simpleperf: find debug files for kernel modules.

Also print a warning when a debug file in symfs_dir can't be used
because of build_id mismatch.

Bug: 161546498
Test: run simpleperf_unit_test
Change-Id: I8d1d538a4a62339d236e665141b114428776fb54

1 files changed, 32 insertions, 16 deletions

diff --git a/simpleperf/dso.cpp b/simpleperf/dso.cpp
index 975a391a..df07393f 100644
--- a/simpleperf/dso.cpp
+++ b/simpleperf/dso.cpp
@@ -106,6 +106,29 @@ void DebugElfFileFinder::SetVdsoFile(const std::string& vdso_file, bool is_64bit
   }
 }
 
+static bool CheckDebugFilePath(const std::string& path, BuildId& build_id,
+                               bool report_build_id_mismatch) {
+  ElfStatus status;
+  auto elf = ElfFile::Open(path, &status);
+  if (!elf) {
+    return false;
+  }
+  BuildId debug_build_id;
+  status = elf->GetBuildId(&debug_build_id);
+  if (status != ElfStatus::NO_ERROR && status != ElfStatus::NO_BUILD_ID) {
+    return false;
+  }
+
+  // Native libraries in apks and kernel modules may not have build ids.
+  // So build_id and debug_build_id can either be empty, or have the same value.
+  bool match = build_id == debug_build_id;
+  if (!match && report_build_id_mismatch) {
+    LOG(WARNING) << path << " isn't used because of build id mismatch: expected " << build_id
+                 << ", real " << debug_build_id;
+  }
+  return match;
+}
+
 std::string DebugElfFileFinder::FindDebugFile(const std::string& dso_path, bool force_64bit,
                                               BuildId& build_id) {
   if (dso_path == "[vdso]") {
@@ -119,22 +142,12 @@ std::string DebugElfFileFinder::FindDebugFile(const std::string& dso_path, bool
     // Try reading build id from file if we don't already have one.
     GetBuildIdFromDsoPath(dso_path, &build_id);
   }
-  auto check_path = [&](const std::string& path) {
-    BuildId debug_build_id;
-    GetBuildIdFromDsoPath(path, &debug_build_id);
-    if (build_id.IsEmpty()) {
-      // Native libraries in apks may not have build ids. When looking for a debug elf file without
-      // build id (build id is empty), the debug file should exist and also not have build id.
-      return IsRegularFile(path) && debug_build_id.IsEmpty();
-    }
-    return build_id == debug_build_id;
-  };
 
   // 1. Try build_id_to_file_map.
   if (!build_id_to_file_map_.empty()) {
     if (!build_id.IsEmpty() || GetBuildIdFromDsoPath(dso_path, &build_id)) {
       auto it = build_id_to_file_map_.find(build_id.ToString());
-      if (it != build_id_to_file_map_.end() && check_path(it->second)) {
+      if (it != build_id_to_file_map_.end() && CheckDebugFilePath(it->second, build_id, false)) {
         return it->second;
       }
     }
@@ -142,18 +155,18 @@ std::string DebugElfFileFinder::FindDebugFile(const std::string& dso_path, bool
   if (!symfs_dir_.empty()) {
     // 2. Try concatenating symfs_dir and dso_path.
     std::string path = GetPathInSymFsDir(dso_path);
-    if (check_path(path)) {
+    if (CheckDebugFilePath(path, build_id, true)) {
       return path;
     }
     // 3. Try concatenating symfs_dir and basename of dso_path.
     path = symfs_dir_ + OS_PATH_SEPARATOR + android::base::Basename(dso_path);
-    if (check_path(path)) {
+    if (CheckDebugFilePath(path, build_id, false)) {
       return path;
     }
   }
   // 4. Try concatenating /usr/lib/debug and dso_path.
   // Linux host can store debug shared libraries in /usr/lib/debug.
-  if (check_path("/usr/lib/debug" + dso_path)) {
+  if (CheckDebugFilePath("/usr/lib/debug" + dso_path, build_id, false)) {
     return "/usr/lib/debug" + dso_path;
   }
   return dso_path;
@@ -688,8 +701,11 @@ std::unique_ptr<Dso> Dso::CreateDso(DsoType dso_type, const std::string& dso_pat
     }
     case DSO_KERNEL:
       return std::unique_ptr<Dso>(new KernelDso(dso_path, dso_path));
-    case DSO_KERNEL_MODULE:
-      return std::unique_ptr<Dso>(new KernelModuleDso(dso_path, dso_path));
+    case DSO_KERNEL_MODULE: {
+      BuildId build_id = FindExpectedBuildIdForPath(dso_path);
+      return std::unique_ptr<Dso>(new KernelModuleDso(
+          dso_path, debug_elf_file_finder_.FindDebugFile(dso_path, force_64bit, build_id)));
+    }
     case DSO_DEX_FILE:
       return std::unique_ptr<Dso>(new DexFileDso(dso_path, dso_path));
     case DSO_UNKNOWN_FILE: