change the way we found matching tapsets

change the way we found matching tapsets

[Li Guanglei]

Hi,
   The syscall table for PowerPC changed from version to version. In 
order to let LKET works for different kernel versions, I have to deal 
with such changes in my tapsets.

   Formerly I usually do that using the conditional preprocessing 
offered by stap. But I found it will become hard to read and will 
become unmaintainable as more kernel versions are involved. For 
example, it's hard to use conditional preprocessing to define the 
following scenario:

   #if arch is ppc64  then
      #if kernel_ver is 2.6.9 then
            probe definitions
      #elseif kernel_ver is 2.6.15.* then
            probe definitions
      #endif
   #elseif arch is i686 then
      ...
   #endif

   So now I am thinking about using different directories for 
different kernel versions. I found that the syscall table stays almost 
the same for each major kernel version, e.g. the syscall table of all 
2.6.15.* are the same. So I want a directory 2.6.15 to handles all 
2.6.15.* versions(including 2.6.15.1, 2.6.15.2 etc).

   But it seems that stap will found in this order:

Searched 'tapsets//2.6.15.4/ppc64/*.stp', match count 0
Searched 'tapsets//2.6.15.4/*.stp', match count 1
Searched 'tapsets//2.6/ppc64/*.stp', match count 0
Searched 'tapsets//2.6/*.stp', match count 0

It won't look at 2.6.15 directory. So can we change the behavior that 
stap search for tapsets, so that I needn't to create the directories 
like 2.6.15.1, 2.6.15.2 etc.

Re: change the way we found matching tapsets

[Frank Ch. Eigler]

Li Guanglei <guanglei@cn.ibm.com> writes:

> [...] I found that the syscall table stays almost
> the same for each major kernel version, e.g. the syscall table of all
> 2.6.15.* are the same. So I want a directory 2.6.15 to handles all
> 2.6.15.* versions(including 2.6.15.1, 2.6.15.2 etc). [...]

Makes sense to me.  The current search path logic was chosen before
this newfangled four-level a.b.c.d version numbering scheme arrived.

- FChE