qemu-kvm/SOURCES/kvm-pc-bios-s390-ccw-Don-t-use-__bss_start-with-the-larl.patch

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2023-11-07 09:43:59 +00:00
From 7495a51c586818925470fb247882f5ba0f7b0ffd Mon Sep 17 00:00:00 2001
From: Thomas Huth <thuth@redhat.com>
Date: Tue, 27 Jun 2023 09:47:03 +0200
Subject: [PATCH 34/37] pc-bios/s390-ccw: Don't use __bss_start with the "larl"
instruction
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Thomas Huth <thuth@redhat.com>
RH-MergeRequest: 180: Fix misaligned symbol error in the s390-ccw image during qemu-kvm build with binutils 2.40
RH-Bugzilla: 2220866
RH-Acked-by: Cédric Le Goater <clg@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Commit: [4/4] 2483a50c0ed37fa29db649ec44220ac83c215698 (thuth/qemu-kvm-cs9)
start.S currently cannot be compiled with Clang 16 and binutils 2.40:
ld: start.o(.text+0x8): misaligned symbol `__bss_start' (0xc1e5) for
relocation R_390_PC32DBL
According to the built-in linker script of ld, the symbol __bss_start
can actually point *before* the .bss section and does not need to have
any alignment, so in certain situations (like when using the internal
assembler of Clang), the __bss_start symbol can indeed be unaligned
and thus it is not suitable for being used with the "larl" instruction
that needs an address that is at least aligned to halfwords.
The problem went unnoticed so far since binutils <= 2.39 did not
check the alignment, but starting with binutils 2.40, such unaligned
addresses are now refused.
Fix it by loading the address indirectly instead.
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2216662
Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
Suggested-by: Andreas Krebbel <andreas.krebbel@de.ibm.com>
Message-Id: <20230629104821.194859-8-thuth@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit 7cd50cbe4ca3e2860b31b06ec92c17c54bd82d48)
---
pc-bios/s390-ccw/start.S | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
index abd6fe6639..22c1c296df 100644
--- a/pc-bios/s390-ccw/start.S
+++ b/pc-bios/s390-ccw/start.S
@@ -19,7 +19,8 @@ _start:
larl %r15,stack + STACK_SIZE - STACK_FRAME_SIZE /* Set up stack */
/* clear bss */
- larl %r2,__bss_start
+ larl %r2,bss_start_literal /* __bss_start might be unaligned ... */
+ lg %r2,0(%r2) /* ... so load it indirectly */
larl %r3,_end
slgr %r3,%r2 /* get sizeof bss */
ltgr %r3,%r3 /* bss empty? */
@@ -45,7 +46,6 @@ done:
memsetxc:
xc 0(1,%r1),0(%r1)
-
/*
* void disabled_wait(void)
*
@@ -113,6 +113,8 @@ io_new_code:
br %r14
.align 8
+bss_start_literal:
+ .quad __bss_start
disabled_wait_psw:
.quad 0x0002000180000000,0x0000000000000000
enabled_wait_psw:
--
2.39.3