[PATCH v2 08/17] perf llvm: Mangle libperf-llvm.so function names

[Ian Rogers]

For a function like llvm_addr2line having the libperf-llvm.so exported
symbol named llvm_addr2line meant that the perf llvm_addr2line could
sometimes erroneously be returned. This led to infinite recursion and
eventual stack overflow. To avoid this conflict add a new
BUILDING_PERF_LLVMSO when libperf-llvm.so is being built and use it to
alter the behavior of MANGLE_PERF_LLVM_API, a macro that prefixes the
name when libperf-llvm.so is being built. The prefixed named avoids
the name collision.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/Makefile.perf           |  3 ++-
 tools/perf/util/llvm-c-helpers.cpp | 29 ++++++++++++++++++-----------
 tools/perf/util/llvm-c-helpers.h   | 24 ++++++++++++++++--------
 3 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index eae77f6af59d..a2886abd4f02 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -1026,7 +1026,8 @@ $(LIBSYMBOL)-clean:
 	$(Q)$(RM) -r -- $(LIBSYMBOL_OUTPUT)
 
 ifdef LIBLLVM_DYNAMIC
-LIBPERF_LLVM_CXXFLAGS := $(call filter-out,-DHAVE_LIBLLVM_DYNAMIC,$(CXXFLAGS)) -DHAVE_LIBLLVM_SUPPORT
+LIBPERF_LLVM_CXXFLAGS := $(call filter-out,-DHAVE_LIBLLVM_DYNAMIC,$(CXXFLAGS))
+LIBPERF_LLVM_CXXFLAGS += -DHAVE_LIBLLVM_SUPPORT -DBUILDING_PERF_LLVMSO
 LIBPERF_LLVM_LIBS = -L$(shell $(LLVM_CONFIG) --libdir) $(LIBLLVM) -lstdc++
 
 $(OUTPUT)$(LIBPERF_LLVM): util/llvm-c-helpers.cpp
diff --git a/tools/perf/util/llvm-c-helpers.cpp b/tools/perf/util/llvm-c-helpers.cpp
index 5a6f76e6b705..8cea380be5c2 100644
--- a/tools/perf/util/llvm-c-helpers.cpp
+++ b/tools/perf/util/llvm-c-helpers.cpp
@@ -99,10 +99,12 @@ static int extract_file_and_line(const DILineInfo &line_info, char **file,
 #endif
 
 extern "C"
-int llvm_addr2line(const char *dso_name __maybe_unused, u64 addr __maybe_unused,
-		   char **file __maybe_unused, unsigned int *line __maybe_unused,
-		   bool unwind_inlines __maybe_unused,
-		   llvm_a2l_frame **inline_frames __maybe_unused)
+int MANGLE_PERF_LLVM_API(llvm_addr2line)(const char *dso_name __maybe_unused,
+                                         u64 addr __maybe_unused,
+                                         char **file __maybe_unused,
+                                         unsigned int *line __maybe_unused,
+                                         bool unwind_inlines __maybe_unused,
+                                         llvm_a2l_frame **inline_frames __maybe_unused)
 {
 #if defined(HAVE_LIBLLVM_SUPPORT) && !defined(HAVE_LIBLLVM_DYNAMIC)
 	LLVMSymbolizer *symbolizer = get_symbolizer();
@@ -177,7 +179,8 @@ int llvm_addr2line(const char *dso_name __maybe_unused, u64 addr __maybe_unused,
 		if (!handle)
 			return 0;
 
-		fn = reinterpret_cast<decltype(fn)>(dlsym(handle, "llvm_addr2line"));
+		fn = reinterpret_cast<decltype(fn)>(
+			dlsym(handle, MANGLE_PERF_LLVM_API_STR(llvm_addr2line)));
 		if (!fn)
 			pr_debug("dlsym failed for llvm_addr2line\n");
 		fn_init = true;
@@ -215,8 +218,9 @@ make_symbol_relative_string(struct dso *dso, const char *sym_name,
 #endif
 
 extern "C"
-char *llvm_name_for_code(struct dso *dso __maybe_unused, const char *dso_name __maybe_unused,
-			 u64 addr __maybe_unused)
+char *MANGLE_PERF_LLVM_API(llvm_name_for_code)(struct dso *dso __maybe_unused,
+					       const char *dso_name __maybe_unused,
+					       u64 addr __maybe_unused)
 {
 #if defined(HAVE_LIBLLVM_SUPPORT) && !defined(HAVE_LIBLLVM_DYNAMIC)
 	LLVMSymbolizer *symbolizer = get_symbolizer();
@@ -242,7 +246,8 @@ char *llvm_name_for_code(struct dso *dso __maybe_unused, const char *dso_name __
 		if (!handle)
 			return NULL;
 
