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# dbx -k /vmunix /dev/mem
This command invokes dbx with the kernel debugging flag, −k, which
maps kernel addresses to make kernel debugging easier. The /vmunix and
/dev/mem parameters cause the debugger to operate on the running kernel.
Once in the dbx environment, you use dbx commands to display process IDs
and trace execution of processes. You can perform the same tasks using the
kdbx debugger. The following example shows the dbx command you use to
display process IDs:
(dbx) kps
PID COMM
00000 kernel idle
00001 init
00014 kloadsrv
00016 update
.
.
.
If you want to trace the execution of the kloadsrv daemon, use the dbx
command to set the $pid symbol to the process ID of the kloadsrv daemon.
Then, enter the t command:
(dbx) set $pid = 14
(dbx) t
> 0 thread_block() ["/usr/sde/build/src/kernel/kern/sched_prim.c":1623, 0xfffffc0000\
43d77c]
1 mpsleep(0xffffffff92586f00, 0x11a, 0xfffffc0000279cf4, 0x0, 0x0) ["/usr/sde/build\
/src/kernel/bsd/kern_synch.c":411, 0xfffffc000040adc0]
2 sosleep(0xffffffff92586f00, 0x1, 0xfffffc000000011a, 0x0, 0xffffffff81274210) ["/usr/sde\
/build/src/kernel/bsd/uipc_socket2.c":654, 0xfffffc0000254ff8]
3 sosbwait(0xffffffff92586f60, 0xffffffff92586f00, 0x0, 0xffffffff92586f00, 0x10180) ["/usr\
/sde/build/src/kernel/bsd/uipc_socket2.c":630, 0xfffffc0000254f64]
4 soreceive(0x0, 0xffffffff9a64f658, 0xffffffff9a64f680, 0x8000004300000000, 0x0) ["/usr/sde\
/build/src/kernel/bsd/uipc_socket.c":1297, 0xfffffc0000253338]
5 recvit(0xfffffc0000456fe8, 0xffffffff9a64f718, 0x14000c6d8, 0xffffffff9a64f8b8,\
0xfffffc000043d724) ["/usr/sde/build/src/kernel/bsd/uipc_syscalls.c":1002,\
0xfffffc00002574f0]
6 recvfrom(0xffffffff81274210, 0xffffffff9a64f8c8, 0xffffffff9a64f8b8, 0xffffffff9a64f8c8,\
0xfffffc0000457570) ["/usr/sde/build/src/kernel/bsd/uipc_syscalls.c":860,\
0xfffffc000025712c]
7 orecvfrom(0xffffffff9a64f8b8, 0xffffffff9a64f8c8, 0xfffffc0000457570, 0x1, 0xfffffc0000456fe8)\
["/usr/sde/build/src/kernel/bsd/uipc_syscalls.c":825, 0xfffffc000025708c]
8 syscall(0x120024078, 0xffffffffffffffff, 0xffffffffffffffff, 0x21, 0x7d) ["/usr/sde\
/build/src/kernel/arch/alpha/syscall_trap.c":515, 0xfffffc0000456fe4
9 _Xsyscall(0x8, 0x12001acb8, 0x14000eed0, 0x4, 0x1400109d0) ["/usr/sde/build\
/src/kernel/arch/alpha/locore.s":1046, 0xfffffc00004486e4]
(dbx) exit
Often, looking at the trace of a process that is hanging or has unexpectedly
stopped running reveals the problem. Once you find the problem, you can
modify system parameters, restart daemons, or take other corrective actions.
For more information about the commands you can use to debug the running
kernel, see Section 2.1 and Section 2.2.
1–4 Introduction to Kernel Debugging