linux-kernel - Re: [PATCH 04/15] binfmt_flat: remove flat_old_ram

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Date:   Tue, 11 Jun 2019 09:36:48 +0200
From:   Christoph Hellwig <hch@....de>
To:     Greg Ungerer <gerg@...ux-m68k.org>
Cc:     Christoph Hellwig <hch@....de>, Michal Simek <monstr@...str.eu>,
        linux-arm-kernel@...ts.infradead.org, linux-c6x-dev@...ux-c6x.org,
        uclinux-h8-devel@...ts.sourceforge.jp,
        linux-m68k@...ts.linux-m68k.org, linux-riscv@...ts.infradead.org,
        linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/15] binfmt_flat: remove flat_old_ram_flag

On Tue, Jun 11, 2019 at 04:04:39PM +1000, Greg Ungerer wrote:
>> index c0e4535dc1ec..18d82fd5f57c 100644
>> --- a/fs/binfmt_flat.c
>> +++ b/fs/binfmt_flat.c
>> @@ -488,7 +488,8 @@ static int load_flat_file(struct linux_binprm *bprm,
>>   	 * fix up the flags for the older format,  there were all kinds
>>   	 * of endian hacks,  this only works for the simple cases
>>   	 */
>> -	if (rev == OLD_FLAT_VERSION && flat_old_ram_flag(flags))
>> +	if (IS_ENABLED(CONFIG_BINFMT_FLAT_OLD_ALWAYS_RAM) &&
>> +	    rev == OLD_FLAT_VERSION)
>
> The flags are from the binary file header here, so this is going to lose
> that check for most platforms (except h8300 where it would always have
> been true).

Indeed.  The old code is:

	if (rev == OLD_FLAT_VERSION && flat_old_ram_flag(flags))
		flags = FLAT_FLAG_RAM;

which for !h8300 evaluates to:

	if (rev == OLD_FLAT_VERSION && flags)
		flags = FLAT_FLAG_RAM;

so basically if any flag was set it was turned into FLAT_FLAG_RAM.
Was that really intentional?  I guess even if it wasn't the is no
point in changing this historic behavior now.

So I guess what we could do it something like:

	if (rev == OLD_FLAT_VERSION &&
	    (flags || IS_ENABLED(CONFIG_BINFMT_FLAT_OLD_ALWAYS_RAM)))
		flags = FLAT_FLAG_RAM;