linux-kernel - Re: [PATCH v2 16/31] arm64: ELF definitions

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Message-ID: <20120816102300.GG31784@mudshark.cambridge.arm.com>
Date:	Thu, 16 Aug 2012 11:23:00 +0100
From:	Will Deacon <will.deacon@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 16/31] arm64: ELF definitions

On Wed, Aug 15, 2012 at 03:15:39PM +0100, Arnd Bergmann wrote:
> On Tuesday 14 August 2012, Catalin Marinas wrote:
> > +
> > +void elf_set_personality(int personality)
> > +{
> > +       switch (personality & PER_MASK) {
> > +       case PER_LINUX:
> > +               clear_thread_flag(TIF_32BIT);
> > +               break;
> > +       case PER_LINUX32:
> > +               set_thread_flag(TIF_32BIT);
> > +               break;
> > +       default:
> > +               pr_warning("Process %s tried to assume unknown personality %d\n",
> > +                          current->comm, personality);
> > +               return;
> > +       }
> > +
> > +       current->personality = personality;
> > +}
> > +EXPORT_SYMBOL(elf_set_personality);
> 
> This looks wrong: PER_LINUX/PER_LINUX32 decides over the output of the
> uname system call, while TIF_32BIT decides over the instruction set
> when returning to user space. You definitely should not set the personality
> to the value you pass from the elf loader. Instead, just do
> 
> #define SET_PERSONALITY(ex) clear_thread_flag(TIF_32BIT);
> #defined COMPAT_SET_PERSONALITY(ex) set_thread_flag(TIF_32BIT);

In this case, won't uname be incorrect (aarch64l) for aarch32 tasks (which
expect something like armv8l)?

Will
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