Revert "ARM: rethook: Add rethook arm implementation"

This reverts commit 515a4917.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

arch/arm/Kconfig

@@ -107,7 +107,6 @@ config ARM
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_NMI
 	select HAVE_OPTPROBES if !THUMB2_KERNEL
-	select HAVE_RETHOOK
 	select HAVE_PERF_EVENTS
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP

arch/arm/include/asm/stacktrace.h

@@ -14,7 +14,7 @@ struct stackframe {
 	unsigned long sp;
 	unsigned long lr;
 	unsigned long pc;
-#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
+#ifdef CONFIG_KRETPROBES
 	struct llist_node *kr_cur;
 	struct task_struct *tsk;
 #endif
@@ -27,7 +27,7 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
 		frame->sp = regs->ARM_sp;
 		frame->lr = regs->ARM_lr;
 		frame->pc = regs->ARM_pc;
-#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
+#ifdef CONFIG_KRETPROBES
 		frame->kr_cur = NULL;
 		frame->tsk = current;
 #endif

arch/arm/kernel/stacktrace.c

 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/export.h>
 #include <linux/kprobes.h>
-#include <linux/rethook.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/stacktrace.h>
@@ -67,11 +66,6 @@ int notrace unwind_frame(struct stackframe *frame)
 	frame->sp = *(unsigned long *)(fp - 8);
 	frame->pc = *(unsigned long *)(fp - 4);
 #endif
-#ifdef CONFIG_RETHOOK
-	if (is_rethook_trampoline(frame->pc))
-		frame->pc = rethook_find_ret_addr(frame->tsk, frame->fp,
-						  &frame->kr_cur);
-#endif
 #ifdef CONFIG_KRETPROBES
 	if (is_kretprobe_trampoline(frame->pc))
 		frame->pc = kretprobe_find_ret_addr(frame->tsk,

arch/arm/probes/Makefile

@@ -6,4 +6,3 @@ obj-$(CONFIG_KPROBES)		+= decode-thumb.o
 else
 obj-$(CONFIG_KPROBES)		+= decode-arm.o
 endif
-obj-$(CONFIG_RETHOOK)		+= rethook.o

arch/arm/probes/rethook.c

-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * arm implementation of rethook. Mostly copied from arch/arm/probes/kprobes/core.c
- */
-
-#include <linux/kprobes.h>
-#include <linux/rethook.h>
-
-/* Called from arch_rethook_trampoline */
-static __used unsigned long arch_rethook_trampoline_callback(struct pt_regs *regs)
-{
-	return rethook_trampoline_handler(regs, regs->ARM_fp);
-}
-NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
-
-/*
- * When a rethook'ed function returns, it returns to arch_rethook_trampoline
- * which calls rethook callback. We construct a struct pt_regs to
- * give a view of registers r0-r11, sp, lr, and pc to the user
- * return-handler. This is not a complete pt_regs structure, but that
- * should be enough for stacktrace from the return handler with or
- * without pt_regs.
- */
-asm(
-	".text\n"
-	".global arch_rethook_trampoline\n"
-	".type arch_rethook_trampoline, %function\n"
-	"arch_rethook_trampoline:\n"
-#ifdef CONFIG_FRAME_POINTER
-	"ldr	lr, =arch_rethook_trampoline	\n\t"
-	/* this makes a framepointer on pt_regs. */
-#ifdef CONFIG_CC_IS_CLANG
-	"stmdb	sp, {sp, lr, pc}	\n\t"
-	"sub	sp, sp, #12		\n\t"
-	/* In clang case, pt_regs->ip = lr. */
-	"stmdb	sp!, {r0 - r11, lr}	\n\t"
-	/* fp points regs->r11 (fp) */
-	"add	fp, sp,	#44		\n\t"
-#else /* !CONFIG_CC_IS_CLANG */
-	/* In gcc case, pt_regs->ip = fp. */
-	"stmdb	sp, {fp, sp, lr, pc}	\n\t"
-	"sub	sp, sp, #16		\n\t"
-	"stmdb	sp!, {r0 - r11}		\n\t"
-	/* fp points regs->r15 (pc) */
-	"add	fp, sp, #60		\n\t"
-#endif /* CONFIG_CC_IS_CLANG */
-#else /* !CONFIG_FRAME_POINTER */
-	"sub	sp, sp, #16		\n\t"
-	"stmdb	sp!, {r0 - r11}		\n\t"
-#endif /* CONFIG_FRAME_POINTER */
-	"mov	r0, sp			\n\t"
-	"bl	arch_rethook_trampoline_callback	\n\t"
-	"mov	lr, r0			\n\t"
-	"ldmia	sp!, {r0 - r11}		\n\t"
-	"add	sp, sp, #16		\n\t"
-#ifdef CONFIG_THUMB2_KERNEL
-	"bx	lr			\n\t"
-#else
-	"mov	pc, lr			\n\t"
-#endif
-	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
-);
-NOKPROBE_SYMBOL(arch_rethook_trampoline);
-
-/*
- * At the entry of function with mcount. The stack and registers are prepared
- * for the mcount function as below.
- *
- * mov     ip, sp
- * push    {fp, ip, lr, pc}
- * sub     fp, ip, #4	; FP[0] = PC, FP[-4] = LR, and FP[-12] = call-site FP.
- * push    {lr}
- * bl      <__gnu_mcount_nc> ; call ftrace
- *
- * And when returning from the function, call-site FP, SP and PC are restored
- * from stack as below;
- *
- * ldm     sp, {fp, sp, pc}
- *
- * Thus, if the arch_rethook_prepare() is called from real function entry,
- * it must change the LR and save FP in pt_regs. But if it is called via
- * mcount context (ftrace), it must change the LR on stack, which is next
- * to the PC (= FP[-4]), and save the FP value at FP[-12].
- */
-void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
-{
-	unsigned long *ret_addr, *frame;
-
-	if (mcount) {
-		ret_addr = (unsigned long *)(regs->ARM_fp - 4);
-		frame = (unsigned long *)(regs->ARM_fp - 12);
-	} else {
-		ret_addr = &regs->ARM_lr;
-		frame = &regs->ARM_fp;
-	}
-
-	rh->ret_addr = *ret_addr;
-	rh->frame = *frame;
-
-	/* Replace the return addr with trampoline addr. */
-	*ret_addr = (unsigned long)arch_rethook_trampoline;
-}
-NOKPROBE_SYMBOL(arch_rethook_prepare);