Date: Fri, 25 Jan 2013 12:22:50 -0800 From: Yuri <yuri@rawbw.com> To: FreeBSD Hackers <hackers@freebsd.org> Subject: Calling ustack(); from DTrace script crashes the user process Message-ID: <5102E99A.2070402@rawbw.com>
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I am calling ustack(); from the 'ioctl' handler called by Xorg process.
My intention is to see the user stack.
On the first few instances I got this error:
dtrace: ERROR: open failed: No such file or directory
-- no file name is mentioned, double-space is printed in the message
After a while the same exact script began to crash Xorg process.
Before crashes occurred I was able to get the truss log, showing that
multiple dev-files failed to open:
5191: open("/dev/dtrace/dtrace",O_RDONLY,00) = 3 (0x3)
5191: open("/dev/dtrace/io",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/dtmalloc",O_RDONLY,00) = 4 (0x4)
5191: open("/dev/dtrace/nfscl",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/nfsclient",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/fbt",O_RDONLY,00) = 5 (0x5)
5191: open("/dev/dtrace/lockstat",O_RDONLY,00) = 6 (0x6)
5191: open("/dev/dtrace/priv",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/sched",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/mac",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/mac_framework",O_RDONLY,00) ERR#2 'No such
file or directory'
5191: open("/dev/dtrace/cbb",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/sctp",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/callout_execute",O_RDONLY,00) ERR#2 'No such
file or directory'
5191: open("/dev/dtrace/vfs",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/proc",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/syscall",O_RDONLY,00) ERR#2 'No such file or
directory'
5191: open("/dev/dtrace/syscall",O_RDONLY,00) ERR#2 'No such file or
directory'
I satisfied all conditions mentioned in https://wiki.freebsd.org/DTrace
on how to run DTrace on 9.0 (I am on 9.1-STABLE). kernel modules are
loaded, see below.
So:
* Why/How ustack kills the user process? (amazing this is even possible)
* Why files like /dev/dtrace/io don't exist?
Maybe some extra-options are required for ustack() to work? If this is
the case this should be mentioned in wiki.
Yuri
# kldstat
Id Refs Address Size Name
3 16 0xffffffff81861000 84c0 opensolaris.ko
4 4 0xffffffff8186a000 53a00 linux.ko
10 1 0xffffffff82612000 9e50 linprocfs.ko
12 1 0xffffffff82627000 25b linux_adobe.ko
13 2 0xffffffff82628000 baa dtraceall.ko
14 1 0xffffffff82629000 4eca profile.ko
15 3 0xffffffff8262e000 4005 cyclic.ko
16 12 0xffffffff82633000 23baaf dtrace.ko
17 1 0xffffffff8286f000 fae8 systrace_freebsd32.ko
18 1 0xffffffff8287f000 109a5 systrace.ko
19 1 0xffffffff82890000 45a8 sdt.ko
20 1 0xffffffff82895000 4938 lockstat.ko
21 1 0xffffffff8289a000 be09 fasttrap.ko
22 1 0xffffffff828a6000 65e2 fbt.ko
23 1 0xffffffff828ad000 4ee4 dtnfsclient.ko
24 1 0xffffffff828b2000 1dbeb nfsclient.ko
25 1 0xffffffff828d0000 47da nfs_common.ko
26 1 0xffffffff828d5000 55ec dtnfscl.ko
27 1 0xffffffff828db000 4597 dtmalloc.ko
28 1 0xffffffff828e0000 44fd dtio.ko
29 1 0xffffffff828e5000 2466 dtrace_test.ko
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