Hi Nick,
On Thu, 15 Mar 2018 17:33:31 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> On Thu, 15 Mar 2018 11:05:01 -0700
> Nick Kirsch <nick@xxxxxxxxxx> wrote:
>
> > Hi!
> >
> > I’m having some issues with symbol resolution; namely, perf probe
> > seems to think it’s happily attaching to the symbol
> > (nfs_readpages:362) I’m looking for and yet it shows up as a
> > different symbol (nfs_symlink_filter+36).
>
> I don't have a 3.10 kernel installed. Below you attach a probe to
> nfs_readpages:46, which is the 46th line after the function entry
> point. Can you do an objdump of the nfs.ko to see where
> nfs_symlink_filter is? As it may just be the symbol that corresponds to
> the location perf found reading the dwarf information.
Could you list the probe event by perf-probe ("perf probe -l")
instead of dumping kprobe_events?
If it is on an incorrect address, the listed line should be wrong.
And could you also check the perf version? ("perf -v")
Old perf might have that problem.
Thanks,
>
> -- Steve
>
>
> >
> > I’d love some help!
> >
> > # uname -a
> >
> > Linux a-b06-u47 3.10.0-693.2.2.el7.x86_64 #1 SMP Sat Sep 9 03:55:24
> > EDT 2017 x86_64 x86_64 x86_64 GNU/Linux
> >
> > # perf probe -v
> > -m /usr/lib/debug/lib/modules/3.10.0-693.2.2.el7.x86_64/kernel/fs/nfs/nfs.ko.debug
> > -a 'nfs_readpages:46 pgm->pg_bytes_written' probe-definition(0):
> > nfs_readpages:46 pgm->pg_bytes_written symbol:nfs_readpages
> > file:(null) line:46 offset:0 return:0 lazy:(null) parsing arg:
> > pgm->pg_bytes_written into pgm, pg_bytes_written(1) 1 arguments No
> > kprobe blacklist support, ignored Open Debuginfo
> > file: /usr/lib/debug/usr/lib/modules/3.10.0-693.2.2.el7.x86_64/kernel/fs/nfs/nfs.ko.debug
> > Try to find probe point from debuginfo. Matched function:
> > nfs_readpages [143625] Probe point found: nfs_readpages+362
> > Searching 'pgm' variable in context.
> > Converting variable pgm into trace event.
> > converting pg_bytes_written in pgm
> > pg_bytes_written type is long unsigned int.
> > Found 1 probe_trace_events.
> > Opening /sys/kernel/debug/tracing//kprobe_events write=1
> > Writing event:
> > p:probe/nfs_readpages /usr/lib/debug/usr/lib/modules/3.10.0-693.2.2.el7.x86_64/kernel/fs/nfs/nfs.ko.debug:nfs_symlink_filler+36
> > pg_bytes_written=+16(%ax):u64 Added new event: probe:nfs_readpages
> > (on nfs_readpages:46
> > in /usr/lib/debug/usr/lib/modules/3.10.0-693.2.2.el7.x86_64/kernel/fs/nfs/nfs.ko.debug
> > with pg_bytes_written=pgm->pg_bytes_written)
> >
> > [root@a-b06-u47 tracing]# cat kprobe_events
> > p:probe/nfs_readpages /usr/lib/debug/usr/lib/modules/3.10.0-693.2.2.el7.x86_64/kernel/fs/nfs/nfs.ko.debug:nfs_symlink_filler+36
> > pg_bytes_written=+16(%ax):u64
> >
> >
> > Thanks!
> >
> > Nick--
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>
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--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
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