-		fn = reinterpret_cast<decltype(fn)>(dlsym(handle, "llvm_name_for_code"));
+		fn = reinterpret_cast<decltype(fn)>(
+			dlsym(handle, MANGLE_PERF_LLVM_API_STR(llvm_name_for_code)));
 		if (!fn)
 			pr_debug("dlsym failed for llvm_name_for_code\n");
 		fn_init = true;
@@ -256,8 +261,9 @@ char *llvm_name_for_code(struct dso *dso __maybe_unused, const char *dso_name __
 }
 
 extern "C"
-char *llvm_name_for_data(struct dso *dso __maybe_unused, const char *dso_name __maybe_unused,
-			 u64 addr __maybe_unused)
+char *MANGLE_PERF_LLVM_API(llvm_name_for_data)(struct dso *dso __maybe_unused,
+					       const char *dso_name __maybe_unused,
+					       u64 addr __maybe_unused)
 {
 #if defined(HAVE_LIBLLVM_SUPPORT) && !defined(HAVE_LIBLLVM_DYNAMIC)
 	LLVMSymbolizer *symbolizer = get_symbolizer();
@@ -283,7 +289,8 @@ char *llvm_name_for_data(struct dso *dso __maybe_unused, const char *dso_name __
 		if (!handle)
 			return NULL;
 
-		fn = reinterpret_cast<decltype(fn)>(dlsym(handle, "llvm_name_for_data"));
+		fn = reinterpret_cast<decltype(fn)>(
+			dlsym(handle, MANGLE_PERF_LLVM_API_STR(llvm_name_for_data)));
 		if (!fn)
 			pr_debug("dlsym failed for llvm_name_for_data\n");
 		fn_init = true;
diff --git a/tools/perf/util/llvm-c-helpers.h b/tools/perf/util/llvm-c-helpers.h
index d2b99637a28a..cfcfd540cdae 100644
--- a/tools/perf/util/llvm-c-helpers.h
+++ b/tools/perf/util/llvm-c-helpers.h
@@ -13,6 +13,14 @@
 extern "C" {
 #endif
 
+/* Support name mangling so that libperf_llvm.so's names don't match those in perf. */
+#ifdef BUILDING_PERF_LLVMSO
+#define MANGLE_PERF_LLVM_API(x) PERF_LLVM_SO_ ## x
+#else
+#define MANGLE_PERF_LLVM_API(x) x
+#endif
+#define MANGLE_PERF_LLVM_API_STR(x) "PERF_LLVM_SO_" #x
+
 struct dso;
 
 struct llvm_a2l_frame {
@@ -37,12 +45,12 @@ struct llvm_a2l_frame {
  * a newly allocated array with that length. The caller is then responsible
  * for freeing both the strings and the array itself.
  */
-int llvm_addr2line(const char* dso_name,
-                   u64 addr,
-                   char** file,
-                   unsigned int* line,
-                   bool unwind_inlines,
-                   struct llvm_a2l_frame** inline_frames);
+int MANGLE_PERF_LLVM_API(llvm_addr2line)(const char *dso_name,
+					 u64 addr,
+					 char **file,
+					 unsigned int *line,
+					 bool unwind_inlines,
+					 struct llvm_a2l_frame **inline_frames);
 
 /*
  * Simple symbolizers for addresses; will convert something like
@@ -50,8 +58,8 @@ int llvm_addr2line(const char* dso_name,
  *
  * The returned value must be freed by the caller, with free().
  */
-char *llvm_name_for_code(struct dso *dso, const char *dso_name, u64 addr);
-char *llvm_name_for_data(struct dso *dso, const char *dso_name, u64 addr);
+char *MANGLE_PERF_LLVM_API(llvm_name_for_code)(struct dso *dso, const char *dso_name, u64 addr);
+char *MANGLE_PERF_LLVM_API(llvm_name_for_data)(struct dso *dso, const char *dso_name, u64 addr);
 
 #ifdef __cplusplus
 }
-- 
2.48.0.rc2.279.g1de40edade-goog