llvm-project/lldb/source/Utility/ModuleCache.cpp

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

#include "ModuleCache.h"

#include "lldb/Core/Log.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/ModuleList.h"
#include "lldb/Core/ModuleSpec.h"
#include "lldb/Host/File.h"
#include "lldb/Host/FileSystem.h"
#include "lldb/Host/LockFile.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/FileUtilities.h"

#include <assert.h>

#include <cstdio>

using namespace lldb;
using namespace lldb_private;

namespace {

const char* kModulesSubdir = ".cache";
const char* kLockDirName = ".lock";
const char* kTempFileName = ".temp";
const char* kTempSymFileName = ".symtemp";
const char* kSymFileExtension = ".sym";
const char* kFSIllegalChars = "\\/:*?\"<>|";

std::string
GetEscapedHostname(const char* hostname)
{
    std::string result(hostname);
    size_t size = result.size();
    for (size_t i = 0; i < size; ++i)
    {
        if ((result[i] >=1 && result[i] <= 31) ||
            strchr(kFSIllegalChars, result[i]) != nullptr)
            result[i] = '_';
    }
    return result;
}

class ModuleLock
{
private:
    File m_file;
    std::unique_ptr<lldb_private::LockFile> m_lock;
    FileSpec m_file_spec;

public:
    ModuleLock (const FileSpec &root_dir_spec, const UUID &uuid, Error& error);
    void Delete ();
};

FileSpec
JoinPath (const FileSpec &path1, const char* path2)
{
    FileSpec result_spec (path1);
    result_spec.AppendPathComponent (path2);
    return result_spec;
}

Error
MakeDirectory (const FileSpec &dir_path)
{
    if (dir_path.Exists ())
    {
        if (!dir_path.IsDirectory ())
            return Error ("Invalid existing path");

        return Error ();
    }

    return FileSystem::MakeDirectory(dir_path, eFilePermissionsDirectoryDefault);
}

FileSpec
GetModuleDirectory (const FileSpec &root_dir_spec, const UUID &uuid)
{
    const auto modules_dir_spec = JoinPath (root_dir_spec, kModulesSubdir);
    return JoinPath (modules_dir_spec, uuid.GetAsString ().c_str ());
}

FileSpec
GetSymbolFileSpec(const FileSpec& module_file_spec)
{
    return FileSpec((module_file_spec.GetPath() + kSymFileExtension).c_str(), false);
}

void
DeleteExistingModule (const FileSpec &root_dir_spec, const FileSpec &sysroot_module_path_spec)
{
    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_MODULES));
    UUID module_uuid;
    {
        auto module_sp = std::make_shared<Module>(ModuleSpec (sysroot_module_path_spec));
        module_uuid = module_sp->GetUUID ();
    }

    if (!module_uuid.IsValid ())
        return;

    Error error;
    ModuleLock lock (root_dir_spec,  module_uuid, error);
    if (error.Fail ())
    {
        if (log)
            log->Printf ("Failed to lock module %s: %s",
                         module_uuid.GetAsString ().c_str (),
                         error.AsCString ());
    }

    auto link_count = FileSystem::GetHardlinkCount (sysroot_module_path_spec);
    if (link_count == -1)
        return;

    if (link_count > 2)  // module is referred by other hosts.
        return;

    const auto module_spec_dir = GetModuleDirectory (root_dir_spec, module_uuid);
    FileSystem::DeleteDirectory (module_spec_dir, true);
    lock.Delete();
}

void
DecrementRefExistingModule (const FileSpec &root_dir_spec, const FileSpec &sysroot_module_path_spec)
{
    // Remove $platform/.cache/$uuid folder if nobody else references it.
    DeleteExistingModule (root_dir_spec, sysroot_module_path_spec);

    // Remove sysroot link.
    FileSystem::Unlink (sysroot_module_path_spec);

    FileSpec symfile_spec = GetSymbolFileSpec (sysroot_module_path_spec);
    if (symfile_spec.Exists ())  // delete module's symbol file if exists.
        FileSystem::Unlink (symfile_spec);
}

