linux-kernel - Re: [PATCH 1/2] kselftests: mm: Fix wrong __NR

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Message-ID: <109a9f01-0c5c-49f3-b956-91bc789a1c44@collabora.com>
Date: Tue, 24 Sep 2024 11:21:36 +0500
From: Muhammad Usama Anjum <Usama.Anjum@...labora.com>
To: Shuah Khan <skhan@...uxfoundation.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>,
 David Hildenbrand <david@...hat.com>, Peter Xu <peterx@...hat.com>,
 "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
 Andrea Arcangeli <aarcange@...hat.com>, Kim Phillips <kim.phillips@....com>
Cc: Usama.Anjum@...labora.com, kernel@...labora.com, linux-mm@...ck.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH 1/2] kselftests: mm: Fix wrong __NR_userfaultfd value

On 9/23/24 9:02 PM, Shuah Khan wrote:
> On 9/22/24 23:35, Muhammad Usama Anjum wrote:
>> ...
>>
>>>> grep -rnIF "#define __NR_userfaultfd"
>>>> tools/include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd
>>>> 282
>>>> arch/x86/include/generated/uapi/asm/unistd_32.h:374:#define
>>>> __NR_userfaultfd 374
>>>> arch/x86/include/generated/uapi/asm/unistd_64.h:327:#define
>>>> __NR_userfaultfd 323
>>>> arch/x86/include/generated/uapi/asm/unistd_x32.h:282:#define
>>>> __NR_userfaultfd (__X32_SYSCALL_BIT + 323)
>>>> arch/arm/include/generated/uapi/asm/unistd-eabi.h:347:#define
>>>> __NR_userfaultfd (__NR_SYSCALL_BASE + 388)
>>>> arch/arm/include/generated/uapi/asm/unistd-oabi.h:359:#define
>>>> __NR_userfaultfd (__NR_SYSCALL_BASE + 388)
>>>> include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
>>>>
>>>> The number is dependent on the architecture. The above data shows that:
>>>> x86    374
>>>> x86_64    323
>>>
>>> Correct and the generated header files do the right thing and it is
>>> good to
>>> include them as this patch does.
>>>
>>> This is a good find and fix. I wish you explained this in your
>>> changelog.
>>> Please add more details when you send v2.
>> I'm sending v2
>>
>>>
>>> There could be other issues lurking based on what I found.
>>>
>>> The other two files are the problem where they hard code it to 282
>>> without
>>> taking the __NR_SYSCALL_BASE for the arch into consideration:
>>>
>>> tools/include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
>>> include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
>>>
>>>>
>>>> I'm unable to find the history of why it is set to 282 in unistd.h and
>>>> when this problem happened.
>>>
>>> According to git history it is added in the following commit to
>>> include/uapi/asm-generic/unistd.h:
>>>
>>> 09f7298100ea9767324298ab0c7979f6d7463183
>>> Subject: [PATCH] userfaultfd: register uapi generic syscall (aarch64)
>>>
>>> and it is added in the following commit to
>>> tools/include/uapi/asm-generic/unistd.h
>>> 34b009cfde2b8ce20a69c7bfd6bad4ce0e7cd970
>>> Subject: [PATCH] tools include: Grab copies of arm64 dependent unistd.h
>>> files
>>>
>>> I think, the above defines from include/uapi/asm-generic/unistd.h and
>>> tools/include/uapi/asm-generic/unistd.h should be removed.
>>>
>>> Maybe others familiar with userfaultfd can determine the best course of
>>> action.
>>> We might have other NR_ defines in these two files that are causing
>>> problems
>>> for tests and tools that we haven't uncovered yet.
>> Added authors of these patches.
>>
> 
> Thank you. Would you be able top follow up on this and send patches
> to remove these defines if it deemed to be the correct solution?
Yeah, sure. I'll follow up and fix the issue.

> 
> thanks,
> -- Shuah
> 
> 

-- 
BR,
Muhammad Usama Anjum