DynamicLoader/POSIX-DYLD/DYLDRendezvous.cpp

//===-- DYLDRendezvous.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
// C++ Includes
// Other libraries and framework includes
#include "lldb/Core/ArchSpec.h"
#include "lldb/Core/Error.h"
#include "lldb/Core/Log.h"
#include "lldb/Core/Module.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Symbol/Symbol.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/Target.h"

#include "DYLDRendezvous.h"

using namespace lldb;
using namespace lldb_private;

/// Locates the address of the rendezvous structure.  Returns the address on
/// success and LLDB_INVALID_ADDRESS on failure.
static addr_t
ResolveRendezvousAddress(Process *process)
{
    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
    addr_t info_location;
    addr_t info_addr;
    Error error;

    // Try to get it from our process.  This might be a remote process and might
    // grab it via some remote-specific mechanism.
    info_location = process->GetImageInfoAddress();
    if (log)
        log->Printf ("%s info_location = 0x%" PRIx64, __FUNCTION__, info_location);

    // If the process fails to return an address, fall back to seeing if the local object file can help us find it.
    if (info_location == LLDB_INVALID_ADDRESS)
    {
        Target *target = process ? &process->GetTarget() : nullptr;
        if (target)
        {
            ObjectFile *obj_file = target->GetExecutableModule()->GetObjectFile();
            Address addr = obj_file->GetImageInfoAddress(target);

            if (addr.IsValid())
            {
                info_location = addr.GetLoadAddress(target);
                if (log)
                    log->Printf ("%s resolved via direct object file approach to 0x%" PRIx64, __FUNCTION__, info_location);
            }
            else
            {
                if (log)
                    log->Printf ("%s FAILED - direct object file approach did not yield a valid address", __FUNCTION__);
            }
        }
    }

    if (info_location == LLDB_INVALID_ADDRESS)
    {
        if (log)
            log->Printf ("%s FAILED - invalid info address", __FUNCTION__);
        return LLDB_INVALID_ADDRESS;
    }

    info_addr = process->ReadPointerFromMemory(info_location, error);
    if (error.Fail())
    {
        if (log)
            log->Printf ("%s FAILED - could not read from the info location: %s", __FUNCTION__, error.AsCString ());
        return LLDB_INVALID_ADDRESS;
    }

    if (info_addr == 0)
    {
        if (log)
            log->Printf ("%s FAILED - the rendezvous address contained at 0x%" PRIx64 " returned a null value", __FUNCTION__, info_location);
        return LLDB_INVALID_ADDRESS;
    }

    return info_addr;
}

DYLDRendezvous::DYLDRendezvous(Process *process)
    : m_process(process),
      m_rendezvous_addr(LLDB_INVALID_ADDRESS),
      m_current(),
      m_previous(),
      m_soentries(),
      m_added_soentries(),
      m_removed_soentries()
{
    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));

    m_thread_info.valid = false;

    // Cache a copy of the executable path
    if (m_process)
    {
        Module *exe_mod = m_process->GetTarget().GetExecutableModulePointer();
        if (exe_mod)
        {
            exe_mod->GetFileSpec().GetPath(m_exe_path, PATH_MAX);
            if (log)
                log->Printf ("DYLDRendezvous::%s exe module executable path set: '%s'", __FUNCTION__, m_exe_path);
        }
        else
        {
            if (log)
                log->Printf ("DYLDRendezvous::%s cannot cache exe module path: null executable module pointer", __FUNCTION__);
        }
    }
}

bool
DYLDRendezvous::Resolve()
{
    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));

    const size_t word_size = 4;
    Rendezvous info;
    size_t address_size;
    size_t padding;
    addr_t info_addr;
    addr_t cursor;

    address_size = m_process->GetAddressByteSize();
    padding = address_size - word_size;
    if (log)
        log->Printf ("DYLDRendezvous::%s address size: %zu, padding %zu", __FUNCTION__, address_size, padding);

    if (m_rendezvous_addr == LLDB_INVALID_ADDRESS)
        cursor = info_addr = ResolveRendezvousAddress(m_process);
    else
        cursor = info_addr = m_rendezvous_addr;
    if (log)
        log->Printf ("DYLDRendezvous::%s cursor = 0x%" PRIx64, __FUNCTION__, cursor);

    if (cursor == LLDB_INVALID_ADDRESS)
        return false;

    if (!(cursor = ReadWord(cursor, &info.version, word_size)))
        return false;

    if (!(cursor = ReadPointer(cursor + padding, &info.map_addr)))
        return false;

    if (!(cursor = ReadPointer(cursor, &info.brk)))
        return false;

    if (!(cursor = ReadWord(cursor, &info.state, word_size)))
        return false;

    if (!(cursor = ReadPointer(cursor + padding, &info.ldbase)))
        return false;

