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    Revert "MIPS: Save/restore MSA context around signals" · 16f77de8
    Paul Burton authored
    This reverts commit eec43a22 "MIPS: Save/restore MSA context around
    signals" and the MSA parts of ca750649
    
     "MIPS: kernel: signal:
    Prevent save/restore FPU context in user memory" (the restore path of
    which appears incorrect anyway...).
    
    The reverted patch took care not to break compatibility with userland
    users of struct sigcontext, but inadvertantly changed the offset of the
    uc_sigmask field of struct ucontext. Thus Linux v3.15 breaks the
    userland ABI. The MSA context will need to be saved via some other
    opt-in mechanism, but for now revert the change to reduce the fallout.
    
    This will have minimal impact upon use of MSA since the only supported
    CPU which includes it (the P5600) is 32-bit and therefore requires that
    the experimental CONFIG_MIPS_O32_FP64_SUPPORT Kconfig option be selected
    before the kernel will set FR=1 for a task, a requirement for MSA use.
    Thus the users of MSA are limited to known small groups of people & this
    patch won't be breaking any previously working MSA-using userland
    outside of experimental settings.
    
    [ralf@linux-mips.org: Fixed rejects.]
    
    Cc: stable@vger.kernel.org
    Reported-by: default avatarJoseph S. Myers <joseph@codesourcery.com>
    Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
    Cc: linux-mips@linux-mips.org
    Cc: stable@vger.kernel.org
    Patchwork: https://patchwork.linux-mips.org/patch/7107/
    
    
    Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    16f77de8