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Subject: Re: [PATCH] x86/ptrace: Remove questionable TS_COMPAT usage in ptrace
To: Andy Lutomirski <luto@amacapital.net>
References: <94bda8cd5f326ae5591c80fb5d7c1c22624accec.1466244711.git.luto@kernel.org>
 <b9f316ca-5f79-91f5-1d19-773679778357@palves.net>
 <CALCETrW9guyn4-SqKaPPvcr7cQ5DskwVSKu+WZhMkG5NZHciAg@mail.gmail.com>
 <CALCETrUBSGtvbnokoFWMW_CNmz-9R+ry85hd3NGkH8vMQtUdjw@mail.gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>, Kees Cook <keescook@chromium.org>,
        Borislav Petkov <bp@alien8.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        X86 ML <x86@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pedro Alves <palves@redhat.com>
From: Pedro Alves <pedro@palves.net>
Message-ID: <d55c856c-c033-154b-c6e0-6245fc78d132@palves.net>
Date: Mon, 20 Jun 2016 11:27:02 +0100
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On 06/19/2016 11:09 PM, Andy Lutomirski wrote:
> 
> The latter bit is a mess and is probably broken on current kernels for
> 64-bit gdb attached to a 32-bit process.  (Is it?  All of this stuff
> is a bit of a pain to test.)

The testcase at:

 https://sourceware.org/ml/gdb/2014-05/msg00004.html

still fails for me on Fedora 23 with git master gdb.

Nevermind the misleading URL, that's a kernel patch.

 $ gcc -g -m32 interrupt.c -o interrupt.32
 ...
 (gdb) r
 Starting program: /home/pedro/tmp/interrupt.32 
 talk to me baby
 ^C
 Program received signal SIGINT, Interrupt.
 0xf7fd9d49 in __kernel_vsyscall ()
 (gdb) p func1()
 $1 = 4
 (gdb) c
 Continuing.
 Unknown error 512
 [Inferior 1 (process 20252) exited with code 01]
 (gdb) 

That was a 64-bit gdb.

Note it doesn't fail with fedora 23's gdb, because of a 
fedora-local workaround.

Thanks,
Pedro Alves