From f523bb2f604c79a38ad878fffee2e458a112b37a Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Mon, 14 Jul 2025 08:15:10 -0400
Subject: [PATCH 01/15] v0

---
 ddprof-lib/build.gradle             |  5 ++-
 ddprof-lib/src/main/asm/safefetch.S | 53 +++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 ddprof-lib/src/main/asm/safefetch.S

diff --git a/ddprof-lib/build.gradle b/ddprof-lib/build.gradle
index 51438cbc..1fcf0699 100644
--- a/ddprof-lib/build.gradle
+++ b/ddprof-lib/build.gradle
@@ -524,6 +524,7 @@ tasks.whenTaskAdded { task ->
             if (compileTask != null) {
               dependsOn compileTask
             }
+            dependsOn asmTask
             linkerArgs.addAll(config.linkerArgs)
             toolChain = task.toolChain
             targetPlatform = task.targetPlatform
@@ -604,7 +605,9 @@ tasks.register('javadocJar', Jar) {
   from javadoc.destinationDir
 }
 
-
+tasks.register('asmTask', Exec) {
+  commandLine 'clang', '-D__aarch64__', 'src/main/asm/safefetch.S', '-o', 'build/obj/safefetch.o'
+}
 
 tasks.register('scanBuild', Exec) {
   workingDir "${projectDir}/src/test/make"
diff --git a/ddprof-lib/src/main/asm/safefetch.S b/ddprof-lib/src/main/asm/safefetch.S
new file mode 100644
index 00000000..3e923461
--- /dev/null
+++ b/ddprof-lib/src/main/asm/safefetch.S
@@ -0,0 +1,53 @@
+
+#define DECLARE_FUNC(func) \
+    .globl func %% \
+    .hidden func %% \
+    .type func, %function %% \
+    func
+
+#if defined(__x86_64__)
+    .text
+
+    # Support for int SafeFetch32(int* address, int defaultval);
+    #
+    #  %rdi : address
+    #  %esi : defaultval
+DECLARE_FUNC(SafeFetch32_impl):
+DECLARE_FUNC(_SafeFetch32_fault):
+    movl (%rdi), %eax       # load target value, may fault
+    ret
+DECLARE_FUNC(_SafeFetch32_continuation):
+    movl %esi, %eax         # return default
+    ret
+
+#elif defined(__aarch64__)
+#ifdef __APPLE__
+    # Support for int SafeFetch32(int* address, int defaultval);
+    #
+    #  x0 : address
+    #  w1 : defaultval
+
+    # needed to align function start to 4 byte
+    .align  6
+DECLARE_FUNC(SafeFetch32_impl):
+DECLARE_FUNC(_SafeFetch32_fault):
+    ldr      w0, [x0]
+    ret
+DECLARE_FUNC(_SafeFetch32_continuation):
+    mov      x0, x1
+    ret
+#else
+    # Support for int SafeFetch32(int* address, int defaultval);
+    #
+    #  x0 : address
+    #  x1 : defaultval
+DECLARE_FUNC(SafeFetch32_impl):
+DECLARE_FUNC(_SafeFetch32_fault):
+    ldr      w0, [x0]
+    ret
+DECLARE_FUNC(_SafeFetch32_continuation):
+    mov      x0, x1
+    ret
+#endif // __APPLE__
+
+#endif

From 35576dc5711efb6dd614f3c7a71d24b966a32d94 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Tue, 15 Jul 2025 10:59:04 -0400
Subject: [PATCH 02/15] v1

