Date: Tue, 10 Dec 2019 15:51:01 -0800 From: David Wolfskill <david@catwhisker.org> To: hackers@freebsd.org Subject: Re: I seem to be getting mixed messages from savecore(8) Message-ID: <20191210235101.GG27431@albert.catwhisker.org> In-Reply-To: <20191208224712.GC1227@albert.catwhisker.org> References: <20191208224712.GC1227@albert.catwhisker.org>
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In case anyone is interested, for the archives:
On Sun, Dec 08, 2019 at 02:47:12PM -0800, David Wolfskill wrote:
> ...
> So: If I understand correctly, "savecore -C" detacts that a dump exists
> on the cited device, but invoking savecore to actually ... save ... the
> dump does not actually do that.
The observed behavior is a result of attempting to implement encrypted
swap: I had successfully arranged to swap to /dev/nda0p5.eli;
apparently performing a read-only open of /dev/nda0p5:
...
1062 int
1063 main(int argc, char **argv)
1064 {
...
1027 /*
1028 * The fileargs capability does not currently provide a way to limit
1029 * ioctls.
1030 */
1031 (void)cap_rights_init(&rights, CAP_PREAD, CAP_WRITE, CAP_IOCTL);
1032 capfa = fileargs_init(argc, argv, checkfor || keep ? O_RDONLY : O_RDWR,
1033 0, &rights, FA_OPEN);
1034 if (capfa == NULL) {
1035 logmsg(LOG_ERR, "fileargs_init(): %m");
1036 exit(1);
1037 }
...
578 static void
579 DoFile(const char *savedir, int savedirfd, const char *device)
580 {
...
618 if (verbose)
619 printf("checking for kernel dump on device %s\n", device);
620
621 fddev = fileargs_open(capfa, device);
622 if (fddev < 0) {
623 logmsg(LOG_ERR, "%s: %m", device);
624 return;
625 }
....
is OK, but read/write ... is not. (Which is not unreasonable.)
> Any suggestions for expressing my request in a way that savecore is a
> bit more likely to accept?
My revised appraoch is to run savecore before starting swapping on
the device (via swapon). That appears to work, though I don't know
if that may cause a problem later on.
(In this environment, swapon is being invoked explicitly in an
/etc/rc.d script, rather than by virtue of /etc/fstab entrues (for
example).)
Peace,
david
--
David H. Wolfskill david@catwhisker.org
Some might think an oath of office is as meaningful as a marriage vow.
See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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