mips: fix setjmp() on n32/n64 (.cpreturn, not .cprestore)
The setjmp() entry point (bsd-setjmp.S) tail-calls __sigsetjmp. For
n32/n64 it set up the GOT pointer with .cpsetup but then used .cprestore
before the jump. .cprestore is the o32 mechanism (it emits an
sw $gp,offset($sp) against a cprestore slot that was never established
here, clobbering the caller's stack); the n32/n64 counterpart that
restores $gp for a tail-call is .cpreturn, which is what the sibling
_setjmp entry point (bsd-_setjmp.S) correctly uses.
The result was that setjmp() (the function entry, as opposed to the
__sigsetjmp macro) corrupted state on n32/n64, and a later libc call
faulted - tst-setjmp crashed with SIGSEGV/SIGILL on all mips64 variants
while o32 (which takes the .cpload path) passed.
Use .cpreturn, matching bsd-_setjmp.S. Verified on qemu-system-mips64
(mips64-be-n32): tst-setjmp passes.
Signed-off-by: Ramin Moussavi <ramin.moussavi@yacoub.de>
ramin