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

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Message-ID: <b3caeb96-2f48-4efd-a56c-e91dae891b48@linuxfoundation.org>
Date: Mon, 16 Sep 2024 19:56:54 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Muhammad Usama Anjum <Usama.Anjum@...labora.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>,
 John Hubbard <jhubbard@...dia.com>, David Hildenbrand <david@...hat.com>
Cc: kernel@...labora.com, linux-mm@...ck.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 1/2] kselftests: mm: Fix wrong __NR_userfaultfd value

On 9/16/24 00:32, Muhammad Usama Anjum wrote:
> On 9/12/24 8:44 PM, Shuah Khan wrote:
>> On 9/12/24 04:31, Muhammad Usama Anjum wrote:
>>> The value of __NR_userfaultfd was changed to 282 when
>>> asm-generic/unistd.h was included. It makes the test to fail every time
>>> as the correct number of this syscall on x86_64 is 323. Fix the header
>>> to asm/unistd.h.
>>>
>>
>> "please elaborate every time" - I just built on my x86_64 and built
>> just fine.
> The build isn't broken.
> 
>> I am not saying this isn't a problem, it is good to
>> understand why and how it is failing before making the change.
> I mean to say that the test is failing at run time because the correct
> userfaultfd syscall isn't being found with __NR_userfaultfd = 282.
> _NR_userfaultfd's value depends on the header. When asm-generic/unistd.h
> is included, its value (282) is wrong. I've tested on x86_64.
> 

Okay - how do you know this is wrong? can you provide more details.

git grep _NR_userfaultfd
include/uapi/asm-generic/unistd.h:#define __NR_userfaultfd 282
include/uapi/asm-generic/unistd.h:__SYSCALL(__NR_userfaultfd, sys_userfaultfd)
tools/include/uapi/asm-generic/unistd.h:#define __NR_userfaultfd 282

> The fix is simple. Add the correct header which has _NR_userfaultfd = 323.

I need more details on this number.

thanks,
-- Shuah