Make the backtrace-data test helper more robust

When unwinding by frame pointer the unwinder might ask for invalid
addresses. We don't have to fail the test in this case. In fact
any broken dwarf information can lead to requests for invalid
addresses, also without frame pointer unwinding.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>

2 files changed, 19 insertions, 3 deletions

diff --git a/tests/ChangeLog b/tests/ChangeLog
index 7031cf57..7040ac84 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,9 @@
+2017-02-09  Ulf Hermann  <ulf.hermann@qt.io>
+
+	* backtrace-data.c: Don't assert that symbols are found.
+	The unwinder is allowed to ask for invalid addresses. We deny
+	such requests, rather than make the test fail.
+
 2016-11-17  Mark Wielaard  <mjw@redhat.com>
 
 	* run-readelf-s.sh: Add --symbols=.dynsym and --symbols=.symtab tests.
diff --git a/tests/backtrace-data.c b/tests/backtrace-data.c
index b7158dae..a387d8ff 100644
--- a/tests/backtrace-data.c
+++ b/tests/backtrace-data.c
@@ -76,10 +76,15 @@ memory_read (Dwfl *dwfl, Dwarf_Addr addr, Dwarf_Word *result,
 
   errno = 0;
   long l = ptrace (PTRACE_PEEKDATA, child, (void *) (uintptr_t) addr, NULL);
-  assert (errno == 0);
+
+  // The unwinder can ask for an invalid address.
+  // Don't assert on that but just politely refuse.
+  if (errno != 0) {
+      errno = 0;
+      return false;
+  }
   *result = l;
 
-  /* We could also return false for failed ptrace.  */
   return true;
 }
 
@@ -103,7 +108,8 @@ maps_lookup (pid_t pid, Dwarf_Addr addr, GElf_Addr *basep)
       unsigned long start, end, offset;
       i = fscanf (f, "%lx-%lx %*s %lx %*x:%*x %*x", &start, &end, &offset);
       assert (errno == 0);
-      assert (i == 3);
+      if (i != 3)
+          break;
       char *filename = strdup ("");
       assert (filename);
       size_t filename_len = 0;
@@ -131,6 +137,8 @@ maps_lookup (pid_t pid, Dwarf_Addr addr, GElf_Addr *basep)
 	}
       free (filename);
     }
+  *basep = 0;
+  return NULL;
 }
 
 /* Add module containing ADDR to the DWFL address space.
@@ -145,6 +153,8 @@ report_module (Dwfl *dwfl, pid_t child, Dwarf_Addr addr)
 {
   GElf_Addr base;
   char *long_name = maps_lookup (child, addr, &base);
+  if (!long_name)
+      return NULL; // not found
   Dwfl_Module *mod = dwfl_report_elf (dwfl, long_name, long_name, -1,
 				      base, false /* add_p_vaddr */);
   assert (mod);