Parse both .rela.dyn and .rela.plt of libraries. (#1074)

Author: krk

ddprof-lib/gtest/build.gradle

@@ -37,42 +37,37 @@ tasks.withType(StripSymbols).configureEach { task ->
   }
 }
 
-def buildResourcesTask = tasks.register("buildResources", Exec) {
+def buildNativeLibsTask = tasks.register("buildNativeLibs") {
   group = 'build'
-  description = "Build the resources for the Google Tests"
+  description = "Build the native libs for the Google Tests"
 
   onlyIf {
     hasGtest && !project.hasProperty('skip-native') && os().isLinux()
   }
 
-  def targetDir = project(':ddprof-lib').file('build/test/resources/unresolved-functions')
-
-  commandLine "sh", "-c", "cd ${project(':ddprof-lib').projectDir}/src/test/resources/unresolved-functions && make TARGET_DIR=${targetDir}"
-
-  inputs.files project(':ddprof-lib').files('src/test/resources/unresolved-functions')
-  outputs.file "${targetDir}/main"
-}
-
-def buildSmallLibTask = tasks.register("buildSmallLib", Exec) {
-  group = 'build'
-  description = "Build the small-lib shared library for the Google Tests"
-
-  onlyIf {
-    hasGtest && !project.hasProperty('skip-native') && os().isLinux()
+  def srcDir = project(':ddprof-lib').file('src/test/resources/native-libs')
+  def targetDir = project(':ddprof-lib').file('build/test/resources/native-libs/')
+
+  // Move the exec calls to the execution phase
+  doLast {
+    srcDir.eachDir { dir ->
+      def libName = dir.name
+      def libDir = file("${targetDir}/${libName}")
+      def libSrcDir = file("${srcDir}/${libName}")
+
+      exec {
+        commandLine "sh", "-c", """
+          echo "Processing library: ${libName} @ ${libSrcDir}"
+          mkdir -p ${libDir}
+          cd ${libSrcDir}
+          make TARGET_DIR=${libDir}
+        """
+      }
+    }
   }
 
-  def sourceDir = project(':ddprof-lib').file('src/test/resources/small-lib')
-  def targetDir = project(':ddprof-lib').file('build/test/resources/small-lib')
-
-  commandLine "sh", "-c", """
-        mkdir -p ${targetDir}
-        cd ${sourceDir} && g++ -fPIC -shared -o ${targetDir}/libsmall-lib.so *.cpp
-    """
-
-  inputs.files fileTree(sourceDir) {
-    include '**/*.cpp'
-  }
-  outputs.file "${targetDir}/libsmall-lib.so"
+  inputs.files project(':ddprof-lib').files('src/test/resources/native-libs/**/*')
+  outputs.dir "${targetDir}"
 }
 
 def gtestAll = tasks.register("gtest") {
@@ -201,7 +196,7 @@ tasks.whenTaskAdded { task ->
             gtestTask.get().dependsOn gtestExecuteTask.get()
             if (os().isLinux()) {
               // custom binaries for tests are built only on linux
-              gtestExecuteTask.get().dependsOn(buildResourcesTask, buildSmallLibTask)
+              gtestExecuteTask.get().dependsOn(buildNativeLibs)
             }
             gtestAll.get().dependsOn gtestExecuteTask.get()
           }

ddprof-lib/src/main/cpp/symbols_linux.cpp

@@ -1,17 +1,6 @@
 /*
- * Copyright 2017 Andrei Pangin
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright The async-profiler authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 
 #ifdef __linux__
@@ -192,21 +181,25 @@ void ElfParser::parseDynamicSection() {
       loadSymbolTable(symtab, syment * nsyms, syment, strtab);
     }
 
