ProcessElfCore.cpp

//===-- ProcessElfCore.cpp --------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// C Includes
#include <stdlib.h>

// C++ Includes
#include <mutex>

// Other libraries and framework includes
#include "lldb/Core/PluginManager.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/ModuleSpec.h"
#include "lldb/Core/Section.h"
#include "lldb/Core/State.h"
#include "lldb/Core/DataBufferHeap.h"
#include "lldb/Core/Log.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/DynamicLoader.h"
#include "lldb/Target/UnixSignals.h"

#include "llvm/Support/ELF.h"

#include "Plugins/ObjectFile/ELF/ObjectFileELF.h"
#include "Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h"

// Project includes
#include "ProcessElfCore.h"
#include "ThreadElfCore.h"

using namespace lldb_private;

ConstString
ProcessElfCore::GetPluginNameStatic()
{
    static ConstString g_name("elf-core");
    return g_name;
}

const char *
ProcessElfCore::GetPluginDescriptionStatic()
{
    return "ELF core dump plug-in.";
}

void
ProcessElfCore::Terminate()
{
    PluginManager::UnregisterPlugin (ProcessElfCore::CreateInstance);
}


lldb::ProcessSP
ProcessElfCore::CreateInstance (lldb::TargetSP target_sp, lldb::ListenerSP listener_sp, const FileSpec *crash_file)
{
    lldb::ProcessSP process_sp;
    if (crash_file)
    {
        // Read enough data for a ELF32 header or ELF64 header
        const size_t header_size = sizeof(llvm::ELF::Elf64_Ehdr);

        lldb::DataBufferSP data_sp (crash_file->ReadFileContents(0, header_size));
        if (data_sp && data_sp->GetByteSize() == header_size &&
            elf::ELFHeader::MagicBytesMatch (data_sp->GetBytes()))
        {
            elf::ELFHeader elf_header;
            DataExtractor data(data_sp, lldb::eByteOrderLittle, 4);
            lldb::offset_t data_offset = 0;
            if (elf_header.Parse(data, &data_offset))
            {
                if (elf_header.e_type == llvm::ELF::ET_CORE)
                    process_sp.reset(new ProcessElfCore (target_sp, listener_sp, *crash_file));
            }
        }
    }
    return process_sp;
}

bool
ProcessElfCore::CanDebug(lldb::TargetSP target_sp, bool plugin_specified_by_name)
{
    // For now we are just making sure the file exists for a given module
    if (!m_core_module_sp && m_core_file.Exists())
    {
        ModuleSpec core_module_spec(m_core_file, target_sp->GetArchitecture());
        Error error (ModuleList::GetSharedModule (core_module_spec, m_core_module_sp,
                                                  NULL, NULL, NULL));
        if (m_core_module_sp)
        {
            ObjectFile *core_objfile = m_core_module_sp->GetObjectFile();
            if (core_objfile && core_objfile->GetType() == ObjectFile::eTypeCoreFile)
                return true;
        }
    }
    return false;
}

//----------------------------------------------------------------------
// ProcessElfCore constructor
//----------------------------------------------------------------------
ProcessElfCore::ProcessElfCore(lldb::TargetSP target_sp, lldb::ListenerSP listener_sp,
                               const FileSpec &core_file) :
    Process (target_sp, listener_sp),
    m_core_module_sp (),
    m_core_file (core_file),
    m_dyld_plugin_name (),
    m_os(llvm::Triple::UnknownOS),
    m_thread_data_valid(false),
    m_thread_data(),
    m_core_aranges ()
{
}

//----------------------------------------------------------------------
// Destructor
//----------------------------------------------------------------------
ProcessElfCore::~ProcessElfCore()
{
    Clear();
    // We need to call finalize on the process before destroying ourselves
    // to make sure all of the broadcaster cleanup goes as planned. If we
    // destruct this class, then Process::~Process() might have problems
    // trying to fully destroy the broadcaster.
    Finalize();
}

