• Matt Brown's avatar
    powerpc/lib/xor_vmx: Ensure no altivec code executes before enable_kernel_altivec() · f718d426
    Matt Brown authored
    The xor_vmx.c file is used for the RAID5 xor operations. In these functions
    altivec is enabled to run the operation and then disabled.
    
    The code uses enable_kernel_altivec() around the core of the algorithm, however
    the whole file is built with -maltivec, so the compiler is within its rights to
    generate altivec code anywhere. This has been seen at least once in the wild:
    
      0:mon> di $xor_altivec_2
      c0000000000b97d0  3c4c01d9	addis   r2,r12,473
      c0000000000b97d4  3842db30	addi    r2,r2,-9424
      c0000000000b97d8  7c0802a6	mflr    r0
      c0000000000b97dc  f8010010	std     r0,16(r1)
      c0000000000b97e0  60000000	nop
      c0000000000b97e4  7c0802a6	mflr    r0
      c0000000000b97e8  faa1ffa8	std     r21,-88(r1)
      ...
      c0000000000b981c  f821ff41	stdu    r1,-192(r1)
      c0000000000b9820  7f8101ce	stvx    v28,r1,r0		<-- POP
      c0000000000b9824  38000030	li      r0,48
      c0000000000b9828  7fa101ce	stvx    v29,r1,r0
      ...
      c0000000000b984c  4bf6a06d	bl      c0000000000238b8 # enable_kernel_altivec
    
    This patch splits the non-altivec code into xor_vmx_glue.c which calls the
    altivec functions in xor_vmx.c. By compiling xor_vmx_glue.c without
    -maltivec we can guarantee that altivec instruction will not be executed
    outside of the enable/disable block.
    Signed-off-by: default avatarMatt Brown <matthew.brown.dev@gmail.com>
    [mpe: Rework change log and include disassembly]
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    f718d426
xor_vmx_glue.c 1.61 KB