+    if (rel != NULL && relsz != 0) {
+      // If a shared library is built without PLT (-fno-plt), relocation entries for imports
+      // can be found in .rela.dyn. However, if both sections exist, .rela.plt entries
+      // should take precedence, that's why we parse .rela.dyn first.
+      for (size_t offs = relcount * relent; offs < relsz; offs += relent) {
+        ElfRelocation *r = (ElfRelocation *)(rel + offs);
+        if (ELF_R_TYPE(r->r_info) == R_GLOB_DAT || ELF_R_TYPE(r->r_info) == R_ABS64) {
+          ElfSymbol *sym = (ElfSymbol *)(symtab + ELF_R_SYM(r->r_info) * syment);
+          if (sym->st_name != 0) {
+            _cc->addImport((void **)(_base + r->r_offset), strtab + sym->st_name);
+          }
+        }
+      }
+    }
+
     if (jmprel != NULL && pltrelsz != 0) {
       // Parse .rela.plt table
       for (size_t offs = 0; offs < pltrelsz; offs += relent) {
         ElfRelocation *r = (ElfRelocation *)(jmprel + offs);
-        ElfSymbol *sym = (ElfSymbol *)(symtab + ELF_R_SYM(r->r_info) * syment);
-        if (sym->st_name != 0) {
-          _cc->addImport((void **)(_base + r->r_offset), strtab + sym->st_name);
-        }
-      }
-    } else if (rel != NULL && relsz != 0) {
-      // Shared library was built without PLT (-fno-plt)
-      // Relocation entries have been moved from .rela.plt to .rela.dyn
-      for (size_t offs = relcount * relent; offs < relsz; offs += relent) {
-        ElfRelocation *r = (ElfRelocation *)(rel + offs);
-        if (ELF_R_TYPE(r->r_info) == R_GLOB_DAT) {
           ElfSymbol *sym =
               (ElfSymbol *)(symtab + ELF_R_SYM(r->r_info) * syment);
           if (sym->st_name != 0) {
@@ -216,7 +209,6 @@ void ElfParser::parseDynamicSection() {
         }
       }
     }
-  }
 }
 
 void ElfParser::parseDwarfInfo() {

ddprof-lib/src/main/cpp/symbols_linux.h

@@ -88,17 +88,32 @@ typedef Elf32_Dyn ElfDyn;
 #endif // __LP64__
 
 #if defined(__x86_64__)
-#define R_GLOB_DAT R_X86_64_GLOB_DAT
+#  define R_GLOB_DAT R_X86_64_GLOB_DAT
+#  define R_ABS64 R_X86_64_64
 #elif defined(__i386__)
-#define R_GLOB_DAT R_386_GLOB_DAT
+#  define R_GLOB_DAT R_386_GLOB_DAT
+#  define R_ABS64 -1
 #elif defined(__arm__) || defined(__thumb__)
-#define R_GLOB_DAT R_ARM_GLOB_DAT
+#  define R_GLOB_DAT R_ARM_GLOB_DAT
+#  define R_ABS64 -1
 #elif defined(__aarch64__)
-#define R_GLOB_DAT R_AARCH64_GLOB_DAT
+#  define R_GLOB_DAT R_AARCH64_GLOB_DAT
+#  define R_ABS64 R_AARCH64_ABS64
 #elif defined(__PPC64__)
-#define R_GLOB_DAT R_PPC64_GLOB_DAT
+#  define R_GLOB_DAT R_PPC64_GLOB_DAT
+#  define R_ABS64 -1
+#elif defined(__riscv) && (__riscv_xlen == 64)
+// RISC-V does not have GLOB_DAT relocation, use something neutral,
+// like the impossible relocation number.
+#  define R_GLOB_DAT -1
+#  define R_ABS64 -1
+#elif defined(__loongarch_lp64)
+// LOONGARCH does not have GLOB_DAT relocation, use something neutral,
+// like the impossible relocation number.
+#  define R_GLOB_DAT -1
+#  define R_ABS64 -1
 #else
-#error "Compiling on unsupported arch"
+#  error "Compiling on unsupported arch"
 #endif
 
 #ifdef __musl__

ddprof-lib/src/test/cpp/elfparser_ut.cpp

@@ -1,8 +1,10 @@
 #ifdef __linux__
 
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
 #include "codeCache.h"
+#include "libraries.h"
 #include "symbols_linux.h"
 #include "log.h"
 