//----------------------------------------------------------------------
// PluginInterface
//----------------------------------------------------------------------
ConstString
ProcessElfCore::GetPluginName()
{
    return GetPluginNameStatic();
}

uint32_t
ProcessElfCore::GetPluginVersion()
{
    return 1;
}

lldb::addr_t
ProcessElfCore::AddAddressRangeFromLoadSegment(const elf::ELFProgramHeader *header)
{
    lldb::addr_t addr = header->p_vaddr;
    FileRange file_range (header->p_offset, header->p_filesz);
    VMRangeToFileOffset::Entry range_entry(addr, header->p_memsz, file_range);

    VMRangeToFileOffset::Entry *last_entry = m_core_aranges.Back();
    if (last_entry &&
        last_entry->GetRangeEnd() == range_entry.GetRangeBase() &&
        last_entry->data.GetRangeEnd() == range_entry.data.GetRangeBase() &&
        last_entry->GetByteSize() == last_entry->data.GetByteSize())
    {
        last_entry->SetRangeEnd (range_entry.GetRangeEnd());
        last_entry->data.SetRangeEnd (range_entry.data.GetRangeEnd());
    }
    else
    {
        m_core_aranges.Append(range_entry);
    }

    return addr;
}

//----------------------------------------------------------------------
// Process Control
//----------------------------------------------------------------------
Error
ProcessElfCore::DoLoadCore ()
{
    Error error;
    if (!m_core_module_sp)
    {
        error.SetErrorString ("invalid core module");
        return error;
    }

    ObjectFileELF *core = (ObjectFileELF *)(m_core_module_sp->GetObjectFile());
    if (core == NULL)
    {
        error.SetErrorString ("invalid core object file");
        return error;
    }

    const uint32_t num_segments = core->GetProgramHeaderCount();
    if (num_segments == 0)
    {
        error.SetErrorString ("core file has no segments");
        return error;
    }

    SetCanJIT(false);

    m_thread_data_valid = true;

    bool ranges_are_sorted = true;
    lldb::addr_t vm_addr = 0;
    /// Walk through segments and Thread and Address Map information.
    /// PT_NOTE - Contains Thread and Register information
    /// PT_LOAD - Contains a contiguous range of Process Address Space
    for(uint32_t i = 1; i <= num_segments; i++)
    {
        const elf::ELFProgramHeader *header = core->GetProgramHeaderByIndex(i);
        assert(header != NULL);

        DataExtractor data = core->GetSegmentDataByIndex(i);

        // Parse thread contexts and auxv structure
        if (header->p_type == llvm::ELF::PT_NOTE)
            ParseThreadContextsFromNoteSegment(header, data);

        // PT_LOAD segments contains address map
        if (header->p_type == llvm::ELF::PT_LOAD)
        {
            lldb::addr_t last_addr = AddAddressRangeFromLoadSegment(header);
            if (vm_addr > last_addr)
                ranges_are_sorted = false;
            vm_addr = last_addr;
        }
    }

    if (!ranges_are_sorted)
        m_core_aranges.Sort();

    // Even if the architecture is set in the target, we need to override
    // it to match the core file which is always single arch.
    ArchSpec arch (m_core_module_sp->GetArchitecture());
    if (arch.IsValid())
        GetTarget().SetArchitecture(arch);

    SetUnixSignals(UnixSignals::Create(GetArchitecture()));

    // Core files are useless without the main executable. See if we can locate the main
    // executable using data we found in the core file notes.
    lldb::ModuleSP exe_module_sp = GetTarget().GetExecutableModule();
    if (!exe_module_sp)
    {
        // The first entry in the NT_FILE might be our executable
        if (!m_nt_file_entries.empty())
        {
            ModuleSpec exe_module_spec;
            exe_module_spec.GetArchitecture() = arch;
            exe_module_spec.GetFileSpec().SetFile(m_nt_file_entries[0].path.GetCString(), false);
            if (exe_module_spec.GetFileSpec())
            {
                exe_module_sp = GetTarget().GetSharedModule(exe_module_spec);
                if (exe_module_sp)
                    GetTarget().SetExecutableModule(exe_module_sp, false);
            }
        }
    }
    return error;
}

lldb_private::DynamicLoader *
ProcessElfCore::GetDynamicLoader ()
{
    if (m_dyld_ap.get() == NULL)
        m_dyld_ap.reset (DynamicLoader::FindPlugin(this, DynamicLoaderPOSIXDYLD::GetPluginNameStatic().GetCString()));
    return m_dyld_ap.get();
}

