Re: [PATCH] mm/mseal: fix mseal documentation for 32-bit kernels

From: Leon Hwang <leon.hwang@linux.dev>
To: Pedro Falcato <pfalcato@suse.de>
Cc: linux-mm@kvack.org, "Jonathan Corbet" <corbet@lwn.net>,
	"Shuah Khan" <skhan@linuxfoundation.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Liam R . Howlett" <liam@infradead.org>,
	"Lorenzo Stoakes" <ljs@kernel.org>,
	"Vlastimil Babka" <vbabka@kernel.org>,
	"Jann Horn" <jannh@google.com>, "Paul Walmsley" <pjw@kernel.org>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Nathan Chancellor" <nathan@kernel.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Nicolas Schier" <nsc@kernel.org>,
	"Thomas Gleixner" <tglx@kernel.org>,
	"Thomas Weißschuh" <thomas.weissschuh@linutronix.de>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Douglas Anderson" <dianders@chromium.org>,
	"Gary Guo" <gary@garyguo.net>,
	"Anand Moon" <linux.amoon@gmail.com>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH] mm/mseal: fix mseal documentation for 32-bit kernels
Date: Tue, 7 Jul 2026 21:48:02 +0800	[thread overview]
Message-ID: <4320145e-a0ba-40f6-b99b-f01f32634f28@linux.dev> (raw)
In-Reply-To: <akzN_HNJJWBW7htL@pedro-suse.lan>

On 2026/7/7 18:01, Pedro Falcato wrote:
> On Fri, Jul 03, 2026 at 10:50:29PM +0800, Leon Hwang wrote:
>> On 2026/7/3 17:44, Pedro Falcato wrote:
[...]
>>>
>>>>  
>>>>    The following architectures currently support this feature: x86-64, arm64,
>>>> -  loongarch and s390.
>>>> +  loongarch, riscv, and s390.
>>>
>>> This is also useless, every 64-bit architecture will support this.
>>
>>
>> Do you mean dropping this sentence, or this change?
> 
> This sentence (this is not architecture specific...).

Got it.

> 
>>
>>>
>>>>  
>>>>    WARNING: This feature breaks programs which rely on relocating
>>>>    or unmapping system mappings. Known broken software at the time
>>>> diff --git a/init/Kconfig b/init/Kconfig
>>>> index 5230d4879b1c..12bb39f637b1 100644
>>>> --- a/init/Kconfig
>>>> +++ b/init/Kconfig
>>>> @@ -2112,7 +2112,7 @@ config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
>>>>  	  from a kernel perspective.
>>>>  
>>>>  	  After the architecture enables this, a distribution can set
>>>> -	  CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature.
>>>> +	  CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature.
>>>>  
>>>>  	  For complete descriptions of memory sealing, please see
>>>>  	  Documentation/userspace-api/mseal.rst
>>>> diff --git a/mm/mseal.c b/mm/mseal.c
>>>> index 9781647483d1..0464c7b94ab9 100644
>>>> --- a/mm/mseal.c
>>>> +++ b/mm/mseal.c
>>>> @@ -132,8 +132,8 @@ static int mseal_apply(struct mm_struct *mm,
>>>>   *   addr is not a valid address (not allocated).
>>>>   *   end (start + len) is not a valid address.
>>>>   *   a gap (unallocated memory) between start and end.
>>>> - *  -EPERM:
>>>> - *  - In 32 bit architecture, sealing is not supported.
>>>> + *  -EINTR:
>>>> + *   interrupted while waiting for the mmap write lock.
>>>>   * Note:
>>>>   *  user can call mseal(2) multiple times, adding a seal on an
>>>>   *  already sealed memory is a no-action (no error).
>>>
>>> And this whole header needs to be deleted as well. No one's looking at
>>> kernel code for documentation (and if they are, we did a horrendous job
>>> at actually documenting the thing).
>>>
>>
>> Just to confirm, do you mean removing the entire function comment above
>> do_mseal()?
> 
> Yes. Again, not your fault, just old gripes :)
> 

Got it.

Thanks,
Leon