From: ebiederm@xmission.com (Eric W. Biederman)
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Brian Gerst <brgerst@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Kees Cook <keescook@chromium.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"the arch\/x86 maintainers" <x86@kernel.org>,
H Peter Anvin <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH 09/20] signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON
Date: Fri, 12 Nov 2021 15:43:23 -0600 [thread overview]
Message-ID: <87wnldnj7o.fsf@email.froward.int.ebiederm.org> (raw)
In-Reply-To: <CAHk-=wjU1Nf+zzFgwE5bAGSq2W9DifmKDsAOFuZcaaHq3vEQ8w@mail.gmail.com> (Linus Torvalds's message of "Fri, 12 Nov 2021 13:24:37 -0800")
Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Fri, Nov 12, 2021 at 1:23 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> But I could see some quick test hack doing it - the IVT at boot is
>> actually not at zero, but at fffxxxxx. 8086 is magic.
>
> .. and it's been too long, and I'm too lazy to check - it may be that
> vm86 mode doesn't even do that magic boot-time address thing.
>
> It's not like we really care about vm86 mode any more, since pretty
> much nobody users it.
As I recall at boot CS == 0xffff0000 EIP == 0x0000fff0 and the cpu is in
16bit mode. Which means the cpu runs the instructions in the last
16bytes of memory at boot up. Which is just enough for a jump somewhere
else. Such as 64K backwards where there is enough space to actual have
enough code to do something.
I don't think vm86 even attempts to emulate that behavior as it is only
concerned about 16bit only cpus and emulation.
In the nobody cares camp I have just sent you a pull request to remove
the ancient (except it wasn't a BUG_ON) and problematic test in the
BUG_ON.
I think that is enough to resolve this.
Eric
next prev parent reply other threads:[~2021-11-12 21:43 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-20 17:32 [PATCH 00/20] exit cleanups Eric W. Biederman
2021-10-20 17:43 ` [PATCH 01/20] exit/doublefault: Remove apparently bogus comment about rewind_stack_do_exit Eric W. Biederman
2021-10-21 16:02 ` Kees Cook
2021-10-20 17:43 ` [PATCH 02/20] exit: Remove calls of do_exit after noreturn versions of die Eric W. Biederman
2021-10-21 16:02 ` Kees Cook
2021-10-21 16:25 ` Eric W. Biederman
2021-10-20 17:43 ` [PATCH 03/20] reboot: Remove the unreachable panic after do_exit in reboot(2) Eric W. Biederman
2021-10-21 16:05 ` Kees Cook
2021-10-20 17:43 ` [PATCH 04/20] signal/sparc32: Remove unreachable do_exit in do_sparc_fault Eric W. Biederman
2021-10-21 16:05 ` Kees Cook
2021-10-20 17:43 ` [PATCH 05/20] signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT Eric W. Biederman
2021-10-21 16:06 ` Kees Cook
2021-10-24 4:24 ` Maciej W. Rozycki
2021-10-25 20:55 ` Eric W. Biederman
2021-10-24 15:27 ` Thomas Bogendoerfer
2021-10-20 17:43 ` [PATCH 06/20] signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) Eric W. Biederman
2021-10-20 19:57 ` Linus Torvalds
2021-10-27 14:24 ` Rich Felker
2021-10-21 16:08 ` Kees Cook
2021-10-20 17:43 ` [PATCH 07/20] signal/powerpc: On swapcontext failure force SIGSEGV Eric W. Biederman
2021-10-21 16:09 ` Kees Cook
2021-10-20 17:43 ` [PATCH 08/20] signal/sparc: In setup_tsb_params convert open coded BUG into BUG Eric W. Biederman
2021-10-21 16:12 ` Kees Cook
2021-10-20 17:43 ` [PATCH 09/20] signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON Eric W. Biederman
