On Tue, May 15, 2018 at 11:04:44PM +0100, Maciej W. Rozycki wrote:
> Having PR_FP_MODE_FRE (i.e. Config5.FRE) set without PR_FP_MODE_FR (i.e.
> Status.FR) is not supported as the lone purpose of Config5.FRE is to
> emulate Status.FR=0 handling on FPU hardware that has Status.FR=1
> hardwired[1][2]. Also we do not handle this case elsewhere, and assume
> throughout our code that TIF_HYBRID_FPREGS and TIF_32BIT_FPREGS cannot
> be set both at once for a task, leading to inconsistent behaviour if
> this does happen.
>
> Return unsuccessfully then from prctl(2) PR_SET_FP_MODE calls requesting
> PR_FP_MODE_FRE to be set with PR_FP_MODE_FR clear. This corresponds to
> modes allowed by `mips_set_personality_fp'.
>
> References:
>
> [1] "MIPS Architecture For Programmers, Vol. III: MIPS32 / microMIPS32
> Privileged Resource Architecture", Imagination Technologies,
> Document Number: MD00090, Revision 6.02, July 10, 2015, Table 9.69
> "Config5 Register Field Descriptions", p. 262
>
> [2] "MIPS Architecture For Programmers, Volume III: MIPS64 / microMIPS64
> Privileged Resource Architecture", Imagination Technologies,
> Document Number: MD00091, Revision 6.03, December 22, 2015, Table
> 9.72 "Config5 Register Field Descriptions", p. 288
>
> Cc: stable@xxxxxxxxxxxxxxx # 4.0+
> Fixes: 9791554b45a2 ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS")
> Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxx>
Thanks, applied to mips-fixes, hopefully for 4.17 (but if it misses
tomorrows linux-next it may have to wait 'til 4.18).
Cheers
James
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