bool
ProcessElfCore::UpdateThreadList (ThreadList &old_thread_list, ThreadList &new_thread_list)
{
    const uint32_t num_threads = GetNumThreadContexts ();
    if (!m_thread_data_valid)
        return false;

    for (lldb::tid_t tid = 0; tid < num_threads; ++tid)
    {
        const ThreadData &td = m_thread_data[tid];
        lldb::ThreadSP thread_sp(new ThreadElfCore (*this, td));
        new_thread_list.AddThread (thread_sp);
    }
    return new_thread_list.GetSize(false) > 0;
}

void
ProcessElfCore::RefreshStateAfterStop ()
{
}

Error
ProcessElfCore::DoDestroy ()
{
    return Error();
}

//------------------------------------------------------------------
// Process Queries
//------------------------------------------------------------------

bool
ProcessElfCore::IsAlive ()
{
    return true;
}

//------------------------------------------------------------------
// Process Memory
//------------------------------------------------------------------
size_t
ProcessElfCore::ReadMemory (lldb::addr_t addr, void *buf, size_t size, Error &error)
{
    // Don't allow the caching that lldb_private::Process::ReadMemory does
    // since in core files we have it all cached our our core file anyway.
    return DoReadMemory (addr, buf, size, error);
}

size_t
ProcessElfCore::DoReadMemory (lldb::addr_t addr, void *buf, size_t size, Error &error)
{
    ObjectFile *core_objfile = m_core_module_sp->GetObjectFile();

    if (core_objfile == NULL)
        return 0;

    // Get the address range
    const VMRangeToFileOffset::Entry *address_range = m_core_aranges.FindEntryThatContains (addr);
    if (address_range == NULL || address_range->GetRangeEnd() < addr)
    {
        error.SetErrorStringWithFormat ("core file does not contain 0x%" PRIx64, addr);
        return 0;
    }

    // Convert the address into core file offset
    const lldb::addr_t offset = addr - address_range->GetRangeBase();
    const lldb::addr_t file_start = address_range->data.GetRangeBase();
    const lldb::addr_t file_end = address_range->data.GetRangeEnd();
    size_t bytes_to_read = size; // Number of bytes to read from the core file
    size_t bytes_copied = 0;     // Number of bytes actually read from the core file
    size_t zero_fill_size = 0;   // Padding
    lldb::addr_t bytes_left = 0; // Number of bytes available in the core file from the given address

    // Figure out how many on-disk bytes remain in this segment
    // starting at the given offset
    if (file_end > file_start + offset)
        bytes_left = file_end - (file_start + offset);

    // Figure out how many bytes we need to zero-fill if we are
    // reading more bytes than available in the on-disk segment
    if (bytes_to_read > bytes_left)
    {
        zero_fill_size = bytes_to_read - bytes_left;
        bytes_to_read = bytes_left;
    }

    // If there is data available on the core file read it
    if (bytes_to_read)
        bytes_copied = core_objfile->CopyData(offset + file_start, bytes_to_read, buf);

    assert(zero_fill_size <= size);
    // Pad remaining bytes
    if (zero_fill_size)
        memset(((char *)buf) + bytes_copied, 0, zero_fill_size);

    return bytes_copied + zero_fill_size;
}

void
ProcessElfCore::Clear()
{
    m_thread_list.Clear();
    m_os = llvm::Triple::UnknownOS;

    SetUnixSignals(std::make_shared<UnixSignals>());
}

void
ProcessElfCore::Initialize()
{
    static std::once_flag g_once_flag;

    std::call_once(g_once_flag, []()
    {
        PluginManager::RegisterPlugin (GetPluginNameStatic(),
          GetPluginDescriptionStatic(), CreateInstance);
    });
}

lldb::addr_t
ProcessElfCore::GetImageInfoAddress()
{
    ObjectFile *obj_file = GetTarget().GetExecutableModule()->GetObjectFile();
    Address addr = obj_file->GetImageInfoAddress(&GetTarget());

    if (addr.IsValid())
        return addr.GetLoadAddress(&GetTarget());
    return LLDB_INVALID_ADDRESS;
}

