[PATCH 2/3] unwind_user/fp: Use dummies instead of ifdef

[Jens Remus <jremus@linux.ibm.com>]

This simplifies the code.   unwind_user_next_fp() does not need to
return -EINVAL if config option HAVE_UNWIND_USER_FP is disabled, as
unwind_user_start() will then not select this unwind method and
unwind_user_next() will therefore not call it.

Note that enabling the config option HAVE_UNWIND_USER_FP without
defining ARCH_INIT_USER_FP_FRAME, ARCH_INIT_USER_FP_ENTRY_FRAME, and
unwind_user_at_function_start() will result in a compile error, which
is helpful when implementing support for unwind user fp in an
architecture.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 include/linux/unwind_user.h | 14 +++++++++++---
 kernel/unwind/user.c        |  4 ----
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/linux/unwind_user.h b/include/linux/unwind_user.h
index 7f7282516bf5..c3ff690a43e2 100644
--- a/include/linux/unwind_user.h
+++ b/include/linux/unwind_user.h
@@ -5,9 +5,17 @@
 #include <linux/unwind_user_types.h>
 #include <asm/unwind_user.h>
 
-#ifndef ARCH_INIT_USER_FP_FRAME
- #define ARCH_INIT_USER_FP_FRAME
-#endif
+#ifndef CONFIG_HAVE_UNWIND_USER_FP
+
+#define ARCH_INIT_USER_FP_FRAME
+#define ARCH_INIT_USER_FP_ENTRY_FRAME
+
+static inline bool unwind_user_at_function_start(struct pt_regs *regs)
+{
+	return false;
+}
+
+#endif /* !CONFIG_HAVE_UNWIND_USER_FP */
 
 int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries);
 
diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 0ca434f86e73..90ab3c1a205e 100644
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -67,7 +67,6 @@ static int unwind_user_next_common(struct unwind_user_state *state,
 
 static int unwind_user_next_fp(struct unwind_user_state *state)
 {
-#ifdef CONFIG_HAVE_UNWIND_USER_FP
 	struct pt_regs *regs = task_pt_regs(current);
 
 	if (state->topmost && unwind_user_at_function_start(regs)) {
@@ -81,9 +80,6 @@ static int unwind_user_next_fp(struct unwind_user_state *state)
 		ARCH_INIT_USER_FP_FRAME(state->ws)
 	};
 	return unwind_user_next_common(state, &fp_frame);
-#else
-	return -EINVAL;
-#endif
 }
 
 static int unwind_user_next(struct unwind_user_state *state)
-- 
2.51.0