[kvm-unit-tests PATCH v2 0/2] s390x: Avoid gcc 12 warnings - Janis Schoetterl-Glausch

From: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
To: Thomas Huth <thuth@redhat.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Janis Schoetterl-Glausch <scgl@linux.ibm.com>,
	David Hildenbrand <david@redhat.com>,
	kvm@vger.kernel.org, linux-s390@vger.kernel.org
Subject: [kvm-unit-tests PATCH v2 0/2] s390x: Avoid gcc 12 warnings
Date: Fri, 20 May 2022 16:05:44 +0200	[thread overview]
Message-ID: <20220520140546.311193-1-scgl@linux.ibm.com> (raw)

gcc 12 warns if a memory operand to inline asm points to memory in the
first 4k bytes. However, in our case, these operands are fine, either
because we actually want to use that memory, or expect and handle the
resulting exception.

v1 -> v2
 * replace mechanism, don't use pragmas, instead use an extern symbol so
   gcc cannot conclude that the pointer is <4k

   This new extern symbol refers to the lowcore. As a result, code
   generation for lowcore accesses becomes worse.

   Alternatives:
    * Don't use extern symbol for lowcore, just for problematic pointers
    * Hide value from gcc via inline asm
    * Disable the warning globally
    * Use memory clobber instead of memory output
      Use address in register input instead of memory input
          (may require WRITE_ONCE)
    * Don't use gcc 12.0, with newer versions --param=min-pagesize=0 might
      avoid the problem

Janis Schoetterl-Glausch (2):
  s390x: Introduce symbol for lowcore and use it
  s390x: Fix gcc 12 warning about array bounds

 lib/s390x/asm/arch_def.h   |  2 ++
 lib/s390x/asm/facility.h   |  4 +--
 lib/s390x/asm/mem.h        |  4 +++
 lib/s390x/css.h            |  2 --
 lib/s390x/css_lib.c        | 12 ++++----
 lib/s390x/fault.c          | 10 +++----
 lib/s390x/interrupt.c      | 61 +++++++++++++++++++-------------------
 lib/s390x/mmu.c            |  3 +-
 s390x/flat.lds             |  1 +
 s390x/snippets/c/flat.lds  |  1 +
 s390x/css.c                |  4 +--
 s390x/diag288.c            |  4 +--
 s390x/edat.c               |  5 ++--
 s390x/emulator.c           | 15 +++++-----
 s390x/mvpg.c               |  7 ++---
 s390x/sclp.c               |  3 +-
 s390x/skey.c               |  2 +-
 s390x/skrf.c               | 11 +++----
 s390x/smp.c                | 23 +++++++-------
 s390x/snippets/c/spec_ex.c |  5 ++--
 20 files changed, 83 insertions(+), 96 deletions(-)

base-commit: 8719e8326101c1be8256617caf5835b57e819339
-- 
2.33.1