getting vm_object from allocated memory in kernel

[Alexej Sokolov]

Hello,
I try to allocate a memory in the system call and then I would like to get
vm_object
of allocated space to remap it later:

/* Syscall func */
static int
syscf(struct thread *td, void *sa)
{
...
        vm_offset_t addr;
...
        MALLOC(addr, vm_offset_t, PAGE_SIZE, M_DEVBUF, M_WAITOK | M_ZERO);

/* Then I try to get vm_obj */
        vm_map_lookup(&kernel_map, addr, VM_PROT_ALL,
                        &myentry, &myobject, &mypindex, &myprot, &mywired);
/* OUT */
        vm_map_lookup_done(&kernel_map, myentry);

/* If i try to make system call it work successful but after a few seconds
happens
    kernel panic */

...
}

could anyone give me a tip what I do wrong ?

# kgdb kernel.debug
vmcore.10
/home/alexandre/alexandre-da/misc/crash
kgdb: kvm_nlist(_stopped_cpus):
kgdb: kvm_nlist(_stoppcbs):
[GDB will not be able to debug user-mode threads: /usr/lib/libthread_db.so:
Undefined symbol "ps_pglobal_lookup"]
GNU gdb 6.1.1 [FreeBSD]
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conditions.
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This GDB was configured as "i386-marcel-freebsd".

Unread portion of the kernel message buffer:
kernel trap 12 with interrupts disabled


Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x14
fault code              = supervisor read, page not present
instruction pointer     = 0x20:0xc0589028
stack pointer           = 0x28:0xe7a83758
frame pointer           = 0x28:0xe7a83774
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = resume, IOPL = 0
current process         = 792 (zsh)
panic: from debugger
Uptime: 20m59s
Physical memory: 2034 MB
Dumping 73 MB: 58 42 26 10

#0  doadump () at pcpu.h:195
195     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb)) bt
#0  doadump () at pcpu.h:195
#1  0xc0558c03 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
#2  0xc0558e2c in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:563
#3  0xc0457927 in db_panic (addr=Could not find the frame base for
"db_panic".
) at /usr/src/sys/ddb/db_command.c:433
#4  0xc0458085 in db_command_loop () at /usr/src/sys/ddb/db_command.c:401
#5  0xc0459ab5 in db_trap (type=12, code=0) at
/usr/src/sys/ddb/db_main.c:222
#6  0xc057ed84 in kdb_trap (type=12, code=0, tf=0xe7a83718) at
/usr/src/sys/kern/subr_kdb.c:502
#7  0xc06b3edf in trap_fatal (frame=0xe7a83718, eva=20) at
/usr/src/sys/i386/i386/trap.c:890
#8  0xc06b489a in trap (frame=0xe7a83718) at
/usr/src/sys/i386/i386/trap.c:280
#9  0xc069dacb in calltrap () at /usr/src/sys/i386/i386/exception.s:139
#10 0xc0589028 in propagate_priority (td=0xc5963210) at
/usr/src/sys/kern/subr_turnstile.c:272
#11 0xc05899a9 in turnstile_wait (ts=0xc5083870, owner=0xc5963210,
queue=Variable "queue" is not available.
) at /usr/src/sys/kern/subr_turnstile.c:739
#12 0xc054cdbd in _mtx_lock_sleep (m=0xc14540e8, tid=3312898576, opts=0,
file=0x0, line=0) at /usr/src/sys/kern/kern_mutex.c:416
#13 0xc054d141 in _mtx_lock_flags (m=0xc14540e8, opts=0, file=0x0, line=0)
at /usr/src/sys/kern/kern_mutex.c:186
#14 0xc066c234 in _vm_map_lock (map=0xc145408c, file=0x0, line=0) at
/usr/src/sys/vm/vm_map.c:449
#15 0xc0669e4a in kmem_malloc (map=0xc145408c, size=4096, flags=259) at
/usr/src/sys/vm/vm_kern.c:296
#16 0xc0660a77 in page_alloc (zone=0xc1445780, bytes=4096, pflag=0xe7a8388f
"\002\200\207D�\003", wait=259) at /usr/src/sys/vm/uma_core.c:955
#17 0xc065fb3c in slab_zalloc (zone=0xc1445780, wait=259) at
/usr/src/sys/vm/uma_core.c:820
#18 0xc0660014 in uma_zone_slab (zone=0xc1445780, flags=3) at
/usr/src/sys/vm/uma_core.c:2010
#19 0xc0663286 in uma_zalloc_arg (zone=0xc1445780, udata=0x0, flags=3) at
/usr/src/sys/vm/uma_core.c:2111
#20 0xc05bf62f in cache_enter (dvp=0xc5724770, vp=0x0, cnp=0xe7a83bd0) at
uma.h:277
#21 0xc06521d8 in ufs_lookup (ap=0xe7a83a00) at
/usr/src/sys/ufs/ufs/ufs_lookup.c:446
#22 0xc06c9ee2 in VOP_CACHEDLOOKUP_APV (vop=0xc073a180, a=0xe7a83a00) at
vnode_if.c:153
#23 0xc05bffa0 in vfs_cache_lookup (ap=0xe7a83a84) at vnode_if.h:83
#24 0xc06cbb26 in VOP_LOOKUP_APV (vop=0xc073a6a0, a=0xe7a83a84) at
vnode_if.c:99
#25 0xc05c64c1 in lookup (ndp=0xe7a83ba8) at vnode_if.h:57
#26 0xc05c7118 in namei (ndp=0xe7a83ba8) at
/usr/src/sys/kern/vfs_lookup.c:219
#27 0xc05d4b5d in kern_stat (td=0xc576d210, path=0xbfbe5238 <Address
0xbfbe5238 out of bounds>, pathseg=UIO_USERSPACE, sbp=0xe7a83c18)
    at /usr/src/sys/kern/vfs_syscalls.c:2109
#28 0xc05d4d0f in stat (td=0xc576d210, uap=0xe7a83cfc) at
/usr/src/sys/kern/vfs_syscalls.c:2093
#29 0xc06b44b7 in syscall (frame=0xe7a83d38) at
/usr/src/sys/i386/i386/trap.c:1035
#30 0xc069db30 in Xint0x80_syscall () at
/usr/src/sys/i386/i386/exception.s:196
#31 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)