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: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

1 files changed, 9 insertions, 0 deletions

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);