Date: Wed, 29 Jul 2009 13:23:46 -0400 From: "Chris Harrer" <cjharrer@comcast.net> To: "'Alfred Perlstein'" <alfred@freebsd.org>, "'John Baldwin'" <jhb@freebsd.org> Cc: freebsd-drivers@freebsd.org Subject: RE: Driver development question Message-ID: <000c01ca1071$54991d70$fdcb5850$@net> In-Reply-To: <20090725035643.GT49724@elvis.mu.org> References: <002801ca06f0$b1d42af0$157c80d0$@net> <200907211743.12667.jhb@freebsd.org> <20090722000713.GZ49724@elvis.mu.org> <200907220819.05087.jhb@freebsd.org> <20090725035643.GT49724@elvis.mu.org>
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Warning LONG message below, I figured I'd give as much information as
possible to try and help me along.
> On Tuesday 21 July 2009 8:07:13 pm Alfred Perlstein wrote:
> > * John Baldwin <jhb@freebsd.org> [090721 14:44] wrote:
> > > On Tuesday 21 July 2009 2:34:21 am Marc Loerner wrote:
> > > > Am Dienstag 21 Juli 2009 00:38:56 schrieb Sam Leffler:
> > > > > John Baldwin wrote:
> > > > > > On Friday 17 July 2009 11:10:17 am Chris Harrer wrote:
> > > > > >> Hi All,
> > > > > >>
> > > > > >> I'm hoping someone can point me in the right direction... I'm
> > > > > >> developing a FreeBSD driver for a PCIe card. The driver
controls a
> > > > > >> hardware device that has DRAM and various state information on
it.
> I'm
> > > > > >> trying to mimic functionality I have for other OS support such
that
> I
> > > > > >> can dump memory and state information from the card to a file I
> create
> > > > > >> from within my driver (kernel module).
> > > > > >>
> > > > > >> For example, in a Linux driver I use filp_open to create the
dump
> file
> > > > > >> (represented by fp), then use fp->f_op->write to put
information
> into
> > > > > >> the file.
> > > > > >>
> > > > > >> FreeBSD doesn't have filp_* API's. I've tried searching for
> example
> > > > > >> drivers and googling for file API's from kernel modules to no
> avail.
> > > > > >> Can someone please offer some guidance as to how I might
proceed
> here?
> > > > > >>
> > > > > >> Thanks in advance and any insight would be most appreciated!
> > > > > >
> > > > > > You can look at sys/kern/kern_ktrace.c to see how the ktrace()
> system
> > > > > > call creates a file. I think in general you will wind up using
> > > > > > NDINIT/namei() (to lookup the vnode for a pathname) and then
> vn_open() /
> > > > > > vn_rdwr() / vn_close().
> > > > >
> > > > > man alq(9).
> > > > >
> > > > >
> > > >
> > > > Why not use kern_open, kern_close, kern_preadv, kern_pwritev?
> > >
> > > Those affect the state of the current process by opening a new file
> > > descriptor, etc. That is generally bad practice for a device driver
to be
> > > interfering with a process' state, and it will not work for kernel
> threads.
> > > You can rather easily have userland open a file and then pass the file
> > > descriptor to a driver which can then do operations on a file
directly.
> >
> > If the vnode operations are annoying to wrap ones head around, one
> > could have the driver defer this this to a kernel resident process
> > that the driver would create on attach.
>
> Kernel processes don't have file descriptor tables.
