sw64: fix incorrect gp after kretprobe triggered

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5XTM4

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SW64 use r26 to calculate gp after function return, so r26 needs to be
restored when kretprobe trampoline is hit.
Signed-off-by: NMao Minkai <maominkai@wxiat.com>
Reviewed-by: NHe Sheng <hesheng@wxiat.com>
Signed-off-by: NGu Zitao <guzitao@wxiat.com>

arch/sw_64/kernel/kprobes/kprobes.c

@@ -284,6 +284,7 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
 
 	orig_ret_address = __kretprobe_trampoline_handler(regs, kretprobe_trampoline, NULL);
 	instruction_pointer(regs) = orig_ret_address;
+	regs->r26 = orig_ret_address;
 
 	/*
 	 * By returning a non-zero value, we are telling