Error
CreateHostSysRootModuleLink (const FileSpec &root_dir_spec, const char *hostname,
                             const FileSpec &platform_module_spec,
                             const FileSpec &local_module_spec,
                             bool delete_existing)
{
    const auto sysroot_module_path_spec = JoinPath (
        JoinPath (root_dir_spec, hostname), platform_module_spec.GetPath ().c_str ());
    if (sysroot_module_path_spec.Exists())
    {
        if (!delete_existing)
            return Error ();

        DecrementRefExistingModule (root_dir_spec, sysroot_module_path_spec);
    }

    const auto error = MakeDirectory (FileSpec (sysroot_module_path_spec.GetDirectory ().AsCString (), false));
    if (error.Fail ())
        return error;

    return FileSystem::Hardlink(sysroot_module_path_spec, local_module_spec);
}

}  // namespace

ModuleLock::ModuleLock (const FileSpec &root_dir_spec, const UUID &uuid, Error& error)
{
    const auto lock_dir_spec = JoinPath (root_dir_spec, kLockDirName);
    error = MakeDirectory (lock_dir_spec);
    if (error.Fail ())
        return;

    m_file_spec = JoinPath (lock_dir_spec, uuid.GetAsString ().c_str ());
    m_file.Open (m_file_spec.GetCString (),
                 File::eOpenOptionWrite | File::eOpenOptionCanCreate | File::eOpenOptionCloseOnExec);
    if (!m_file)
    {
        error.SetErrorToErrno ();
        return;
    }

    m_lock.reset (new lldb_private::LockFile (m_file.GetDescriptor ()));
    error = m_lock->WriteLock (0, 1);
    if (error.Fail ())
        error.SetErrorStringWithFormat ("Failed to lock file: %s", error.AsCString ());
}

void ModuleLock::Delete ()
{
    if (!m_file)
        return;

    m_file.Close ();
    FileSystem::Unlink (m_file_spec);
}

/////////////////////////////////////////////////////////////////////////

Error
ModuleCache::Put (const FileSpec &root_dir_spec,
                  const char *hostname,
                  const ModuleSpec &module_spec,
                  const FileSpec &tmp_file,
                  const FileSpec &target_file)
{
    const auto module_spec_dir = GetModuleDirectory (root_dir_spec, module_spec.GetUUID ());
    const auto module_file_path = JoinPath (module_spec_dir, target_file.GetFilename ().AsCString ());

    const auto tmp_file_path = tmp_file.GetPath ();
    const auto err_code = llvm::sys::fs::rename (tmp_file_path.c_str (), module_file_path.GetPath ().c_str ());
    if (err_code)
        return Error ("Failed to rename file %s to %s: %s",
                      tmp_file_path.c_str (), module_file_path.GetPath ().c_str (), err_code.message ().c_str ());

    const auto error = CreateHostSysRootModuleLink(root_dir_spec, hostname, target_file, module_file_path, true);
    if (error.Fail ())
        return Error ("Failed to create link to %s: %s", module_file_path.GetPath ().c_str (), error.AsCString ());
    return Error ();
}

Error
ModuleCache::Get (const FileSpec &root_dir_spec,
                  const char *hostname,
                  const ModuleSpec &module_spec,
                  ModuleSP &cached_module_sp,
                  bool *did_create_ptr)
{
    const auto find_it = m_loaded_modules.find (module_spec.GetUUID ().GetAsString());
    if (find_it != m_loaded_modules.end ())
    {
        cached_module_sp = (*find_it).second.lock ();
        if (cached_module_sp)
            return Error ();
        m_loaded_modules.erase (find_it);
    }

    const auto module_spec_dir = GetModuleDirectory (root_dir_spec, module_spec.GetUUID ());
    const auto module_file_path = JoinPath (module_spec_dir, module_spec.GetFileSpec ().GetFilename ().AsCString ());

    if (!module_file_path.Exists ())
        return Error ("Module %s not found", module_file_path.GetPath ().c_str ());
    if (module_file_path.GetByteSize () != module_spec.GetObjectSize ())
        return Error ("Module %s has invalid file size", module_file_path.GetPath ().c_str ());

