linux-kernel - Re: [PATCH v4 5/6] add listmount(2) syscall

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Message-ID: <28c6b616-84d7-4f7e-bf82-eb32e53e631b@roeck-us.net>
Date: Wed, 10 Jan 2024 21:12:10 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Miklos Szeredi <mszeredi@...hat.com>, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
 linux-man@...r.kernel.org, linux-security-module@...r.kernel.org,
 Karel Zak <kzak@...hat.com>, Ian Kent <raven@...maw.net>,
 David Howells <dhowells@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <christian@...uner.io>, Amir Goldstein
 <amir73il@...il.com>, Matthew House <mattlloydhouse@...il.com>,
 Florian Weimer <fweimer@...hat.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v4 5/6] add listmount(2) syscall

On 1/10/24 16:32, Linus Torvalds wrote:
> On Wed, 10 Jan 2024 at 14:23, Guenter Roeck <linux@...ck-us.net> wrote:
>>
>> with this patch in the tree, all sh4 builds fail with ICE.
>>
>> during RTL pass: final
>> In file included from fs/namespace.c:11:
>> fs/namespace.c: In function '__se_sys_listmount':
>> include/linux/syscalls.h:258:9: internal compiler error: in change_address_1, at emit-rtl.c:2275
> 
> We do have those very ugly SYSCALL_DEFINEx() macros, but I'm not
> seeing _anything_ that would be odd about the listmount case.
> 
> And the "__se_sys" thing in particular is just a fairly trivial wrapper.
> 
> It does use that asmlinkage_protect() thing, and it is unquestionably
> horrendously ugly (staring too long at <linux/syscalls.h> has been
> known to cause madness and despair), but we do that for *every* single
> system call and I don't see why the new listmount entry would be
> different.
> 

I don't have much of a clue either, but here is a hint: The problem is
only seen if CONFIG_MMU=n. I tested with all configurations in
arch/sh/configs.

Guenter