[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

--- Comment #3 from Frank Ch. Eigler <fche at redhat dot com> ---
stap -DSTP_NO_VERREL_CHECK overrides one type of check;
stap -DSTP_NO_BUILDID_CHECK overrides another.

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

Serhei Makarov <me at serhei dot io> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |me at serhei dot io

--- Comment #4 from Serhei Makarov <me at serhei dot io> ---
In fact, recent investigation shows that the version checking based on
Modsymvers (kernel ABI match) and build-id (probed programs) may not be nearly
strict enough for some cases.

To start with, I pushed a patch to force guru-mode modules (much more likely to
crash on the wrong kernel version) to build with CONFIG_MODVERSIONS= and thus
use the older 'vermagic' module mechanism. However, further investigation is
needed to decide how the version-checking mechanisms should work.

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

--- Comment #5 from Frank Ch. Eigler <fche at redhat dot com> ---
commit c8084763b75fe may be breaking stap -g modules on non-fedora kernel
configs.

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |25580


Referenced Bugs:

https://sourceware.org/bugzilla/show_bug.cgi?id=25580
[Bug 25580] lp tracker
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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

--- Comment #6 from Serhei Makarov <me at serhei dot io> ---
This issue came up again in connection with PR25580. My current thinking
outlined below.

Desired: We want to compile a guru-mode module and ship the compiled module.
The module should continue to load on new kernel versions,
as long as the stap compiler would have produced the same module as before.

SystemTap compiles modules differently depending on
- kernel version (explicitly checked by #if preprocessor conditionals)
  - However, the explicit kernel-version #if are written only for
already-released versions. Therefore, the appearance of a new version won't
cause any of these checks to trigger.
- modsymvers (built into the kernel-module build system)
- stapconf results (may change with future kernel version or config tweaks)
- (anything else?)

Checking for modsymvers is given to us by the kernel-module build system.
Although modsymvers only tracks changes to the public kernel ABI,
SystemTap uses both public and private ABIs.
However, changes to private ABIs not detected by stapconf would
not cause the same SystemTap version to start compiling things differently.
In essence, we already assume that updating the kernel but not the SystemTap
module will be safe in this situation.

For the stapconf result, we need to evaluate if the stapconf results are
actually useful to guard against breakage in new kernel versions.

If they are useful, we may need to generate a table of stapconf results for
each new kernel and have it be checked on module load, similarly to modsymvers.
(Not every module uses every stapconf result.)

If they are not, it's sufficient to add an option to relax any explicit
kernel-version checks and then close this bug.

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

--- Comment #7 from Serhei Makarov <me at serhei dot io> ---
Re-enabled the strict vermagic check for guru-mode scripts
after investigating PR24720 and re-testing the patch on PPC.

Also disabled the vacuous UTS_VERSION/UTS_RELEASE checks unless enabled with
STP_ENABLE_VERREL_CHECK.

Before closing the PR, should give a bit of time to see what happens in
testing,
and document in NEWS that the UTS_VERSION/UTS_RELEASE check setting is now
controlled with STP_ENABLE_VERREL_CHECK.

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

--- Comment #8 from Serhei Makarov <me at serhei dot io> ---
Closing the PR as of commit c545de0a9261
Will keep an eye out for the potential issue with PR24720.

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=10280

Serhei Makarov <me at serhei dot io> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #9 from Serhei Makarov <me at serhei dot io> ---
closed

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[Bug translator/10280] New: allow relaxing of `uname -r` matching runtime assertion

[fche at redhat dot com]

On ABI-compatible kernel series such as RHEL5, a module compiled against
an older kernel can sometimes be loaded correctly on later kernels of the
same series.  Systemtap prohibits this by checks in translate.cxx 
(c_unparser:;emit_module_init) that matches UTS_RELEASE against the
compile-time `uname -r`.  This check is valuable in some contexts, but
seems counterproductive here.  So let's give users an option to remove
this check.  

(Perhaps it could be heuristically automated if no highly release/build-specific
data such as debuginfo is used in a given script.)

-- 
           Summary: allow relaxing of `uname -r` matching runtime assertion
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10280

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[Bug translator/10280] allow relaxing of `uname -r` matching runtime assertion ro ABI-compatible kernel series

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2009-07-02 13:55 -------
See also bug #10350.  An empty list of "debuginfo required" may be
used as a trigger for a notification that this script could be eligible
for ABI-portable execution.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|allow relaxing of `uname -r`|allow relaxing of `uname -r`
                   |matching runtime assertion  |matching runtime assertion
                   |                            |ro ABI-compatible kernel
                   |                            |series


http://sourceware.org/bugzilla/show_bug.cgi?id=10280

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