Commit fed240d9 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt (VMware)
Browse files

ARM: Recover kretprobe modified return address in stacktrace 



Since the kretprobe replaces the function return address with
the kretprobe_trampoline on the stack, arm unwinder shows it
instead of the correct return address.

This finds the correct return address from the per-task
kretprobe_instances list and verify it is in between the
caller fp and callee fp.

Note that this supports both GCC and clang if CONFIG_FRAME_POINTER=y
and CONFIG_ARM_UNWIND=n. For the ARM unwinder, this is still
not working correctly.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 7e9bf33b

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ config ARM 
	bool

	default y

	select ARCH_32BIT_OFF_T

	select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE if HAVE_KRETPROBES && FRAME_POINTER && !ARM_UNWIND

	select ARCH_HAS_BINFMT_FLAT

	select ARCH_HAS_DEBUG_VIRTUAL if MMU

	select ARCH_HAS_DMA_WRITE_COMBINE if !ARM_DMA_MEM_BUFFERABLE

arch/arm/include/asm/stacktrace.h

+9 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
#define __ASM_STACKTRACE_H



#include <asm/ptrace.h>

#include <linux/llist.h>



struct stackframe {

	/*
@@ -13,6 +14,10 @@ struct stackframe { 
	unsigned long sp;

	unsigned long lr;

	unsigned long pc;

#ifdef CONFIG_KRETPROBES

	struct llist_node *kr_cur;

	struct task_struct *tsk;

#endif

};



static __always_inline
@@ -22,6 +27,10 @@ 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

		frame->kr_cur = NULL;

		frame->tsk = current;

#endif

}



extern int unwind_frame(struct stackframe *frame);

arch/arm/kernel/return_address.c

+4 −0
Original line number Diff line number Diff line
@@ -42,6 +42,10 @@ void *return_address(unsigned int level) 
	frame.sp = current_stack_pointer;

	frame.lr = (unsigned long)__builtin_return_address(0);

	frame.pc = (unsigned long)return_address;

#ifdef CONFIG_KRETPROBES

	frame.kr_cur = NULL;

	frame.tsk = current;

#endif



	walk_stackframe(&frame, save_return_addr, &data);

arch/arm/kernel/stacktrace.c

+14 −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/sched.h>

#include <linux/sched/debug.h>

#include <linux/stacktrace.h>
@@ -65,6 +66,11 @@ int notrace unwind_frame(struct stackframe *frame) 
	frame->sp = *(unsigned long *)(fp - 8);

	frame->pc = *(unsigned long *)(fp - 4);

#endif

#ifdef CONFIG_KRETPROBES

	if (is_kretprobe_trampoline(frame->pc))

		frame->pc = kretprobe_find_ret_addr(frame->tsk,

					(void *)frame->fp, &frame->kr_cur);

#endif



	return 0;

}
@@ -156,6 +162,10 @@ static noinline void __save_stack_trace(struct task_struct *tsk, 
		frame.lr = (unsigned long)__builtin_return_address(0);

		frame.pc = (unsigned long)__save_stack_trace;

	}

#ifdef CONFIG_KRETPROBES

	frame.kr_cur = NULL;

	frame.tsk = tsk;

#endif



	walk_stackframe(&frame, save_trace, &data);

}
@@ -173,6 +183,10 @@ void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 
	frame.sp = regs->ARM_sp;

	frame.lr = regs->ARM_lr;

	frame.pc = regs->ARM_pc;

#ifdef CONFIG_KRETPROBES

	frame.kr_cur = NULL;

	frame.tsk = current;

#endif



	walk_stackframe(&frame, save_trace, &data);

}