PNaCl Dynamic Linking: Using unordered_set to disallow duplicate modules.

src/untrusted/pll_loader/pll_loader.cc

Index: src/untrusted/pll_loader/pll_loader.cc
diff --git a/src/untrusted/pll_loader/pll_loader.cc b/src/untrusted/pll_loader/pll_loader.cc
index aa7724e0c02ae42149d6f13dbdb39152ac9a2116..c447b9ae525497cfcc247ec900faa1e24804aa03 100644
--- a/src/untrusted/pll_loader/pll_loader.cc
+++ b/src/untrusted/pll_loader/pll_loader.cc
@@ -21,6 +21,18 @@ void *TLSBlockGetter(PLLTLSBlockGetter *closure) {
   return closure->arg;
 }
 
+// Given a pathname, return the filename it points to (or NULL if the path
+// ends with '/').
+const char *GetSoname(const char *path) {

[Mark Seaborn, 2016/03/25 17:57:28]

I'm not sure it makes sense to add this because we don't really want the PLL
loader to be parsing filenames, only constructing them (i.e. building "directory
+ soname" when searching).

How about instead:

* Leave the behaviour of AddByFilename() as it is.

* Add a couple of new methods:

const PLLRoot *AddBySoname(const char *soname);
void SetSonameSearchPath(const std::vector<std::string> &dir_list);

* Change pll_loader_test to exercise those new methods (in addition to
AddByFilename()) and to test that AddBySoname() de-dups.

[Sean Klein, 2016/03/25 18:43:57]

Yeah, it felt like a temporary solution anyway (I was never under the impression
"GetSoname" would stick around once we got directory searching working).

I'll update to the new version. If possible, I might try to hide "AddByFilename"
from the API, and instead use directory/soname setting functions instead.

+  const char *base = path;
+  while (*path) {
+    if (*path == '/')
+      base = path + 1;
+    path++;
+  }
+  return base;
+}
+
 }  // namespace
 
 uint32_t PLLModule::HashString(const char *sp) {
@@ -85,6 +97,15 @@ void *PLLModule::InstantiateTLSBlock() {
 }
 
 void ModuleSet::AddByFilename(const char *filename) {
+  std::string soname(GetSoname(filename));
+  if (soname.empty()) {
+    NaClLog(LOG_FATAL, "Invalid PLL Path: %s\n", filename);
+  }
+  if (sonames_.count(soname) != 0) {
+    NaClLog(LOG_FATAL, "PLL Loader found duplicate PLL: %s\n", filename);
+  }
+  sonames_.insert(soname);
+
   void *pso_root;
   int err = pnacl_load_elf_file(filename, &pso_root);
   if (err != 0) {