trace: riscv: Remove deprecated kprobe on ftrace support

Since commit 7caa9765 ("ftrace: riscv: move from REGS to ARGS"),
kprobe on ftrace is not supported by riscv, because riscv's support for
FTRACE_WITH_REGS has been replaced with support for FTRACE_WITH_ARGS, and
KPROBES_ON_FTRACE will be supplanted by FPROBES. So remove the deprecated
kprobe on ftrace support, which is misunderstood.
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20240613111347.1745379-1-ruanjinjie@huawei.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -154,7 +154,6 @@ config RISCV
 	select HAVE_KERNEL_UNCOMPRESSED if !XIP_KERNEL && !EFI_ZBOOT
 	select HAVE_KERNEL_ZSTD if !XIP_KERNEL && !EFI_ZBOOT
 	select HAVE_KPROBES if !XIP_KERNEL
-	select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL
 	select HAVE_KRETPROBES if !XIP_KERNEL
 	# https://github.com/ClangBuiltLinux/linux/issues/1881
 	select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if !LD_IS_LLD

arch/riscv/kernel/probes/Makefile

 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o simulate-insn.o
 obj-$(CONFIG_RETHOOK)		+= rethook.o rethook_trampoline.o
-obj-$(CONFIG_KPROBES_ON_FTRACE)	+= ftrace.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o decode-insn.o simulate-insn.o
 CFLAGS_REMOVE_simulate-insn.o = $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_rethook.o = $(CC_FLAGS_FTRACE)

arch/riscv/kernel/probes/ftrace.c

-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/kprobes.h>
-
-/* Ftrace callback handler for kprobes -- called under preepmt disabled */
-void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
-			   struct ftrace_ops *ops, struct ftrace_regs *fregs)
-{
-	struct kprobe *p;
-	struct pt_regs *regs;
-	struct kprobe_ctlblk *kcb;
-	int bit;
-
-	if (unlikely(kprobe_ftrace_disabled))
-		return;
-
-	bit = ftrace_test_recursion_trylock(ip, parent_ip);
-	if (bit < 0)
-		return;
-
-	p = get_kprobe((kprobe_opcode_t *)ip);
-	if (unlikely(!p) || kprobe_disabled(p))
-		goto out;
-
-	regs = ftrace_get_regs(fregs);
-	kcb = get_kprobe_ctlblk();
-	if (kprobe_running()) {
-		kprobes_inc_nmissed_count(p);
-	} else {
-		unsigned long orig_ip = instruction_pointer(regs);
-
-		instruction_pointer_set(regs, ip);
-
-		__this_cpu_write(current_kprobe, p);
-		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-		if (!p->pre_handler || !p->pre_handler(p, regs)) {
-			/*
-			 * Emulate singlestep (and also recover regs->pc)
-			 * as if there is a nop
-			 */
-			instruction_pointer_set(regs,
-				(unsigned long)p->addr + MCOUNT_INSN_SIZE);
-			if (unlikely(p->post_handler)) {
-				kcb->kprobe_status = KPROBE_HIT_SSDONE;
-				p->post_handler(p, regs, 0);
-			}
-			instruction_pointer_set(regs, orig_ip);
-		}
-
-		/*
-		 * If pre_handler returns !0, it changes regs->pc. We have to
-		 * skip emulating post_handler.
-		 */
-		__this_cpu_write(current_kprobe, NULL);
-	}
-out:
-	ftrace_test_recursion_unlock(bit);
-}
-NOKPROBE_SYMBOL(kprobe_ftrace_handler);
-
-int arch_prepare_kprobe_ftrace(struct kprobe *p)
-{
-	p->ainsn.api.insn = NULL;
-	return 0;
-}