@@ -27,7 +29,7 @@ TEST(Elf, readSymTable) {
         exit(1);
     }
     char path[PATH_MAX];
-    snprintf(path, sizeof(path) - 1, "%s/../build/test/resources/unresolved-functions/main", cwd);
+    snprintf(path, sizeof(path) - 1, "%s/../build/test/resources/native-libs/unresolved-functions/main", cwd);
     if (access(path, R_OK) != 0) {
         fprintf(stdout, "Missing test resource %s. Skipping the test\n", path);
         exit(0);
@@ -36,6 +38,57 @@ TEST(Elf, readSymTable) {
     ElfParser::parseFile(&cc, nullptr, path, false);
 }
 
+class ElfReladyn : public ::testing::Test {
+  protected:
+    Libraries* _libs = nullptr;
+    CodeCache* _libreladyn = nullptr;
+
+    // This method is called before each test.
+    void SetUp() override {
+        char cwd[PATH_MAX - 64];
+        if (getcwd(cwd, sizeof(cwd)) == nullptr) {
+            exit(1);
+        }
+        char path[PATH_MAX];
+        snprintf(path, sizeof(path) - 1, "%s/../build/test/resources/native-libs/reladyn-lib/libreladyn.so", cwd);
+        if (access(path, R_OK) != 0) {
+            fprintf(stdout, "Missing test resource %s. Skipping the test\n", path);
+            exit(0);
+        }
+        void* handle = dlopen(path, RTLD_NOW);
+        ASSERT_THAT(handle, ::testing::NotNull());
+
+        _libs = Libraries::instance();
+        _libs->updateSymbols(false);
+        _libreladyn = _libs->findLibraryByName("libreladyn");
+        ASSERT_THAT(_libreladyn, ::testing::NotNull());
+    }
+
+    // This method is called after each test.
+    void TearDown() override {
+        // Clean up resources.
+    }
+
+    CodeCache* libreladyn() {
+        return _libreladyn;
+    }
+};
+
+TEST_F(ElfReladyn, resolveFromRela_plt) {
+    void* sym = libreladyn()->findImport(im_pthread_create);
+    ASSERT_THAT(sym, ::testing::NotNull());
+}
+
+TEST_F(ElfReladyn, resolveFromRela_dyn_R_GLOB_DAT) {
+    void* sym = libreladyn()->findImport(im_pthread_setspecific);
+    ASSERT_THAT(sym, ::testing::NotNull());
+}
+
+TEST_F(ElfReladyn, resolveFromRela_dyn_R_ABS64) {
+    void* sym = libreladyn()->findImport(im_pthread_exit);
+    ASSERT_THAT(sym, ::testing::NotNull());
+}
+
 class ElfTest : public ::testing::Test {
 protected:
     void SetUp() override {
@@ -247,7 +300,7 @@ TEST_P(ElfTestParam, invalidElfSmallMappingAfterUnmap) {
 
     // Construct the path to the test resource
     char path[PATH_MAX];
-    snprintf(path, sizeof(path) - 1, "%s/../build/test/resources/small-lib/libsmall-lib.so", cwd);
+    snprintf(path, sizeof(path) - 1, "%s/../build/test/resources/native-libs/small-lib/libsmall-lib.so", cwd);
     if (access(path, R_OK) != 0) {
         fprintf(stdout, "Missing test resource %s. Skipping the test\n", path);
         exit(1);

ddprof-lib/src/test/resources/native-libs/reladyn-lib/Makefile

@@ -0,0 +1,3 @@
+TARGET_DIR = ../build/test/resources/native-libs/reladyn-lib
+all:
+	g++ -fPIC -shared -o $(TARGET_DIR)/libreladyn.so reladyn.c

