Glue things together into a pipeline

1 files changed, 256 insertions, 0 deletions

diff --git a/scout.cc b/scout.cc
new file mode 100644
index 0000000..6c3ddb5
--- /dev/null
+++ b/scout.cc
@@ -0,0 +1,256 @@
+// Patch's jump destinations searcher
+// Copyright (C) 2024  Nguyễn Gia Phong
+//
+// This file is part of taosc.
+//
+// Taosc is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Taosc is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with taosc.  If not, see <https://www.gnu.org/licenses/>.
+
+// Dyninst headers
+#include <CFG.h>
+#include <CodeObject.h>
+#include <Graph.h>
+#include <Instruction.h>
+#include <InstructionDecoder.h>
+#include <slicing.h>
+
+using AbstractRegion = Dyninst::AbsRegion;
+using Address = Dyninst::Address;
+using AssignmentConverter = Dyninst::AssignmentConverter;
+using AssignmentPtr = Dyninst::Assignment::Ptr;
+using Block = Dyninst::ParseAPI::Block;
+using CodeObject = Dyninst::ParseAPI::CodeObject;
+using CodeRegion = Dyninst::ParseAPI::CodeRegion;
+using CodeSource = Dyninst::ParseAPI::SymtabCodeSource;
+using Edge = Dyninst::Edge;
+using EdgeIterator = Dyninst::EdgeIterator;
+using Function = Dyninst::ParseAPI::Function;
+using Graph = Dyninst::Graph;
+using Instruction = Dyninst::InstructionAPI::Instruction;
+using InstructionCategory = Dyninst::InstructionAPI::InsnCategory;
+using InstructionDecoder = Dyninst::InstructionAPI::InstructionDecoder;
+using NodeIterator = Dyninst::NodeIterator;
+using SliceNode = Dyninst::SliceNode;
+using Slicer = Dyninst::Slicer;
+
+#include <cassert>
+#include <filesystem>
+#include <functional>
+#include <iostream>
+#include <map>
+#include <queue>
+
+/// Collect elements from given iterator into a vector
+template <class Element, class Iterator>
+  std::vector <Element*>
+  range (auto iter)
+  {
+    Iterator begin, end;
+    std::vector <Element*> result;
+    for (iter (begin, end); begin != end; ++begin)
+      result.push_back (static_cast <Element*> ((*begin).get ()));
+    return result;
+  }
+
+class SlicerHelper
+  {
+    CodeSource& cs;
+    InstructionDecoder decoder;
+    Slicer::Predicates predicates;
+    AssignmentConverter ac {true, true};
+    std::set <Address> seen;
+    std::vector <std::vector <Address>> bfs_slices;
+
+  public:
+    SlicerHelper (CodeSource& cs)
+    : cs {cs},
+      decoder {(const void*) nullptr, 1, cs.getArch ()},
+      ac {true, true} // enable caching and stack analysis
+    {
+      this->predicates.setSearchForControlFlowDep(true);
+    }
+
+    /// Decode instruction at given address
+    Instruction
+    decode (Address addr)
+    {
+      auto const& insn = this->decoder.decode ((const unsigned char*)
+        this->cs.getPtrToInstruction (addr));
+      assert (insn.size () > 0);
+      return insn;
+    }
+
+    /// Collect the interprocedure backward slice at addr in BFS order
+    void
+    slice (Instruction const& insn, Address addr, Function* fun, Block* blk)
+    {
+      std::vector <AssignmentPtr> assignments;
+      this->ac.convert (insn, addr, fun, blk, assignments);
+      if (assignments.empty ())
+        return;
+      for (auto const& asgn : assignments)
+        {
+          this->bfs_slices.emplace_back ();
+          Slicer s {asgn, blk, fun};
+          auto const& slice = s.backwardSlice (this->predicates);
+#define ITER(i, E, I, x, f) \
+  for (auto const& i : range <E, I> ([x] (auto& b, auto& e) { x->f (b, e); }))
+          ITER (node, SliceNode, NodeIterator, slice, exitNodes)
+            {
+              this->seen.insert (node->addr ());
+              std::queue <SliceNode*> q; // breadth-first traversal
+              q.push (node);
+              while (!q.empty ())
+                {
+                  auto const& parent = q.front ();
+                  q.pop ();
+                  this->bfs_slices.back ().push_back (parent->addr ());
+                  ITER (edge, Edge, EdgeIterator, parent, ins)
+#undef ITER
+                    {
+                      auto const& child = edge->source ();
