Revert^2: InMemoryDexClassLoader in ClassLoaderContext follow-up

Address follow-up comments on Ic64065819018a1e56dee0f65405d26beb8fd7bbd.
In particular, the classpath elements of IMC are replaced with
"<unknown>" magic value to make it clear that the dex location is bogus,
and a clarifying comment is added.

Previously this CL would fail on target because IMC classpath was not
being replaced with "<unknown>" and context matching failed. This was
only a problem on target because
OatFile::ResolveRelativeEncodedDexLocation ignores non-absolute
locations on host.

This reverts commit 93d99f3665cbd890509f4c707e1a62c5f26d320e.

Test: m test-art-gtest-class_loader_context_test
Bug: 72131483
Change-Id: I27cbfa69c24d412cc1b6bcce88218cc95e324ef5

1 files changed, 19 insertions, 3 deletions

diff --git a/runtime/class_loader_context.cc b/runtime/class_loader_context.cc
index 428bf30500..2b62d59118 100644
--- a/runtime/class_loader_context.cc
+++ b/runtime/class_loader_context.cc
@@ -54,6 +54,7 @@ static constexpr char kClassLoaderSharedLibrarySeparator = '#';
 static constexpr char kClassLoaderSeparator = ';';
 static constexpr char kClasspathSeparator = ':';
 static constexpr char kDexFileChecksumSeparator = '*';
+static constexpr char kInMemoryDexClassLoaderDexLocationMagic[] = "<unknown>";
 
 ClassLoaderContext::ClassLoaderContext()
     : special_shared_library_(false),
@@ -170,6 +171,8 @@ std::unique_ptr<ClassLoaderContext::ClassLoaderInfo> ClassLoaderContext::ParseCl
       // Checksums are not provided and dex locations themselves have no meaning
       // (although we keep them in the spec to simplify parsing). Treat this as
       // an unknown class loader.
+      // We can hit this case if dex2oat is invoked with a spec containing IMC.
+      // Because the dex file data is only available at runtime, we cannot proceed.
       return nullptr;
     }
   }
@@ -198,6 +201,7 @@ std::unique_ptr<ClassLoaderContext::ClassLoaderInfo> ClassLoaderContext::ParseCl
   std::unique_ptr<ClassLoaderInfo> info(new ClassLoaderInfo(class_loader_type));
 
   if (!parse_checksums) {
+    DCHECK(class_loader_type != kInMemoryDexClassLoader);
     Split(classpath, kClasspathSeparator, &info->classpath);
   } else {
     std::vector<std::string> classpath_elements;
@@ -212,6 +216,10 @@ std::unique_ptr<ClassLoaderContext::ClassLoaderInfo> ClassLoaderContext::ParseCl
       if (!android::base::ParseUint(dex_file_with_checksum[1].c_str(), &checksum)) {
         return nullptr;
       }
+      if ((class_loader_type == kInMemoryDexClassLoader) &&
+          (dex_file_with_checksum[0] != kInMemoryDexClassLoaderDexLocationMagic)) {
+        return nullptr;
+      }
 
       info->classpath.push_back(dex_file_with_checksum[0]);
       info->checksums.push_back(checksum);
@@ -417,6 +425,8 @@ bool ClassLoaderContext::OpenDexFiles(InstructionSet isa,
   while (!work_list.empty()) {
     ClassLoaderInfo* info = work_list.back();
     work_list.pop_back();
+    DCHECK(info->type != kInMemoryDexClassLoader) << __FUNCTION__ << " not supported for IMC";
+
     size_t opened_dex_files_index = info->opened_dex_files.size();
     for (const std::string& cp_elem : info->classpath) {
       // If path is relative, append it to the provided base directory.
@@ -625,8 +635,10 @@ void ClassLoaderContext::EncodeContextInternal(const ClassLoaderInfo& info,
     if (k > 0) {
       out << kClasspathSeparator;
     }
-    // Find paths that were relative and convert them back from absolute.
-    if (!base_dir.empty() && location.substr(0, base_dir.length()) == base_dir) {
+    if (info.type == kInMemoryDexClassLoader) {
+      out << kInMemoryDexClassLoaderDexLocationMagic;
+    } else if (!base_dir.empty() && location.substr(0, base_dir.length()) == base_dir) {
+      // Find paths that were relative and convert them back from absolute.
       out << location.substr(base_dir.length() + 1).c_str();
     } else {
       out << location.c_str();
@@ -1051,7 +1063,11 @@ bool ClassLoaderContext::CreateInfoFromClassLoader(
 
   // Now that `info` is in the chain, populate dex files.
   for (const DexFile* dex_file : dex_files_loaded) {
-    info->classpath.push_back(dex_file->GetLocation());
+    // Dex location of dex files loaded with InMemoryDexClassLoader is always bogus.
+    // Use a magic value for the classpath instead.
+    info->classpath.push_back((type == kInMemoryDexClassLoader)
+        ? kInMemoryDexClassLoaderDexLocationMagic
+        : dex_file->GetLocation());
     info->checksums.push_back(dex_file->GetLocationChecksum());
     info->opened_dex_files.emplace_back(dex_file);
   }