struct stat st_kernel, st_fs;
u_long l;
- if (argc < 3) {
- fprintf(stderr,"Usage:\n\t%s kernel fs\n");
+ prog= *argv;
+ while ((ch = getopt(argc, argv, "f")) != EOF)
+ switch(ch) {
+ case 'f':
+ force = 1 - force;
+ break;
+ default:
+ errs++;
+ }
+ argc -= optind;
+ argv += optind;
+
+ if (errs || argc != 2) {
+ fprintf(stderr,"Usage:\n\t%s [-f] kernel fs\n", prog);
exit(2);
}
+ --argv; /* original prog did not use getopt(3) */
fd_kernel = open(argv[1],O_RDWR);
if (fd_kernel < 0) { perror(argv[1]); exit(2); }
fstat(fd_kernel,&st_kernel);
@@ -51,16 +68,17 @@
goto found;
fprintf(stderr,"MFS filesystem signature not found in %s\n",argv[1]);
exit(1);
- found:
- for(l=0,q= p + SBOFF; l < st_fs.st_size - SBOFF ; l++,q++ )
- if (*q)
- goto fail;
+found:
+ if (!force)
+ for(l=0,q= p + SBOFF; l < st_fs.st_size - SBOFF ; l++,q++ )
+ if (*q)
+ goto fail;
memcpy(p+SBOFF,buf_fs+SBOFF,st_fs.st_size-SBOFF);
lseek(fd_kernel,0L,SEEK_SET);
if (st_kernel.st_size != write(fd_kernel,buf_kernel,st_kernel.st_size))
{ perror(argv[1]); exit(2); }
exit(0);
- fail:
+fail:
l += SBOFF;
fprintf(stderr,"Obstruction in kernel after %ld bytes (%ld Kbyte)\n",
l, l/1024);
@@ -68,3 +86,12 @@
(u_long)st_fs.st_size, (u_long)st_fs.st_size/1024);
exit(1);
}
+
+/*
+ * I added a '-f' option to force writing the image into the kernel, even when
+ * there is already data (i.e. not zero) in the written area. This is useful
+ * to rewrite a changed MFS-image. Beware: If the written image is larger than
+ * the space reserved in the kernel (with option MFS_ROOT) then
+ * THIS WILL CORRUPT THE KERNEL!
+ * */
>Audit-Trail:
>Unformatted:
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