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ARM: Recover kretprobe modified return address in stacktrace

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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: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2021-10-21 09:55:35 +09:00 committed by Steven Rostedt (VMware)
parent 7e9bf33b81
commit fed240d9c9
4 changed files with 28 additions and 0 deletions
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1
arch/arm/Kconfig
View File

@ -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

9
arch/arm/include/asm/stacktrace.h
View File

@ -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);

4
arch/arm/kernel/return_address.c
View File

@ -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);

14
arch/arm/kernel/stacktrace.c
View File

@ -1,5 +1,6 @@
// 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);
}