linux-kernel - [PATCH v3] x86: Disable image size check for test builds

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Message-ID: <20250417010950.2203847-1-linux@roeck-us.net>
Date: Wed, 16 Apr 2025 18:09:50 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: x86@...nel.org
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH v3] x86: Disable image size check for test builds

64-bit allyesconfig builds fail with

x86_64-linux-ld: kernel image bigger than KERNEL_IMAGE_SIZE

Bisect points to commit 6f110a5e4f99 ("Disable SLUB_TINY for build
testing") as the responsible commit. Reverting that patch does indeed
fix the problem. Further analysis shows that disabling SLUB_TINY enables
KASAN, and that KASAN is responsible for the image size increase.

Solve the build problem by disabling the image size check for test
builds.

Fixes: 6f110a5e4f99 ("Disable SLUB_TINY for build testing")
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
v3: Disabled image size check instead of disabling KASAN
    Updated subject to match change
    Updated Cc: list to reflect affected maintainers

v2: Disabled KASAN unconditionally for test builds
    Link: https://lore.kernel.org/lkml/20250416230559.2017012-1-linux@roeck-us.net/

Link to RFC:
    https://lore.kernel.org/lkml/20250414011345.2602656-1-linux@roeck-us.net/

 arch/x86/kernel/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index ccdc45e5b759..647d4f47486d 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -468,8 +468,10 @@ SECTIONS
 /*
  * The ASSERT() sink to . is intentional, for binutils 2.14 compatibility:
  */
+#ifndef CONFIG_COMPILE_TEST
 . = ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
 	   "kernel image bigger than KERNEL_IMAGE_SIZE");
+#endif
 
 /* needed for Clang - see arch/x86/entry/entry.S */
 PROVIDE(__ref_stack_chk_guard = __stack_chk_guard);
-- 
2.45.2