From 36096575ed213a491e60b822ec84e2365a2de0d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Fri, 6 Apr 2018 16:38:24 +0200
Subject: [PATCH] Remove necessity to copy the stack

---
 Makefile                                  |  2 +-
 include/dwarfinterpret/DwarfInterpret.hpp |  4 ---
 include/dwarfinterpret/StackDump.hpp      | 28 ----------------
 src/DwarfInterpret.cpp                    | 10 +++---
 src/StackDump.cpp                         | 40 -----------------------
 test/Makefile                             |  4 +--
 6 files changed, 6 insertions(+), 82 deletions(-)
 delete mode 100644 include/dwarfinterpret/StackDump.hpp
 delete mode 100644 src/StackDump.cpp

diff --git a/Makefile b/Makefile
index b500bbc..e9220e2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 LIB_DIR=lib
 TARGET=$(LIB_DIR)/libdwarfinterpret.so
-SRC=src/DwarfInterpret.cpp src/MemoryMap.cpp src/StackDump.cpp
+SRC=src/DwarfInterpret.cpp src/MemoryMap.cpp
 
 INCLUDE_DIR=include
 
diff --git a/include/dwarfinterpret/DwarfInterpret.hpp b/include/dwarfinterpret/DwarfInterpret.hpp
index 13122ff..1a9bd44 100644
--- a/include/dwarfinterpret/DwarfInterpret.hpp
+++ b/include/dwarfinterpret/DwarfInterpret.hpp
@@ -12,7 +12,6 @@
 #include <dwarfpp/root.hpp>
 
 #include "MemoryMap.hpp"
-#include "StackDump.hpp"
 
 #define OF_WHAT_EXCEPTION(cl_name) \
     cl_name: public WhatException { \
@@ -95,10 +94,7 @@ class DwarfInterpret {
 
         /// An unwind context, holding registers
         struct UnwindContext {
-            UnwindContext(const StackDump& dump): stack(dump) {}
-
             // Let's pretend this is enough
-            StackDump stack;
             uintptr_t rip;
             uintptr_t rsp;
             uintptr_t rbp;
diff --git a/include/dwarfinterpret/StackDump.hpp b/include/dwarfinterpret/StackDump.hpp
deleted file mode 100644
index 2686378..0000000
--- a/include/dwarfinterpret/StackDump.hpp
+++ /dev/null
@@ -1,28 +0,0 @@
-#pragma once
-
-#include <memory>
-#include <cstdint>
-
-#include <dwarfinterpret/MemoryMap.hpp>
-
-class StackDump {
-    public:
-        static StackDump snapshot(uintptr_t rsp); ///< Take an instant snapshot
-
-        StackDump(const StackDump& oth); ///< copy
-        StackDump& operator=(const StackDump& oth); ///< copy
-
-        template <typename T> T deref(uintptr_t pos) const {
-            return *((T*)(stack.get() + pos - offset));
-        }
-        uintptr_t at(uintptr_t pos) const {
-            return deref<uintptr_t>(pos);
-        }
-
-    private:
-        StackDump();
-
-        typedef char cell_t;
-        std::shared_ptr<cell_t> stack;
-        uintptr_t offset; ///< such that stack[stack_addr - offset] is ok
-};
diff --git a/src/DwarfInterpret.cpp b/src/DwarfInterpret.cpp
index fceaa9e..a2a733f 100644
--- a/src/DwarfInterpret.cpp
+++ b/src/DwarfInterpret.cpp
@@ -159,7 +159,7 @@ DwarfInterpret::reg_content_t DwarfInterpret::interpret_dw_register(
                 interpret_dw_register(row, DW_FRAME_CFA_COL3, ctx);
             int cfa_offset = reg.saved_at_offset_from_cfa_r();
             reg_content_t addr = cfa_loc + cfa_offset;
-            reg_content_t value = ctx.stack.deref<reg_content_t>(addr);
+            reg_content_t value = *((reg_content_t*) addr);
             cerr << "@@ Interpreting CFA offset: CFA is " << hex
                  << cfa_loc << " + offset " << dec << cfa_offset << hex
                  << " = " << addr
@@ -193,12 +193,10 @@ DwarfInterpret::UnwindContext DwarfInterpret::get_current_unwind_context() {
     // context snapshot naively taken from inside this function). Unwinding
     // it some number of times should yield the expected context
 
-    uintptr_t rsp;
-    get_cpu_register(REG_RSP, rsp);
 
-    UnwindContext ctx(StackDump::snapshot(rsp));
+    UnwindContext ctx;
     get_cpu_register(REG_RIP, ctx.rip);
-    ctx.rsp = rsp;
+    get_cpu_register(REG_RSP, ctx.rsp);
     get_cpu_register(REG_RBP, ctx.rbp);
 
     cerr << "CREATING CONTEXT. %rsp=0x" << hex
@@ -222,7 +220,7 @@ DwarfInterpret::UnwindContext DwarfInterpret::unwind_context(
 
     DwarfRow cur_row = dwarf_row_at(ctx.rip);
     const core::Cie& cie = *cie_at(ctx.rip);
-    UnwindContext new_context(ctx.stack);
+    UnwindContext new_context;
     cerr << "Obtaining previous context as reg "
          << cie.get_return_address_register_rule()
          << " at current IP = "
diff --git a/src/StackDump.cpp b/src/StackDump.cpp
deleted file mode 100644
index 6e3bbce..0000000
--- a/src/StackDump.cpp
+++ /dev/null
@@ -1,40 +0,0 @@
-#include <dwarfinterpret/StackDump.hpp>
-
-#include <dwarfinterpret/MemoryMap.hpp>
-#include <cassert>
-#include <iostream>  // FIXME
-#include <cstring>
-
-using namespace std;
-
-StackDump StackDump::snapshot(uintptr_t rsp) {
-    StackDump stack;
-
-    MemoryMap memory_map;
-    const MemoryMap::MapEntry& stack_region =
-        memory_map[memory_map.id_of_address(rsp)];
-
-    assert(stack_region.pathname == "[stack]");
-    size_t stack_size = stack_region.mem_region.end - rsp;
-    stack.stack = std::shared_ptr<cell_t>(new cell_t[stack_size]);
-    cerr << "memcpy'ing " << stack_size << " bytes" << endl;
-    memcpy(stack.stack.get(), (void*)rsp, stack_size); // FIXME way too brutal
-
-    stack.offset = rsp;
-
-    return stack;
-}
-
-StackDump::StackDump()
-    : stack(nullptr), offset(0)
-{}
-
-StackDump::StackDump(const StackDump& oth) {
-    this->operator=(oth);
-}
-
-StackDump& StackDump::operator=(const StackDump& oth) {
-    stack = oth.stack;
-    offset = oth.offset;
-    return *this;
-}
diff --git a/test/Makefile b/test/Makefile
index 56c9fa0..6d7c41b 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -4,8 +4,6 @@ CXXLIBS=-ldwarfpp -ldwarf -lelf -lc++fileno -ldwarfinterpret
 CXXDIRS=-I../include -L../lib
 
 
-OBJS = $(SRC:.cpp=.o)
-
 ###############################################################################
 
 all: $(TARGET)
@@ -22,4 +20,4 @@ dump_my_stack.bin: dump_my_stack.o
 .PRECIOUS: %.o
 
 clean:
-	rm -f $(OBJS) $(TARGET)
+	rm -f *.o *.bin