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

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Date: Sat, 27 Jan 2024 02:00:47 +0800
From: Xi Ruoyao <xry111@...111.site>
To: Jiaxun Yang <jiaxun.yang@...goat.com>, "linux-mips@...r.kernel.org"
	 <linux-mips@...r.kernel.org>
Cc: linux-kernel@...r.kernel.org, Thomas Bogendoerfer
	 <tsbogend@...ha.franken.de>, libc-alpha@...rceware.org, 
	regressions@...ts.linux.dev
Subject: Re: Strange EFAULT on mips64el returned by syscall when another
 thread is forking

On Fri, 2024-01-26 at 20:58 +0800, Xi Ruoyao wrote:
> On Fri, 2024-01-26 at 12:33 +0000, Jiaxun Yang wrote:
> > 
> > 
> > 在2024年1月24日一月 上午10:42，Xi Ruoyao写道：
> > > Hi,
> > > 
> > > When I'm testing Glibc master branch for upcoming 2.39 release, I
> > > noticed an alarming test failure on mips64el:
> > 
> > So apparently it should be tracked as a regression.
> > 
> > #regzbot ^introduced 4bce37a68ff884e821a02a731897a8119e0c37b7
> > 
> > Should we revert it for now?
> 
> I'd say "yes" if we cannot easily patch instruction_pointer() to handle
> delay slot.  Anyway the reversion will be a MIPS-only change.

Phew.  Just tried it and:

arch/mips/mm/fault.c: In function ‘__do_page_fault’:
arch/mips/mm/fault.c:111:26: error: passing argument 1 of ‘expand_stack’ from incompatible pointer type [-Werror=incompatible-pointer-types]
  111 |         if (expand_stack(vma, address))
      |                          ^~~
      |                          |
      |                          struct vm_area_struct *
In file included from ./include/linux/pid_namespace.h:7,
                 from ./include/linux/ptrace.h:10,
                 from arch/mips/mm/fault.c:16:
/include/linux/mm.h:3431:56: note: expected ‘struct mm_struct *’ but argument is of type ‘struct vm_area_struct *’
 3431 | struct vm_area_struct *expand_stack(struct mm_struct * mm, unsigned long addr);
      |                                     ~~~~~~~~~~~~~~~~~~~^~
cc1: some warnings being treated as errors

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University