linux-kernel - Re: [PATCH] uprobes/x86: fix detection of 32-bit user mode

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Date:   Sat, 24 Aug 2019 01:44:18 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Sebastian Mayr <me@....st>
cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH] uprobes/x86: fix detection of 32-bit user mode

On Sat, 24 Aug 2019, Thomas Gleixner wrote:
> On Sun, 28 Jul 2019, Sebastian Mayr wrote:
> 
> > -static inline int sizeof_long(void)
> > +static inline int sizeof_long(struct pt_regs *regs)
> >  {
> > -	return in_ia32_syscall() ? 4 : 8;
> 
>   This wants a comment.
> 
> > +	return user_64bit_mode(regs) ? 8 : 4;

The more simpler one liner is to check

    test_thread_flag(TIF_IA32)

which is only true for IA32 and independent of syscalls, exceptions ...

Thanks,

	tglx