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Reading registers, printing source line
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Simon Brand committed Feb 22, 2017
1 parent 77598d9 commit d7bb7b6
Showing 1 changed file with 131 additions and 20 deletions.
151 changes: 131 additions & 20 deletions src/minidbg.cpp
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
#include <string>
#include <fstream>
#include <iostream>
#include <utility>
#include <cstdio>
Expand All @@ -14,6 +15,31 @@

#include "linenoise.h"

class breakpoint {
public:
breakpoint(pid_t pid, std::intptr_t addr) : m_pid{pid}, m_addr{addr}, m_enabled{false}, m_saved_data{} {}
void enable() {
m_saved_data = ptrace(PTRACE_PEEKTEXT, m_pid, (void*)m_addr, 0);
auto int3 = 0xcc;
auto data_with_int3 = (m_saved_data & ~0xff | int3);
ptrace(PTRACE_POKETEXT, m_pid, (void*)m_addr, data_with_int3);

m_enabled = true;
}

void disable() {
ptrace(PTRACE_POKETEXT, m_pid, (void*)m_addr, m_saved_data);
m_enabled = false;
}

std::intptr_t get_address() { return m_addr; }
private:
pid_t m_pid;
std::intptr_t m_addr;
bool m_enabled;
unsigned m_saved_data;
};

class debugger {
public:
debugger (std::string prog_name, pid_t pid)
Expand All @@ -25,51 +51,68 @@ class debugger {
}

void run();
void dump_registers();
void continue_execution();
void single_step_instruction();
siginfo_t get_signal_info();
void set_breakpoint_at_address(std::intptr_t addr);
void set_breakpoint_at_source_line(const std::string& file, std::size_t line);
void set_breakpoint_at_source_line(const std::string& file, unsigned line);
void print_source(const std::string& file_name, unsigned line, unsigned n_lines_context=2);

private:
void handle_command(const std::string& line);
void handle_sigtrap(siginfo_t info);
void wait_for_signal();
uint64_t get_pc();
std::string get_current_line_entry();
void set_pc(uint64_t pc);
void decrement_pc();
dwarf::line_table::entry get_current_line_entry();

std::string m_prog_name;
pid_t m_pid;
dwarf::dwarf m_dwarf;
elf::elf m_elf;
unsigned m_saved_data;
std::unique_ptr<breakpoint> m_breakpoint;
};

uint64_t debugger::get_pc() {
struct user_regs_struct regs;
std::cout << ptrace(PTRACE_GETREGS, m_pid, nullptr, &regs) << std::endl;
ptrace(PTRACE_GETREGS, m_pid, nullptr, &regs);
return regs.rip;
}

std::string debugger::get_current_line_entry() {
void debugger::set_pc(uint64_t pc) {
struct user_regs_struct regs;
ptrace(PTRACE_GETREGS, m_pid, nullptr, &regs);
regs.rip = pc;
ptrace(PTRACE_SETREGS, m_pid, nullptr, &regs);
}

void debugger::decrement_pc() {
struct user_regs_struct regs;
ptrace(PTRACE_GETREGS, m_pid, nullptr, &regs);
regs.rip -= 1;
ptrace(PTRACE_SETREGS, m_pid, nullptr, &regs);
}

dwarf::line_table::entry debugger::get_current_line_entry() {
auto pc = get_pc();

for (auto &cu : m_dwarf.compilation_units()) {
if (die_pc_range(cu.root()).contains(pc)) {
return "";//at_name(cu.root());
// Map PC to a line
auto &lt = cu.get_line_table();
auto it = lt.find_address(pc);
if (it == lt.end()) {
return "";
throw std::out_of_range{"Cannot find line entry"};
}
else {
return it->get_description();
return *it;
}
}
}

return "";
throw std::out_of_range{"Cannot find line entry"};
}

void debugger::run() {
Expand All @@ -81,6 +124,29 @@ void debugger::run() {
}
}

void debugger::print_source(const std::string& file_name, unsigned line, unsigned n_lines_context) {
std::ifstream file {file_name};
auto start_line = line < n_lines_context ? 0 : line - n_lines_context;
auto end_line = line + n_lines_context + (line < n_lines_context ? n_lines_context - line : 0) + 1;

char c{};
auto current_line = 1u;
while (current_line != start_line && file.get(c)) {
if (c == '\n') {
++current_line;
}
}
std::cout << (current_line==line ? "> " : " ");
while (current_line != end_line && file.get(c)) {
std::cout << c;
if (c == '\n') {
++current_line;
std::cout << (current_line==line ? "> " : " ");
}
}
std::cout << std::endl;
}

