Breakpad processor: Support AMD64 stack unwinding driven by DWARF CFI.

This adds support for 'STACK CFI' records (DWARF CFI) to the AMD64
stack walker. This is necessary for the stack trace to include any
frames other than the youngest. Unit tests are included.

a=jimblandy, r=mmentovai


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@554 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 30 insertions, 14 deletions

diff --git a/src/google_breakpad/processor/stack_frame_cpu.h b/src/google_breakpad/processor/stack_frame_cpu.h
index c5bddffb..0996886f 100644
--- a/src/google_breakpad/processor/stack_frame_cpu.h
+++ b/src/google_breakpad/processor/stack_frame_cpu.h
@@ -139,28 +139,44 @@ struct StackFramePPC : public StackFrame {
 };
 
 struct StackFrameAMD64 : public StackFrame {
-  // ContextValidity has one entry for each relevant hardware pointer register
-  // (%rip and %rsp) and one entry for each nonvolatile (callee-save) register.
-  //FIXME: validate this list
+  // ContextValidity has one entry for each register that we might be able
+  // to recover.
   enum ContextValidity {
-    CONTEXT_VALID_NONE = 0,
-    CONTEXT_VALID_RIP  = 1 << 0,
-    CONTEXT_VALID_RSP  = 1 << 1,
-    CONTEXT_VALID_RBP  = 1 << 2,
+    CONTEXT_VALID_NONE  = 0,
+    CONTEXT_VALID_RAX   = 1 << 0,
+    CONTEXT_VALID_RDX   = 1 << 1,
+    CONTEXT_VALID_RCX   = 1 << 2,
+    CONTEXT_VALID_RBX   = 1 << 3,
+    CONTEXT_VALID_RSI   = 1 << 4,
+    CONTEXT_VALID_RDI   = 1 << 5,
+    CONTEXT_VALID_RBP   = 1 << 6,
+    CONTEXT_VALID_RSP   = 1 << 7,
+    CONTEXT_VALID_R8    = 1 << 8,
+    CONTEXT_VALID_R9    = 1 << 9,
+    CONTEXT_VALID_R10   = 1 << 10,
+    CONTEXT_VALID_R11   = 1 << 11,
+    CONTEXT_VALID_R12   = 1 << 12,
+    CONTEXT_VALID_R13   = 1 << 13,
+    CONTEXT_VALID_R14   = 1 << 14,
+    CONTEXT_VALID_R15   = 1 << 15,
+    CONTEXT_VALID_RIP   = 1 << 16,
     CONTEXT_VALID_ALL  = -1
   };
 
   StackFrameAMD64() : context(), context_validity(CONTEXT_VALID_NONE) {}
 
-  // Register state.  This is only fully valid for the topmost frame in a
-  // stack.  In other frames, the values of nonvolatile registers may be
-  // present, given sufficient debugging information.  Refer to
-  // context_validity.
+  // Register state. This is only fully valid for the topmost frame in a
+  // stack. In other frames, which registers are present depends on what
+  // debugging information we had available. Refer to context_validity.
   MDRawContextAMD64 context;
 
-  // context_validity is actually ContextValidity, but int is used because
-  // the OR operator doesn't work well with enumerated types.  This indicates
-  // which fields in context are valid.
+  // For each register in context whose value has been recovered, we set
+  // the corresponding CONTEXT_VALID_ bit in context_validity.
+  //
+  // context_validity's type should actually be ContextValidity, but
+  // we use int instead because the bitwise inclusive or operator
+  // yields an int when applied to enum values, and C++ doesn't
+  // silently convert from ints to enums.
   int context_validity;
 };