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Re: [PATCH 1/5] xen/x86: always consider '/' as a division in assembly
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Wed, 11 Feb 2026 11:01:11 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- Delivery-date: Wed, 11 Feb 2026 11:02:31 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-index: AQHcm0PRpWbQ66MnpUKRg8FXLXanDLV9VOKA
- Thread-topic: [PATCH 1/5] xen/x86: always consider '/' as a division in assembly
Hi Roger,
> On 11 Feb 2026, at 11:46, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>
> On x86 GNU assembler will consider '/' as the start of comment marker for
> some ELF targets. This is incorrect with Xen's usage, which does use '/'
> in assembly files as a mathematical operator.
>
> The behavior of the assembler can be altered by passing the --divide
> option; unconditionally pass this option when available to force the
> expected behavior.
Works to build x86 and arm still working on Mac OS.
>
> Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Cheers
Bertrand
> ---
> Changes since v1:
> - Guard option setting to x86 only.
> - Adjust comment.
> ---
> xen/Makefile | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/xen/Makefile b/xen/Makefile
> index a054315fa4a2..4c83e2a46477 100644
> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -413,6 +413,13 @@ ifneq ($(CONFIG_CC_IS_CLANG),y)
> CFLAGS += -Wa,--strip-local-absolute
> endif
>
> +ifeq ($(CONFIG_X86),y)
> +# The GNU assembler will interpret '/' as a comment start marker instead of a
> +# divide for some ELF targets. Pass --divide when when available to signal
> '/'
> +# is always used as an operator in assembly.
> +$(call cc-option-add,CFLAGS,CC,-Wa$$(comma)--divide)
> +endif
> +
> $(call cc-option-add,AFLAGS,CC,-Wa$$(comma)--noexecstack)
>
> LDFLAGS-$(call ld-option,--warn-rwx-segments) += --no-warn-rwx-segments
> --
> 2.51.0
>
>
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