Revert "powerpc: Add rethook support"

This reverts commit 02752bd9.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

arch/powerpc/Kconfig

@@ -229,7 +229,6 @@ config PPC
 	select HAVE_PERF_EVENTS_NMI		if PPC64
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
-	select HAVE_RETHOOK			if KPROBES
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RELIABLE_STACKTRACE
 	select HAVE_RSEQ

arch/powerpc/kernel/Makefile

@@ -115,7 +115,6 @@ obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_OPTPROBES)		+= optprobes.o optprobes_head.o
 obj-$(CONFIG_KPROBES_ON_FTRACE)	+= kprobes-ftrace.o
-obj-$(CONFIG_RETHOOK)		+= rethook.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o
 obj-$(CONFIG_PPC_UDBG_16550)	+= legacy_serial.o udbg_16550.o
 obj-$(CONFIG_SWIOTLB)		+= dma-swiotlb.o

arch/powerpc/kernel/rethook.c

-// 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)
-{
-	unsigned long orig_ret_address;
-
-	orig_ret_address = rethook_trampoline_handler(regs, 0);
-	/*
-	 * 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
-	 * __kretprobe_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;
-
-	return 0;
-}
-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 = 0;
-
-	/* Replace the return addr with trampoline addr */
-	regs->link = (unsigned long)arch_rethook_trampoline;
-}
-NOKPROBE_SYMBOL(arch_prepare_kretprobe);
-
-static struct kprobe trampoline_p = {
-	.addr = (kprobe_opcode_t *) &arch_rethook_trampoline,
-	.pre_handler = trampoline_rethook_handler
-};
-
-static int init_arch_rethook(void)
-{
-	return register_kprobe(&trampoline_p);
-}
-
-core_initcall(init_arch_rethook);