D14179.diff
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	Index: head/lib/libc/mips/gen/_ctx_start.S
	===================================================================
	--- head/lib/libc/mips/gen/_ctx_start.S
	+++ head/lib/libc/mips/gen/_ctx_start.S
	@@ -28,11 +28,25 @@
	__FBSDID("$FreeBSD$");

	/*
	- * XXX gp?
	+ * This requires makecontext() to setup a valid GP for locating
	+ * _ctx_done rather than deriving GP from T9 on entry. Currently this
	+ * uses the GP inherited from getcontext() assuming that getcontext()
	+ * is in the same shared object as _ctx_done(). For N32 and N64, GP
	+ * is caller-save so will be preserved across the call to the callback
	+ * function. For O32, GP is callee-save, so save it in a different
	+ * caller-save register (S1) while invoking the callback. This is
	+ * done instead of the usual SETUP_GP/SAVE_GP to avoid disturbing the
	+ * stack frame setup by makecontext() for the callback function.
	*/
	ENTRY(_ctx_start)
	+#ifdef __mips_o32
	+ move s1, gp
	+#endif
	jalr t9

	+#ifdef __mips_o32
	+ move gp, s1
	+#endif
	move a0, s0
	PTR_LA t9, _ctx_done
	jalr t9