---
 ddprof-lib/build.gradle                       | 18 +++++++++++++++++-
 .../src/main/{asm => assembler}/safefetch.S   | 19 +++++++++++++++----
 2 files changed, 32 insertions(+), 5 deletions(-)
 rename ddprof-lib/src/main/{asm => assembler}/safefetch.S (76%)

diff --git a/ddprof-lib/build.gradle b/ddprof-lib/build.gradle
index 1fcf0699..d1e0df92 100644
--- a/ddprof-lib/build.gradle
+++ b/ddprof-lib/build.gradle
@@ -3,6 +3,7 @@ plugins {
   id 'java'
   id 'maven-publish'
   id 'signing'
+  id 'assembler'
 
   id 'com.github.ben-manes.versions' version '0.27.0'
   id 'de.undercouch.download' version '4.1.1'
@@ -606,7 +607,22 @@ tasks.register('javadocJar', Jar) {
 }
 
 tasks.register('asmTask', Exec) {
-  commandLine 'clang', '-D__aarch64__', 'src/main/asm/safefetch.S', '-o', 'build/obj/safefetch.o'
+  String reportedArch = System.getProperty('os.arch')
+  String arch
+  if (reportedArch == 'x86_64') {
+    arch = '-D__x86_64__'
+  } else {
+    arch = '-D__aarch64__'
+  }
+
+  String os
+  if (osIdentifier() == 'macos') {
+    os = '-D__APPLE__'
+  } else {
+    os = '-D__LINUX__'
+  }
+
+  commandLine 'gcc', arch, os, 'src/main/assembler/safefetch.S', '-c', 'build/obj/safefetch.o'
 }
 
 tasks.register('scanBuild', Exec) {
diff --git a/ddprof-lib/src/main/asm/safefetch.S b/ddprof-lib/src/main/assembler/safefetch.S
similarity index 76%
rename from ddprof-lib/src/main/asm/safefetch.S
rename to ddprof-lib/src/main/assembler/safefetch.S
index 3e923461..5e66d385 100644
--- a/ddprof-lib/src/main/asm/safefetch.S
+++ b/ddprof-lib/src/main/assembler/safefetch.S
@@ -1,9 +1,20 @@
+#ifdef __APPLE__
+  # macOS prefixes symbols with _
+  #define SYMBOL(s) _ ## s
+
+  #define DECLARE_FUNC(func) \
+    .globl SYMBOL(func) %% \
+    .private_extern SYMBOL(func) %% \
+    SYMBOL(func)
+#else
+  #define SYMBOL(s) s
 
-#define DECLARE_FUNC(func) \
-    .globl func %% \
-    .hidden func %% \
-    .type func, %function %% \
+  #define DECLARE_FUNC(func) \
+    .globl func ; \
+    .hidden func ; \
+    .type func, %function ; \
     func
+#endif // __APPLE__
 
 #if defined(__x86_64__)
     .text

From 21f328725ba5322351daddb8fb75aa9996f00b9a Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Tue, 15 Jul 2025 15:52:33 -0400
Subject: [PATCH 03/15] v3

---
 ddprof-lib/build.gradle                  |  4 +--
 ddprof-lib/src/main/cpp/profiler.cpp     |  7 +++++
 ddprof-lib/src/main/cpp/safeAccess.cpp   | 39 ++++++++++++++----------
 ddprof-lib/src/main/cpp/safeAccess.h     | 12 +++-----
 ddprof-lib/src/main/cpp/vmStructs_dd.cpp |  5 ---
 ddprof-lib/src/main/cpp/vmStructs_dd.h   |  2 --
 6 files changed, 36 insertions(+), 33 deletions(-)

diff --git a/ddprof-lib/build.gradle b/ddprof-lib/build.gradle
index d1e0df92..494a0c7d 100644
--- a/ddprof-lib/build.gradle
+++ b/ddprof-lib/build.gradle
@@ -3,7 +3,6 @@ plugins {
   id 'java'
   id 'maven-publish'
   id 'signing'
-  id 'assembler'
 
