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From:   Daniel Axtens <dja@axtens.net>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        Andrew Morton <akpm@linux-foundation.org>, arnd@arndb.de
Cc:     linux-arch@vger.kernel.org, linux-s390@vger.kernel.org,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 2/4] mm: Make generic arch_is_kernel_initmem_freed() do what it says
In-Reply-To: <1d40783e676e07858be97d881f449ee7ea8adfb1.1633001016.git.christophe.leroy@csgroup.eu>
References: <9ecfdee7dd4d741d172cb93ff1d87f1c58127c9a.1633001016.git.christophe.leroy@csgroup.eu> <1d40783e676e07858be97d881f449ee7ea8adfb1.1633001016.git.christophe.leroy@csgroup.eu>
Date:   Fri, 01 Oct 2021 17:14:41 +1000
Message-ID: <87ilyhmd26.fsf@linkitivity.dja.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

>  #ifdef __KERNEL__
> +/*
> + * Check if an address is part of freed initmem. After initmem is freed,
> + * memory can be allocated from it, and such allocations would then have
> + * addresses within the range [_stext, _end].
> + */
> +#ifndef arch_is_kernel_initmem_freed
> +static int arch_is_kernel_initmem_freed(unsigned long addr)
> +{
> +	if (system_state < SYSTEM_FREEING_INITMEM)
> +		return 0;
> +
> +	return init_section_contains((void *)addr, 1);

Is init_section_contains sufficient here?

include/asm-generic/sections.h says:
 * [__init_begin, __init_end]: contains .init.* sections, but .init.text.*
 *                   may be out of this range on some architectures.
 * [_sinittext, _einittext]: contains .init.text.* sections

init_section_contains only checks __init_*:
static inline bool init_section_contains(void *virt, size_t size)
{
	return memory_contains(__init_begin, __init_end, virt, size);
}

Do we need to check against _sinittext and _einittext?

Your proposed generic code will work for powerpc and s390 because those
archs only test against __init_* anyway. I don't know if any platform
actually does place .init.text outside of __init_begin=>__init_end, but
the comment seems to suggest that they could.

Kind regards,
Daniel