Add support uClibc++ excpetions. This involves additional handling for relative relation types, additional support for unwinding, as well as additional changes. The culmination of a big effort fromo Leo Aloe3132

binfmt/libelf/libelf_load.c

@@ -245,6 +245,9 @@ static inline int elf_loadfile(FAR struct elf_loadinfo_s *loadinfo)
 int elf_load(FAR struct elf_loadinfo_s *loadinfo)
 {
   size_t heapsize;
+#ifdef CONFIG_UCLIBCXX_EXCEPTION
+  int exidx;
+#endif
   int ret;
 
   bvdbg("loadinfo: %p\n", loadinfo);
@@ -328,6 +331,18 @@ int elf_load(FAR struct elf_loadinfo_s *loadinfo)
     }
 #endif
 
+#ifdef CONFIG_UCLIBCXX_EXCEPTION
+  exidx = elf_findsection(loadinfo, CONFIG_ELF_EXIDX_SECTNAME);
+  if (exidx < 0)
+    {
+      bvdbg("elf_findsection: Exception Index section not found: %d\n", exidx);
+    }
+  else
+    {
+      up_init_exidx(loadinfo->shdr[exidx].sh_addr, loadinfo->shdr[exidx].sh_size);
+    }
+#endif
+
 #ifdef CONFIG_ARCH_ADDRENV
   /* Restore the original address environment */