linux-kernel - Re: [PATCH AUTOSEL 5.4 05/16] arm64/mm: Define dummy pud_user

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Date:   Mon, 16 Jan 2023 18:30:47 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        kernel test robot <lkp@...el.com>, akpm@...ux-foundation.org,
        anshuman.khandual@....com, wangkefeng.wang@...wei.com,
        liushixin2@...wei.com, david@...hat.com, tongtiangen@...wei.com,
        yuzhao@...gle.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH AUTOSEL 5.4 05/16] arm64/mm: Define dummy pud_user_exec()
 when using 2-level page-table

On Mon, Jan 16, 2023 at 09:05:08AM -0500, Sasha Levin wrote:
> From: Will Deacon <will@...nel.org>
> 
> [ Upstream commit 4e4ff23a35ee3a145fbc8378ecfeaab2d235cddd ]
> 
> With only two levels of page-table, the generic 'pud_*' macros are
> implemented using dummy operations in pgtable-nopmd.h. Since commit
> 730a11f982e6 ("arm64/mm: add pud_user_exec() check in
> pud_user_accessible_page()"), pud_user_accessible_page() unconditionally
> calls pud_user_exec(), which is an arm64-specific helper and therefore
> isn't defined by pgtable-nopmd.h. This results in a build failure for
> configurations with only two levels of page table:
> 
>    arch/arm64/include/asm/pgtable.h: In function 'pud_user_accessible_page':
> >> arch/arm64/include/asm/pgtable.h:870:51: error: implicit declaration of function 'pud_user_exec'; did you mean 'pmd_user_exec'? [-Werror=implicit-function-declaration]
>      870 |         return pud_leaf(pud) && (pud_user(pud) || pud_user_exec(pud));
>          |                                                   ^~~~~~~~~~~~~
>          |                                                   pmd_user_exec
> 
> Fix the problem by defining pud_user_exec() as pud_user() in this case.
> 
> Link: https://lore.kernel.org/r/202301080515.z6zEksU4-lkp@intel.com
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Will Deacon <will@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

I don't think this patch should be backported to 5.4. It is a fix for a
commit that went in shortly before this one (730a11f982e6). The latter
commit does have a Fixes tag but I guess Will thought it's not worth a
cc stable (and it's up to 5.19 anyway).

-- 
Catalin