Add ability to evaluate registers' values (UNTESTED)

include/DwarfInterpret.hpp

@@ -2,7 +2,13 @@
 
 #include <string>
 #include <memory>
+#include <cstdint>
 
+#include <dwarfpp/lib.hpp>
+#include <dwarfpp/regs.hpp>
+#include <dwarfpp/frame.hpp>
+#include <dwarfpp/attr.hpp>
+#include <dwarfpp/frame.hpp>
 #include <dwarfpp/root.hpp>
 
 class DwarfInterpret {
@@ -15,7 +21,20 @@ class DwarfInterpret {
     public:
         class NotInstanciated: public std::exception {};
         class AlreadyInstanciated: public std::exception {};
+        class ValuelessRegister: public std::exception {};
+        class NotImplemented: public std::exception {};
+        class FailedGetContext: public std::exception {};
 
+        typedef dwarf::core::FrameSection::register_def DwarfRegister;
+        typedef std::set<std::pair<int, DwarfRegister> > DwarfRow; // FIXME
+
+        typedef uintptr_t reg_content_t;
+
+    private:
+        //typedef std::set<std::pair<int, DwarfRegister> > DwarfRow;
+
+
+    public:
         DwarfInterpret(DwarfInterpret const&) = delete;
         void operator=(DwarfInterpret const&) = delete;
 
@@ -24,12 +43,22 @@ class DwarfInterpret {
 
         int get_elf_machine() const { return elf_machine; }
 
-        // FIXME DEBUG vvv
-        void dbg_dump_ra();
+        reg_content_t interpret_dw_register(
+                const DwarfRow& row,
+                const DwarfRegister& reg
+                ) const;
+        reg_content_t interpret_dw_register(
+                const DwarfRow& row,
+                int reg_id
+                ) const;
 
     private:
         DwarfInterpret(const std::string& elf_path);
 
+        DwarfRegister get_column(const DwarfRow& row, int column) const;
+        reg_content_t get_cpu_register(int reg_id) const;
+
+
     private: // members
         static std::unique_ptr<DwarfInterpret> instance;
 

src/DwarfInterpret.cpp

@@ -15,9 +15,16 @@
 #include <dwarfpp/root.hpp>
 #include <gelf.h>
 
+#include <ucontext.h>
+
+#include "register_map.hpp"
+
 using namespace std;
 using namespace dwarf;
 
+
+std::unique_ptr<DwarfInterpret> DwarfInterpret::instance(nullptr);
+
 DwarfInterpret::DwarfInterpret(const std::string& elf_path)
     : root_die(fileno(std::ifstream(elf_path)))
 {
@@ -45,14 +52,58 @@ DwarfInterpret& DwarfInterpret::instanciate(const std::string& elf_path) {
     return *(DwarfInterpret::instance);
 }
 
-// BEGIN DEBUG
-using core::FrameSection;
-typedef FrameSection::register_def register_def;
+DwarfInterpret::reg_content_t DwarfInterpret::interpret_dw_register(
+        const DwarfInterpret::DwarfRow& row,
+        const DwarfInterpret::DwarfRegister& reg
+        ) const
+{
+    switch(reg.k) {
+        case core::FrameSection::register_def::INDETERMINATE:
+        case core::FrameSection::register_def::UNDEFINED:
+            throw ValuelessRegister();
 
-typedef std::set<std::pair<int, register_def> > DwarfRow;
+        case core::FrameSection::register_def::REGISTER: {
+            ostringstream exprs;
+            int dwarf_regnum = reg.register_plus_offset_r().first;
+            assert(dwarf_regnum != DW_FRAME_CFA_COL3);
+            int cpu_regnum = REG_DWARF_TO_UCONTEXT[dwarf_regnum];
+
+            reg_content_t* cpu_content =
+                (reg_content_t*) get_cpu_register(cpu_regnum);
+            reg_content_t* addr =
+                cpu_content + reg.register_plus_offset_r().second;
+
+            return *addr;
+        } break;
+
+        case core::FrameSection::register_def::SAVED_AT_OFFSET_FROM_CFA: {
+            reg_content_t* cfa_loc =
+                (reg_content_t*) interpret_dw_register(row, DW_FRAME_CFA_COL3);
+            reg_content_t* addr = cfa_loc;
+            return *addr;
+        } break;
+
+        case core::FrameSection::register_def::SAVED_AT_EXPR:
+            throw NotImplemented();
+            break;
+        case core::FrameSection::register_def::VAL_IS_OFFSET_FROM_CFA:
+        case core::FrameSection::register_def::VAL_OF_EXPR:
+        default:
+            throw NotImplemented();
+            break;
+    }
+}
+
+DwarfInterpret::reg_content_t DwarfInterpret::interpret_dw_register(
+        const DwarfInterpret::DwarfRow& row,
+        int reg_id
+        ) const
+{
+    return interpret_dw_register(row, get_column(row, reg_id));
+}
 
 template<typename Key>
-typename std::set<std::pair<int, Key> >::const_iterator find_column(
+static typename std::set<std::pair<int, Key> >::const_iterator find_column(
         const std::set<std::pair<int, Key> >& set,
         int key)
 {
@@ -69,116 +120,24 @@ typename std::set<std::pair<int, Key> >::const_iterator find_column(
     return it;
 }
 