   id 'com.github.ben-manes.versions' version '0.27.0'
   id 'de.undercouch.download' version '4.1.1'
@@ -621,8 +620,7 @@ tasks.register('asmTask', Exec) {
   } else {
     os = '-D__LINUX__'
   }
-
-  commandLine 'gcc', arch, os, 'src/main/assembler/safefetch.S', '-c', 'build/obj/safefetch.o'
+  commandLine 'gcc', arch, os, 'src/main/assembler/safefetch.S', '-c', 'safefetch.o'
 }
 
 tasks.register('scanBuild', Exec) {
diff --git a/ddprof-lib/src/main/cpp/profiler.cpp b/ddprof-lib/src/main/cpp/profiler.cpp
index efdae02a..0787ad0f 100644
--- a/ddprof-lib/src/main/cpp/profiler.cpp
+++ b/ddprof-lib/src/main/cpp/profiler.cpp
@@ -878,6 +878,13 @@ bool Profiler::crashHandler(int signo, siginfo_t *siginfo, void *ucontext) {
     return false;
   }
 
+  if (SafeAccess::handle_safefetch(signo, pc, ucontext)) {
+    if (thrd != nullptr) {
+      thrd->exitCrashHandler();
+    }
+    return true;
+  }
+
   uintptr_t length = SafeAccess::skipLoad(pc);
   if (length > 0) {
     // Skip the fault instruction, as if it successfully loaded NULL
diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index 82aceeeb..8307b991 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -16,23 +16,30 @@
 
 
 #include "safeAccess.h"
+#include <ucontext.h>
 
-SafeAccess::SafeFetch32 SafeAccess::_safeFetch32Func = nullptr;
-
-void SafeAccess::initSafeFetch(CodeCache* libjvm) {
-  // Hotspot JVM's safefetch implementation appears better, e.g. it actually returns errorValue,
-  // when the address is invalid. let's use it whenever possible.
-  // When the methods are not available, fallback to SafeAccess::load32() implementation.
-  _safeFetch32Func = (SafeFetch32)libjvm->findSymbol("SafeFetch32_impl");
-  if (_safeFetch32Func == nullptr && !WX_MEMORY) {
-    // jdk11 stub implementation other than Macosx/aarch64
-    void** entry = (void**)libjvm->findSymbol("_ZN12StubRoutines18_safefetch32_entryE");
-    if (entry != nullptr && *entry != nullptr) {
-      _safeFetch32Func = (SafeFetch32)*entry;
+
+#ifdef __APPLE__
+
+#if defined(__x86_64)
+  #define context_pc context_rip
+#elif defined(__aarch64__)
+  #define DU3_PREFIX(s, m) __ ## s.__ ## m
+  #define context_pc uc_mcontext->DU3_PREFIX(ss,pc)
+#endif
+
+#endif
+
+extern "C" char _SafeFetch32_continuation[] __attribute__ ((visibility ("hidden")));
+extern "C" char _SafeFetch32_fault[] __attribute__ ((visibility ("hidden")));
+
+bool SafeAccess::handle_safefetch(int sig, uintptr_t pc, void* context) {
+  ucontext_t* uc = (ucontext_t*)context;
+  if ((sig == SIGSEGV || sig == SIGBUS) && uc != nullptr) {
+    if (pc == (uintptr_t)_SafeFetch32_fault) {
+      uc->context_pc == (uintptr_t)_SafeFetch32_continuation;
+      return true;
     }
   }
-  // Fallback
-  if (_safeFetch32Func == nullptr) {
-    _safeFetch32Func = (SafeFetch32)load32;
-  }
+  return false;
 }
diff --git a/ddprof-lib/src/main/cpp/safeAccess.h b/ddprof-lib/src/main/cpp/safeAccess.h
index 993c359c..921cfa49 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.h
+++ b/ddprof-lib/src/main/cpp/safeAccess.h
@@ -22,6 +22,8 @@
 #include <cassert>
 #include <stdint.h>
 
