PNaCl Dynamic Linking: Using unordered_set to disallow duplicate modules.

src/untrusted/pll_loader/pll_loader.cc

 // Copyright 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 "native_client/src/untrusted/pll_loader/pll_loader.h"
 
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 
 #include <algorithm>
 
 #include "native_client/src/shared/platform/nacl_log.h"
 #include "native_client/src/untrusted/pnacl_dynloader/dynloader.h"
 
 namespace {
 
 // This is a simple implementation that does not support multiple threads.
 // It demonstrates how we can optimize if we know that pthread_create()
@@ skipping 58 matching lines @@
   if (posix_memalign(&base, alignment, root_->tls_template_total_size) != 0) {
     NaClLog(LOG_FATAL, "InstantiateTLSBlock: Allocation failed\n");
   }
   memcpy(base, root_->tls_template, root_->tls_template_data_size);
   size_t bss_size = (root_->tls_template_total_size -
                      root_->tls_template_data_size);
   memset((char *) base + root_->tls_template_data_size, 0, bss_size);
   return base;
 }
 
+void ModuleSet::SetSonameSearchPaths(const std::vector<std::string> &dir_list) {
+  search_paths_ = dir_list;
+}
+
+void ModuleSet::AddBySoname(const char *soname) {
+  // TODO(smklein): Deduplicate rather than failing once dependencies are added.
+  if (sonames_.count(soname) != 0) {
+    NaClLog(LOG_FATAL, "PLL Loader found duplicate soname: %s\n", soname);
+  }
+  sonames_.insert(soname);
+
+  // Actually load the module implied by the soname.
+  struct stat buf;

[Mark Seaborn, 2016/03/26 00:30:10]

Nit: putting this immediately before the stat() call is more idiomatic (i.e. put
var definitions as closer as possible to their uses), and just as efficient.

[Sean Klein, 2016/03/26 00:47:25]

Done.

+  for (auto path : search_paths_) {
+    // Appending "/" might be unnecessary, but "foo/bar" and "foo//bar" should
+    // point to the same file.
+    path.append("/");
+    path.append(soname);
+    if (stat(path.c_str(), &buf) == 0) {
+      AddByFilename(path.c_str());
+      return;
+    }
+  }
+
+  NaClLog(LOG_FATAL, "PLL Loader cannot find shared object file: %s\n", soname);
+}
+
 void ModuleSet::AddByFilename(const char *filename) {
   void *pso_root;
   int err = pnacl_load_elf_file(filename, &pso_root);
   if (err != 0) {
     NaClLog(LOG_FATAL, "pnacl_load_elf_file() failed: errno=%d\n", err);
   }
   modules_.push_back(PLLModule((const PLLRoot *) pso_root));
 }
 
 void *ModuleSet::GetSym(const char *name) {
@@ skipping 16 matching lines @@
       *(uintptr_t *) module.root()->imported_ptrs[index] += sym_value;
     }
 
     // Initialize TLS.
     if (PLLTLSBlockGetter *tls_block_getter = module.root()->tls_block_getter) {
       tls_block_getter->func = TLSBlockGetter;
       tls_block_getter->arg = module.InstantiateTLSBlock();
     }
   }
 }