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

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Message-Id: <20251028-uml-offsets-circular-v1-1-601c363cfaaa@weissschuh.net>
Date: Tue, 28 Oct 2025 10:02:55 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Richard Weinberger <richard@....at>, 
 Anton Ivanov <anton.ivanov@...bridgegreys.com>, 
 Johannes Berg <johannes@...solutions.net>, 
 Tiwei Bie <tiwei.btw@...group.com>
Cc: Johannes Berg <johannes.berg@...el.com>, linux-um@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH] um: Avoid circular dependency on asm-offsets in pgtable.h

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
 
 #define VMALLOC_OFFSET	(__va_space)
 #define VMALLOC_START	((high_physmem + VMALLOC_OFFSET) & ~(VMALLOC_OFFSET-1))

---
base-commit: aa3e6faf620b1091ae85b07c0106918d48fcce05
change-id: 20251028-uml-offsets-circular-64bd45b0e172

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>