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https://github.com/RGBCube/serenity
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Userland: Add "functrace" utility
functrace traces the function calls a program makes. It's like strace, but for userspace. It works by using Debugging functionality to insert breakpoints at call&ret instructions.
This commit is contained in:
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8 changed files with 175 additions and 4 deletions
213
Libraries/LibDebug/DebugSession.cpp
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213
Libraries/LibDebug/DebugSession.cpp
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/*
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* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "DebugSession.h"
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#include <AK/Optional.h>
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#include <stdlib.h>
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DebugSession::DebugSession(int pid)
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: m_debugee_pid(pid)
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, m_executable(String::format("/proc/%d/exe", pid))
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, m_elf(reinterpret_cast<u8*>(m_executable.data()), m_executable.size())
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{
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}
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DebugSession::~DebugSession()
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{
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if (!m_is_debugee_dead) {
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if (ptrace(PT_DETACH, m_debugee_pid, 0, 0) < 0) {
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perror("PT_DETACH");
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}
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}
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}
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OwnPtr<DebugSession> DebugSession::exec_and_attach(const String& command)
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{
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int pid = fork();
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if (!pid) {
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if (ptrace(PT_TRACE_ME, 0, 0, 0) < 0) {
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perror("PT_TRACE_ME");
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exit(1);
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}
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auto parts = command.split(' ');
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ASSERT(!parts.is_empty());
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const char** args = (const char**)calloc(parts.size() + 1, sizeof(const char*));
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for (size_t i = 0; i < parts.size(); i++) {
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args[i] = parts[i].characters();
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}
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int rc = execvp(args[0], const_cast<char**>(args));
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if (rc < 0) {
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perror("execvp");
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}
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ASSERT_NOT_REACHED();
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}
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if (waitpid(pid, nullptr, WSTOPPED) != pid) {
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perror("waitpid");
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return nullptr;
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}
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if (ptrace(PT_ATTACH, pid, 0, 0) < 0) {
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perror("PT_ATTACH");
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return nullptr;
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}
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if (waitpid(pid, nullptr, WSTOPPED) != pid) {
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perror("waitpid");
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return nullptr;
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}
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if (ptrace(PT_CONTINUE, pid, 0, 0) < 0) {
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perror("continue");
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return nullptr;
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}
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// We want to continue until the exit from the 'execve' sycsall.
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// This ensures that when we start debugging the process
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// it executes the target image, and not the forked image of the tracing process.
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// NOTE: we only need to do this when we are debugging a new process (i.e not attaching to a process that's already running!)
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if (waitpid(pid, nullptr, WSTOPPED) != pid) {
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perror("wait_pid");
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return nullptr;
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}
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return make<DebugSession>(pid);
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}
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bool DebugSession::poke(u32* address, u32 data)
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{
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if (ptrace(PT_POKE, m_debugee_pid, (void*)address, data) < 0) {
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perror("PT_POKE");
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return false;
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}
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return true;
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}
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Optional<u32> DebugSession::peek(u32* address) const
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{
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Optional<u32> result;
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int rc = ptrace(PT_PEEK, m_debugee_pid, (void*)address, 0);
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if (errno == 0)
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result = static_cast<u32>(rc);
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return result;
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}
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bool DebugSession::insert_breakpoint(void* address)
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{
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// We insert a software breakpoint by
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// patching the first byte of the instruction at 'address'
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// with the breakpoint instruction (int3)
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if (m_breakpoints.contains(address))
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return false;
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auto original_bytes = peek(reinterpret_cast<u32*>(address));
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if (!original_bytes.has_value())
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return false;
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BreakPoint breakpoint { address, original_bytes.value(), BreakPointState::Disabled };
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m_breakpoints.set(address, breakpoint);
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enable_breakpoint(breakpoint);
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return true;
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}
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bool DebugSession::disable_breakpoint(const BreakPoint& breakpoint)
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{
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ASSERT(m_breakpoints.contains(breakpoint.address));
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if (!poke(reinterpret_cast<u32*>(reinterpret_cast<char*>(breakpoint.address)), breakpoint.original_first_word))
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return false;
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auto bp = m_breakpoints.get(breakpoint.address).value();
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bp.state = BreakPointState::Disabled;
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m_breakpoints.set(bp.address, bp);
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return true;
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}
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bool DebugSession::enable_breakpoint(const BreakPoint& breakpoint)
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{
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ASSERT(m_breakpoints.contains(breakpoint.address));
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if (!poke(reinterpret_cast<u32*>(breakpoint.address), (breakpoint.original_first_word & ~(uint32_t)0xff) | BREAKPOINT_INSTRUCTION))
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return false;
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auto bp = m_breakpoints.get(breakpoint.address).value();
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bp.state = BreakPointState::Enabled;
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m_breakpoints.set(bp.address, bp);
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return true;
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}
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PtraceRegisters DebugSession::get_registers() const
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{
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PtraceRegisters regs;
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if (ptrace(PT_GETREGS, m_debugee_pid, ®s, 0) < 0) {
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perror("PT_GETREGS");
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ASSERT_NOT_REACHED();
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}
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return regs;
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}
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void DebugSession::set_registers(const PtraceRegisters& regs)
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{
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if (ptrace(PT_SETREGS, m_debugee_pid, reinterpret_cast<void*>(&const_cast<PtraceRegisters&>(regs)), 0) < 0) {
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perror("PT_SETREGS");
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ASSERT_NOT_REACHED();
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}
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}
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void DebugSession::continue_debugee()
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{
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if (ptrace(PT_CONTINUE, m_debugee_pid, 0, 0) < 0) {
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perror("continue");
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ASSERT_NOT_REACHED();
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}
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}
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void* DebugSession::single_step()
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{
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auto regs = get_registers();
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constexpr u32 TRAP_FLAG = 0x100;
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regs.eflags |= TRAP_FLAG;
