[Bug 1564918] Re: glibc/s390: Save and restore fprs/vrs while resolving symbols.

[Gary Gaydos]

** Package changed: ubuntu => glibc (Ubuntu)

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Title:
  glibc/s390: Save and restore fprs/vrs while resolving symbols.

Status in glibc package in Ubuntu:
  New

Bug description:
  == Comment: #0 - Stefan Liebler <STLI at de.ibm.com> - 2016-04-01 08:33:44 ==
  On s390, no fpr/vrs were saved while resolving a symbol
  via _dl_runtime_resolve/_dl_runtime_profile.

  According to the abi, the fpr-arguments are defined as call clobbered.
  In leaf-functions, gcc 4.9 and newer can use fprs for saving/restoring gprs
  instead of saving them to the stack.
  If gcc do this in one of the resolver-functions, then the floating point
  arguments of a library-function are invalid for the first library-function-call.
  Thus, this patch (see below) saves/restores the fprs around the resolving code.

  The same could occur for vector registers. Furthermore an ifunc-resolver
  could also clobber the vector/floating point argument registers.
  Thus this patch provides the further variants _dl_runtime_resolve_vx/
  _dl_runtime_profile_vx, which are used if the kernel claims, that
  we run on a machine with vector registers.

  Furthermore, if _dl_runtime_profile calls _dl_call_pltexit,
  the pointers to inregs-/outregs-structs were setup invalid.
  Now they point to the correct location in the stack-frame.
  Before branching back to the caller, the return values are now
  restored instead of containing the return values of the
  _dl_call_pltexit() call.
  On s390-32, an endless loop occurs if _dl_call_pltexit() should be called.
  Now, this code-path branches to this function instead of just after the
  preceding basr-instruction.

  (Picked from upstream commits 4603c51ef7989d7eb800cdd6f42aab206f891077
  and d8a012c5c9e4bfc1b8db2bc6deacb85b44a2e1eb)


  Starting with z13, vector registers can also occur as argument registers.
  Thus the passed input/output register structs for
  la_s390_[32|64]_gnu_plt[enter|exit] functions should reflect those new
  registers. This patch extends these structs La_s390_regs and La_s390_retval
  and adjusts _dl_runtime_profile() to handle those fields in case of
  running on a z13 machine.

  (picked from upstream commit 5cdd1989d1d2f135d02e66250f37ba8e767f9772)


  
  These upstream patches are also backported to glibc 2.23 release branch:
  S390: Save and restore fprs/vrs while resolving symbols.
  https://sourceware.org/git/?p=glibc.git;a=commit;h=d93f04543c68c461bd90294751f5fa532a24680c

  S390: Extend structs La_s390_regs / La_s390_retval with vector-registers.
  https://sourceware.org/git/?p=glibc.git;a=commit;h=0eb234232eaf925fe4dca3bd60a3e1b4a7ab2882

  Please pull both and add it to ubuntu glibc package.

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