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

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Date:	Wed, 15 Aug 2012 14:15:39 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v2 16/31] arm64: ELF definitions

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);

I also don't see a reason to export this. You'd have trouble loading
the elf interpreter module from user space without the elf interpreter.

	Arnd
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