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Date:   Fri, 26 Aug 2022 21:00:05 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Alexander Potapenko <glider@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Marco Elver <elver@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 11/44] kmsan: add KMSAN runtime core
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On Fri, 26 Aug 2022 17:07:34 +0200 Alexander Potapenko <glider@google.com> wrote:

>
> ...
>
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -14,6 +14,7 @@
>  #include <linux/pid.h>
>  #include <linux/sem.h>
>  #include <linux/shm.h>
> +#include <linux/kmsan.h>
>  #include <linux/mutex.h>
>  #include <linux/plist.h>
>  #include <linux/hrtimer.h>
> @@ -1355,6 +1356,10 @@ struct task_struct {
>  #endif
>  #endif
>  
> +#ifdef CONFIG_KMSAN
> +	struct kmsan_ctx		kmsan_ctx;
> +#endif
> +
>  #if IS_ENABLED(CONFIG_KUNIT)
>  	struct kunit			*kunit_test;
>  #endif

This change causes the arm allnoconfig build to fail.

In file included from <command-line>:
./include/linux/page-flags.h: In function '_compound_head':
./include/linux/page-flags.h:253:44: error: invalid use of undefined type 'const struct page'
  253 |         unsigned long head = READ_ONCE(page->compound_head);
      |                                            ^~
././include/linux/compiler_types.h:335:23: note: in definition of macro '__compiletime_assert'
  335 |                 if (!(condition))                                       \
      |                       ^~~~~~~~~

[10,000 lines snipped]

A simple `make init/do_mounts.o' sets it off.

It's Friday night and I got tired of trying to work out why :(

I don't think it's kmsan's fault - seems to be somewhere between
include/linux/topology.h and its use of
arch/arm/include/asm/topology.h.

Shudder.  arm defconfig is OK.  I think I'll pretend I didn't see this
and push it out anyway and see if someone else has the patience.