stack_walker: adapt to switch generation policies

stack_walker/Makefile

@@ -2,17 +2,21 @@ CXX=g++
 CXXLIBS=-ldl
 CXXFLAGS=-O2 -fPIC -Wall -Wextra
 
-TARGET=libstack_walker.so
+TARGET_BASE=libstack_walker
+TARGETS=$(TARGET_BASE).global.so $(TARGET_BASE).per_func.so
 OBJS=stack_walker.o
 
-all: $(TARGET)
+all: $(TARGETS)
 
-$(TARGET): $(OBJS)
+$(TARGET_BASE).%.so: $(OBJS:.o=.%.o)
 	$(CXX) $(CXXFLAGS) -shared $< $(CXXLIBS) -o $@
 
-%.o: %.cpp
-	$(CXX) $(CXXFLAGS) -c $< -o $@
+%.global.o: %.cpp
+	$(CXX) $(CXXFLAGS) -DSGP_GLOBAL_SWITCH -c $< -o $@
+
+%.per_func.o: %.cpp
+	$(CXX) $(CXXFLAGS) -DSGP_SWITCH_PER_FUNC -c $< -o $@
 
 
 clean:
-	rm -f $(OBJS) $(TARGET)
+	rm -f $(OBJS) $(TARGET_BASE)*.so

stack_walker/stack_walker.cpp

@@ -9,6 +9,7 @@
 #include <string>
 #include <map>
 
+#define UNUSED(x) (void)(x)
 
 typedef void* dl_handle_t;
 
@@ -173,6 +174,7 @@ MemoryMapEntry* get_mmap_entry(uintptr_t pc) {
  * symbols, depending on the state of the experiment. This is an abstraction
  * function. */
 _fde_func_t fde_handler_for_pc(uintptr_t pc, MemoryMapEntry& mmap_entry) {
+#ifdef SGP_SWITCH_PER_FUNC
     // Get the lookup function
     _fde_func_t (*lookup)(uintptr_t) =
         (_fde_func_t (*)(uintptr_t)) (
@@ -191,6 +193,21 @@ _fde_func_t fde_handler_for_pc(uintptr_t pc, MemoryMapEntry& mmap_entry) {
         return nullptr;
 
     return rfunc;
+#elif SGP_GLOBAL_SWITCH
+    UNUSED(pc);
+    _fde_func_t global_switch =
+        (_fde_func_t) (dlsym(mmap_entry.eh_dl_handle, "_eh_elf"));
+
+    if(global_switch == nullptr)
+        return nullptr;
+
+    return global_switch;
+#else
+    UNUSED(pc);
+    UNUSED(mmap_entry);
+    assert(false); // Please compile with either -DSCP_SWITCH_PER_FUNC or
+                   // -DSCP_GLOBAL_SWITCH
+#endif
 }
 
 bool unwind_context(unwind_context_t& ctx) {

tests/Makefile

@@ -2,7 +2,7 @@ CXX=g++
 CXXFLAGS=-Wall -Wextra -O0 -g -I../stack_walker -rdynamic
 
 stack_walked.bin: stack_walked.cpp
-	$(CXX) $(CXXFLAGS) -o $@ $^ -L../stack_walker -ldl -lstack_walker
+	$(CXX) $(CXXFLAGS) -o $@ $^ -L../stack_walker -ldl -lstack_walker.global
 
 clean:
 	rm *.bin