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Subject: Re: [PATCH] uprobes/x86: fix detection of 32-bit user mode
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <alpine.DEB.2.21.1908240202220.1939@nanos.tec.linutronix.de>
Date:   Fri, 23 Aug 2019 17:13:25 -0700
Cc:     Sebastian Mayr <me@sam.st>, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Dmitry Safonov <dsafonov@virtuozzo.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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Message-Id: <DE4AECCC-AFBE-4DA7-A229-B6B870E06B1D@amacapital.net>
References: <20190728152617.7308-1-me@sam.st> <alpine.DEB.2.21.1908232343470.1939@nanos.tec.linutronix.de> <alpine.DEB.2.21.1908240142000.1939@nanos.tec.linutronix.de> <32D5D6B1-B29E-426E-90B6-48565A3B8F3B@amacapital.net> <alpine.DEB.2.21.1908240200070.1939@nanos.tec.linutronix.de> <alpine.DEB.2.21.1908240202220.1939@nanos.tec.linutronix.de>
To:     Thomas Gleixner <tglx@linutronix.de>
Sender: linux-kernel-owner@vger.kernel.org
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> On Aug 23, 2019, at 5:03 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>=20
>> On Sat, 24 Aug 2019, Thomas Gleixner wrote:
>> On Fri, 23 Aug 2019, Andy Lutomirski wrote:
>>>> On Aug 23, 2019, at 4:44 PM, Thomas Gleixner <tglx@linutronix.de> wrote=
:
>>>>=20
>>>>>> On Sat, 24 Aug 2019, Thomas Gleixner wrote:
>>>>>> On Sun, 28 Jul 2019, Sebastian Mayr wrote:
>>>>>>=20
>>>>>> -static inline int sizeof_long(void)
>>>>>> +static inline int sizeof_long(struct pt_regs *regs)
>>>>>> {
>>>>>> -    return in_ia32_syscall() ? 4 : 8;
>>>>>=20
>>>>> This wants a comment.
>>>>>=20
>>>>>> +    return user_64bit_mode(regs) ? 8 : 4;
>>>>=20
>>>> The more simpler one liner is to check
>>>>=20
>>>>   test_thread_flag(TIF_IA32)
>>>=20
>>> I still want to finish killing TIF_IA32 some day.  Let=E2=80=99s please n=
ot add new users.
>>=20
>> Well, yes and no. This needs to be backported ....
>=20
> And TBH the magic in user_64bit_mode() is not pretty either.
>=20
>=20

It=E2=80=99s only magic on Xen. I should probably stick a cpu_feature_enable=
d(X86_FEATURE_XENPV) in there instead.=