From d13b625cc5fd22912763a11b442a5a8a2a4c2e3f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Mon, 23 Apr 2018 16:46:03 +0200
Subject: [PATCH] SimpleDwarf, DwarfReader: fix machine registers

---
 src/DwarfReader.cpp | 31 +++++++++++++++++++++++--------
 src/DwarfReader.hpp |  5 ++++-
 src/SimpleDwarf.cpp | 13 ++++++-------
 src/SimpleDwarf.hpp |  3 ++-
 4 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/src/DwarfReader.cpp b/src/DwarfReader.cpp
index c6a6858..1573cb6 100644
--- a/src/DwarfReader.cpp
+++ b/src/DwarfReader.cpp
@@ -32,6 +32,8 @@ SimpleDwarf::Fde DwarfReader::read_fde(const core::Fde& fde) const {
     output.end_ip = fde.get_low_pc() + fde.get_func_length();
 
     auto rows = fde.decode().rows;
+    const core::Cie& cie = *fde.find_cie();
+    int ra_reg = cie.get_return_address_register_rule();
 
     for(const auto row_pair: rows) {
         SimpleDwarf::DwRow cur_row;
@@ -47,22 +49,29 @@ SimpleDwarf::Fde DwarfReader::read_fde(const core::Fde& fde) const {
             else {
                 try {
                     SimpleDwarf::MachineRegister reg_type =
-                        from_dwarfpp_reg(cell.first);
-                    cur_row.regs[reg_type] = read_register(cell.second);
+                        from_dwarfpp_reg(cell.first, ra_reg);
+                    switch(reg_type) {
+                        case SimpleDwarf::REG_RBP:
+                            cur_row.rbp = read_register(cell.second);
+                            break;
+                        case SimpleDwarf::REG_RA:
+                            cur_row.ra = read_register(cell.second);
+                            break;
+                        default:
+                            break;
+                    }
                 }
                 catch(UnsupportedRegister) {} // Just ignore it.
             }
         }
 
-        if(cur_row.cfa.type == SimpleDwarf::DwRegister::REG_UNDEFINED
-                || (cur_row.regs[SimpleDwarf::REG_RIP].type
-                    == SimpleDwarf::DwRegister::REG_UNDEFINED)
-                || (cur_row.regs[SimpleDwarf::REG_RSP].type
-                    == SimpleDwarf::DwRegister::REG_UNDEFINED))
+        if(cur_row.cfa.type == SimpleDwarf::DwRegister::REG_UNDEFINED)
         {
             // Not set
             throw InvalidDwarf();
         }
+
+        output.rows.push_back(cur_row);
     }
 
     return output;
@@ -101,7 +110,13 @@ SimpleDwarf::DwRegister DwarfReader::read_register(
     return output;
 }
 
-SimpleDwarf::MachineRegister DwarfReader::from_dwarfpp_reg(int reg_id) const {
+SimpleDwarf::MachineRegister DwarfReader::from_dwarfpp_reg(
+        int reg_id,
+        int ra_reg
+        ) const
+{
+    if(reg_id == ra_reg)
+        return SimpleDwarf::REG_RA;
     switch(reg_id) {
         case lib::DWARF_X86_64_RIP:
             return SimpleDwarf::REG_RIP;
diff --git a/src/DwarfReader.hpp b/src/DwarfReader.hpp
index 0d4505c..034d055 100644
--- a/src/DwarfReader.hpp
+++ b/src/DwarfReader.hpp
@@ -29,7 +29,10 @@ class DwarfReader {
         SimpleDwarf::DwRegister read_register(
                 const dwarf::core::FrameSection::register_def& reg) const;
 
-        SimpleDwarf::MachineRegister from_dwarfpp_reg(int reg_id) const;
+        SimpleDwarf::MachineRegister from_dwarfpp_reg(
+                int reg_id,
+                int ra_reg=-1
+                ) const;
 
         class UnsupportedRegister: public std::exception {};
 
diff --git a/src/SimpleDwarf.cpp b/src/SimpleDwarf.cpp
index 350fbde..c556734 100644
--- a/src/SimpleDwarf.cpp
+++ b/src/SimpleDwarf.cpp
@@ -30,12 +30,12 @@ std::ostream& operator<<(std::ostream& out, const SimpleDwarf::DwRegister& reg)
             break;
         case SimpleDwarf::DwRegister::REG_REGISTER:
             out << reg.reg
-                << ((reg.offset >= 0) ? '+' : '-')
+                << ((reg.offset >= 0) ? "+" : "")
                 << reg.offset;
             break;
         case SimpleDwarf::DwRegister::REG_CFA_OFFSET:
             out << 'c'
-                << ((reg.offset >= 0) ? '+' : '-')
+                << ((reg.offset >= 0) ? "+" : "")
                 << reg.offset;
             break;
         case SimpleDwarf::DwRegister::REG_NOT_IMPLEMENTED:
@@ -47,10 +47,9 @@ std::ostream& operator<<(std::ostream& out, const SimpleDwarf::DwRegister& reg)
 
 std::ostream& operator<<(std::ostream& out, const SimpleDwarf::DwRow& row) {
     out << std::hex << row.ip << std::dec
-        << '\t' << row.cfa;
-    for(size_t r_id = 0; r_id < SimpleDwarf::HANDLED_REGISTERS_COUNT; ++r_id) {
-        out << '\t' << row.regs[r_id];
-    }
+        << '\t' << row.cfa
+        << '\t' << row.rbp
+        << '\t' << row.ra;
     out << std::endl;
     return out;
 }
@@ -59,7 +58,7 @@ std::ostream& operator<<(std::ostream& out, const SimpleDwarf::Fde& fde) {
     out << "FDE: "
         << std::hex << fde.beg_ip << " … " << fde.end_ip << std::dec
         << std::endl
-        << "IP\tCFA\tRIP\tRSP\tRBP\tRA"
+        << "IP\tCFA\tRBP\tRA"
         << std::endl;
     for(const auto& row: fde.rows)
         out << row;
diff --git a/src/SimpleDwarf.hpp b/src/SimpleDwarf.hpp
index 5110110..67158f1 100644
--- a/src/SimpleDwarf.hpp
+++ b/src/SimpleDwarf.hpp
@@ -43,7 +43,8 @@ struct SimpleDwarf {
     struct DwRow {
         uintptr_t ip; ///< Instruction pointer
         DwRegister cfa; ///< Canonical Frame Address
-        DwRegister regs[HANDLED_REGISTERS_COUNT]; ///< Saved machine registers
+        DwRegister rbp; ///< Base pointer register
+        DwRegister ra; ///< Return address
 
         friend std::ostream& operator<<(std::ostream &, const DwRow&);
     };