Markos Chandras <markos.chandras@xxxxxxxxxx> writes:
> The previous implementation did not cover all possible FPU combinations
> and it silently allowed ABI incompatible objects to be loaded with the
> wrong ABI. For example, the previous logic would set the FP_64 ABI as
> the matching ABI for an FP_XX object combined with an FP_64A object.
> This was wrong, and the matching ABI should have been FP_64A.
> The previous logic is now replaced with a new one which determines
> the appropriate FPU mode to be used rather than the FP ABI. This has
> the advantage that the entire logic is much simpler since it is the FPU
> mode we are interested in rather than the FP ABI resulting to code
> simplifications.
>
> Cc: Matthew Fortune <Matthew.Fortune@xxxxxxxxxx>
> Cc: Paul Burton <paul.burton@xxxxxxxxxx>
> Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
> ---
> arch/mips/include/asm/elf.h | 10 +-
> arch/mips/kernel/elf.c | 303 +++++++++++++++++++++++++++-----------------
> 2 files changed, 194 insertions(+), 119 deletions(-)
This patch (well, the variant that made it into 4.0-rc1) breaks
MIPS_ABI_FP_DOUBLE (the gcc default) apps on MIPS32.
> +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.
> - clear_thread_flag(TIF_HYBRID_FPREGS);
> + switch (state->overall_fp_mode) {
> + case FP_FRE:
> + set_thread_fp_mode(1, 0);
> + break;
> + case FP_FR0:
> + set_thread_fp_mode(0, 1);
> + break;
> + case FP_FR1:
> + set_thread_fp_mode(0, 0);
> break;
> -
> default:
> - case FP_ERROR:
> BUG();
> }
> }
> --
> 2.2.2
>
--
Måns Rullgård
mans@xxxxxxxxx
