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

Author: krk

Makefile

@@ -37,6 +37,7 @@ JAVA=$(JAVA_HOME)/bin/java
 JAVA_TARGET=8
 JAVAC_OPTIONS=--release $(JAVA_TARGET) -Xlint:-options
 
+TEST_LIB_DIR=build/test/lib
 LOG_DIR=build/test/logs
 LOG_LEVEL=
 SKIP=
@@ -115,13 +116,7 @@ ifneq (,$(findstring $(ARCH_TAG),x86 x64 arm64))
 endif
 
 
-.PHONY: all jar release build-test test native clean coverage clean-coverage build-test-java build-test-cpp test-cpp test-java format-md check-md
-
-check-md:
-	prettier -c README.md "docs/**/*.md"
-
-format-md:
-	prettier -w README.md "docs/**/*.md"
+.PHONY: all jar release build-test test native clean coverage clean-coverage build-test-java build-test-cpp build-test-libs test-cpp test-java check-md format-md
 
 all: build/bin build/lib build/$(LIB_PROFILER) build/$(ASPROF) jar build/$(JFRCONV)
 
@@ -186,23 +181,26 @@ build/$(CONVERTER_JAR): $(CONVERTER_SOURCES) $(RESOURCES)
 
 build/test/cpptests: $(CPP_TEST_SOURCES) $(CPP_TEST_HEADER) $(SOURCES) $(HEADERS) $(RESOURCES) $(JAVA_HELPER_CLASSES)
 	mkdir -p build/test
-
 ifeq ($(MERGE),true)
 	for f in src/*.cpp test/native/*.cpp; do echo '#include "'$$f'"'; done |\
 	$(CXX) $(CPPFLAGS) $(CXXFLAGS) $(DEFS) $(INCLUDES) $(CPP_TEST_INCLUDES) -fPIC -o $@ -xc++ - $(LIBS)
 else
 	$(CXX) $(CPPFLAGS) $(CXXFLAGS) $(DEFS) $(INCLUDES) $(CPP_TEST_INCLUDES) -fPIC -o $@ $(SOURCES) $(CPP_TEST_SOURCES) $(LIBS)
 endif
 
-build-test-java: all build/$(TEST_JAR)
+build-test-java: all build/$(TEST_JAR) build-test-libs
 
-build-test-cpp: build/test/cpptests
+build-test-cpp: build/test/cpptests build-test-libs
 
 build-test: build-test-cpp build-test-java
 
+build-test-libs:
+	@mkdir -p $(TEST_LIB_DIR)
+	$(CC) -shared -fPIC -o $(TEST_LIB_DIR)/libreladyn.$(SOEXT) test/native/libs/reladyn.c
+
 test-cpp: build-test-cpp
 	echo "Running cpp tests..."
-	build/test/cpptests
+	LD_LIBRARY_PATH="$(TEST_LIB_DIR)" build/test/cpptests
 
 test-java: build-test-java
 	echo "Running tests against $(LIB_PROFILER)"
@@ -228,6 +226,12 @@ native:
 	tar xfO async-profiler-$(PROFILER_VERSION)-linux-arm64.tar.gz */build/libasyncProfiler.so > native/linux-arm64/libasyncProfiler.so
 	unzip -p async-profiler-$(PROFILER_VERSION)-macos.zip */build/libasyncProfiler.dylib > native/macos/libasyncProfiler.dylib
 
+check-md:
+	prettier -c README.md "docs/**/*.md"
+
+format-md:
+	prettier -w README.md "docs/**/*.md"
+
 clean-coverage:
 	$(RM) -rf build/test/cpptests build/test/coverage
 

src/symbols_linux.cpp

@@ -145,22 +145,29 @@ typedef Elf32_Dyn  ElfDyn;
 
 #if defined(__x86_64__)
 #  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_ABS64 -1
 #elif defined(__arm__) || defined(__thumb__)
 #  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_ABS64 R_AARCH64_ABS64
 #elif defined(__PPC64__)
 #  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"
 #endif
@@ -385,6 +392,21 @@ void ElfParser::parseDynamicSection() {
         }
 
         const char* base = this->base();
+        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) {
@@ -394,18 +416,6 @@ void ElfParser::parseDynamicSection() {
                     _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) {
-                        _cc->addImport((void**)(base + r->r_offset), strtab + sym->st_name);
-                    }
-               }
-            }
         }
     }
 }

test/native/libs/reladyn.c

@@ -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;
+}

test/native/symbolsLinuxTest.cpp

@@ -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__