Markos Chandras <markos.chandras@xxxxxxxxxx> writes:
> Hi,
>
> On Tue, Feb 24, 2015 at 01:17:33PM +0000, Måns Rullgård wrote:
>> This patch (well, the variant that made it into 4.0-rc1) breaks
>> MIPS_ABI_FP_DOUBLE (the gcc default) apps on MIPS32.
>>
>
> Thanks for the report.
>
>> > +void mips_set_personality_fp(struct arch_elf_state *state)
>> > +{
>> > + /*
>> > + * This function is only ever called for O32 ELFs so we should
>> > + * not be worried about N32/N64 binaries.
>> > + */
>> >
>> > - case MIPS_ABI_FP_XX:
>> > - case MIPS_ABI_FP_ANY:
>> > - if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT))
>> > - set_thread_flag(TIF_32BIT_FPREGS);
>> > - else
>> > - clear_thread_flag(TIF_32BIT_FPREGS);
>> > + if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT))
>> > + return;
>>
>> The problem is here. In a 32-bit configuration, MIPS_O32_FP64_SUPPORT
>> is always disabled, so the FP mode doesn't get set. Simply deleting
>> those two lines makes things work again, but that's probably not the
>> right fix.
>>
> I had the impression that the loader would have set the FP mode earlier on.
> But that only may happen with the latest version of the tools.
>
> Perhaps instead of dropping these two lines we need a similar check on the
> arch_elf_pt_proc so we don't mess with the default FPI abi?
>
> Having said that, dropping these two lines should be fine, it just means you
> do a little bit of extra work when loading your ELF files to check for ABI
> compatibility which shouldn't matter in your case.
There's another early return like this in arch_check_elf() which should
probably go as well, or everything will end up with the default mode.
--
Måns Rullgård
mans@xxxxxxxxx