+extern "C" int SafeFetch32_impl(int* adr, int errValue);
+
 #ifdef __clang__
 #define NOINLINE __attribute__((noinline))
 #else
@@ -30,18 +32,14 @@
 #define NOADDRSANITIZE __attribute__((no_sanitize("address")))
 
 class SafeAccess {
-private:
-   typedef int (*SafeFetch32)(int* ptr, int errorValue);
-   static SafeFetch32 _safeFetch32Func;
-
 public:
-  static void initSafeFetch(CodeCache* libjvm);
 
   static inline int safeFetch32(int* ptr, int errorValue) {
-    assert(_safeFetch32Func != nullptr);
-    return _safeFetch32Func(ptr, errorValue);
+    return SafeFetch32_impl(ptr, errorValue);
   }
 
+  static bool handle_safefetch(int sig, uintptr_t pc, void* context);
+
   NOINLINE NOADDRSANITIZE __attribute__((aligned(16))) static void *load(void **ptr) {
     return *ptr;
   }
diff --git a/ddprof-lib/src/main/cpp/vmStructs_dd.cpp b/ddprof-lib/src/main/cpp/vmStructs_dd.cpp
index 4dc043a5..d8efce3b 100644
--- a/ddprof-lib/src/main/cpp/vmStructs_dd.cpp
+++ b/ddprof-lib/src/main/cpp/vmStructs_dd.cpp
@@ -44,7 +44,6 @@ namespace ddprof {
     initOffsets();
     initJvmFunctions();
     initUnsafeFunctions();
-    initSafeFetch(libjvm);
   }
 
   void VMStructs_::initOffsets() {
@@ -99,10 +98,6 @@ namespace ddprof {
     }
   }
 
-  void VMStructs_::initSafeFetch(CodeCache* libjvm) {
-    SafeAccess::initSafeFetch(libjvm);
-  }
-
   const void *VMStructs_::findHeapUsageFunc() {
     if (VM::hotspot_version() < 17) {
       // For JDK 11 it is really unreliable to find the memory_usage function -
diff --git a/ddprof-lib/src/main/cpp/vmStructs_dd.h b/ddprof-lib/src/main/cpp/vmStructs_dd.h
index 431aa432..c4547140 100644
--- a/ddprof-lib/src/main/cpp/vmStructs_dd.h
+++ b/ddprof-lib/src/main/cpp/vmStructs_dd.h
@@ -52,8 +52,6 @@ namespace ddprof {
     static void initOffsets();
     static void initJvmFunctions();
     static void initUnsafeFunctions();
-    // We need safe access for all jdk versions
-    static void initSafeFetch(CodeCache* libjvm);
 
     static void checkNativeBinding(jvmtiEnv *jvmti, JNIEnv *jni, jmethodID method,
                                   void *address);

From fc66365e6752d4beae848f1a20517224e0d755e1 Mon Sep 17 00:00:00 2001
From: Jaroslav Bachorik <j.bachorik@gmail.com>
Date: Wed, 16 Jul 2025 11:54:18 +0200
Subject: [PATCH 04/15] Fix the assembler gradle task

---
 ddprof-lib/build.gradle       | 43 +++++++++++++++++++++++++++--------
 ddprof-lib/gtest/build.gradle |  7 +++++-
 2 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/ddprof-lib/build.gradle b/ddprof-lib/build.gradle
index 494a0c7d..773ecb01 100644
--- a/ddprof-lib/build.gradle
+++ b/ddprof-lib/build.gradle
@@ -516,14 +516,18 @@ tasks.whenTaskAdded { task ->
             onlyIf {
               config.active
             }
+
             group = 'build'
             description = "Link the ${config.name} build of the library"
             source = fileTree("$buildDir/obj/main/${config.name}")
+            source.from(file("${projectDir}/build/obj/main/asm/assembly.o"))
+
             linkedFile = file("$buildDir/lib/main/${config.name}/${osIdentifier()}/${archIdentifier()}/libjavaProfiler.${os().isLinux() ? 'so' : 'dylib'}")
             def compileTask = tasks.findByName("compileLib${config.name.capitalize()}".toString())
             if (compileTask != null) {
               dependsOn compileTask
             }
+            def asmTask = tasks.findByName("asm")
             dependsOn asmTask
             linkerArgs.addAll(config.linkerArgs)
             toolChain = task.toolChain
@@ -605,31 +609,52 @@ tasks.register('javadocJar', Jar) {
   from javadoc.destinationDir
 }
 
