From 76076791b9640b76e39bd8429fbd889e22d90d8a Mon Sep 17 00:00:00 2001
From: Derek Parker <parkerderek86@gmail.com>
Date: Fri, 16 Jan 2015 15:30:22 -0600
Subject: [PATCH] Fix stack frame calculation bug

There were certain instances where the calculation of the stack frame
was incorrect, causing for garbage to be returned by a print command.
---
 dwarf/frame/entries.go | 1 -
 dwarf/frame/table.go   | 8 +-------
 proctl/variables.go    | 9 ++++-----
 3 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/dwarf/frame/entries.go b/dwarf/frame/entries.go
index 39f760a7..b5e74529 100644
--- a/dwarf/frame/entries.go
+++ b/dwarf/frame/entries.go
@@ -50,7 +50,6 @@ func (fde *FrameDescriptionEntry) EstablishFrame(pc uint64) *FrameContext {
 
 func (fde *FrameDescriptionEntry) ReturnAddressOffset(pc uint64) int64 {
 	frame := fde.EstablishFrame(pc)
-
 	return frame.cfa.offset + frame.regs[fde.CIE.ReturnAddressRegister].offset
 }
 
diff --git a/dwarf/frame/table.go b/dwarf/frame/table.go
index 24cc04fc..84c5f407 100644
--- a/dwarf/frame/table.go
+++ b/dwarf/frame/table.go
@@ -157,15 +157,9 @@ func (frame *FrameContext) ExecuteUntilPC(instructions []byte) {
 	// We only need to execute the instructions until
 	// ctx.loc > ctx.addess (which is the address we
 	// are currently at in the traced process).
-	for frame.address != frame.loc && frame.buf.Len() > 0 {
+	for frame.address > frame.loc && frame.buf.Len() > 0 {
 		executeDwarfInstruction(frame)
 	}
-	// make sure we get the update cfa offset
-	cfa := frame.CFAOffset()
-	for ncfa := cfa; ncfa == cfa && frame.buf.Len() > 0; {
-		executeDwarfInstruction(frame)
-		ncfa = frame.CFAOffset()
-	}
 }
 
 func executeDwarfInstruction(frame *FrameContext) {
diff --git a/proctl/variables.go b/proctl/variables.go
index 91ba35c9..20a1ea48 100644
--- a/proctl/variables.go
+++ b/proctl/variables.go
@@ -511,9 +511,8 @@ func (thread *ThreadContext) executeStackProgram(instructions []byte) (int64, er
 	}
 
 	fctx := fde.EstablishFrame(regs.PC())
-	cfaOffset := fctx.CFAOffset() + int64(regs.SP())
-
-	address, err := op.ExecuteStackProgram(cfaOffset, instructions)
+	cfa := fctx.CFAOffset() + int64(regs.SP())
+	address, err := op.ExecuteStackProgram(cfa, instructions)
 	if err != nil {
 		return 0, err
 	}
@@ -625,13 +624,13 @@ func (thread *ThreadContext) extractValue(instructions []byte, addr int64, typ i
 }
 
 func (thread *ThreadContext) readString(addr uintptr, size int64) (string, error) {
+	// deref the pointer to the string
 	val, err := thread.readMemory(addr, uintptr(size))
 	if err != nil {
 		return "", err
 	}
-
-	// deref the pointer to the string
 	addr = uintptr(binary.LittleEndian.Uint64(val))
+
 	val, err = thread.readMemory(addr, 16)
 	if err != nil {
 		return "", err