// SPDX-License-Identifier: GPL-2.0-only/* * PowerPC implementation of rethook. This depends on kprobes. */ #include <linux/kprobes.h>#include <linux/rethook.h> /* * Function return trampoline: *     - init_kprobes() establishes a probepoint here *     - When the probed function returns, this probe *         causes the handlers to fire */asm(".global arch_rethook_trampoline\n"	".type arch_rethook_trampoline, @function\n"	"arch_rethook_trampoline:\n"	"nop\n"	"blr\n"	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"); /* * Called when the probe at kretprobe trampoline is hit */static int trampoline_rethook_handler(struct kprobe *p, struct pt_regs *regs){	return !rethook_trampoline_handler(regs, regs->gpr[1]);}NOKPROBE_SYMBOL(trampoline_rethook_handler); void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount){	rh->ret_addr = regs->link;	rh->frame = regs->gpr[1]; 	/* Replace the return addr with trampoline addr */	regs->link = (unsigned long)arch_rethook_trampoline;}NOKPROBE_SYMBOL(arch_rethook_prepare); /* This is called from rethook_trampoline_handler(). */void arch_rethook_fixup_return(struct pt_regs *regs, unsigned long orig_ret_address){	/*	 * We get here through one of two paths:	 * 1. by taking a trap -> kprobe_handler() -> here	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here	 *	 * When going back through (1), we need regs->nip to be setup properly	 * as it is used to determine the return address from the trap.	 * For (2), since nip is not honoured with optprobes, we instead setup	 * the link register properly so that the subsequent 'blr' in	 * arch_rethook_trampoline jumps back to the right instruction.	 *	 * For nip, we should set the address to the previous instruction since	 * we end up emulating it in kprobe_handler(), which increments the nip	 * again.	 */	regs_set_return_ip(regs, orig_ret_address - 4);	regs->link = orig_ret_address;}NOKPROBE_SYMBOL(arch_rethook_fixup_return); static struct kprobe trampoline_p = {	.addr = (kprobe_opcode_t *) &arch_rethook_trampoline,	.pre_handler = trampoline_rethook_handler}; /* rethook initializer */int __init arch_init_kprobes(void){	return register_kprobe(&trampoline_p);}