[PATCH v3 9/9] ARM: Recover kretprobe modified return address in stacktrace
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: 2021-10-21 00:55:42
Also in:
lkml
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
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> --- Changes in v2: - Compile this code only when CONFIG_KRETPROBES=y --- arch/arm/Kconfig | 1 + arch/arm/include/asm/stacktrace.h | 9 +++++++++ arch/arm/kernel/return_address.c | 4 ++++ arch/arm/kernel/stacktrace.c | 14 ++++++++++++++ 4 files changed, 28 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index fc196421b2ce..bb4f1872967c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig@@ -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
diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
index 2d76a2e29f05..8f54f9ad8a9b 100644
--- a/arch/arm/include/asm/stacktrace.h
+++ b/arch/arm/include/asm/stacktrace.h@@ -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);
diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c
index 7b42ac010fdf..00c11579406c 100644
--- a/arch/arm/kernel/return_address.c
+++ b/arch/arm/kernel/return_address.c@@ -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);
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index db798eac7431..75e905508f27 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c@@ -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); }
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