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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 "android-base/strings.h"
     39 #include "private/CachedProperty.h"
     40 #include "private/libc_logging.h"
     41 
     42 LinkerLogger g_linker_logger;
     43 bool g_greylist_disabled = false;
     44 
     45 static uint32_t ParseProperty(const std::string& value) {
     46   if (value.empty()) {
     47     return 0;
     48   }
     49 
     50   std::vector<std::string> options = android::base::Split(value, ",");
     51 
     52   uint32_t flags = 0;
     53 
     54   for (const auto& o : options) {
     55     if (o == "dlerror") {
     56       flags |= kLogErrors;
     57     } else if (o == "dlopen") {
     58       flags |= kLogDlopen;
     59     } else if (o == "dlsym") {
     60       flags |= kLogDlsym;
     61     } else {
     62       __libc_format_log(ANDROID_LOG_WARN, "linker", "Ignoring unknown debug.ld option \"%s\"",
     63                         o.c_str());
     64     }
     65   }
     66 
     67   return flags;
     68 }
     69 
     70 static void GetAppSpecificProperty(char* buffer) {
     71   // Get process basename.
     72   const char* process_name_start = basename(g_argv[0]);
     73 
     74   // Remove ':' and everything after it. This is the naming convention for
     75   // services: https://developer.android.com/guide/components/services.html
     76   const char* process_name_end = strchr(process_name_start, ':');
     77 
     78   std::string process_name = (process_name_end != nullptr) ?
     79                              std::string(process_name_start, (process_name_end - process_name_start)) :
     80                              std::string(process_name_start);
     81 
     82   std::string property_name = std::string("debug.ld.app.") + process_name;
     83   __system_property_get(property_name.c_str(), buffer);
     84 }
     85 
     86 void LinkerLogger::ResetState() {
     87   // The most likely scenario app is not debuggable and
     88   // is running on a user build, in which case logging is disabled.
     89   if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0) {
     90     return;
     91   }
     92 
     93   // This is a convenient place to check whether the greylist should be disabled for testing.
     94   static CachedProperty greylist_disabled("debug.ld.greylist_disabled");
     95   bool old_value = g_greylist_disabled;
     96   g_greylist_disabled = (strcmp(greylist_disabled.Get(), "true") == 0);
     97   if (g_greylist_disabled != old_value) {
     98     __libc_format_log(ANDROID_LOG_INFO, "linker", "%s greylist",
     99                       g_greylist_disabled ? "Disabling" : "Enabling");
    100   }
    101 
    102   flags_ = 0;
    103 
    104   // For logging, check the flag applied to all processes first.
    105   static CachedProperty debug_ld_all("debug.ld.all");
    106   flags_ |= ParseProperty(debug_ld_all.Get());
    107 
    108   // Ignore processes started without argv (http://b/33276926).
    109   if (g_argv[0] == nullptr) {
    110     return;
    111   }
    112 
    113   // Otherwise check the app-specific property too.
    114   // We can't easily cache the property here because argv[0] changes.
    115   char debug_ld_app[PROP_VALUE_MAX] = {};
    116   GetAppSpecificProperty(debug_ld_app);
    117   flags_ |= ParseProperty(debug_ld_app);
    118 }
    119 
    120 void LinkerLogger::Log(uint32_t type, const char* format, ...) {
    121   if ((flags_ & type) == 0) {
    122     return;
    123   }
    124 
    125   va_list ap;
    126   va_start(ap, format);
    127   __libc_format_log_va_list(ANDROID_LOG_DEBUG, "linker", format, ap);
    128   va_end(ap);
    129 }
    130