Commit 515a4917 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Alexei Starovoitov
Browse files

ARM: rethook: Add rethook arm implementation 



Add rethook arm implementation. Most of the code has been copied from
kretprobes on arm.
Since the arm's ftrace implementation is a bit special, this needs a
special care using from fprobe.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735289643.1084943.15184590256680485720.stgit@devnote2
parent 02752bd9

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -107,6 +107,7 @@ 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

+2 −2
Original line number Diff line number Diff line
@@ -14,7 +14,7 @@ struct stackframe { 
	unsigned long sp;

	unsigned long lr;

	unsigned long pc;

#ifdef CONFIG_KRETPROBES

#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)

	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;

#ifdef CONFIG_KRETPROBES

#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)

		frame->kr_cur = NULL;

		frame->tsk = current;

#endif

arch/arm/kernel/stacktrace.c

+6 −0
Original line number Diff line number Diff line 
// 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>
@@ -66,6 +67,11 @@ 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

+1 −0
Original line number Diff line number Diff line
@@ -6,3 +6,4 @@ obj-$(CONFIG_KPROBES) += decode-thumb.o 
else

obj-$(CONFIG_KPROBES)		+= decode-arm.o

endif

obj-$(CONFIG_RETHOOK)		+= rethook.o

arch/arm/probes/rethook.c

0 → 100644
+103 −0
Original line number Diff line number Diff line 
// 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);