[Bug 1971612] Re: [UBUNTU 22.04] GLIBC: Adding new s390 platform IBM z16

[Frank Heimes]

ignoring impish, since it's eol

2.36-0ubuntu2 is still in kinetic-proposed, hence status Fix Committed

** Changed in: glibc (Ubuntu Impish)
       Status: Fix Committed => Invalid

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Title:
  [UBUNTU 22.04] GLIBC: Adding new s390 platform IBM z16

Status in Ubuntu on IBM z Systems:
  In Progress
Status in glibc package in Ubuntu:
  Fix Committed
Status in glibc source package in Impish:
  Invalid
Status in glibc source package in Jammy:
  Fix Released
Status in glibc source package in Kinetic:
  Fix Committed

Bug description:
  SRU Justification:
  ==================

  [Impact]

   * This is a hardware enablement SRU to improve IBM z16 support.

   * A fatal glibc error is dumped if glibc was build with an
     architecture level set for z16, but run on an older machine.
     (See dl-hwcap-check.h.)

   * Hence z16 is added as new s390 platform,

   * the new IBM z16 is added to platform string array,

   * the macro _DL_PLATFORMS_COUNT is incremented.

   * '_dl_hwcaps_subdir' is extended by "z16" if HWCAP_S390_VXRS_PDE2
     is set,

   * and 'tst-glibc-hwcaps.c' is extended in order to test z16 via
     new marker5.

  [Test Plan]

   * An IBM zSystems (or LinuxONE) system,
     with Ubuntu 22.04 LTS installed.

   * Install the updated libc6 package on different zSystems
     hardware generations for regression testing, since
     the patched libc6 should not cause any changed behavior
     or impact on existing IBM zSystems hardware.

   * Test of the glibc-hwcaps feature is covered by tst-glibc-hwcaps.c test
     from glibc-testsuite.

   * In short: Different shared libraries are placed in the z16/z15/...
     subdirectories.
     A runtime-check tests whether the correct library was loaded on
     the particular machine.

   * IBM is going to test this feature on a z16 as soon as a patched
     libc6 package is available.

  [Where problems could occur]

   * There could be problems with the newly introduced marker5
     (libmarkermod5-1.so) in sysdeps/s390/s390-64/Makefile.
     These should largely occur already at build time,
     or in 'tst-glibc-hwcaps.c'.

   * The increased 'DL_PLATFORMS_COUNT' shouldn't harm.

   * Problems could occur is the hardware capabilities (hwcap) are not properly
     identified at 'dl-hwcap-check.h' and 'dl-hwcaps-subdirs.c'.

   * Wrong (not existing) capabilities might be assumed that could
     eventually lead to crashes in attempts to use them.

   * The majority of the changes are under sysdeps/s390 and with that
     hardware specific, other are in script and Makefile.

  [Other Info]

   * IBM z16 exploitation is introduced with 22.04 LTS, hence
     this patch is not needed for older Ubuntu releases.
  __________

  After IBM z16 has been announced, we need to add the new s390 platform
  in glibc.

  S390: Add new s390 platform z16.
  https://sourceware.org/git/?p=glibc.git;a=commit;h=2376944b9e5c0364b9fb473e4d8dabca31b57167

  Backport to glibc 2.35 release branch:
  https://sourceware.org/git/?p=glibc.git;a=commit;h=6583d534458e7f8beec8d0766b6db0bdaae6749c

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