linux-kernel - Re: [PATCH] um: Avoid circular dependency on asm-offsets in pgtable.h

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Message-Id: <20251028101750.3263748-1-tiwei.bie@linux.dev>
Date: Tue, 28 Oct 2025 18:17:50 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: linux@...ssschuh.net
Cc: richard@....at,
	anton.ivanov@...bridgegreys.com,
	johannes@...solutions.net,
	johannes.berg@...el.com,
	linux-um@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	tiwei.btw@...group.com,
	tiwei.bie@...ux.dev
Subject: Re: [PATCH] um: Avoid circular dependency on asm-offsets in pgtable.h

On Tue, 28 Oct 2025 10:02:55 +0100, Thomas Weißschuh wrote:
> Recent changes have added an include of as-layout.h to pgtable.h.
> However this introduces a circular dependency during asm-offsets
> generation as as-layout.h depends on asm-offsets and pgtable.h is an
> input for asm-offsets.
> 
> Building from a clean state results in the following error:
> 
>   CC      arch/um/kernel/asm-offsets.s
> In file included from arch/um/include/asm/pgtable.h:48,
>                  from include/linux/pgtable.h:6,
>                  from include/linux/mm.h:31,
>                  from include/linux/pid_namespace.h:7,
>                  from include/linux/ptrace.h:10,
>                  from include/linux/audit.h:13,
>                  from arch/um/kernel/asm-offsets.c:8:
> arch/um/include/shared/as-layout.h:9:10: fatal error: generated/asm-offsets.h: No such file or directory
>     9 | #include <generated/asm-offsets.h>
>       |          ^~~~~~~~~~~~~~~~~~~~~~~~~
> compilation terminated.
> make[4]: *** [scripts/Makefile.build:182: arch/um/kernel/asm-offsets.s] Error 1
> 
> As the inclusion of as-layout.h in pgtable.h is not yet needed while
> asm-offsets are generated, break the dependency here.
> 
> Fixes: a7f7dbae94a5 ("um: Remove file-based iomem emulation support")
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  arch/um/include/asm/pgtable.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
> index 1a0d7405e97c..3b42b0f45bf6 100644
> --- a/arch/um/include/asm/pgtable.h
> +++ b/arch/um/include/asm/pgtable.h
> @@ -45,7 +45,9 @@ extern unsigned long *empty_zero_page;
>   * area for the same reason. ;)
>   */
>  
> +#ifndef COMPILE_OFFSETS
>  #include <as-layout.h> /* for high_physmem */
> +#endif

Oops, my bad. Thanks for the fix!

Reviewed-by: Tiwei Bie <tiwei.btw@...group.com>

Regards,
Tiwei