    // The rendezvous was successfully read.  Update our internal state.
    m_rendezvous_addr = info_addr;
    m_previous = m_current;
    m_current = info;

    return UpdateSOEntries();
}

bool
DYLDRendezvous::IsValid()
{
    return m_rendezvous_addr != LLDB_INVALID_ADDRESS;
}

bool
DYLDRendezvous::UpdateSOEntries()
{
    SOEntry entry;

    if (m_current.map_addr == 0)
        return false;

    // When the previous and current states are consistent this is the first
    // time we have been asked to update.  Just take a snapshot of the currently
    // loaded modules.
    if (m_previous.state == eConsistent && m_current.state == eConsistent)
        return TakeSnapshot(m_soentries);

    // If we are about to add or remove a shared object clear out the current
    // state and take a snapshot of the currently loaded images.
    if (m_current.state == eAdd || m_current.state == eDelete)
    {
        assert(m_previous.state == eConsistent);
        m_soentries.clear();
        m_added_soentries.clear();
        m_removed_soentries.clear();
        return TakeSnapshot(m_soentries);
    }
    assert(m_current.state == eConsistent);

    // Otherwise check the previous state to determine what to expect and update
    // accordingly.
    if (m_previous.state == eAdd)
        return UpdateSOEntriesForAddition();
    else if (m_previous.state == eDelete)
        return UpdateSOEntriesForDeletion();

    return false;
}

bool
DYLDRendezvous::UpdateSOEntriesForAddition()
{
    SOEntry entry;
    iterator pos;

    assert(m_previous.state == eAdd);

    if (m_current.map_addr == 0)
        return false;

    for (addr_t cursor = m_current.map_addr; cursor != 0; cursor = entry.next)
    {
        if (!ReadSOEntryFromMemory(cursor, entry))
            return false;

        // Only add shared libraries and not the executable.
        // On Linux this is indicated by an empty path in the entry.
        // On FreeBSD it is the name of the executable.
        if (entry.path.empty() || ::strcmp(entry.path.c_str(), m_exe_path) == 0)
            continue;

        pos = std::find(m_soentries.begin(), m_soentries.end(), entry);
        if (pos == m_soentries.end())
        {
            m_soentries.push_back(entry);
            m_added_soentries.push_back(entry);
        }
    }

    return true;
}

bool
DYLDRendezvous::UpdateSOEntriesForDeletion()
{
    SOEntryList entry_list;
    iterator pos;

    assert(m_previous.state == eDelete);

    if (!TakeSnapshot(entry_list))
        return false;

    for (iterator I = begin(); I != end(); ++I)
    {
        pos = std::find(entry_list.begin(), entry_list.end(), *I);
        if (pos == entry_list.end())
            m_removed_soentries.push_back(*I);
    }

    m_soentries = entry_list;
    return true;
}

bool
DYLDRendezvous::TakeSnapshot(SOEntryList &entry_list)
{
    SOEntry entry;

    if (m_current.map_addr == 0)
        return false;

    for (addr_t cursor = m_current.map_addr; cursor != 0; cursor = entry.next)
    {
        if (!ReadSOEntryFromMemory(cursor, entry))
            return false;

        // Only add shared libraries and not the executable.
        // On Linux this is indicated by an empty path in the entry.
        // On FreeBSD it is the name of the executable.
        if (entry.path.empty() || ::strcmp(entry.path.c_str(), m_exe_path) == 0)
            continue;

        entry_list.push_back(entry);
    }

    return true;
}

addr_t
DYLDRendezvous::ReadWord(addr_t addr, uint64_t *dst, size_t size)
{
    Error error;

    *dst = m_process->ReadUnsignedIntegerFromMemory(addr, size, 0, error);
    if (error.Fail())
        return 0;

    return addr + size;
}

addr_t
DYLDRendezvous::ReadPointer(addr_t addr, addr_t *dst)
{
    Error error;

