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

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Message-ID: <e4e2095e-3280-4bfc-8129-80b8d00d146d@collabora.com>
Date: Mon, 23 Sep 2024 10:35:52 +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

...

>> 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.

> 
> thanks,
> -- Shuah

-- 
BR,
Muhammad Usama Anjum