/// Core files PT_NOTE segment descriptor types
enum {
    NT_PRSTATUS     = 1,
    NT_FPREGSET,
    NT_PRPSINFO,
    NT_TASKSTRUCT,
    NT_PLATFORM,
    NT_AUXV,
    NT_FILE = 0x46494c45
};

namespace FREEBSD {

enum {
    NT_PRSTATUS      = 1,
    NT_FPREGSET,
    NT_PRPSINFO,
    NT_THRMISC       = 7,
    NT_PROCSTAT_AUXV = 16,
    NT_PPC_VMX       = 0x100
};

}

// Parse a FreeBSD NT_PRSTATUS note - see FreeBSD sys/procfs.h for details.
static void
ParseFreeBSDPrStatus(ThreadData &thread_data, DataExtractor &data,
                     ArchSpec &arch)
{
    lldb::offset_t offset = 0;
    bool lp64 = (arch.GetMachine() == llvm::Triple::aarch64 ||
                 arch.GetMachine() == llvm::Triple::mips64 ||
                 arch.GetMachine() == llvm::Triple::ppc64 ||
                 arch.GetMachine() == llvm::Triple::x86_64);
    int pr_version = data.GetU32(&offset);

    Log *log (GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
    if (log)
    {
        if (pr_version > 1)
            log->Printf("FreeBSD PRSTATUS unexpected version %d", pr_version);
    }

    // Skip padding, pr_statussz, pr_gregsetsz, pr_fpregsetsz, pr_osreldate
    if (lp64)
        offset += 32;
    else
        offset += 16;

    thread_data.signo = data.GetU32(&offset); // pr_cursig
    thread_data.tid = data.GetU32(&offset); // pr_pid
    if (lp64)
        offset += 4;

    size_t len = data.GetByteSize() - offset;
    thread_data.gpregset = DataExtractor(data, offset, len);
}

static void
ParseFreeBSDThrMisc(ThreadData &thread_data, DataExtractor &data)
{
    lldb::offset_t offset = 0;
    thread_data.name = data.GetCStr(&offset, 20);
}

/// Parse Thread context from PT_NOTE segment and store it in the thread list
/// Notes:
/// 1) A PT_NOTE segment is composed of one or more NOTE entries.
/// 2) NOTE Entry contains a standard header followed by variable size data.
///   (see ELFNote structure)
/// 3) A Thread Context in a core file usually described by 3 NOTE entries.
///    a) NT_PRSTATUS - Register context
///    b) NT_PRPSINFO - Process info(pid..)
///    c) NT_FPREGSET - Floating point registers
/// 4) The NOTE entries can be in any order
/// 5) If a core file contains multiple thread contexts then there is two data forms
///    a) Each thread context(2 or more NOTE entries) contained in its own segment (PT_NOTE)
///    b) All thread context is stored in a single segment(PT_NOTE).
///        This case is little tricker since while parsing we have to find where the
///        new thread starts. The current implementation marks beginning of
///        new thread when it finds NT_PRSTATUS or NT_PRPSINFO NOTE entry.
///    For case (b) there may be either one NT_PRPSINFO per thread, or a single
///    one that applies to all threads (depending on the platform type).
void
ProcessElfCore::ParseThreadContextsFromNoteSegment(const elf::ELFProgramHeader *segment_header,
                                                   DataExtractor segment_data)
{
    assert(segment_header && segment_header->p_type == llvm::ELF::PT_NOTE);

    lldb::offset_t offset = 0;
    std::unique_ptr<ThreadData> thread_data(new ThreadData);
    bool have_prstatus = false;
    bool have_prpsinfo = false;

    ArchSpec arch = GetArchitecture();
    ELFLinuxPrPsInfo prpsinfo;
    ELFLinuxPrStatus prstatus;
    size_t header_size;
    size_t len;

    // Loop through the NOTE entires in the segment
    while (offset < segment_header->p_filesz)
    {
        ELFNote note = ELFNote();
        note.Parse(segment_data, &offset);

        // Beginning of new thread
        if ((note.n_type == NT_PRSTATUS && have_prstatus) ||
            (note.n_type == NT_PRPSINFO && have_prpsinfo))
        {
            assert(thread_data->gpregset.GetByteSize() > 0);
            // Add the new thread to thread list
            m_thread_data.push_back(*thread_data);
            *thread_data = ThreadData();
            have_prstatus = false;
            have_prpsinfo = false;
        }

        size_t note_start, note_size;
        note_start = offset;
        note_size = llvm::alignTo(note.n_descsz, 4);

