Adjust MD_CONTEXT_CPU_MASK to reflect reality, fix some code so it can handle dumps using the old value for MD_CONTEXT_ARM

The value of MD_CONTEXT_CPU_MASK in use assumes that only the lower 6 bits are used for flags, and the upper 26 bits are for the CPU type. However, as of Windows 7 SP1, the 7th bit is being used as a flag (per http://msdn.microsoft.com/en-us/library/hh134238%28v=vs.85%29.aspx and the Windows SDK headers). Adjusting MD_CONTEXT_CPU_MASK works, but unfortunately that masks off the existing value of MD_CONTEXT_ARM. This patch also changes the value of MD_CONTEXT_ARM and adjusts the minidump context reading machinery to gracefully handle minidumps with the old value.
R=mark at http://breakpad.appspot.com/302001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@831 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 11 insertions, 0 deletions

diff --git a/src/processor/minidump.cc b/src/processor/minidump.cc
index 9e084401..331ebd9e 100644
--- a/src/processor/minidump.cc
+++ b/src/processor/minidump.cc
@@ -410,6 +410,17 @@ bool MinidumpContext::Read(u_int32_t expected_size) {
       Swap(&context_flags);
 
     u_int32_t cpu_type = context_flags & MD_CONTEXT_CPU_MASK;
+    if (cpu_type == 0) {
+      // Unfortunately the flag for MD_CONTEXT_ARM that was taken
+      // from a Windows CE SDK header conflicts in practice with
+      // the CONTEXT_XSTATE flag. MD_CONTEXT_ARM has been renumbered,
+      // but handle dumps with the legacy value gracefully here.
+      if (context_flags & MD_CONTEXT_ARM_OLD) {
+        context_flags |= MD_CONTEXT_ARM;
+        context_flags &= ~MD_CONTEXT_ARM_OLD;
+        cpu_type = MD_CONTEXT_ARM;
+      }
+    }
 
     // Allocate the context structure for the correct CPU and fill it.  The
     // casts are slightly unorthodox, but it seems better to do that than to