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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include "linker_logger.h"
     30 
     31 #include <string.h>
     32 #include <sys/prctl.h>
     33 #include <unistd.h>
     34 
     35 #include <string>
     36 #include <vector>
     37 
     38 #include <async_safe/log.h>
     39 
     40 #include "android-base/strings.h"
     41 #include "private/CachedProperty.h"
     42 
     43 LinkerLogger g_linker_logger;
     44 bool g_greylist_disabled = false;
     45 
     46 static uint32_t ParseProperty(const std::string& value) {
     47   if (value.empty()) {
     48     return 0;
     49   }
     50 
     51   std::vector<std::string> options = android::base::Split(value, ",");
     52 
     53   uint32_t flags = 0;
     54 
     55   for (const auto& o : options) {
     56     if (o == "dlerror") {
     57       flags |= kLogErrors;
     58     } else if (o == "dlopen") {
     59       flags |= kLogDlopen;
     60     } else if (o == "dlsym") {
     61       flags |= kLogDlsym;
     62     } else {
     63       async_safe_format_log(ANDROID_LOG_WARN, "linker", "Ignoring unknown debug.ld option \"%s\"",
     64                             o.c_str());
     65     }
     66   }
     67 
     68   return flags;
     69 }
     70 
     71 static void GetAppSpecificProperty(char* buffer) {
     72   // Get process basename.
     73   const char* process_name_start = basename(g_argv[0]);
     74 
     75   // Remove ':' and everything after it. This is the naming convention for
     76   // services: https://developer.android.com/guide/components/services.html
     77   const char* process_name_end = strchr(process_name_start, ':');
     78 
     79   std::string process_name = (process_name_end != nullptr) ?
     80                              std::string(process_name_start, (process_name_end - process_name_start)) :
     81                              std::string(process_name_start);
     82 
     83   std::string property_name = std::string("debug.ld.app.") + process_name;
     84   __system_property_get(property_name.c_str(), buffer);
     85 }
     86 
     87 void LinkerLogger::ResetState() {
     88   // The most likely scenario app is not debuggable and
     89   // is running on a user build, in which case logging is disabled.
     90   if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0) {
     91     return;
     92   }
     93 
     94   // This is a convenient place to check whether the greylist should be disabled for testing.
     95   static CachedProperty greylist_disabled("debug.ld.greylist_disabled");
     96   bool old_value = g_greylist_disabled;
     97   g_greylist_disabled = (strcmp(greylist_disabled.Get(), "true") == 0);
     98   if (g_greylist_disabled != old_value) {
     99     async_safe_format_log(ANDROID_LOG_INFO, "linker", "%s greylist",
    100                           g_greylist_disabled ? "Disabling" : "Enabling");
    101   }
    102 
    103   flags_ = 0;
    104 
    105   // For logging, check the flag applied to all processes first.
    106   static CachedProperty debug_ld_all("debug.ld.all");
    107   flags_ |= ParseProperty(debug_ld_all.Get());
    108 
    109   // Ignore processes started without argv (http://b/33276926).
    110   if (g_argv[0] == nullptr) {
    111     return;
    112   }
    113 
    114   // Otherwise check the app-specific property too.
    115   // We can't easily cache the property here because argv[0] changes.
    116   char debug_ld_app[PROP_VALUE_MAX] = {};
    117   GetAppSpecificProperty(debug_ld_app);
    118   flags_ |= ParseProperty(debug_ld_app);
    119 }
    120 
    121 void LinkerLogger::Log(uint32_t type, const char* format, ...) {
    122   if ((flags_ & type) == 0) {
    123     return;
    124   }
    125 
    126   va_list ap;
    127   va_start(ap, format);
    128   async_safe_format_log_va_list(ANDROID_LOG_DEBUG, "linker", format, ap);
    129   va_end(ap);
    130 }
    131