        // Store the NOTE information in the current thread
        DataExtractor note_data (segment_data, note_start, note_size);
        note_data.SetAddressByteSize(m_core_module_sp->GetArchitecture().GetAddressByteSize());
        if (note.n_name == "FreeBSD")
        {
            m_os = llvm::Triple::FreeBSD;
            switch (note.n_type)
            {
                case FREEBSD::NT_PRSTATUS:
                    have_prstatus = true;
                    ParseFreeBSDPrStatus(*thread_data, note_data, arch);
                    break;
                case FREEBSD::NT_FPREGSET:
                    thread_data->fpregset = note_data;
                    break;
                case FREEBSD::NT_PRPSINFO:
                    have_prpsinfo = true;
                    break;
                case FREEBSD::NT_THRMISC:
                    ParseFreeBSDThrMisc(*thread_data, note_data);
                    break;
                case FREEBSD::NT_PROCSTAT_AUXV:
                    // FIXME: FreeBSD sticks an int at the beginning of the note
                    m_auxv = DataExtractor(segment_data, note_start + 4, note_size - 4);
                    break;
                case FREEBSD::NT_PPC_VMX:
                    thread_data->vregset = note_data;
                    break;
                default:
                    break;
            }
        }
        else if (note.n_name == "CORE")
        {
            switch (note.n_type)
            {
                case NT_PRSTATUS:
                    have_prstatus = true;
                    prstatus.Parse(note_data, arch);
                    thread_data->signo = prstatus.pr_cursig;
                    thread_data->tid = prstatus.pr_pid;
                    header_size = ELFLinuxPrStatus::GetSize(arch);
                    len = note_data.GetByteSize() - header_size;
                    thread_data->gpregset = DataExtractor(note_data, header_size, len);
                    break;
                case NT_FPREGSET:
                    thread_data->fpregset = note_data;
                    break;
                case NT_PRPSINFO:
                    have_prpsinfo = true;
                    prpsinfo.Parse(note_data, arch);
                    thread_data->name = prpsinfo.pr_fname;
                    SetID(prpsinfo.pr_pid);
                    break;
                case NT_AUXV:
                    m_auxv = DataExtractor(note_data);
                    break;
                case NT_FILE:
                    {
                        m_nt_file_entries.clear();
                        lldb::offset_t offset = 0;
                        const uint64_t count = note_data.GetAddress(&offset);
                        note_data.GetAddress(&offset); // Skip page size
                        for (uint64_t i = 0; i<count; ++i)
                        {
                            NT_FILE_Entry entry;
                            entry.start = note_data.GetAddress(&offset);
                            entry.end = note_data.GetAddress(&offset);
                            entry.file_ofs = note_data.GetAddress(&offset);
                            m_nt_file_entries.push_back(entry);
                        }
                        for (uint64_t i = 0; i<count; ++i)
                        {
                            const char *path = note_data.GetCStr(&offset);
                            if (path && path[0])
                                m_nt_file_entries[i].path.SetCString(path);
                        }
                    }
                    break;
                default:
                    break;
            }
        }

        offset += note_size;
    }
    // Add last entry in the note section
    if (thread_data && thread_data->gpregset.GetByteSize() > 0)
    {
        m_thread_data.push_back(*thread_data);
    }
}

uint32_t
ProcessElfCore::GetNumThreadContexts ()
{
    if (!m_thread_data_valid)
        DoLoadCore();
    return m_thread_data.size();
}

ArchSpec
ProcessElfCore::GetArchitecture()
{
    ObjectFileELF *core_file = (ObjectFileELF *)(m_core_module_sp->GetObjectFile());
    ArchSpec arch;
    core_file->GetArchitecture(arch);
    return arch;
}

const lldb::DataBufferSP
ProcessElfCore::GetAuxvData()
{
    const uint8_t *start = m_auxv.GetDataStart();
    size_t len = m_auxv.GetByteSize();
    lldb::DataBufferSP buffer(new lldb_private::DataBufferHeap(start, len));
    return buffer;
}