• Paul Burton's avatar
    MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS · 9791554b
    Paul Burton authored
    Userland code may be built using an ABI which permits linking to objects
    that have more restrictive floating point requirements. For example,
    userland code may be built to target the O32 FPXX ABI. Such code may be
    linked with other FPXX code, or code built for either one of the more
    restrictive FP32 or FP64. When linking with more restrictive code, the
    overall requirement of the process becomes that of the more restrictive
    code. The kernel has no way to know in advance which mode the process
    will need to be executed in, and indeed it may need to change during
    execution. The dynamic loader is the only code which will know the
    overall required mode, and so it needs to have a means to instruct the
    kernel to switch the FP mode of the process.
    
    This patch introduces 2 new options to the prctl syscall which provide
    such a capability. The FP mode of the process is represented as a
    simple bitmask combining a number of mode bits mirroring those present
    in the hardware. Userland can either retrieve the current FP mode of
    the process:
    
      mode = prctl(PR_GET_FP_MODE);
    
    or modify the current FP mode of the process:
    
      err = prctl(PR_SET_FP_MODE, new_mode);
    Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
    Cc: Matthew Fortune <matthew.fortune@imgtec.com>
    Cc: Markos Chandras <markos.chandras@imgtec.com>
    Cc: linux-mips@linux-mips.org
    Patchwork: https://patchwork.linux-mips.org/patch/8899/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    9791554b
traps.c 55.5 KB