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Blame SOURCES/kvm-pc-bios-s390-ccw-Silence-GCC-11-stringop-overflow-wa.patch

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From c5b348e6d0334333295332c55fc4be51ce2668b8 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
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Date: Thu, 22 Apr 2021 16:59:11 +0200
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Subject: [PATCH 33/39] pc-bios/s390-ccw: Silence GCC 11 stringop-overflow
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 warning
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Jon Maloy <jmaloy@redhat.com>
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RH-MergeRequest: 24: v7:  Add support for building qemu-kvm with clang and safe-stack
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RH-Commit: [6/11] 92851a154f2425363aa1f5ed2bb12740f589229e (jmaloy/qemu-kvm-centos-jon)
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RH-Bugzilla: 1939509 1940132
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RH-Acked-by: Danilo Cesar Lemes de Paula <ddepaula@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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When building on Fedora 34 (gcc version 11.0.0 20210210) we get:
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  In file included from pc-bios/s390-ccw/main.c:11:
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  In function ‘memset’,
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      inlined from ‘boot_setup’ at pc-bios/s390-ccw/main.c:185:5,
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      inlined from ‘main’ at pc-bios/s390-ccw/main.c:288:5:
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  pc-bios/s390-ccw/libc.h:28:14: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
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     28 |         p[i] = c;
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        |         ~~~~~^~~
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The offending code is:
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  memset((char *)S390EP, 0, 6);
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where S390EP is a const address:
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  #define S390EP 0x10008
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The compiler doesn't know how big that pointed area is, so it assume that
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its length is zero. This has been reported as BZ#99578 to GCC:
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"gcc-11 -Warray-bounds or -Wstringop-overread warning when accessing a
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pointer from integer literal"
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578
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As this warning does us more harm than good in the BIOS code (where
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lot of direct accesses to low memory are done), silence this warning
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for all BIOS objects.
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Suggested-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Message-Id: <20210422145911.2513980-1-philmd@redhat.com>
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Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
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Message-Id: <20210502174836.838816-4-thuth@redhat.com>
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[thuth: Use the pre-existing cc-option macro instead of adding a new one]
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Reviewed-by: Cornelia Huck <cohuck@redhat.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit da231910d33084ccf63f07de210b145e0fa31d98)
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 pc-bios/s390-ccw/Makefile | 1 +
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 1 file changed, 1 insertion(+)
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diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
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index f0fe84c9eb..83fb1afb73 100644
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--- a/pc-bios/s390-ccw/Makefile
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+++ b/pc-bios/s390-ccw/Makefile
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@@ -30,6 +30,7 @@ OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o menu.o \
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 	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o dasd-ipl.o
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 QEMU_CFLAGS := -Wall $(filter -W%, $(QEMU_CFLAGS))
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+QEMU_CFLAGS += $(call cc-option,-Werror $(QEMU_CFLAGS),-Wno-stringop-overflow)
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 QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -fno-common -fPIE
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 QEMU_CFLAGS += -fwrapv -fno-strict-aliasing -fno-asynchronous-unwind-tables
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 QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
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-- 
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2.27.0
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