Re: Strange EFAULT on mips64el returned by syscall when another thread is forking

From: Xi Ruoyao <xry111@xry111.site>
To: Andreas Schwab <schwab@suse.de>, Ben Hutchings <ben@decadent.org.uk>
Cc: linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	libc-alpha@sourceware.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: Strange EFAULT on mips64el returned by syscall when another thread is forking
Date: Thu, 25 Jan 2024 05:38:16 +0800	[thread overview]
Message-ID: <0625c3286a515ccb2ff5f7f58fd2019f81dd512e.camel@xry111.site> (raw)
In-Reply-To: <e8583a3ab0522b4e75ba0ada47b6f093b186fa81.camel@xry111.site>

On Thu, 2024-01-25 at 05:32 +0800, Xi Ruoyao wrote:

/* snip */

> and the "interesting" aspects:
> 
> 1. If I change the third parameter of "read" to any value >= 8, it no
> longer fails.  But it fails with any integer in [1, 8).
> 2. It fails no matter if I initialize buf.
> 3. It does not fail on arm64 (the only other port using
> lock_mm_and_find_vma I have access to).

Correction: I'd not realized many ports use lock_mm_and_find_vma even
before this series of changes.  I also have access to x86_64 and
loongarch64, and the failure seems specific to MIPS.

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University