-tasks.register('asmTask', Exec) {
-  String reportedArch = System.getProperty('os.arch')
-  String arch
-  if (reportedArch == 'x86_64') {
+tasks.register('asm', Exec) {
+  group = 'build'
+
+  def arch
+  if (archIdentifier() == 'x64') {
     arch = '-D__x86_64__'
   } else {
     arch = '-D__aarch64__'
   }
 
-  String os
+  def os
   if (osIdentifier() == 'macos') {
     os = '-D__APPLE__'
   } else {
     os = '-D__LINUX__'
   }
-  commandLine 'gcc', arch, os, 'src/main/assembler/safefetch.S', '-c', 'safefetch.o'
+  def asmDir = file("${projectDir}/src/main/assembler")
+  if (!asmDir.exists()) {
+    // no assembler files found, skipping
+    return
+  }
+
+  doLast {
+    // Ensure the output directory exists
+    file("${projectDir}/build/obj/main/asm").mkdirs()
+  }
+
+  // collect all assembler files and compile them
+  workingDir asmDir
+  inputs.files fileTree("${projectDir}/src/main/assembler") {
+    include '**/*.S'
+  }
+  def asmFiles = inputs.files.collect { it.absolutePath }
+  outputs.dir "${projectDir}/build/obj/main/asm"
+  // use gcc to compile assembler files
+  commandLine 'gcc', arch, os, '-c', '-x', 'assembler-with-cpp',
+  *asmFiles, '-o', "${projectDir}/build/obj/main/asm/assembly.o"
 }
 
 tasks.register('scanBuild', Exec) {
   workingDir "${projectDir}/src/test/make"
   commandLine 'scan-build'
   args "-o", "${projectDir}/build/reports/scan-build",
-    "--force-analyze-debug-code",
-    "--use-analyzer", "/usr/bin/clang++",
-    "make", "-j4",  "clean", "all"
+  "--force-analyze-debug-code",
+  "--use-analyzer", "/usr/bin/clang++",
+  "make", "-j4",  "clean", "all"
 }
 
 tasks.withType(Test) {
diff --git a/ddprof-lib/gtest/build.gradle b/ddprof-lib/gtest/build.gradle
index d2604ff8..1792aefd 100644
--- a/ddprof-lib/gtest/build.gradle
+++ b/ddprof-lib/gtest/build.gradle
@@ -154,7 +154,10 @@ tasks.whenTaskAdded { task ->
             group = 'verification'
             description = "Run all Google Tests for the ${config.name} build of the library"
           }
-          project(':ddprof-lib').file("src/test/cpp/").eachFile {
+          def libProject = project(':ddprof-lib')
+          def asmTask = libProject.tasks.findByName("asm")
+
+          libProject.file("src/test/cpp/").eachFile {
 
             def testFile = it
             def testName = it.name.substring(0, it.name.lastIndexOf('.'))
@@ -167,6 +170,7 @@ tasks.whenTaskAdded { task ->
               group = 'build'
               description = "Link the Google Test for the ${config.name} build of the library"
               source = fileTree("$buildDir/obj/gtest/${config.name}/${testName}")
+              source.from(file("${rootDir}/ddprof-lib/build/obj/main/asm/assembly.o"))
               linkedFile = binary
               if (config.name != 'release') {
                 // linking the gtests using the minimizing release flags is making gtest unhappy
@@ -183,6 +187,7 @@ tasks.whenTaskAdded { task ->
               libs = task.libs
               inputs.files source
               outputs.file linkedFile
+              dependsOn asmTask
             }
             def gtestExecuteTask = tasks.register("gtest${config.name.capitalize()}_${testName}", Exec) {
               onlyIf {

