linker/linker_utils.cpp

/*
 * Copyright (C) 2015 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "linker_utils.h"

#include "linker_debug.h"
#include "linker_globals.h"

#include "android-base/strings.h"

#include <sys/stat.h>
#include <unistd.h>

void format_string(std::string* str, const std::vector<std::pair<std::string, std::string>>& params) {
  size_t pos = 0;
  while (pos < str->size()) {
    pos = str->find("$", pos);
    if (pos == std::string::npos) break;
    for (const auto& param : params) {
      const std::string& token = param.first;
      const std::string& replacement = param.second;
      if (str->substr(pos + 1, token.size()) == token) {
        str->replace(pos, token.size() + 1, replacement);
        // -1 to compensate for the ++pos below.
        pos += replacement.size() - 1;
        break;
      } else if (str->substr(pos + 1, token.size() + 2) == "{" + token + "}") {
        str->replace(pos, token.size() + 3, replacement);
        pos += replacement.size() - 1;
        break;
      }
    }
    // Skip $ in case it did not match any of the known substitutions.
    ++pos;
  }
}

std::string dirname(const char* path) {
  const char* last_slash = strrchr(path, '/');

  if (last_slash == path) {
    return "/";
  } else if (last_slash == nullptr) {
    return ".";
  } else {
    return std::string(path, last_slash - path);
  }
}

bool normalize_path(const char* path, std::string* normalized_path) {
  // Input should be an absolute path
  if (path[0] != '/') {
    PRINT("normalize_path - invalid input: \"%s\", the input path should be absolute", path);
    return false;
  }

  const size_t len = strlen(path) + 1;
  char buf[len];

  const char* in_ptr = path;
  char* out_ptr = buf;

  while (*in_ptr != 0) {
    if (*in_ptr == '/') {
      char c1 = in_ptr[1];
      if (c1 == '.') {
        char c2 = in_ptr[2];
        if (c2 == '/') {
          in_ptr += 2;
          continue;
        } else if (c2 == '.' && (in_ptr[3] == '/' || in_ptr[3] == 0)) {
          in_ptr += 3;
          while (out_ptr > buf && *--out_ptr != '/') {
          }
          if (in_ptr[0] == 0) {
            // retain '/' (or write the initial '/' for "/..")
            *out_ptr++ = '/';
          }
          continue;
        }
      } else if (c1 == '/') {
        ++in_ptr;
        continue;
      }
    }
    *out_ptr++ = *in_ptr++;
  }

  *out_ptr = 0;
  *normalized_path = buf;
  return true;
}

bool file_is_in_dir(const std::string& file, const std::string& dir) {
  const char* needle = dir.c_str();
  const char* haystack = file.c_str();
  size_t needle_len = strlen(needle);

  return strncmp(haystack, needle, needle_len) == 0 &&
         haystack[needle_len] == '/' &&
         strchr(haystack + needle_len + 1, '/') == nullptr;
}

bool file_is_under_dir(const std::string& file, const std::string& dir) {
  const char* needle = dir.c_str();
  const char* haystack = file.c_str();
  size_t needle_len = strlen(needle);

  return strncmp(haystack, needle, needle_len) == 0 &&
         haystack[needle_len] == '/';
}

const char* const kZipFileSeparator = "!/";

bool parse_zip_path(const char* input_path, std::string* zip_path, std::string* entry_path) {
  std::string normalized_path;
  if (!normalize_path(input_path, &normalized_path)) {
    return false;
  }

  const char* const path = normalized_path.c_str();
  TRACE("Trying zip file open from path \"%s\" -> normalized \"%s\"", input_path, path);

  // Treat an '!/' separator inside a path as the separator between the name
  // of the zip file on disk and the subdirectory to search within it.
  // For example, if path is "foo.zip!/bar/bas/x.so", then we search for
  // "bar/bas/x.so" within "foo.zip".
  const char* const separator = strstr(path, kZipFileSeparator);
  if (separator == nullptr) {
    return false;
  }

  char buf[512];
  if (strlcpy(buf, path, sizeof(buf)) >= sizeof(buf)) {
    PRINT("Warning: ignoring very long library path: %s", path);
    return false;
  }

  buf[separator - path] = '\0';

  *zip_path = buf;
  *entry_path = &buf[separator - path + 2];

  return true;
}

constexpr off64_t kPageMask = ~static_cast<off64_t>(PAGE_SIZE-1);

off64_t page_start(off64_t offset) {
  return offset & kPageMask;
}

bool safe_add(off64_t* out, off64_t a, size_t b) {
  CHECK(a >= 0);
  if (static_cast<uint64_t>(INT64_MAX - a) < b) {
    return false;
  }

  *out = a + b;
  return true;
}

size_t page_offset(off64_t offset) {
  return static_cast<size_t>(offset & (PAGE_SIZE-1));
}

void split_path(const char* path, const char* delimiters,
                std::vector<std::string>* paths) {
  if (path != nullptr && path[0] != 0) {
    *paths = android::base::Split(path, delimiters);
  }
}

void resolve_paths(std::vector<std::string>& paths,
                   std::vector<std::string>* resolved_paths) {
  resolved_paths->clear();
  for (const auto& path : paths) {
    // skip empty paths
    if (path.empty()) {
      continue;
    }
    std::string resolved = resolve_path(path);
    if (!resolved.empty()) {
      resolved_paths->push_back(std::move(resolved));
    }
  }
}

std::string resolve_path(const std::string& path) {
  char resolved_path[PATH_MAX];
  const char* original_path = path.c_str();
  if (realpath(original_path, resolved_path) != nullptr) {
    struct stat s;
    if (stat(resolved_path, &s) == -1) {
      DL_WARN("Warning: cannot stat file \"%s\": %s (ignoring)", resolved_path, strerror(errno));
      return "";
    }
    if (!S_ISDIR(s.st_mode)) {
      DL_WARN("Warning: \"%s\" is not a directory (ignoring)", resolved_path);
      return "";
    }
    return resolved_path;
  } else {
    std::string normalized_path;
    if (!normalize_path(original_path, &normalized_path)) {
      DL_WARN("Warning: unable to normalize \"%s\" (ignoring)", original_path);
      return "";
    }

    std::string zip_path;
    std::string entry_path;
    if (parse_zip_path(normalized_path.c_str(), &zip_path, &entry_path)) {
      if (realpath(zip_path.c_str(), resolved_path) == nullptr) {
        DL_WARN("Warning: unable to resolve \"%s\": %s (ignoring)",
                zip_path.c_str(), strerror(errno));
        return "";
      }

      return std::string(resolved_path) + kZipFileSeparator + entry_path;
    } else {
      struct stat s;
      if (stat(normalized_path.c_str(), &s) == 0 && S_ISDIR(s.st_mode)) {
        // Path is not a zip path, but an existing directory. Then add it
        // although we failed to resolve it. b/119656753
        return normalized_path;
      }
    }
  }
  return "";
}

bool is_first_stage_init() {
  static bool ret = (getpid() == 1 && access("/proc/self/exe", F_OK) == -1);
  return ret;
}