-register_def get_column(const DwarfRow& row, int column) {
-    auto it = find_column<register_def>(row, column);
+DwarfInterpret::DwarfRegister DwarfInterpret::get_column(
+        const DwarfInterpret::DwarfRow& row,
+        int column
+        ) const
+{
+    auto it = find_column<DwarfRegister>(row, column);
     if(it == row.end())
         throw std::out_of_range("No such column");
     return it->second;
 }
 
-struct ColumnQuery {
-    const DwarfRow& row;
-    int column;
-    ColumnQuery(const DwarfRow& row, int column):
-        row(row), column(column) {}
-};
+DwarfInterpret::reg_content_t DwarfInterpret::get_cpu_register(
+        int reg_id) const
+{
+    ucontext_t context;
+    if(getcontext(&context) != 0)
+        throw FailedGetContext();
 
-ostream& operator<<(ostream& os, const register_def& reg) {
-    switch(reg.k) {
-        case FrameSection::register_def::INDETERMINATE:
-        case FrameSection::register_def::UNDEFINED:
-            return os << "u";
-
-        case FrameSection::register_def::REGISTER: {
-            ostringstream exprs;
-            int regnum = reg.register_plus_offset_r().first;
-            string regname;
-            if (regnum == DW_FRAME_CFA_COL3) regname = "X";
-                // DON'T confuse this case with 'c', which means
-                // SAVED_AT_OFFSET_FROM_CFA
-            else
-                regname = dwarf::lib::dwarf_regnames_for_elf_machine(
-                        DwarfInterpret::acquire().get_elf_machine())[regnum];
-            exprs << regname << std::showpos << std::dec << setw(0)
-                  << (int) reg.register_plus_offset_r().second;
-
-            return os << exprs.str();
-        } break;
-
-        case FrameSection::register_def::SAVED_AT_OFFSET_FROM_CFA: {
-            ostringstream exprs;
-            exprs << "c" << std::showpos << std::dec
-                  << reg.saved_at_offset_from_cfa_r();
-            return os << exprs.str();
-        } break;
-        case FrameSection::register_def::SAVED_AT_EXPR:
-            return os << "exp";
-            break;
-        case FrameSection::register_def::VAL_IS_OFFSET_FROM_CFA:
-        case FrameSection::register_def::VAL_OF_EXPR:
-        default:
-            return os << "BLAH";
-            break;
-    }
-}
-
-ostream& operator<<(ostream& os, const ColumnQuery& query) {
-    try {
-        register_def regdef = get_column(query.row, query.column);
-        return os << regdef;
-    } catch(const std::out_of_range&) {
-        return os << "u";
-    }
-}
-
-void extract_ra_of_fde(const core::FrameSection& fs, const core::Fde& fde) {
-    auto decoded = fde.decode();
-    const core::Cie& cie = *(fde.find_cie());
-
-    int ra_col = cie.get_return_address_register_rule();
-    int cfa_col = DW_FRAME_CFA_COL3;
-
-    for(const auto& row: decoded.rows) {
-        cout
-            << std::hex << std::setfill('0')
-            << std::setw(2 * cie.get_address_size())
-            << row.first.lower() << ' '
-            << setfill(' ')
-            << setw(8) << ColumnQuery(row.second, cfa_col) << ' '
-            << setw(6) << ColumnQuery(row.second, ra_col)
-            << endl
-            << std::dec;
-    }
-}
-// END DEBUG
-
-void DwarfInterpret::dbg_dump_ra() {
-    dwarf::core::FrameSection& frame_section =
-        root_die.get_frame_section();
-    std::vector<FrameSection::fde_iterator> fdes;
-    for(auto fde_it = frame_section.fde_begin();
-            fde_it != frame_section.fde_end();
-            ++fde_it)
-    {
-        fdes.push_back(fde_it);
-    }
-
-    std::sort(fdes.begin(), fdes.end(),
-            [&frame_section]
-            (const FrameSection::fde_iterator& f1,
-             const FrameSection::fde_iterator& f2)
-            {
-                assert(f1 != frame_section.end());
-                assert(f2 != frame_section.end());
-                return f1->get_offset() < f2->get_offset();
-            });
-
-    // FDEs are sorted, now we can extract RAs for each of them
-    for(const auto& fde: fdes) {
-        cout << "==== FDE at offset "
-             << std::hex << fde->get_fde_offset() << std::dec
-             << " ====" << endl;
-        extract_ra_of_fde(frame_section, *fde);
-        cout << endl;
-    }
+    // Let the user deal with reg_id correctness
+    return context.uc_mcontext.gregs[reg_id];
 }

src/register_map.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <ucontext.h>
+
+constexpr int REG_DWARF_TO_UCONTEXT[] = {
+  REG_RAX,
+  REG_RDX,
+  REG_RCX,
+  REG_RBX,
+  REG_RSI,
+  REG_RDI,
+  REG_RBP,
+  REG_RSP,
+  REG_R8,
+  REG_R9,
+  REG_R10,
+  REG_R11,
+  REG_R12,
+  REG_R13,
+  REG_R14,
+  REG_R15,
+  REG_RIP,
+};