2023-07-17 08:44:00 +00:00
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From 7495a51c586818925470fb247882f5ba0f7b0ffd Mon Sep 17 00:00:00 2001
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2023-07-12 13:31:57 +00:00
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From: Thomas Huth <thuth@redhat.com>
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Date: Tue, 27 Jun 2023 09:47:03 +0200
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2023-07-17 08:44:00 +00:00
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Subject: [PATCH 34/37] pc-bios/s390-ccw: Don't use __bss_start with the "larl"
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2023-07-12 13:31:57 +00:00
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instruction
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2023-07-17 08:44:00 +00:00
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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: Thomas Huth <thuth@redhat.com>
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RH-MergeRequest: 180: Fix misaligned symbol error in the s390-ccw image during qemu-kvm build with binutils 2.40
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RH-Bugzilla: 2220866
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RH-Acked-by: Cédric Le Goater <clg@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [4/4] 2483a50c0ed37fa29db649ec44220ac83c215698 (thuth/qemu-kvm-cs9)
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2023-07-12 13:31:57 +00:00
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start.S currently cannot be compiled with Clang 16 and binutils 2.40:
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ld: start.o(.text+0x8): misaligned symbol `__bss_start' (0xc1e5) for
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relocation R_390_PC32DBL
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According to the built-in linker script of ld, the symbol __bss_start
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can actually point *before* the .bss section and does not need to have
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any alignment, so in certain situations (like when using the internal
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assembler of Clang), the __bss_start symbol can indeed be unaligned
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and thus it is not suitable for being used with the "larl" instruction
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that needs an address that is at least aligned to halfwords.
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The problem went unnoticed so far since binutils <= 2.39 did not
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check the alignment, but starting with binutils 2.40, such unaligned
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addresses are now refused.
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Fix it by loading the address indirectly instead.
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Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2216662
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Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
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Suggested-by: Andreas Krebbel <andreas.krebbel@de.ibm.com>
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Message-Id: <20230629104821.194859-8-thuth@redhat.com>
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Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit 7cd50cbe4ca3e2860b31b06ec92c17c54bd82d48)
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---
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pc-bios/s390-ccw/start.S | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
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index abd6fe6639..22c1c296df 100644
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--- a/pc-bios/s390-ccw/start.S
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+++ b/pc-bios/s390-ccw/start.S
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@@ -19,7 +19,8 @@ _start:
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larl %r15,stack + STACK_SIZE - STACK_FRAME_SIZE /* Set up stack */
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/* clear bss */
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- larl %r2,__bss_start
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+ larl %r2,bss_start_literal /* __bss_start might be unaligned ... */
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+ lg %r2,0(%r2) /* ... so load it indirectly */
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larl %r3,_end
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slgr %r3,%r2 /* get sizeof bss */
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ltgr %r3,%r3 /* bss empty? */
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@@ -45,7 +46,6 @@ done:
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memsetxc:
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xc 0(1,%r1),0(%r1)
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-
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/*
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* void disabled_wait(void)
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*
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@@ -113,6 +113,8 @@ io_new_code:
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br %r14
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.align 8
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+bss_start_literal:
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+ .quad __bss_start
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disabled_wait_psw:
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.quad 0x0002000180000000,0x0000000000000000
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enabled_wait_psw:
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--
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2.39.3
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