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// Copyright 2014 The Chromium Authors. 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.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// 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 <dlfcn.h>
#include <stdio.h>
#include <string.h>
#include <sys/prctl.h>
#include <unistd.h>
// This is a wrapper to run position independent executables on Android ICS,
// where the linker doesn't support PIE. This requires the PIE binaries to be
// built with CFLAGS +=-fvisibility=default -fPIE, and LDFLAGS += -rdynamic -pie
// such that the main() symbol remains exported and can be dlsym-ed.
#define ERR_PREFIX "[PIE Loader] "
typedef int (*main_t)(int, char**);
int main(int argc, char** argv) {
if (argc < 2) {
printf("Usage: %s path_to_pie_executable [args]\n", argv[0]);
return -1;
}
// Shift left the argv[]. argv is what /proc/PID/cmdline prints out. In turn
// cmdline is what Android "ps" prints out. In turn "ps" is what many scripts
// look for to decide which processes to kill / killall.
int i;
char* next_argv_start = argv[0];
for (i = 1; i < argc; ++i) {
const size_t argv_len = strlen(argv[i]) + 1;
memmove(argv[i - 1], argv[i], argv_len);
next_argv_start += argv_len;
argv[i] = next_argv_start;
}
argv[argc - 1] = NULL; // The last argv must be a NULL ptr.
// Set also the proc name accordingly (/proc/PID/comm).
prctl(PR_SET_NAME, (long) argv[0]);
// dlopen should not fail, unless:
// - The target binary does not exists:
// - The dependent .so libs cannot be loaded.
// In both cases, just bail out with an explicit error message.
void* handle = dlopen(argv[0], RTLD_NOW);
if (handle == NULL) {
printf(ERR_PREFIX "dlopen() failed: %s.\n", dlerror());
return -1;
}
main_t pie_main = (main_t) dlsym(handle, "main");
if (pie_main) {
return pie_main(argc - 1, argv);
}
// If we reached this point dlsym failed, very likely because the target
// binary has not been compiled with the proper CFLAGS / LDFLAGS.
// At this point the most sensible thing to do is running that normally
// via exec and hope that the target binary wasn't a PIE.
execv(argv[0], argv);
// exevc is supposed to never return, unless it fails.
printf(ERR_PREFIX "Both dlsym() and the execv() fallback failed.\n");
perror("execv");
return -1;
}
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