+                      if (this->seen.count (child->addr ()) > 0)
+                        continue;
+                      this->seen.insert (child->addr ());
+                      q.push (static_cast <SliceNode*> (child.get ()));
+                    }
+                }
+            }
+        }
+    }
+
+    /// Flatten stored BFS slices in round-robin order
+    std::vector <Address> const
+    slice_zip ()
+    {
+      std::vector <Address> result;
+      size_t n = 0;
+      for (auto const& v : this->bfs_slices)
+        {
+          if (result.empty () || v[0] != result.back ())
+            result.push_back (v[0]);
+          n = std::max (n, v.size ());
+        }
+      for (size_t i = 1; i < n; ++i)
+        for (auto const& v : this->bfs_slices)
+          if (i < v.size ())
+            result.push_back (v[i]);
+      return result;
+    }
+  };
+
+/// Find next basic block's entry after given address, reparsing if necessary
+Block*
+next_block (CodeObject& co, CodeRegion* region, Address address)
+{
+  auto blk = co.findBlockByEntry (region, address);
+  if (blk != nullptr)
+    return blk;
+  co.parse (address, true);
+  blk = co.findBlockByEntry (region, address);
+  return (blk != nullptr) ? blk : co.findNextBlock (region, address);
+}
+
+/// Find block containing given address
+Block*
+find_block (CodeSource& cs, CodeObject& co, Address target_addr)
+{
+  if (!cs.isCode (target_addr))
+    {
+      std::cerr << std::hex << target_addr
+        << " does not point to an instruction\n";
+      return nullptr;
+    }
+  std::set <CodeRegion*> regions;
+  if (cs.findRegions (target_addr, regions) != 1)
+    {
+      std::cerr << "expected 1 region containing instruction, found "
+        << regions.size () << '\n';
+      return nullptr;
+    }
+  for (auto const& region : regions)
+    {
+      std::set <Block*> blocks;
+      if (co.findBlocks (region, target_addr, blocks) > 0)
+        for (auto const& blk : blocks) // TODO: choose the best block
+          return blk;
+
+      auto* blk = next_block (co, region, region->low ());
+      while (blk != nullptr && target_addr > blk->last ())
+        blk = next_block (co, region, blk->end ());
+      if (blk == nullptr)
+        return nullptr;
+      assert (target_addr >= blk->start () && target_addr < blk->end ());
+      return blk;
+    }
+#if defined(__cpp_lib_unreachable) && (__cpp_lib_unreachable >= 202202L)
+  std::unreachable ();
+#else
+  __builtin_unreachable(); // GCC or Clang
+#endif
+}
+
+/// Slice backward from return instructions
+std::vector <Address> const
+returns_slice (CodeSource& cs, Function* fun, Address target_addr)
+{
+  SlicerHelper helper {cs};
+  for (auto const& blk : fun->blocks ())
+    for (auto [addr, step] = std::tuple {blk->start (), 0ul};
+         addr < blk->end ();
+         addr += step)
+      {
+        auto const& insn = helper.decode (addr);
+        step = insn.size ();
+        if (insn.getCategory () == InstructionCategory::c_ReturnInsn)
+          helper.slice (insn, addr, fun, blk);
+      }
+  return helper.slice_zip ();
+}
+
+int
+main (int argc, char** argv)
+{
+  if (argc != 3)
+    {
+      std::cerr << "Usage: " << std::filesystem::path (argv[0]).filename ()
+        << " binary instruction-address\n";
+      return -1;
+    }
+  CodeSource cs {argv[1]};
+  Address target_addr;
+  {
+    std::stringstream ss;
+    ss << std::hex << argv[2];
+    ss >> target_addr;
+  }
+  CodeObject co {&cs};
+  co.parse (); // parsed functions have same lifetime as co
+  auto const& block = find_block (cs, co, target_addr);
+  if (block == nullptr)
+    {
+      std::cerr << "block containing instruction not found\n";
+      return -1;
+    }
+  std::vector<Function*> functions;
+  block->getFuncs (functions);
+  if (functions.size () != 1)
+    {
+      std::cerr << "0 or multiple functions containing instruction found\n";
+      return -1;
+    }
+  for (auto* fun : functions)
+    for (auto const& addr : returns_slice (cs, fun, target_addr))
+      std::cout << std::hex << addr << '\n';
+  return 0;
+}