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

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Message-Id: <20250416182828.9e2b312a75ed90b706483250@linux-foundation.org>
Date: Wed, 16 Apr 2025 18:28:28 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Guenter Roeck <linux@...ck-us.net>
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 Wed, 16 Apr 2025 17:17:00 -0700 Guenter Roeck <linux@...ck-us.net> wrote:

> 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?
> 
> I tried increasing the limit. It didn't work. With the RFC I sent earlier
> I made it dependent on allmodconfig, but Linus said I should just disable
> it for test builds (which was the cases anyway until commit 6f110a5e4f99).
> 
> Personally I don't have a preference either way. I can also do nothing and
> stop testing allyesconfig. That would help reducing the load on my testbed,
> so I would be all for it.

How about this?



--- a/arch/x86/kernel/vmlinux.lds.S~a
+++ a/arch/x86/kernel/vmlinux.lds.S
@@ -466,10 +466,19 @@ SECTIONS
 }
 
 /*
- * The ASSERT() sink to . is intentional, for binutils 2.14 compatibility:
+ * COMPILE_TEST kernels can be large - CONFIG_KASAN, for example, can cause
+ * this.  Let's assume that nobody will be running a COMPILE_TEST kernel and
+ * let's assert that fuller build coverage is more valuable than being able to
+ * run a COMPILE_TEST kernel.
+ */
+#ifndef CONFIG_COMPILE_TEST
+/*
+/*
+ * The ASSERT() sync to . is intentional, for binutils 2.14 compatibility:
  */
 . = 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);
_


(contains gratuitous s/sink/sync/)


I'd like to add

#else
	WARN((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
 	   "kernel image bigger than KERNEL_IMAGE_SIZE - kernel probably will not work");
#endif	/* CONFIG_COMPILE_TEST */

but I lack the patience to figure out how to do that.