Move main executable handling out of procmaps parser loop.

If the mapping for the main executable needed to be merged (for
example, if it was linked with lld and therefore contains an r mapping
followed by an r/x mapping), we would never reach the code that makes
it the first module. Handle that situation by moving that code into
a separate loop.

This fixes an issue where breakpad_unittests fails on Android devices
when linked with lld. It appears that the glibc dynamic loader
happens to always load executables (or at least the executables that
we create) at a lower address than DSOs, so we never hit this bug on
desktop Linux.

Testing: "make check" with both gold and lld as linker. Also
breakpad_unittests when patched into Chromium on Linux (lld) and
Android (gold and lld).

Bug: chromium:469376
Change-Id: I6329e4afd2f1bf44c25a6c3e684495e21dba83a6
Reviewed-on: https://chromium-review.googlesource.com/722286
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

1 files changed, 21 insertions, 19 deletions

diff --git a/src/client/linux/minidump_writer/linux_dumper.cc b/src/client/linux/minidump_writer/linux_dumper.cc
index 0013824b..9a7a8542 100644
--- a/src/client/linux/minidump_writer/linux_dumper.cc
+++ b/src/client/linux/minidump_writer/linux_dumper.cc
@@ -611,6 +611,7 @@ bool LinuxDumper::EnumerateMappings() {
             }
           }
           MappingInfo* const module = new(allocator_) MappingInfo;
+          mappings_.push_back(module);
           my_memset(module, 0, sizeof(MappingInfo));
           module->system_mapping_info.start_addr = start_addr;
           module->system_mapping_info.end_addr = end_addr;
@@ -623,31 +624,32 @@ bool LinuxDumper::EnumerateMappings() {
             if (l < sizeof(module->name))
               my_memcpy(module->name, name, l);
           }
-          // If this is the entry-point mapping, and it's not already the
-          // first one, then we need to make it be first.  This is because
-          // the minidump format assumes the first module is the one that
-          // corresponds to the main executable (as codified in
-          // processor/minidump.cc:MinidumpModuleList::GetMainModule()).
-          if (entry_point_loc &&
-              (entry_point_loc >=
-                  reinterpret_cast<void*>(module->start_addr)) &&
-              (entry_point_loc <
-                  reinterpret_cast<void*>(module->start_addr+module->size)) &&
-              !mappings_.empty()) {
-            // push the module onto the front of the list.
-            mappings_.resize(mappings_.size() + 1);
-            for (size_t idx = mappings_.size() - 1; idx > 0; idx--)
-              mappings_[idx] = mappings_[idx - 1];
-            mappings_[0] = module;
-          } else {
-            mappings_.push_back(module);
-          }
         }
       }
     }
     line_reader->PopLine(line_len);
   }
 
+  if (entry_point_loc) {
+    for (size_t i = 0; i < mappings_.size(); ++i) {
+      MappingInfo* module = mappings_[i];
+
+      // If this module contains the entry-point, and it's not already the first
+      // one, then we need to make it be first.  This is because the minidump
+      // format assumes the first module is the one that corresponds to the main
+      // executable (as codified in
+      // processor/minidump.cc:MinidumpModuleList::GetMainModule()).
+      if ((entry_point_loc >= reinterpret_cast<void*>(module->start_addr)) &&
+          (entry_point_loc <
+           reinterpret_cast<void*>(module->start_addr + module->size))) {
+        for (size_t j = i; j > 0; j--)
+          mappings_[j] = mappings_[j - 1];
+        mappings_[0] = module;
+        break;
+      }
+    }
+  }
+
   sys_close(fd);
 
   return !mappings_.empty();