Add elf_local_rip to UnwindContext (debug tool)

include/dwarfinterpret/DwarfInterpret.hpp

@@ -107,6 +107,9 @@ class DwarfInterpret {
             uintptr_t rip;
             uintptr_t rsp;
             uintptr_t rbp;
+
+            /// This context's `RIP` minus its ELF file load offset
+            uintptr_t elf_local_rip() const;
         };
 
     public:  // methods
@@ -180,6 +183,12 @@ class DwarfInterpret {
          */
         UnwindContext unwind_context(const UnwindContext& ctx);
 
+        /** Get the offset for the instruction pointer.
+         *
+         * This offset is such that `actual_rip - pc_offset` is the ELF-local
+         * PC (ie. what readelf gives). */
+        uintptr_t get_pc_offset() const { return pc_offset; }
+
     private:
         DwarfInterpret(const MemoryMap::MapEntry& memory_object);
 

src/DwarfInterpret.cpp

@@ -36,6 +36,11 @@ using namespace dwarf;
 MemoryMap DwarfInterpret::memory_map;
 map<int, unique_ptr<DwarfInterpret> > DwarfInterpret::instances;
 
+uintptr_t DwarfInterpret::UnwindContext::elf_local_rip() const {
+    return rip - DwarfInterpret::acquire(rip).get_pc_offset();
+}
+
+
 DwarfInterpret::DwarfInterpret(const MemoryMap::MapEntry& memory_object)
     : map_entry(memory_object)
 {
@@ -205,13 +210,17 @@ DwarfInterpret::UnwindContext DwarfInterpret::unwind_context(
         // An undefined RA means we've reached the end of the call stack
         throw FirstUnwindFrame();
     }
-    new_context.rbp = interpret_dw_register(
-            cur_row,
-            lib::DWARF_X86_64_RBP,
-            ctx);
-    if(new_context.rbp == 0) {
-        // A null rbp means we've reached the end of the call stack
-        throw FirstUnwindFrame();
+    try {
+        new_context.rbp = interpret_dw_register(
+                cur_row,
+                lib::DWARF_X86_64_RBP,
+                ctx);
+        if(new_context.rbp == 0) {
+            // A null rbp means we've reached the end of the call stack
+            throw FirstUnwindFrame();
+        }
+    } catch(const std::out_of_range& e) {
+        new_context.rbp = 0;  // The base pointer does not exist
     }
 
     new_context.rsp = interpret_dw_register(

test/dump_my_stack.cpp

@@ -28,7 +28,11 @@ void dump_my_stack() {
                 (dl_rc && dl_inf.dli_sname) ? dl_inf.dli_sname : "(no symbol)",
                 cur_map_entry.pathname.c_str());
         fflush(stdout);
-        unw_context = dw.unwind_context(unw_context);
+        try {
+            unw_context = dw.unwind_context(unw_context);
+        } catch(const DwarfInterpret::FirstUnwindFrame& exn) {
+            return;
+        }
     }
 }
 
@@ -36,7 +40,8 @@ void fill_my_stack(int stack_depth) {
     if(stack_depth == 0)
         dump_my_stack();
 
-    fill_my_stack(stack_depth - 1);
+    else
+        fill_my_stack(stack_depth - 1);
 }
 
 int main(int argc, char** argv) {