bool is_prefix(const std::string& s, const std::string& of) {
if (s.size() > of.size()) return false;
return std::equal(s.begin(), s.end(), of.begin());
Expand All @@ -102,8 +168,12 @@ void debugger::handle_sigtrap(siginfo_t info) {
switch (info.si_code) {
case SI_KERNEL:
case TRAP_BRKPT:
std::cout << "Hit breakpoint" << std::endl;
{
std::cout << "Hit breakpoint at address 0x" << std::hex << get_pc() << std::endl;
auto line_entry = get_current_line_entry();
print_source(line_entry.file->path, line_entry.line);
return;
}
case TRAP_TRACE:
std::cout << "Finished single stepping" << std::endl;
return;
Expand Down Expand Up @@ -133,6 +203,14 @@ void debugger::wait_for_signal() {
}

void debugger::continue_execution() {
if (m_breakpoint && m_breakpoint->get_address() == get_pc() - 1) {
m_breakpoint->disable();
dump_registers();
decrement_pc();
dump_registers();
// single_step_instruction();
// m_breakpoint->enable();
}
ptrace(PTRACE_CONT, m_pid, nullptr, nullptr);
wait_for_signal();
}
Expand All @@ -144,15 +222,12 @@ void debugger::single_step_instruction() {

void debugger::set_breakpoint_at_address(std::intptr_t addr) {
std::cout << "Set breakpoint at address 0x" << std::hex << addr << std::endl;
m_saved_data = ptrace(PTRACE_PEEKTEXT, m_pid, (void*)addr, 0);
auto int3 = 0xcc;
auto data_with_int3 = (m_saved_data & ~0xff | int3);
ptrace(PTRACE_POKETEXT, m_pid, (void*)addr, data_with_int3);
m_breakpoint = std::make_unique<breakpoint>(m_pid, addr);
m_breakpoint->enable();
}

void debugger::set_breakpoint_at_source_line(const std::string& file, std::size_t line) {
void debugger::set_breakpoint_at_source_line(const std::string& file, unsigned line) {
for (const auto& cu : m_dwarf.compilation_units()) {
std::cerr << at_name(cu.root()) << std::endl;
if (is_suffix(file, at_name(cu.root()))) {
const auto& lt = cu.get_line_table();

Expand All @@ -166,14 +241,50 @@ void debugger::set_breakpoint_at_source_line(const std::string& file, std::size_
}
}

void debugger::dump_registers() {
struct user_regs_struct regs;
ptrace(PTRACE_GETREGS, m_pid, nullptr, &regs);
std::cout << "r15" << ' ' << std::hex << regs.r15 << std::endl;
std::cout << "r14" << ' ' << std::hex << regs.r14 << std::endl;
std::cout << "r13" << ' ' << std::hex << regs.r13 << std::endl;
std::cout << "r12" << ' ' << std::hex << regs.r12 << std::endl;
std::cout << "bp" << ' ' << std::hex << regs.rbp << std::endl;
std::cout << "bx" << ' ' << std::hex << regs.rbx << std::endl;
std::cout << "r11" << ' ' << std::hex << regs.r11 << std::endl;
std::cout << "r10" << ' ' << std::hex << regs.r10 << std::endl;
std::cout << "r9" << ' ' << std::hex << regs.r9 << std::endl;
std::cout << "r8" << ' ' << std::hex << regs.r8 << std::endl;
std::cout << "ax" << ' ' << std::hex << regs.rax << std::endl;
std::cout << "cx" << ' ' << std::hex << regs.rcx << std::endl;
std::cout << "dx" << ' ' << std::hex << regs.rdx << std::endl;
std::cout << "si" << ' ' << std::hex << regs.rsi << std::endl;
std::cout << "di" << ' ' << std::hex << regs.rdi << std::endl;
std::cout << "orig_ax" << ' ' << std::hex << regs.orig_rax << std::endl;
std::cout << "ip" << ' ' << std::hex << regs.rip << std::endl;
std::cout << "cs" << ' ' << std::hex << regs.cs << std::endl;
std::cout << "flags" << ' ' << std::hex << regs.eflags << std::endl;
std::cout << "sp" << ' ' << std::hex << regs.rsp << std::endl;
std::cout << "ss" << ' ' << std::hex << regs.ss << std::endl;
std::cout << "fs_base" << ' ' << std::hex << regs.fs_base << std::endl;
std::cout << "gs_base" << ' ' << std::hex << regs.gs_base << std::endl;
std::cout << "ds" << ' ' << std::hex << regs.ds << std::endl;
std::cout << "es" << ' ' << std::hex << regs.es << std::endl;
std::cout << "fs" << ' ' << std::hex << regs.fs << std::endl;
std::cout << "gs" << ' ' << std::hex << regs.gs << std::endl;
}

void debugger::handle_command(const std::string& line) {
if (line == "cont") {
if (is_prefix(line, "cont")) {
continue_execution();
}
else if (line == "line") {
std::cout << get_current_line_entry() << std::endl;
else if (is_prefix(line, "line")) {
auto line_entry = get_current_line_entry();
std::cout << line_entry.file->path << ':' << line_entry.line << std::endl;
}
else if (line == "pc") {
else if (is_prefix(line, "registers")) {
dump_registers();
}
else if (is_prefix(line, "pc")) {
std::cout << std::hex << get_pc() << std::endl;
}
else if(is_prefix(line, "break")) {
Expand Down

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