Page fault at USB attachment code

[Farhan Khan]

Hi all,

I am writing a simple USB network device driver skeleton, just to learn the framework. What I think is fairly simple code is having a kernel panic when it hits the attachment code.

The code and kgdb output are below. I apologize, its been some time since I used kgdb, so I am not sure what the next step I should do to debug this.

---------------------
static int
skel_usb_attach(device_t self)
{
 struct usb_attach_arg *uaa = device_get_ivars(self);
 struct skel_usb_softc *uc = device_get_softc(self);
 struct skel_softc *sc = uc->sc_sc;
 struct ieee80211com *ic = &sc->sc_ic;

 device_set_usb_desc(self);
 uc->uc_udev = uaa->device;
 sc->sc_dev = self;
 ic->ic_name = device_get_nameunit(self);

 return 0;
}
---------------------

When I run kgdb, I get the following output.

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sudo kgdb -n last
GNU gdb (GDB) 8.3.1 [GDB v8.3.1 for FreeBSD]
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Reading symbols from /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.full...

Unread portion of the kernel message buffer:
Matched!
skel0 on uhub0
skel0: <ATHEROS USB2.0 WLAN, rev 1.10/ff.ff, addr 2> on usbus0

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address = 0x7170
fault code = supervisor write data, page not present
instruction pointer = 0x20:0xffffffff8271f094
stack pointer = 0x28:0xfffffe00036f5930
frame pointer = 0x28:0xfffffe00036f5950
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
current process = 15 (usbus0)
trap number = 12
panic: page fault
cpuid = 0
time = 1577299341
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00036f5590
vpanic() at vpanic+0x17e/frame 0xfffffe00036f55f0
panic() at panic+0x43/frame 0xfffffe00036f5650
trap_fatal() at trap_fatal+0x386/frame 0xfffffe00036f56b0
trap_pfault() at trap_pfault+0x99/frame 0xfffffe00036f5730
trap() at trap+0x2a3/frame 0xfffffe00036f5860
calltrap() at calltrap+0x8/frame 0xfffffe00036f5860
--- trap 0xc, rip = 0xffffffff8271f094, rsp = 0xfffffe00036f5930, rbp = 0xfffffe00036f5950 ---
skel_usb_attach() at skel_usb_attach+0x34/frame 0xfffffe00036f5950
device_attach() at device_attach+0x3ca/frame 0xfffffe00036f5990
device_probe_and_attach() at device_probe_and_attach+0x70/frame 0xfffffe00036f59c0
usb_probe_and_attach_sub() at usb_probe_and_attach_sub+0x150/frame 0xfffffe00036f5a10
usb_probe_and_attach() at usb_probe_and_attach+0x463/frame 0xfffffe00036f5ae0
uhub_explore() at uhub_explore+0x753/frame 0xfffffe00036f5b50
usb_bus_explore() at usb_bus_explore+0x11a/frame 0xfffffe00036f5b70
usb_process() at usb_process+0x103/frame 0xfffffe00036f5bb0
fork_exit() at fork_exit+0x80/frame 0xfffffe00036f5bf0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00036f5bf0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
KDB: enter: panic

warning: Could not load shared library symbols for if_skel_usb.ko.
Do you need "set solib-search-path" or "set sysroot"?
---------------------

Note: I am testing this with an Atheros USB device.

Thanks!

--
Farhan Khan
PGP Fingerprint: 1312 89CE 663E 1EB2 179C 1C83 C41D 2281 F8DA C0DE