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From 609d8661171760c7ead04f64359d47a77c31d474 Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Fri, 23 Apr 2021 10:30:51 +0200
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Subject: [PATCH 29/39] pc-bios/s390-ccw: Use reset_psw pointer instead of
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hard-coded null pointer
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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: [2/11] c65a986104a1830847e772879ca6eaf76c86b2f3 (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 compiling the s390-ccw bios with clang, it emits a warning like this:
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pc-bios/s390-ccw/jump2ipl.c:86:9: warning: indirection of non-volatile null
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pointer will be deleted, not trap [-Wnull-dereference]
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if (*((uint64_t *)0) & RESET_PSW_MASK) {
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^~~~~~~~~~~~~~~~
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pc-bios/s390-ccw/jump2ipl.c:86:9: note: consider using __builtin_trap() or
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qualifying pointer with 'volatile'
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We could add a "volatile" here to shut it up, but on the other hand,
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we also have a pointer variable called "reset_psw" in this file already
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that points to the PSW at address 0, so we can simply use that pointer
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variable instead.
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Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Message-Id: <20210423142440.582188-1-thuth@redhat.com>
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Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit ff77712a8a2e15e5901fad35b9a6bb65974b2e4a)
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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/jump2ipl.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
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index b9c70d64a5..73e4367e09 100644
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--- a/pc-bios/s390-ccw/jump2ipl.c
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+++ b/pc-bios/s390-ccw/jump2ipl.c
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@@ -82,8 +82,8 @@ void jump_to_low_kernel(void)
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jump_to_IPL_code(KERN_IMAGE_START);
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}
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- /* Trying to get PSW at zero address */
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- if (*((uint64_t *)0) & RESET_PSW_MASK) {
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+ /* Trying to get PSW at zero address (pointed to by reset_psw) */
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+ if (*reset_psw & RESET_PSW_MASK) {
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/*
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* Surely nobody will try running directly from lowcore, so
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* let's use 0 as an indication that we want to load the reset
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--
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2.27.0
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