PNaCl Dynamic Linking: Added portable dependencies to shared objects.

src/untrusted/pll_loader/pll_loader_main.cc

 // Copyright (c) 2016 The Native Client Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdint.h>
 #include <stdio.h>
 
 #include "native_client/src/include/elf32.h"
 #include "native_client/src/include/elf_auxv.h"
 #include "native_client/src/untrusted/nacl/nacl_irt.h"
 #include "native_client/src/untrusted/pll_loader/pll_loader.h"
 
 
 typedef void (*start_func_t)(int argc, char **argv, char **envp,
                              Elf32_auxv_t *auxv);
 
 int main(int argc, char **argv, char **envp) {
-  // The PLL format does not include module dependencies yet, so all the
-  // modules must be specified on the command line.
-  if (argc <= 2) {
-    fprintf(stderr, "Usage: pll_loader <ELF file>...\n");
+  if (argc != 3) {
+    fprintf(stderr, "Usage: pll_loader <Directory path> <ELF file>\n");
     return 1;
   }
 
   ModuleSet modset;
-  for (int i = 1; i < argc; i++) {
-    modset.AddByFilename(argv[i]);
-  }
+  std::vector<std::string> search_path;
+  search_path.push_back(argv[1]);
+  modset.SetSonameSearchPath(search_path);
+
+  modset.AddBySoname(argv[2]);

[Mark Seaborn, 2016/03/30 23:24:57]

Can you make this one AddByFilename() rather than AddBySoname(), since
executables won't usually be expected to be on the library search path?

[Sean Klein, 2016/04/01 23:12:24]

Done.

   modset.ResolveRefs();
 
   Elf32_auxv_t auxv[2];
   auxv[0].a_type = AT_SYSINFO;
   auxv[0].a_un.a_val = (uintptr_t) __nacl_irt_query;
   auxv[1].a_type = AT_NULL;
   auxv[1].a_un.a_val = 0;
 
   start_func_t start_func =
     (start_func_t) (uintptr_t) modset.GetSym("__libc_start");
   if (start_func == NULL) {
     fprintf(stderr, "Entry point symbol \"__libc_start\" not defined\n");
     return 1;
   }
   start_func(argc, argv, envp, auxv);
 
   return 0;
 }