    *dst = m_process->ReadPointerFromMemory(addr, error);
    if (error.Fail())
        return 0;

    return addr + m_process->GetAddressByteSize();
}

std::string
DYLDRendezvous::ReadStringFromMemory(addr_t addr)
{
    std::string str;
    Error error;
    size_t size;
    char c;

    if (addr == LLDB_INVALID_ADDRESS)
        return std::string();

    for (;;) {
        size = m_process->DoReadMemory(addr, &c, 1, error);
        if (size != 1 || error.Fail())
            return std::string();
        if (c == 0)
            break;
        else {
            str.push_back(c);
            addr++;
        }
    }

    return str;
}

bool
DYLDRendezvous::ReadSOEntryFromMemory(lldb::addr_t addr, SOEntry &entry)
{
    entry.clear();

    entry.link_addr = addr;

    if (!(addr = ReadPointer(addr, &entry.base_addr)))
        return false;

    // mips adds an extra load offset field to the link map struct on
    // FreeBSD and NetBSD (need to validate other OSes).
    // http://svnweb.freebsd.org/base/head/sys/sys/link_elf.h?revision=217153&view=markup#l57
    const ArchSpec &arch = m_process->GetTarget().GetArchitecture();
    if (arch.GetCore() == ArchSpec::eCore_mips64)
    {
        assert (arch.GetTriple().getOS() == llvm::Triple::FreeBSD ||
                arch.GetTriple().getOS() == llvm::Triple::NetBSD);
        addr_t mips_l_offs;
        if (!(addr = ReadPointer(addr, &mips_l_offs)))
            return false;
        if (mips_l_offs != 0 && mips_l_offs != entry.base_addr)
            return false;
    }

    if (!(addr = ReadPointer(addr, &entry.path_addr)))
        return false;

    if (!(addr = ReadPointer(addr, &entry.dyn_addr)))
        return false;

    if (!(addr = ReadPointer(addr, &entry.next)))
        return false;

    if (!(addr = ReadPointer(addr, &entry.prev)))
        return false;

    entry.path = ReadStringFromMemory(entry.path_addr);

    return true;
}


bool
DYLDRendezvous::FindMetadata(const char *name, PThreadField field, uint32_t& value)
{
    Target& target = m_process->GetTarget();

    SymbolContextList list;
    if (!target.GetImages().FindSymbolsWithNameAndType (ConstString(name), eSymbolTypeAny, list))
        return false;

    Address address = list[0].symbol->GetAddress();
    addr_t addr = address.GetLoadAddress (&target);
    if (addr == LLDB_INVALID_ADDRESS)
        return false;

    Error error;
    value = (uint32_t)m_process->ReadUnsignedIntegerFromMemory(addr + field*sizeof(uint32_t), sizeof(uint32_t), 0, error);
    if (error.Fail())
        return false;

    if (field == eSize)
        value /= 8; // convert bits to bytes

    return true;
}

const DYLDRendezvous::ThreadInfo&
DYLDRendezvous::GetThreadInfo()
{
    if (!m_thread_info.valid)
    {
        bool ok = true;

        ok &= FindMetadata ("_thread_db_pthread_dtvp", eOffset, m_thread_info.dtv_offset);
        ok &= FindMetadata ("_thread_db_dtv_dtv", eSize, m_thread_info.dtv_slot_size);
        ok &= FindMetadata ("_thread_db_link_map_l_tls_modid", eOffset, m_thread_info.modid_offset);
        ok &= FindMetadata ("_thread_db_dtv_t_pointer_val", eOffset, m_thread_info.tls_offset);

        if (ok)
            m_thread_info.valid = true;
    }

    return m_thread_info;
}

void
DYLDRendezvous::DumpToLog(Log *log) const
{
    int state = GetState();

    if (!log)
        return;

    log->PutCString("DYLDRendezvous:");
    log->Printf("   Address: %" PRIx64, GetRendezvousAddress());
    log->Printf("   Version: %" PRIu64, GetVersion());
    log->Printf("   Link   : %" PRIx64, GetLinkMapAddress());
    log->Printf("   Break  : %" PRIx64, GetBreakAddress());
    log->Printf("   LDBase : %" PRIx64, GetLDBase());
    log->Printf("   State  : %s",
                (state == eConsistent) ? "consistent" :
                (state == eAdd)        ? "add"        :
                (state == eDelete)     ? "delete"     : "unknown");

    iterator I = begin();
    iterator E = end();

    if (I != E)
        log->PutCString("DYLDRendezvous SOEntries:");

    for (int i = 1; I != E; ++I, ++i)
    {
        log->Printf("\n   SOEntry [%d] %s", i, I->path.c_str());
        log->Printf("      Base : %" PRIx64, I->base_addr);
        log->Printf("      Path : %" PRIx64, I->path_addr);
        log->Printf("      Dyn  : %" PRIx64, I->dyn_addr);
        log->Printf("      Next : %" PRIx64, I->next);
        log->Printf("      Prev : %" PRIx64, I->prev);
    }
}