linux-kernel - Re: [PATCH] mips: fix shmctl/semctl/msgctl syscall for o32

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Message-ID: <Z5s-csyOKMCvH3ct@alpha.franken.de>
Date: Thu, 30 Jan 2025 09:55:14 +0100
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Arnd Bergmann <arnd@...db.de>
Cc: Ism Hong <ism.hong@...il.com>, Christian Brauner <brauner@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Heiko Carstens <hca@...ux.ibm.com>, Jeff Xu <jeffxu@...omium.org>,
	Christian Göttsche <cgzones@...glemail.com>,
	"open list:MIPS" <linux-mips@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mips: fix shmctl/semctl/msgctl syscall for o32

On Mon, Jan 27, 2025 at 10:20:49PM +0100, Arnd Bergmann wrote:
> On Mon, Jan 6, 2025, at 12:52, Ism Hong wrote:
> > The commit 275f22148e87 ("ipc: rename old-style shmctl/semctl/msgctl
> > syscalls") switched various architectures to use sys_old_*ctl() with
> > ipc_parse_version, including mips n32/n64. However, for mips o32, commit
> > 0d6040d46817 ("arch: add split IPC system calls where needed") added
> > separate IPC syscalls without properly using the old-style handlers.
> >
> > This causes applications using uClibc-ng to fail with -EINVAL when
> > calling semctl/shmctl/msgctl with IPC_64 flag, as uClibc-ng uses the
> > syscall numbers from kernel headers to determine whether to use the IPC
> > multiplexer or split syscalls. In contrast, glibc is unaffected as it
> > uses a unified feature test macro __ASSUME_DIRECT_SYSVIPC_SYSCALLS
> > (disabled for mips-o32) to make this decision.
> >
> > Fix this by switching the o32 ABI entries for semctl, shmctl and msgctl
> > to use the old-style handlers, matching the behavior of other
> > architectures and fixing compatibility with uClibc-ng.
> >
> > Signed-off-by: Ism Hong <ism.hong@...il.com>
> 
> I just saw this making it into mainline and had another look, sorry
> I hadn't caught it earlier.
> 
> It was an intentional decision to use the new-style IPC_64
> semantics on architectures that didn't already have the
> separate system call.
> 
> You may not like that choice, but it's been done this way
> for seven years now, and as far as I can tell, glibc relies
> on this behavior.
> 
> I think this commit should be reverted, and uclibc be changed
> to implement the kernel ABI for these syscalls.

I've prepared the revert

Thomas.

-- 
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