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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 30 Mar 2017 12:29:21 -0700
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Subject: Re: syscall_get_error() && TS_ checks
To: Andy Lutomirski <luto@amacapital.net>
Cc: Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
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        Jan Kratochvil <jan.kratochvil@redhat.com>,
        Pedro Alves <palves@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "the arch/x86 maintainers" <x86@kernel.org>,
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On Thu, Mar 30, 2017 at 12:21 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>
> Huh?  Aren't those REX prefixes interpreted as INC instructions or
> similar in compat mode?

Hmm. I think you're right. So it's not like x32 that runs in long mode
but then would use the 64-bit ptrace interface anyway.

Your statement that 64-bit gdb sometimes uses 32-bit compat ptrace
makes me shudder. Why?

Don't even tell me. I suspect I'm happier not knowing.

                   Linus