stap and staprun use cases

[David Smith]

Martin Hunt wrote:
> With the changes we are working on to split users into two groups, it is
> a good time to consider how those two groups will use stap and staprun.
> With this in mind, we can make the necessary tweaks to the user
> interface.
> 
> 1. stapdev
> 
> 1A. Compile and Run a script.  Same as now.
>> stap script
> 
> 1B. Just compile a script.  When doing this it will always be desirable
> to give it a meaningful name.
> 
> Now.
>> stap -p4 -km name
>> cp /tmp/stapXXXX/name.ko [destination]
>> rm -rf /tmp/stapXXX
> 
> Proposed.
>> stap -m name
> name.ko is put in the current directory. Module is lot loaded.

With the proposed syntax, you can't name a module and run it in one 
command, as you can now ("stap -m name foo.stp").

Note that you are describing bug #4295, which grew out of #4281.  See 
the latter for a long discussion on this issue.  If I remember 
correctly, we could never come to consensus on this issue.

> 1C. Compile and install a script so stapusr users may use it.
> Now.
>> stap -p4 -km name
>> cp /tmp/stapXXXX/name.ko /lib/modules/`uname -r`/systemtap
>> rm -rf /tmp/stapXXX
> 
> Proposed. add "-i" option for install. Change "-m" to put module in
> current directory and not load it.
>> stap -im name

Unless the /lib/modules/`uname -r`/systemtap directory is writable by 
the stapdev group, this will fail.

> 1D. Load and run a module.
>>From /lib/modules/`uname -r`/systemtap:
>> staprun module[.ko]
> 
>>From anywhere:
>> staprun /path/to/module[.ko]

I believe that currently the '.ko' is required.

> 2. stapusr
> 
> 2A. Compile and Run a script.  Not allowed.
> Proposed:
> stap should reject attempts to compile script unless
> "-m" or "-pX" where X < 5. This is optional. staprun
> will not load the script
> 
> 2B. Just compile a script. Same as 1B. All (not just stapusr) users may
> compile scripts. Justification: Allows users to check that scripts
> compile. Allows them to then use su or sudo and install the module in
> the case where they are not, for some reason, in stapdev.

If they have root access (either through su or sudo) they don't need to 
install the module to run it - "sudo stap foo.stp" should work correctly.

> 2C. Compile and install a script so stapusr users may use it.
> Proposed: Not allowed. stapdev and root users only.
> 
> 2D. Load and run a module.
>>From /lib/modules/`uname -r`/systemtap:
>> staprun module[.ko]
>>From anywhere: Not allowed.

I'm thinking of allowing the above case, by looking in 
/lib/modules/`uname -r`/systemtap for module.ko.  I'm trying to figure 
out the best way to implement it.

>> staprun /path/to/module[.ko]
> If /path/to != "/lib/modules/`uname -r`/systemtap"
> then print error message.

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
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