    // We may have already cached module but downloaded from an another host - in this case let's create a link to it.
    auto error = CreateHostSysRootModuleLink(root_dir_spec, hostname, module_spec.GetFileSpec(), module_file_path, false);
    if (error.Fail ())
        return Error ("Failed to create link to %s: %s", module_file_path.GetPath().c_str(), error.AsCString());

    auto cached_module_spec (module_spec);
    cached_module_spec.GetUUID ().Clear ();  // Clear UUID since it may contain md5 content hash instead of real UUID.
    cached_module_spec.GetFileSpec () = module_file_path;
    cached_module_spec.GetPlatformFileSpec () = module_spec.GetFileSpec ();
    
    error = ModuleList::GetSharedModule(cached_module_spec,
                                        cached_module_sp,
                                        nullptr,
                                        nullptr,
                                        did_create_ptr,
                                        false);
    if (error.Fail())
        return error;

    FileSpec symfile_spec = GetSymbolFileSpec(cached_module_sp->GetFileSpec ());
    if (symfile_spec.Exists ())
        cached_module_sp->SetSymbolFileFileSpec (symfile_spec);

    m_loaded_modules.insert (std::make_pair (module_spec.GetUUID ().GetAsString (), cached_module_sp));

    return Error ();
}

Error
ModuleCache::GetAndPut (const FileSpec &root_dir_spec,
                        const char *hostname,
                        const ModuleSpec &module_spec,
                        const ModuleDownloader &module_downloader,
                        const SymfileDownloader &symfile_downloader,
                        lldb::ModuleSP &cached_module_sp,
                        bool *did_create_ptr)
{
    const auto module_spec_dir = GetModuleDirectory (root_dir_spec, module_spec.GetUUID ());
    auto error = MakeDirectory (module_spec_dir);
    if (error.Fail ())
        return error;

    ModuleLock lock (root_dir_spec,  module_spec.GetUUID (), error);
    if (error.Fail ())
        return Error("Failed to lock module %s: %s", module_spec.GetUUID ().GetAsString().c_str(), error.AsCString ());

    const auto escaped_hostname(GetEscapedHostname(hostname));
    // Check local cache for a module.
    error = Get (root_dir_spec, escaped_hostname.c_str(), module_spec, cached_module_sp, did_create_ptr);
    if (error.Success ())
        return error;

    const auto tmp_download_file_spec = JoinPath (module_spec_dir, kTempFileName);
    error = module_downloader (module_spec, tmp_download_file_spec);
    llvm::FileRemover tmp_file_remover (tmp_download_file_spec.GetPath ().c_str ());
    if (error.Fail ())
        return Error("Failed to download module: %s", error.AsCString ());

    // Put downloaded file into local module cache.
    error = Put (root_dir_spec, escaped_hostname.c_str(), module_spec, tmp_download_file_spec, module_spec.GetFileSpec ());
    if (error.Fail ())
        return Error ("Failed to put module into cache: %s", error.AsCString ());

    tmp_file_remover.releaseFile ();
    error = Get (root_dir_spec, escaped_hostname.c_str(), module_spec, cached_module_sp, did_create_ptr);
    if (error.Fail ())
        return error;

    // Fetching a symbol file for the module
    const auto tmp_download_sym_file_spec = JoinPath (module_spec_dir, kTempSymFileName);
    error = symfile_downloader (cached_module_sp, tmp_download_sym_file_spec);
    llvm::FileRemover tmp_symfile_remover (tmp_download_sym_file_spec.GetPath ().c_str ());
    if (error.Fail ())
        // Failed to download a symfile but fetching the module was successful. The module might
        // contain the neccessary symbols and the debugging is also possible without a symfile.
        return Error ();

    error = Put (root_dir_spec, escaped_hostname.c_str(), module_spec, tmp_download_sym_file_spec, GetSymbolFileSpec(module_spec.GetFileSpec ()));
    if (error.Fail ())
        return Error ("Failed to put symbol file into cache: %s", error.AsCString ());
    
    tmp_symfile_remover.releaseFile();

    FileSpec symfile_spec = GetSymbolFileSpec (cached_module_sp->GetFileSpec ());
    cached_module_sp->SetSymbolFileFileSpec (symfile_spec);
    return Error ();
}