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set_registers(regs);
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continue_debugee();
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if (waitpid(m_debugee_pid, 0, WSTOPPED) != m_debugee_pid) {
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perror("waitpid");
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ASSERT_NOT_REACHED();
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}
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regs = get_registers();
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regs.eflags &= ~(TRAP_FLAG);
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set_registers(regs);
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return (void*)regs.eip;
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}
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186
Libraries/LibDebug/DebugSession.h
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186
Libraries/LibDebug/DebugSession.h
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/*
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* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Demangle.h>
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#include <AK/HashMap.h>
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#include <AK/MappedFile.h>
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#include <AK/Optional.h>
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#include <AK/OwnPtr.h>
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#include <AK/String.h>
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#include <LibC/sys/arch/i386/regs.h>
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#include <LibELF/Loader.h>
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#include <signal.h>
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#include <stdio.h>
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#include <sys/ptrace.h>
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#include <sys/wait.h>
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#include <unistd.h>
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class DebugSession {
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public:
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static OwnPtr<DebugSession> exec_and_attach(const String& command);
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// Has to be public for OwnPtr::make
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DebugSession(int pid);
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~DebugSession();
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int pid() const { return m_debugee_pid; }
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bool poke(u32* address, u32 data);
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Optional<u32> peek(u32* address) const;
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enum class BreakPointState {
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Enabled,
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Disabled,
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};
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struct BreakPoint {
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void* address;
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u32 original_first_word;
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BreakPointState state;
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};
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bool insert_breakpoint(void* address);
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bool disable_breakpoint(const BreakPoint&);
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bool enable_breakpoint(const BreakPoint&);
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PtraceRegisters get_registers() const;
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void set_registers(const PtraceRegisters&);
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void continue_debugee();
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void* single_step();
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template<typename Callback>
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void run(Callback callback);
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const ELF::Loader& elf() const { return m_elf; }
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const MappedFile& executable() const { return m_executable; }
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enum DebugDecision {
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Continue,
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SingleStep,
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Detach,
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Kill,
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};
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enum DebugBreakReason {
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Breakpoint,
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Exited,
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};
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private:
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// x86 breakpoint instruction "int3"
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static constexpr u8 BREAKPOINT_INSTRUCTION
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= 0xcc;
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int m_debugee_pid { -1 };
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bool m_is_debugee_dead { false };
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MappedFile m_executable;
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ELF::Loader m_elf;
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HashMap<void*, BreakPoint> m_breakpoints;
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};
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template<typename Callback>
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void DebugSession::run(Callback callback)
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{
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enum class State {
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FreeRun,
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ConsecutiveBreakpoint,
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SingleStep,
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};
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State state { State::FreeRun };
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for (;;) {
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if (state == State::FreeRun) {
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continue_debugee();
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int wstatus = 0;
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if (waitpid(m_debugee_pid, &wstatus, WSTOPPED | WEXITED) != m_debugee_pid) {
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perror("waitpid");
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ASSERT_NOT_REACHED();
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}
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// FIXME: This check actually only checks whether the debugee
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// stopped because it hit a breakpoint/is in single stepping mode or not
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if (WSTOPSIG(wstatus) != SIGTRAP) {
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callback(DebugBreakReason::Exited, Optional<PtraceRegisters>());
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m_is_debugee_dead = true;
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break;
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}
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}
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auto regs = get_registers();
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Optional<BreakPoint> current_breakpoint;
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if (state == State::FreeRun) {
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current_breakpoint = m_breakpoints.get((void*)((u32)regs.eip - 1));
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} else {
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current_breakpoint = m_breakpoints.get((void*)regs.eip);
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}
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if (current_breakpoint.has_value()) {
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// We want to make the breakpoint transparrent to the user of the debugger
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regs.eip = reinterpret_cast<u32>(current_breakpoint.value().address);
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set_registers(regs);
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disable_breakpoint(current_breakpoint.value());
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}
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DebugDecision decision = callback(DebugBreakReason::Breakpoint, regs);
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if (decision == DebugDecision::Continue) {
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state = State::FreeRun;
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}
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if (current_breakpoint.has_value()) {
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// Re-enable the breakpoint
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auto stopped_address = single_step();
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enable_breakpoint(current_breakpoint.value());
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// If there is another breakpoint after the current one,
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// Then we are already on it (because of single_step)
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auto breakpoint_at_next_instruction = m_breakpoints.get(stopped_address);
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if (breakpoint_at_next_instruction.has_value()
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&& breakpoint_at_next_instruction.value().state == BreakPointState::Enabled) {
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state = State::ConsecutiveBreakpoint;
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}
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}
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if (decision == DebugDecision::SingleStep) {
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state = State::SingleStep;
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} else {
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// TODO: implement DebugDecision:: Kill, Detach
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ASSERT(decision == DebugDecision::Continue);
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}
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if (state == State::SingleStep) {
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single_step();
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}
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}
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}
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11
Libraries/LibDebug/Makefile
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11
Libraries/LibDebug/Makefile
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OBJS = \
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DebugSession.o
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LIBRARY = libdebug.a
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install:
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mkdir -p $(SERENITY_BASE_DIR)/Root/usr/include/LibDebug/
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cp *.h $(SERENITY_BASE_DIR)/Root/usr/include/LibDebug/
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cp $(LIBRARY) $(SERENITY_BASE_DIR)/Root/usr/lib/
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include ../../Makefile.common
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