linux-kernel - Re: [PATCH v2] x86/Kconfig: Fix allyesconfig

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Message-ID: <a589599f-e069-4aaf-aed6-5cc02b322f1f@roeck-us.net>
Date: Wed, 16 Apr 2025 17:42:10 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Andrew Morton <akpm@...ux-foundation.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>, kasan-dev@...glegroups.com,
 linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2] x86/Kconfig: Fix allyesconfig

On 4/16/25 17:03, Andrew Morton wrote:
> On Wed, 16 Apr 2025 16:05:59 -0700 Guenter Roeck <linux@...ck-us.net> wrote:
> 
>> 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 KASAN for test builds.
>>
> 
> Excluding KASAN from COMPILE_TEST builds is regrettable.
> 
> Can we address this some other way?  One way might be to alter or
> disable the KERNEL_IMAGE_SIZE check if COMPILE_TEST?  That will be sad
> for anyone who tries to boot a COMPILE_TEST kernel, but who the heck
> does that?

As mentioned before, increasing KERNEL_IMAGE_SIZE did not help.
However, it turns out that this works:

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

I'll send v3.

Guenter