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Re: [PATCH v2 4/4] pc-bios/s390-ccw: Don't use __bss_start with the "lar

From: Eric Farman
Subject: Re: [PATCH v2 4/4] pc-bios/s390-ccw: Don't use __bss_start with the "larl" instruction
Date: Tue, 27 Jun 2023 06:44:32 -0400
User-agent: Evolution 3.48.3 (3.48.3-1.fc38)

On Tue, 2023-06-27 at 09:47 +0200, Thomas Huth wrote:
> 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 using the real start address of the .bss section instead.
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2216662
> Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
> Suggested-by: Nick Clifton <nickc@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  pc-bios/s390-ccw/start.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Eric Farman <farman@linux.ibm.com>

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