Re: Unknown symbol error using stap in 2.6.31 on ARM

[Cipher Chen <cipher dot chen2012 at gmail dot com>]

On Thu, Jan 3, 2013 at 2:44 AM, Josh Stone <jistone@redhat.com> wrote:
> On 12/30/2012 04:40 AM, Cipher Chen wrote:
>> On Sun, Dec 30, 2012 at 5:23 PM, Alexander Lochmann wrote:
>>> try to run stap with "--compatible=1.8".
>>> Stap needs uprobe support for some builtin functions as weel. Using this
>>> option it will use old fashion builtin function.
>>
>>     I'm not sure this would help, since I've already tried version 1.8
>> and snapshot 20122222(?), too(I mean re-install the whole systemtap).
>> And it didn't work either.(current used is 2.0)
>>     Anyway, I'll try that again tomorrow.
>
> I gather from the name "ntfs_watching" that you're not actually trying
> to probe any userspace?  In that case, Alex is referring to the
> probefunc() change, which --compatible=1.8 ought to fix.  I also
> recently added a ppfunc() to git which acts like the old way, parsing
> the function name out of pp().
>
> In any case, it would help if you shared the script you're using, or at
> least enough of it that triggers the issue.
>

In fact, that wasn't a real utrace patch for ARM. I downloaded
utrace.patch for 2.6.31, patched it and wrote some similarly functions
for ARM by myself which were needed when building the kernel, since
that's a really old kernel.

ntfs_watching.stp is a simple script, the only user-space probe would be:
probe process("/path/to/ntfsmount/").function("*") {
  printf("%s\n", probefunc())
}

Thanks,
Cipher

> Thanks,
> Josh