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parisc: Fix validity check of pointer size argument in new CAS implementation
As noted by Christoph Biedl, passing a pointer size of 4 in the new CAS implementation causes a kernel crash. The attached patch corrects the off by one error in the argument validity check. In reviewing the code, I noticed that we only perform word operations with the pointer size argument. The subi instruction intentionally uses a word condition on 64-bit kernels. Nullification was used instead of a cmpib instruction as the branch should never be taken. The shlw pseudo-operation generates a depw,z instruction and it clears the target before doing a shift left word deposit. Thus, we don't need to clip the upper 32 bits of this argument on 64-bit kernels. Tested with a gcc testsuite run with a 64-bit kernel. The gcc atomic code in libgcc is the only direct user of the new CAS implementation that I am aware of. Signed-off-by: John David Anglin <dave.anglin@bell.net> Cc: stable@vger.kernel.org # 3.13+ Signed-off-by: Helge Deller <deller@gmx.de>
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@ -690,15 +690,15 @@ cas_action:
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/* ELF32 Process entry path */
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lws_compare_and_swap_2:
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#ifdef CONFIG_64BIT
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/* Clip the input registers */
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/* Clip the input registers. We don't need to clip %r23 as we
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only use it for word operations */
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depdi 0, 31, 32, %r26
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depdi 0, 31, 32, %r25
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depdi 0, 31, 32, %r24
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depdi 0, 31, 32, %r23
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#endif
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/* Check the validity of the size pointer */
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subi,>>= 4, %r23, %r0
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subi,>>= 3, %r23, %r0
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b,n lws_exit_nosys
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/* Jump to the functions which will load the old and new values into
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