powerpc ftrace broken due to "manual merge of the ftrace tree with the arm64 tree"

Qian Cai
2019-11-15T20:28:57Z

# echo function >/sys/kernel/debug/tracing/current_tracer

It hangs forever with today's linux-next on powerpc. Reverted the conflict fix
[1] as below fixes the issue.

[1] https://lore.kernel.org/linux-next/20191115135357.10386fac@canb.auug.org.au/

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-
generic/vmlinux.lds.h
index 7d0d03a03d4d..a92222f79b53 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -136,29 +136,20 @@
#endif

#ifdef CONFIG_FTRACE_MCOUNT_RECORD
-/*
- * The ftrace call sites are logged to a section whose name depends on the
- * compiler option used. A given kernel image will only use one, AKA
- * FTRACE_CALLSITE_SECTION. We capture all of them here to avoid header
- * dependencies for FTRACE_CALLSITE_SECTION's definition.
- */
-/*
- * Need to also make ftrace_graph_stub point to ftrace_stub
- * so that the same stub location may have different protocols
- * and not mess up with C verifiers.
- */
-#define MCOUNT_REC() . = ALIGN(8); \
+#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY
+#define MCOUNT_REC() . = ALIGN(8) \
__start_mcount_loc = .; \
- KEEP(*(__mcount_loc)) \
KEEP(*(__patchable_function_entries)) \
__stop_mcount_loc = .; \
ftrace_graph_stub = ftrace_stub;
#else
-# ifdef CONFIG_FUNCTION_TRACER
-#  define MCOUNT_REC() ftrace_graph_stub = ftrace_stub;
-# else
-#  define MCOUNT_REC()
-# endif
+#define MCOUNT_REC() . = ALIGN(8); \
+ __start_mcount_loc = .; \
+ KEEP(*(__mcount_loc)) \
+ __stop_mcount_loc = .;
+#endif
+#else
+#define MCOUNT_REC()
#endif

#ifdef CONFIG_TRACE_BRANCH_PROFILING