ddprof-lib/src/test/resources/native-libs/reladyn-lib/reladyn.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright The async-profiler authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <pthread.h>
+#include <stdio.h>
+// Force pthread_setspecific into .rela.dyn with R_X86_64_GLOB_DAT.
+int (*indirect_pthread_setspecific)(pthread_key_t, const void*);
+// Force pthread_exit into .rela.dyn with R_X86_64_64.
+void (*static_pthread_exit)(void*) = pthread_exit;
+void* thread_function(void* arg) {
+    printf("Thread running\n");
+    return NULL;
+}
+// Not indended to be executed.
+int reladyn() {
+    pthread_t thread;
+    pthread_key_t key;
+    pthread_key_create(&key, NULL);
+    // Direct call, forces into .rela.plt.
+    pthread_create(&thread, NULL, thread_function, NULL);
+    // Assign to a function pointer at runtime, forces into .rela.dyn as R_X86_64_GLOB_DAT.
+    indirect_pthread_setspecific = pthread_setspecific;
+    indirect_pthread_setspecific(key, "Thread-specific value");
+    // Use pthread_exit via the static pointer, forces into .rela.dyn as R_X86_64_64.
+    static_pthread_exit(NULL);
+    return 0;
+}

ddprof-lib/src/test/resources/native-libs/small-lib/Makefile

@@ -0,0 +1,3 @@
+TARGET_DIR = ../build/test/resources/native-libs/small-lib
+all:
+	g++ -fPIC -shared -o $(TARGET_DIR)/libsmall-lib.so small_lib.cpp

ddprof-lib/src/test/resources/small-lib/small_lib.cpp renamed to ddprof-lib/src/test/resources/native-libs/small-lib/small_lib.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright The async-profiler authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <pthread.h>
+#include <stdio.h>
+
+// Force pthread_setspecific into .rela.dyn with R_X86_64_GLOB_DAT.
+int (*indirect_pthread_setspecific)(pthread_key_t, const void*);
+
+// Force pthread_exit into .rela.dyn with R_X86_64_64.
+void (*static_pthread_exit)(void*) = pthread_exit;
+
+void* thread_function(void* arg) {
+    printf("Thread running\n");
+    return NULL;
+}
+
+// Not indended to be executed.
+int reladyn() {
+    pthread_t thread;
+    pthread_key_t key;
+
+    pthread_key_create(&key, NULL);
+
+    // Direct call, forces into .rela.plt.
+    pthread_create(&thread, NULL, thread_function, NULL);
+
+    // Assign to a function pointer at runtime, forces into .rela.dyn as R_X86_64_GLOB_DAT.
+    indirect_pthread_setspecific = pthread_setspecific;
+    indirect_pthread_setspecific(key, "Thread-specific value");
+
+    // Use pthread_exit via the static pointer, forces into .rela.dyn as R_X86_64_64.
+    static_pthread_exit(NULL);
+
+    return 0;
+}

ddprof-lib/src/test/resources/small-lib/small_lib.h renamed to ddprof-lib/src/test/resources/native-libs/small-lib/small_lib.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright The async-profiler authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifdef __linux__
+
+#include "codeCache.h"
+#include "profiler.h"
+#include "testRunner.hpp"
+#include <dlfcn.h>
+
+#define ASSERT_RESOLVE(id)                                                             \
+    {                                                                                  \
+        void* result = dlopen("libreladyn.so", RTLD_NOW); /* see reladyn.c */          \
+        ASSERT(result);                                                                \
+        Profiler::instance()->updateSymbols(false);                                    \
+        CodeCache* libreladyn = Profiler::instance()->findLibraryByName("libreladyn"); \
+        ASSERT(libreladyn);                                                            \
+        void* sym = libreladyn->findImport(id);                                        \
+        ASSERT(sym);                                                                   \
+    }
+
+TEST_CASE(ResolveFromRela_plt) {
+    ASSERT_RESOLVE(im_pthread_create);
+}
+
+TEST_CASE(ResolveFromRela_dyn_R_GLOB_DAT) {
+    ASSERT_RESOLVE(im_pthread_setspecific);
+}
+
+TEST_CASE(ResolveFromRela_dyn_R_ABS64) {
+    ASSERT_RESOLVE(im_pthread_exit);
+}
+
+#endif // __linux__