From: Andy Lutomirski <luto@amacapital.net>
To: NeilBrown <neilb@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Dmitry Safonov <dsafonov@virtuozzo.com>,
Andrew Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>,
Brian Gerst <brgerst@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-tip-commits@vger.kernel.org, jsimmons@infradead.org
Subject: Re: in_compat_syscall() returns from kernel thread for X86_32.
Date: Wed, 17 Oct 2018 19:37:42 -0700 [thread overview]
Message-ID: <CALCETrXB8PE4Ue0BeD0wUS9psLLjpv_pt+nj=SEaj+Nb_dZzUA@mail.gmail.com> (raw)
In-Reply-To: <87h8hkc9fd.fsf@notabene.neil.brown.name>
On Wed, Oct 17, 2018 at 6:48 PM NeilBrown <neilb@suse.com> wrote:
>
>
> Was: Re: [tip:x86/asm] x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()
> On Tue, Apr 19 2016, tip-bot for Dmitry Safonov wrote:
>
> > Commit-ID: abfb9498ee1327f534df92a7ecaea81a85913bae
> > Gitweb: http://git.kernel.org/tip/abfb9498ee1327f534df92a7ecaea81a85913bae
> > Author: Dmitry Safonov <dsafonov@virtuozzo.com>
> > AuthorDate: Mon, 18 Apr 2016 16:43:43 +0300
> > Committer: Ingo Molnar <mingo@kernel.org>
> > CommitDate: Tue, 19 Apr 2016 10:44:52 +0200
> >
> > x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()
> >
> ...
> > @@ -318,7 +318,7 @@ static inline bool is_x32_task(void)
> >
> > static inline bool in_compat_syscall(void)
> > {
> > - return is_ia32_task() || is_x32_task();
> > + return in_ia32_syscall() || in_x32_syscall();
> > }
>
> Hi,
> I'm reply to this patch largely to make sure I get the right people
> .....
>
> This test is always true when CONFIG_X86_32 is set, as that forces
> in_ia32_syscall() to true.
> However we might not be in a syscall at all - we might be running a
> kernel thread which is always in 64 mode.
> Every other implementation of in_compat_syscall() that I found is
> dependant on a thread flag or syscall register flag, and so returns
> "false" in a kernel thread.
>
> Might something like this be appropriate?
>
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index 2ff2a30a264f..c265b40a78f2 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -219,7 +219,7 @@ static inline int arch_within_stack_frames(const void * const stack,
> #ifndef __ASSEMBLY__
>
> #ifdef CONFIG_X86_32
> -#define in_ia32_syscall() true
> +#define in_ia32_syscall() (!(current->flags & PF_KTHREAD))
> #else
> #define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
> current_thread_info()->status & TS_COMPAT)
>
> This came up in the (no out-of-tree) lustre filesystem where some code
> needs to assume 32-bit mode in X86_32 syscalls, and 64-bit mode in kernel
> threads.
>
I could get on board with:
({WARN_ON_ONCE(current->flags & PF_KTHREAD); true})
The point of these accessors is to be used *in a syscall*.
What on Earth is Lustre doing that makes it have this problem?
next prev parent reply other threads:[~2018-10-18 2:37 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-11 15:22 [PATCH] x86/vdso: add mremap hook to vm_special_mapping Dmitry Safonov
2016-04-11 15:41 ` kbuild test robot
2016-04-11 15:54 ` Dmitry Safonov
2016-04-14 16:32 ` [PATCHv2] " Dmitry Safonov
2016-04-14 22:58 ` Andy Lutomirski
2016-04-15 8:46 ` Dmitry Safonov
2016-04-15 9:18 ` Ingo Molnar
2016-04-15 9:51 ` Dmitry Safonov
2016-04-15 12:08 ` Dmitry Safonov
2016-04-15 13:20 ` [PATCHv3 1/2] " Dmitry Safonov
2016-04-15 13:20 ` [PATCHv3 2/2] x86: rename is_{ia32,x32}_task to in_{ia32,x32}_syscall Dmitry Safonov
2016-04-15 16:52 ` Andy Lutomirski
2016-04-15 16:55 ` Dmitry Safonov
2016-04-15 13:53 ` [PATCHv3 1/2] x86/vdso: add mremap hook to vm_special_mapping kbuild test robot
2016-04-15 14:12 ` [PATCHv4 " Dmitry Safonov
2016-04-15 14:12 ` [PATCHv4 2/2] x86: rename is_{ia32,x32}_task to in_{ia32,x32}_syscall Dmitry Safonov
2016-04-15 16:58 ` [PATCHv4 1/2] x86/vdso: add mremap hook to vm_special_mapping Andy Lutomirski
2016-04-18 11:18 ` Dmitry Safonov
2016-04-18 15:37 ` Andy Lutomirski
2016-04-18 13:43 ` [PATCHv5 1/3] x86: rename is_{ia32,x32}_task to in_{ia32,x32}_syscall Dmitry Safonov
2016-04-18 13:43 ` [PATCHv5 2/3] x86/vdso: add mremap hook to vm_special_mapping Dmitry Safonov
2016-04-18 14:03 ` kbuild test robot
2016-04-18 14:17 ` [PATCHv6 " Dmitry Safonov
2016-04-18 14:23 ` [PATCHv7 " Dmitry Safonov
2016-04-20 16:22 ` Dmitry Safonov
2016-04-21 19:52 ` Andy Lutomirski
2016-04-22 10:45 ` Dmitry Safonov
2016-04-23 23:09 ` [PATCHv5 " kbuild test robot
2016-04-18 13:43 ` [PATCHv5 3/3] selftest/x86: add mremap vdso 32-bit test Dmitry Safonov
2016-04-21 20:01 ` Andy Lutomirski
2016-04-22 11:34 ` Dmitry Safonov
2016-04-19 9:34 ` [tip:x86/asm] x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall() tip-bot for Dmitry Safonov
2016-04-19 11:15 ` Ingo Molnar
2016-04-19 11:35 ` Borislav Petkov
2016-04-19 17:00 ` H. Peter Anvin
2016-04-19 16:04 ` Andy Lutomirski
2016-04-22 8:36 ` Ingo Molnar
2018-10-18 1:47 ` in_compat_syscall() returns from kernel thread for X86_32 NeilBrown
2018-10-18 2:37 ` Andy Lutomirski [this message]
2018-10-18 2:49 ` Al Viro
2018-10-18 4:36 ` NeilBrown
2018-10-18 17:26 ` Andy Lutomirski
2018-10-20 6:02 ` Andreas Dilger
2018-10-20 7:58 ` Andy Lutomirski
2018-10-24 1:47 ` NeilBrown
2018-10-24 13:15 ` Theodore Y. Ts'o
2018-10-24 14:32 ` Theodore Y. Ts'o
2019-01-11 22:21 ` Pavel Machek
2018-10-25 3:46 ` NeilBrown
2018-10-25 4:45 ` Andy Lutomirski
2016-04-25 11:37 ` [PATCHv8 1/2] x86/vdso: add mremap hook to vm_special_mapping Dmitry Safonov
2016-04-25 11:37 ` [PATCHv8 2/2] selftest/x86: add mremap vdso test Dmitry Safonov
2016-04-25 21:39 ` Andy Lutomirski
2016-04-25 21:38 ` [PATCHv8 1/2] x86/vdso: add mremap hook to vm_special_mapping Andy Lutomirski
[not found] ` <e0a10957-ddf7-1bc4-fad6-8b5836628fce@virtuozzo.com>
2016-05-05 11:52 ` Ingo Molnar
2016-05-05 11:55 ` Dmitry Safonov
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