Date: Thu, 27 Mar 1997 18:56:02 +0100 (MET) From: hans@brandinnovators.com (Hans Zuidam) To: hackers@freebsd.org Subject: driver panic Message-ID: <199703271756.SAA00260@truk.brandinnovators.com>
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Hi,
I have a driver which does:
/*
* As long as there's data, try to fill the output buffer to
* it's maximum size. If the number of bytes is not a multiple
* of four round down, effectively forgetting up to three bytes.
*/
while ((n = min((BUFSIZE - bp->b_olen), uio->uio_resid)) != 0) {
if (n & 0x3) n &= ~0x3;
if (n > 0) {
uiomove(((u_char *) bp->b_obuf) + bp->b_olen, n, uio);
bp->b_olen += n;
}
else {
splx(s);
return 0;
}
/*
* As long as there's something in the output buffer, write it.
*/
while (bp->b_olen) {
...
}
...
}
while a test program did:
u_long wo = 0L;
r = write(fd, (char *) wo, 4);
which is obviously wrong. What makes me wonder is why this causes
a page fault. As far as I can see uiomove() is the only one
accessing the write buffer. When I do the right thing (i.e. (char *) &wo)
everything is fine. Anyone any idea?
Thanks in advance,
Hans
--
H. Zuidam E-Mail: hans@brandinnovators.com
Brand Innovators B.V. P-Mail: P.O. Box 1377
de Pinckart 54 5602 BJ Eindhoven, The Netherlands
5674 CC Nuenen Tel. +31 40 2631134, Fax. +31 40 2831138
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