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ae62fbb5f1
This fixes a bug which can cause corruption of the floating-point state on return from a signal handler. If we have a signal handler that has used the floating-point registers, and it happens to context-switch to another task while copying the interrupted floating-point state from the user stack into the thread struct (e.g. because of a page fault, or because it gets preempted), the context switch code will think that the FP registers contain valid FP state that needs to be copied into the thread_struct, and will thus overwrite the values that the signal return code has put into the thread_struct. This can occur because we clear the MSR bits that indicate the presence of valid FP state after copying the state into the thread_struct. To fix this we just move the clearing of the MSR bits to before the copy. A similar potential problem also occurs with the Altivec state, and this fixes that in the same way. Signed-off-by: Paul Mackerras <paulus@samba.org>