Fix pc/function name for signal handler frame.

This refactors the step function slightly to split it up into
distinct pieces since the code needs to handle a signal handler
versus normal step slightly differently.

Add a new error for an invalid elf.

Modify libbacktrace code to handle new error code.

Bug: 130302288

Test: libbacktrace/libunwindstack unit tests.
Change-Id: I3fb9b00c02d2cf2cc5911541bba0346c6f39b8e6

1 files changed, 11 insertions, 13 deletions

diff --git a/libunwindstack/LocalUnwinder.cpp b/libunwindstack/LocalUnwinder.cpp
index 5b2fadf..5d81200 100644
--- a/libunwindstack/LocalUnwinder.cpp
+++ b/libunwindstack/LocalUnwinder.cpp
@@ -111,6 +111,14 @@ bool LocalUnwinder::Unwind(std::vector<LocalFrameData>* frame_info, size_t max_f
       pc_adjustment = 0;
     }
     step_pc -= pc_adjustment;
+
+    bool finished = false;
+    if (elf->StepIfSignalHandler(rel_pc, regs.get(), process_memory_.get())) {
+      step_pc = rel_pc;
+    } else if (!elf->Step(step_pc, regs.get(), process_memory_.get(), &finished)) {
+      finished = true;
+    }
+
     // Skip any locations that are within this library.
     if (num_frames != 0 || !ShouldSkipLibrary(map_info->name)) {
       // Add frame information.
@@ -124,22 +132,12 @@ bool LocalUnwinder::Unwind(std::vector<LocalFrameData>* frame_info, size_t max_f
       }
       num_frames++;
     }
-    if (!elf->valid()) {
-      break;
-    }
-    if (frame_info->size() == max_frames) {
-      break;
-    }
 
-    adjust_pc = true;
-    bool finished;
-    if (!elf->Step(rel_pc, step_pc, regs.get(), process_memory_.get(), &finished) || finished) {
-      break;
-    }
-    // pc and sp are the same, terminate the unwind.
-    if (cur_pc == regs->pc() && cur_sp == regs->sp()) {
+    if (finished || frame_info->size() == max_frames ||
+        (cur_pc == regs->pc() && cur_sp == regs->sp())) {
       break;
     }
+    adjust_pc = true;
   }
   return num_frames != 0;
 }