Hi All,
I'm hoping you can provide a bit more guidance here as I'm still struggling
with this and I'm running out of ideas. Again, what I want to do is, some
event (interrupt from an intelligent PCIe card indicating it's "dead") will
cause me to:
1) Open/create a file
2) write raw/random/non-patterned/variable sized data to the file
3) close/save the file
from within my device driver. To this point, I've tried several things
using vn_open, vn_open_cred, alq_open and cutting/massaging the code from
alq_open with no success. I've done this from within the context of my
interrupt handler as well as a timer (callout_init, callout_reset) thread as
well as from a thread I create with kproc_create. In each and every
instance, I get the following crash:
(gdb) bt 15
#0 _mtx_lock_flags (m=0xc0, opts=0x0, file=0xffffffff80611dc0
"/src/FreeBSD/HECTOR/src/sys/kern/vfs_subr.c", line=0x847) at
/src/FreeBSD/HECTOR/src/sys/kern/kern_mutex.c:195
#1 0xffffffff803c8431 in vref (vp=0x0) at
/src/FreeBSD/HECTOR/src/sys/kern/vfs_subr.c:2119
#2 0xffffffff803c02de in namei (ndp=0xffffff80003bfdf2) at
/src/FreeBSD/HECTOR/src/sys/kern/vfs_lookup.c:229
#3 0xffffffff803d6100 in vn_open_cred (ndp=0xffffff80003bfdf2,
flagp=0xffffff8000045a2c, cmode=0x180, cred=0xffffff00014d5000, fp=0x0) at
/src/FreeBSD/HECTOR/src/sys/kern/vfs_vnops.c:133
#4 0xffffffff8023497a in sxg_dump_open_file (adapter=0xffffff80003b4000) at
/src/FreeBSD/HECTOR/src/sys/dev/sxg/sxg.c:5064
#5 0xffffffff8023524a in sxg_dump_thread (arg=<value optimized out>) at
/src/FreeBSD/HECTOR/src/sys/dev/sxg/sxg.c:5170
#6 0xffffffff80235398 in sxg_check_for_hang_timer (arg1=<value optimized
out>) at /src/FreeBSD/HECTOR/src/sys/dev/sxg/sxg.c:4956
#7 0xffffffff80350741 in softclock (arg=<value optimized out>) at
/src/FreeBSD/HECTOR/src/sys/kern/kern_timeout.c:411
#8 0xffffffff80318b08 in intr_event_execute_handlers (p=<value optimized
out>, ie=0xffffff00014d5600) at
/src/FreeBSD/HECTOR/src/sys/kern/kern_intr.c:1146
#9 0xffffffff80319762 in ithread_loop (arg=0xffffff00014da8a0) at
/src/FreeBSD/HECTOR/src/sys/kern/kern_intr.c:1159
#10 0xffffffff80316a9a in fork_exit (callout=0xffffffff803196b0
<ithread_loop>, arg=0xffffff00014da8a0, frame=0xffffff8000045c90) at
/src/FreeBSD/HECTOR/src/sys/kern/kern_fork.c:829
#11 0xffffffff8054dd5e in fork_trampoline () at
/src/FreeBSD/HECTOR/src/sys/amd64/amd64/exception.S:552
#12 0x0000000000000000 in ?? ()
The offending "SIGSEGV, Segmentation fault" is from the following code
(frame 2):
if (dp == NULL) {
dp = fdp->fd_cdir; <----- fdp->fd_cdir = 0
VREF(dp);
FILEDESC_SUNLOCK(fdp);
if (ndp->ni_startdir != NULL) {
vfslocked =
VFS_LOCK_GIANT(ndp->ni_startdir->v_mount);
vrele(ndp->ni_startdir);
VFS_UNLOCK_GIANT(vfslocked);
}
}
The *fdp structure looks like:
(gdb) print *fdp
$4 = {
fd_ofiles = 0xffffff0001345680,
fd_ofileflags = 0xffffff0001345720 "",
fd_cdir = 0x0,
fd_rdir = 0x0,
fd_jdir = 0x0,
fd_nfiles = 0x14,
fd_map = 0xffffff0001345738,
fd_lastfile = 0xffffffff,
fd_freefile = 0x0,
fd_cmask = 0x12,
fd_refcnt = 0x1,
fd_holdcnt = 0x1,
fd_sx = {
lock_object = {
lo_name = 0xffffffff805fc20d "filedesc structure",
lo_flags = 0x2330000,
lo_data = 0x0,
lo_witness = 0xffffff8000206c00
},
sx_lock = 0x11
},
fd_kqlist = {
slh_first = 0x0
},
fd_holdleaderscount = 0x0,
fd_holdleaderswakeup = 0x0
}
In this particular instance, I created a nameidata structure via NDINIT that
is:
(gdb) print *ndp
$2 = {
ni_dirp = 0xffffff8000045a30 "/var/tmp/sxgdump",
ni_segflg = UIO_SYSSPACE,
ni_startdir = 0x0,
ni_rootdir = 0x0,
ni_topdir = 0x0,
ni_dirfd = 0xffffff9c,
ni_vp = 0x0,
ni_dvp = 0x0,
ni_pathlen = 0x11,
ni_next = 0x0,
ni_loopcnt = 0x0,
ni_cnd = {
cn_nameiop = 0x1,
cn_flags = 0x520000c,
cn_thread = 0xffffff00014eb390,
cn_cred = 0xffffff00014d5000,
cn_lkflags = 0x0,
cn_pnbuf = 0xffffff000620c000 "/var/tmp/sxgdump",
cn_nameptr = 0x0,
cn_namelen = 0x0,
cn_consume = 0x0
}
}
I appreciate the guidance you've given to date and I hope you can provide a
few more words of wisdom to me.
Thanks in advance!
Chris
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