Date: Tue, 22 Mar 2005 10:33:55 -0600 From: "Henry Miller" <hank@blackhole.com> To: freebsd-scsi@freebsd.org Subject: scsi_ch issues Message-ID: <380-220053222163355859@blackhole.com>
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I posted a summery of this to -questions earlier this morning (you
can read it there if you want background), I've dug into it more, and
I think there is a bug in =20
cam/scsi/scsi=5Fch=2Ec
function chgetelemstatus=2E
The short summery is my tape changer says that PVOLTAG in pg=5Fhdr is=20
FALSE, (or zeroed latter) in the first request of=20
scsi=5Fread=5Felement=5Fstatus() (which freeBSD uses only to get the lengt=
h
of the data) on one of my changers, and thus chio(1) will not show
the bar code label=2E pg=5Fhdr is not updated to reflect the location
of result of the second call, when this flag is set=2E Worse, it looks
like the results of the first call is a dead pointer by the time it
checks anyway=2E Unless free/malloc work different in the kernel from
userland this is a problem=2E
I've sniped out a lot of extra code so you can see what I mean=2E =20
data =3D (caddr=5Ft)malloc(1024, M=5FDEVBUF, M=5FWAITOK);
--- Fill data to get size
pg=5Fhdr =3D \* data + some offset *\
/*
* Reallocate storage for descriptors and get them from the
* device=2E
*/
free(data, M=5FDEVBUF);
data =3D (caddr=5Ft)malloc(size, M=5FDEVBUF, M=5FWAITOK);
--- Fill data=20
copy=5Felement=5Fstatus(softc, pg=5Fhdr->flags, desc, ces);
Note that pg=5Fhdr is not valid at this point anyway=2E
This more or less happens in 4=2Ex, 5=2Ex and current if I read the code
correctly=2E
Can someone who knows kernel code better than I look at this=2E =20
Should I send a pr=3F
Here is a patch against 4=2E9 (where I first found this problem) that
might help to understand the fix=2E I think it needs to be ported to
all versions=2E (and perhaps netbsd if there is where we get the
code=3F) =20
*** scsi=5Fch=2Ec=2Eold Tue Mar 22 11:16:15 2005
--- scsi=5Fch=2Ec Tue Mar 22 11:09:13 2005
***************
*** 1184,1189 ****
--- 1184,1192 ----
* Fill in the user status array=2E
*/
st=5Fhdr =3D (struct read=5Felement=5Fstatus=5Fheader *)data;
+ pg=5Fhdr =3D (struct read=5Felement=5Fstatus=5Fpage=5Fheader
*)((uintptr=5Ft)st=5Fhdr
+
+ sizeof(struct read=5Felement=5Fstatus=5Fheader));
+
avail =3D scsi=5F2btoul(st=5Fhdr->count);
if (avail !=3D cesr->cesr=5Felement=5Fcount) {
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