2021-10-21 16:15 ` Kees Cook
2021-11-12 15:40 ` Eric W. Biederman
2021-11-12 17:51 ` Brian Gerst
2021-11-12 19:57 ` Eric W. Biederman
2021-11-12 20:40 ` Linus Torvalds
2021-11-12 21:03 ` Eric W. Biederman
2021-11-12 21:23 ` Linus Torvalds
2021-11-12 21:24 ` Linus Torvalds
2021-11-12 21:37 ` [GIT PULL ] signal/vm86_32: Remove pointless test in BUG_ON Eric W. Biederman
2021-11-13 19:15 ` pr-tracker-bot
2021-11-12 21:43 ` Eric W. Biederman [this message]
2021-10-20 17:43 ` [PATCH 10/20] signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved Eric W. Biederman
2021-10-21 16:16 ` Kees Cook
2021-10-21 17:02 ` Eric W. Biederman
2021-10-21 20:33 ` Kees Cook
2021-10-21 23:08 ` Andy Lutomirski
2021-10-24 16:06 ` Eric W. Biederman
[not found] ` <875ytkygfj.fsf_-_@disp2133>
2021-10-25 21:12 ` [PATCH v2 10/32] " Linus Torvalds
2021-10-25 21:28 ` Eric W. Biederman
2021-10-25 22:25 ` Andy Lutomirski
2021-10-25 23:45 ` Linus Torvalds
2021-10-26 0:21 ` Andy Lutomirski
2021-10-20 17:43 ` [PATCH 11/20] signal/s390: Use force_sigsegv in default_trap_handler Eric W. Biederman
2021-10-21 16:17 ` Kees Cook
2021-10-26 9:38 ` Christian Borntraeger
2021-10-28 15:56 ` Eric W. Biederman
2021-10-29 19:32 ` Eric W. Biederman
2021-10-20 17:43 ` [PATCH 12/20] exit/kthread: Have kernel threads return instead of calling do_exit Eric W. Biederman
2021-10-21 11:12 ` Christoph Hellwig
2021-10-21 15:11 ` Eric W. Biederman
2021-10-21 16:21 ` Kees Cook
2021-10-20 17:43 ` [PATCH 13/20] signal: Implement force_fatal_sig Eric W. Biederman
2021-10-20 20:05 ` Linus Torvalds
2021-10-20 21:25 ` Eric W. Biederman
2021-10-25 22:41 ` Andy Lutomirski
2021-10-25 23:15 ` Linus Torvalds
2021-10-26 4:45 ` Eric W. Biederman
2021-10-26 4:57 ` Eric W. Biederman
2021-10-26 16:15 ` Linus Torvalds
2021-10-28 16:33 ` Eric W. Biederman
2021-10-21 16:24 ` Kees Cook
2021-10-21 16:33 ` Eric W. Biederman
2021-10-21 16:39 ` Kees Cook
2021-10-20 17:44 ` [PATCH 14/20] exit/syscall_user_dispatch: Send ordinary signals on failure Eric W. Biederman
2021-10-21 16:25 ` Kees Cook
2021-10-21 16:37 ` Eric W. Biederman
2021-10-21 16:40 ` Kees Cook
2021-10-21 17:05 ` Eric W. Biederman
2021-10-25 22:32 ` Andy Lutomirski
2021-10-21 16:35 ` Gabriel Krisman Bertazi
2021-10-20 17:44 ` [PATCH 15/20] signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails Eric W. Biederman
2021-10-21 16:34 ` Kees Cook
2021-10-21 16:56 ` Eric W. Biederman
2021-10-20 17:44 ` [PATCH 16/20] signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig Eric W. Biederman
2021-10-21 16:34 ` Kees Cook
2021-10-20 17:44 ` [PATCH 17/20] signal/x86: In emulate_vsyscall force a signal instead of calling do_exit Eric W. Biederman
2021-10-21 16:36 ` Kees Cook
2021-10-20 17:44 ` [PATCH 18/20] exit/rtl8723bs: Replace the macro thread_exit with a simple return 0 Eric W. Biederman
2021-10-21 7:06 ` Greg KH
2021-10-21 15:06 ` Eric W. Biederman
2021-10-21 16:37 ` Kees Cook
2021-10-20 17:44 ` [PATCH 19/20] exit/rtl8712: " Eric W. Biederman
2021-10-21 7:07 ` Greg KH
2021-10-21 16:37 ` Kees Cook
2021-10-20 17:44 ` [PATCH 20/20] exit/r8188eu: " Eric W. Biederman
2021-10-21 7:07 ` Greg KH
2021-10-21 16:37 ` Kees Cook
2021-10-20 21:51 ` [PATCH 21/20] signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV) Eric W. Biederman
2021-10-21 8:09 ` Geert Uytterhoeven
2021-10-21 13:33 ` Eric W. Biederman
2021-10-21 8:32 ` Philippe Mathieu-Daudé
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