[PATCH] x86/unwind: fix oprofile module link error

[Josh Poimboeuf]

When compiling on x86 with CONFIG_OPROFILE=m and CONFIG_FRAME_POINTER=n,
the oprofile module fails to link:

  ERROR: ftrace_graph_ret_addr" [arch/x86/oprofile/oprofile.ko] undefined!

The problem was introduced when oprofile was converted to use the new
x86 unwinder.  When frame pointers are disabled, the "guess" unwinder's
unwind_get_return_address() is an inline function which calls
ftrace_graph_ret_addr(), which is not exported.

Fix it by converting the "guess" version of unwind_get_return_address()
to an exported out-of-line function, just like its frame pointer
counterpart.

Fixes: ec2ad9ccf12d ("oprofile/x86: Convert x86_backtrace() to use the new unwinder")
Reported-by: Karl Beldan <karl.beldan@xxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 arch/x86/include/asm/unwind.h  | 14 ++------------
 arch/x86/kernel/unwind_guess.c | 10 ++++++++++
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index c4b6d1c..46de9ac 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -23,6 +23,8 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
 
 bool unwind_next_frame(struct unwind_state *state);
 
+unsigned long unwind_get_return_address(struct unwind_state *state);
+
 static inline bool unwind_done(struct unwind_state *state)
 {
 	return state->stack_info.type == STACK_TYPE_UNKNOWN;
@@ -48,8 +50,6 @@ unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
 	return state->bp + 1;
 }
 
-unsigned long unwind_get_return_address(struct unwind_state *state);
-
 #else /* !CONFIG_FRAME_POINTER */
 
 static inline
@@ -58,16 +58,6 @@ unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
 	return NULL;
 }
 
-static inline
-unsigned long unwind_get_return_address(struct unwind_state *state)
-{
-	if (unwind_done(state))
-		return 0;
-
-	return ftrace_graph_ret_addr(state->task, &state->graph_idx,
-				     *state->sp, state->sp);
-}
-
 #endif /* CONFIG_FRAME_POINTER */
 
 #endif /* _ASM_X86_UNWIND_H */
diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c
index b5a834c..9298993 100644
--- a/arch/x86/kernel/unwind_guess.c
+++ b/arch/x86/kernel/unwind_guess.c
@@ -5,6 +5,16 @@
 #include <asm/stacktrace.h>
 #include <asm/unwind.h>
 
+unsigned long unwind_get_return_address(struct unwind_state *state)
+{
+	if (unwind_done(state))
+		return 0;
+
+	return ftrace_graph_ret_addr(state->task, &state->graph_idx,
+				     *state->sp, state->sp);
+}
+EXPORT_SYMBOL_GPL(unwind_get_return_address);
+
 bool unwind_next_frame(struct unwind_state *state)
 {
 	struct stack_info *info = &state->stack_info;
-- 
2.7.4