From cb1d58302ded7e047bd0d00464338ef164910efd Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Mon, 7 Jan 2013 20:04:23 -0800
Subject: [PATCH] Bug 827691 - Treat [stack:nnnn] entries in /proc/self/maps as
 anonymous memory.  r=jlebar.

--HG--
extra : rebase_source : bfe5db77f0a4329a6cafeecfdb9b9de605f53bc5
---
 xpcom/base/MapsMemoryReporter.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/xpcom/base/MapsMemoryReporter.cpp b/xpcom/base/MapsMemoryReporter.cpp
index 2ef4c2667f10..692484bc9e95 100644
--- a/xpcom/base/MapsMemoryReporter.cpp
+++ b/xpcom/base/MapsMemoryReporter.cpp
@@ -335,6 +335,19 @@ MapsReporter::ParseMapping(
   return NS_OK;
 }
 
+static bool
+IsAnonymous(const nsACString &aName)
+{
+  // Recent kernels (e.g. 3.5) have multiple [stack:nnnn] entries, where |nnnn|
+  // is a thread ID.  However, [stack:nnnn] entries count both stack memory
+  // *and* anonymous memory because the kernel only knows about the start of
+  // each thread stack, not its end.  So we treat such entries as anonymous
+  // memory instead of stack.  This is consistent with older kernels that don't
+  // even show [stack:nnnn] entries.
+  return aName.IsEmpty() ||
+         StringBeginsWith(aName, NS_LITERAL_CSTRING("[stack:"));
+}
+
 void
 MapsReporter::GetReporterNameAndDescription(
   const char *aPath,
@@ -376,7 +389,7 @@ MapsReporter::GetReporterNameAndDescription(
                  "perform some privileged actions without the overhead of a "
                  "syscall.");
   }
-  else if (!basename.IsEmpty()) {
+  else if (!IsAnonymous(basename)) {
     nsAutoCString dirname;
     GetDirname(absPath, dirname);