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Commit 2ab4447a authored by Yurii Zubrytskyi's avatar Yurii Zubrytskyi
Browse files

[res] Don't stat asset providers on RO filesystems 

IsUpToDate() is one of the most often called functions, let's
make sure it only performs a syscall if it makes any sense and
the underlying file can really change.

Bug: 237583012
Test: build + boot + UTs
Change-Id: Ie5999ddadf10b56f35354d00ad3402b229ffa2c3
parent 9d22537e

libs/androidfw/AssetsProvider.cpp

+30 −17
Original line number Diff line number Diff line
@@ -104,6 +104,8 @@ std::unique_ptr<ZipAssetsProvider> ZipAssetsProvider::Create(std::string path, 
  }



  struct stat sb{.st_mtime = -1};

  // Skip all up-to-date checks if the file won't ever change.

  if (!isReadonlyFilesystem(path.c_str())) {

    if ((released_fd < 0 ? stat(path.c_str(), &sb) : fstat(released_fd, &sb)) < 0) {

      // Stat requires execute permissions on all directories path to the file. If the process does

      // not have execute permissions on this file, allow the zip to be opened but IsUpToDate() will
@@ -111,6 +113,7 @@ std::unique_ptr<ZipAssetsProvider> ZipAssetsProvider::Create(std::string path, 
      LOG(WARNING) << "Failed to stat file '" << path << "': "

                   << base::SystemErrorCodeToString(errno);

    }

  }



  return std::unique_ptr<ZipAssetsProvider>(

      new ZipAssetsProvider(handle, PathOrDebugName{std::move(path),
@@ -136,12 +139,15 @@ std::unique_ptr<ZipAssetsProvider> ZipAssetsProvider::Create(base::unique_fd fd, 
  }



  struct stat sb{.st_mtime = -1};

  // Skip all up-to-date checks if the file won't ever change.

  if (!isReadonlyFilesystem(released_fd)) {

    if (fstat(released_fd, &sb) < 0) {

      // Stat requires execute permissions on all directories path to the file. If the process does

      // not have execute permissions on this file, allow the zip to be opened but IsUpToDate() will

      // always have to return true.

    LOG(WARNING) << "Failed to fstat file '" << friendly_name << "': "

                 << base::SystemErrorCodeToString(errno);

      LOG(WARNING) << "Failed to fstat file '" << friendly_name

                   << "': " << base::SystemErrorCodeToString(errno);

    }

  }



  return std::unique_ptr<ZipAssetsProvider>(
@@ -278,6 +284,9 @@ const std::string& ZipAssetsProvider::GetDebugName() const { 
}



bool ZipAssetsProvider::IsUpToDate() const {

  if (last_mod_time_ == -1) {

    return true;

  }

  struct stat sb{};

  if (fstat(GetFileDescriptor(zip_handle_.get()), &sb) < 0) {

    // If fstat fails on the zip archive, return true so the zip archive the resource system does
@@ -291,7 +300,7 @@ DirectoryAssetsProvider::DirectoryAssetsProvider(std::string&& path, time_t last 
    : dir_(std::forward<std::string>(path)), last_mod_time_(last_mod_time) {}



std::unique_ptr<DirectoryAssetsProvider> DirectoryAssetsProvider::Create(std::string path) {

  struct stat sb{};

  struct stat sb;

  const int result = stat(path.c_str(), &sb);

  if (result == -1) {

    LOG(ERROR) << "Failed to find directory '" << path << "'.";
@@ -307,8 +316,9 @@ std::unique_ptr<DirectoryAssetsProvider> DirectoryAssetsProvider::Create(std::st 
    path += OS_PATH_SEPARATOR;

  }



  return std::unique_ptr<DirectoryAssetsProvider>(new DirectoryAssetsProvider(std::move(path),

                                                                              sb.st_mtime));

  const bool isReadonly = isReadonlyFilesystem(path.c_str());

  return std::unique_ptr<DirectoryAssetsProvider>(

      new DirectoryAssetsProvider(std::move(path), isReadonly ? -1 : sb.st_mtime));

}



std::unique_ptr<Asset> DirectoryAssetsProvider::OpenInternal(const std::string& path,
@@ -338,7 +348,10 @@ const std::string& DirectoryAssetsProvider::GetDebugName() const { 
}



bool DirectoryAssetsProvider::IsUpToDate() const {

  struct stat sb{};

  if (last_mod_time_ == -1) {

    return true;

  }

  struct stat sb;

  if (stat(dir_.c_str(), &sb) < 0) {

    // If stat fails on the zip archive, return true so the zip archive the resource system does

    // attempt to refresh the ApkAsset.

libs/androidfw/include/androidfw/misc.h

+4 −0
Original line number Diff line number Diff line
@@ -44,6 +44,10 @@ FileType getFileType(const char* fileName); 
/* get the file's modification date; returns -1 w/errno set on failure */

time_t getFileModDate(const char* fileName);



// Check if |path| or |fd| resides on a readonly filesystem.

bool isReadonlyFilesystem(const char* path);

bool isReadonlyFilesystem(int fd);



}; // namespace android



#endif // _LIBS_ANDROID_FW_MISC_H

libs/androidfw/misc.cpp

+38 −6
Original line number Diff line number Diff line
@@ -21,12 +21,17 @@ 
//

#include <androidfw/misc.h>



#include <sys/stat.h>

#include "android-base/logging.h"



#ifndef _WIN32

#include <sys/statvfs.h>

#include <sys/vfs.h>

#endif  // _WIN32



#include <cstring>

#include <errno.h>

#include <cstdio>



using namespace android;

#include <errno.h>

#include <sys/stat.h>



namespace android {
@@ -41,8 +46,7 @@ FileType getFileType(const char* fileName) 
        if (errno == ENOENT || errno == ENOTDIR)

            return kFileTypeNonexistent;

        else {

            fprintf(stderr, "getFileType got errno=%d on '%s'\n",

                errno, fileName);

            PLOG(ERROR) << "getFileType(): stat(" << fileName << ") failed";

            return kFileTypeUnknown;

        }

    } else {
@@ -82,4 +86,32 @@ time_t getFileModDate(const char* fileName) 
    return sb.st_mtime;

}



#ifdef _WIN32

// No need to implement these for Windows, the functions only matter on a device.

bool isReadonlyFilesystem(const char*) {

    return false;

}

bool isReadonlyFilesystem(int) {

    return false;

}

#else   // _WIN32

bool isReadonlyFilesystem(const char* path) {

    struct statfs sfs;

    if (::statfs(path, &sfs)) {

        PLOG(ERROR) << "isReadonlyFilesystem(): statfs(" << path << ") failed";

        return false;

    }

    return (sfs.f_flags & ST_RDONLY) != 0;

}



bool isReadonlyFilesystem(int fd) {

    struct statfs sfs;

    if (::fstatfs(fd, &sfs)) {

        PLOG(ERROR) << "isReadonlyFilesystem(): fstatfs(" << fd << ") failed";

        return false;

    }

    return (sfs.f_flags & ST_RDONLY) != 0;

}

#endif  // _WIN32



}; // namespace android