Make x86-64 stack walking work for Native Client minidumps

For NaCl, a stack walker should ignore the top 32 bits of %rip, %rsp
and %rbp, otherwise it will try to read from %r15-extended stack
addresses and look up symbol info for %r15-extended code addresses,
which will fail.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3424
TEST=tested manually with a NaCl minidump

Review URL: https://breakpad.appspot.com/591002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1173 4c0a9323-5329-0410-9bdc-e9ce6186880e

2 files changed, 16 insertions, 4 deletions

diff --git a/src/google_breakpad/processor/system_info.h b/src/google_breakpad/processor/system_info.h
index 4a250482..9583d9e8 100644
--- a/src/google_breakpad/processor/system_info.h
+++ b/src/google_breakpad/processor/system_info.h
@@ -63,10 +63,11 @@ struct SystemInfo {
   string os;
 
   // A short form of the os string, using lowercase letters and no spaces,
-  // suitable for use in a filesystem.  Possible values are "windows",
-  // "mac", and "linux".  Empty if the information is not present in the dump
-  // or if the OS given by the dump is unknown.  The values stored in this
-  // field should match those used by MinidumpSystemInfo::GetOS.
+  // suitable for use in a filesystem.  Possible values include "windows",
+  // "mac", "linux" and "nacl".  Empty if the information is not present
+  // in the dump or if the OS given by the dump is unknown.  The values
+  // stored in this field should match those used by
+  // MinidumpSystemInfo::GetOS.
   string os_short;
 
   // A string identifying the version of the operating system, such as
diff --git a/src/processor/stackwalker_amd64.cc b/src/processor/stackwalker_amd64.cc
index 656af183..737a2496 100644
--- a/src/processor/stackwalker_amd64.cc
+++ b/src/processor/stackwalker_amd64.cc
@@ -40,6 +40,7 @@
 #include "google_breakpad/processor/memory_region.h"
 #include "google_breakpad/processor/source_line_resolver_interface.h"
 #include "google_breakpad/processor/stack_frame_cpu.h"
+#include "google_breakpad/processor/system_info.h"
 #include "processor/cfi_frame_info.h"
 #include "processor/logging.h"
 #include "processor/stackwalker_amd64.h"
@@ -222,6 +223,16 @@ StackFrame* StackwalkerAMD64::GetCallerFrame(const CallStack* stack) {
   if (!new_frame.get())
     return NULL;
 
+  if (system_info_->os_short == "nacl") {
+    // Apply constraints from Native Client's x86-64 sandbox.  These
+    // registers have the 4GB-aligned sandbox base address (from r15)
+    // added to them, and only the bottom 32 bits are relevant for
+    // stack walking.
+    new_frame->context.rip = static_cast<uint32_t>(new_frame->context.rip);
+    new_frame->context.rsp = static_cast<uint32_t>(new_frame->context.rsp);
+    new_frame->context.rbp = static_cast<uint32_t>(new_frame->context.rbp);
+  }
+
   // Treat an instruction address of 0 as end-of-stack.
   if (new_frame->context.rip == 0)
     return NULL;