Re: [PATCH v3] tracing: Function stack size and its name mismatch in arm64

[Steven Rostedt]

On Fri, 2 Aug 2019 11:22:59 -0400
Steven Rostedt <rost...@goodmis.org> wrote:

> I think you are not explaining the issue correctly. From looking at the
> document, I think what you want to say is that the LR is saved *after*
> the data for the function. Is that correct? If so, then yes, it would
> cause the stack tracing algorithm to be incorrect.
> 

[..]

> Can someone confirm that this is the real issue?

Does this patch fix your issue?

-- Steve

diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 5ab5200b2bdc..13a4832cfb00 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -13,6 +13,7 @@
 #define HAVE_FUNCTION_GRAPH_FP_TEST
 #define MCOUNT_ADDR            ((unsigned long)_mcount)
 #define MCOUNT_INSN_SIZE       AARCH64_INSN_SIZE
+#define ARCH_RET_ADDR_AFTER_LOCAL_VARS 1
 
 #ifndef __ASSEMBLY__
 #include <linux/compat.h>
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 5d16f73898db..050c6bd9beac 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -158,6 +158,18 @@ static void check_stack(unsigned long ip, unsigned long 
*stack)
                        i++;
        }
 
+#ifdef ARCH_RET_ADDR_AFTER_LOCAL_VARS
+       /*
+        * Most archs store the return address before storing the
+        * function's local variables. But some archs do this backwards.
+        */
+       if (x > 1) {
+               memmove(&stack_trace_index[0], &stack_trace_index[1],
+                       sizeof(stack_trace_index[0]) * (x - 1));
+               x--;
+       }
+#endif
+
        stack_trace_nr_entries = x;
 
        if (task_stack_end_corrupted(current)) {

diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 5ab5200b2bdc..13a4832cfb00 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -13,6 +13,7 @@
 #define HAVE_FUNCTION_GRAPH_FP_TEST
 #define MCOUNT_ADDR		((unsigned long)_mcount)
 #define MCOUNT_INSN_SIZE	AARCH64_INSN_SIZE
+#define ARCH_RET_ADDR_AFTER_LOCAL_VARS 1
 
 #ifndef __ASSEMBLY__
 #include <linux/compat.h>
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 5d16f73898db..050c6bd9beac 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -158,6 +158,18 @@ static void check_stack(unsigned long ip, unsigned long *stack)
 			i++;
 	}
 
+#ifdef ARCH_RET_ADDR_AFTER_LOCAL_VARS
+	/*
+	 * Most archs store the return address before storing the
+	 * function's local variables. But some archs do this backwards.
+	 */
+	if (x > 1) {
+		memmove(&stack_trace_index[0], &stack_trace_index[1],
+			sizeof(stack_trace_index[0]) * (x - 1));
+		x--;
+	}
+#endif
+
 	stack_trace_nr_entries = x;
 
 	if (task_stack_end_corrupted(current)) {