From 7b48662cada5c42986044e008ff66aa94b44c539 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Wed, 16 Jul 2025 11:05:11 -0400
Subject: [PATCH 05/15] v5

---
 ddprof-lib/src/main/cpp/profiler.cpp     | 15 +++----
 ddprof-lib/src/main/cpp/safeAccess.cpp   | 21 +++++-----
 ddprof-lib/src/main/cpp/safeAccess.h     |  2 +-
 ddprof-lib/src/test/cpp/safefetch_ut.cpp | 51 ++++++++++++++++++++++++
 4 files changed, 71 insertions(+), 18 deletions(-)
 create mode 100644 ddprof-lib/src/test/cpp/safefetch_ut.cpp

diff --git a/ddprof-lib/src/main/cpp/profiler.cpp b/ddprof-lib/src/main/cpp/profiler.cpp
index 0787ad0f..30a4576b 100644
--- a/ddprof-lib/src/main/cpp/profiler.cpp
+++ b/ddprof-lib/src/main/cpp/profiler.cpp
@@ -867,6 +867,14 @@ bool Profiler::crashHandler(int signo, siginfo_t *siginfo, void *ucontext) {
     // we are already in a crash handler; don't recurse!
     return false;
   }
+
+  if (SafeAccess::handle_safefetch(signo, ucontext)) {
+    if (thrd != nullptr) {
+      thrd->exitCrashHandler();
+    }
+    return true;
+  }
+
   uintptr_t fault_address = (uintptr_t)siginfo->si_addr;
   StackFrame frame(ucontext);
   uintptr_t pc = frame.pc();
@@ -878,13 +886,6 @@ bool Profiler::crashHandler(int signo, siginfo_t *siginfo, void *ucontext) {
     return false;
   }
 
-  if (SafeAccess::handle_safefetch(signo, pc, ucontext)) {
-    if (thrd != nullptr) {
-      thrd->exitCrashHandler();
-    }
-    return true;
-  }
-
   uintptr_t length = SafeAccess::skipLoad(pc);
   if (length > 0) {
     // Skip the fault instruction, as if it successfully loaded NULL
diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index 8307b991..c803cd3f 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -16,25 +16,26 @@
 
 
 #include "safeAccess.h"
+#include <signal.h>
 #include <ucontext.h>
 
-
 #ifdef __APPLE__
-
-#if defined(__x86_64)
-  #define context_pc context_rip
-#elif defined(__aarch64__)
-  #define DU3_PREFIX(s, m) __ ## s.__ ## m
-  #define context_pc uc_mcontext->DU3_PREFIX(ss,pc)
-#endif
-
+    #if defined(__x86_64)
+      #define context_pc context_rip
+    #elif defined(__aarch64__)
+      #define DU3_PREFIX(s, m) __ ## s.__ ## m
+      #define context_pc uc_mcontext->DU3_PREFIX(ss,pc)
+    #endif
+#else
+   #define context_pc uc_mcontext.gregs[REG_RIP]
 #endif
 
 extern "C" char _SafeFetch32_continuation[] __attribute__ ((visibility ("hidden")));
 extern "C" char _SafeFetch32_fault[] __attribute__ ((visibility ("hidden")));
 
-bool SafeAccess::handle_safefetch(int sig, uintptr_t pc, void* context) {
+bool SafeAccess::handle_safefetch(int sig, void* context) {
   ucontext_t* uc = (ucontext_t*)context;
+  uintptr_t pc = uc->context_pc;
   if ((sig == SIGSEGV || sig == SIGBUS) && uc != nullptr) {
     if (pc == (uintptr_t)_SafeFetch32_fault) {
       uc->context_pc == (uintptr_t)_SafeFetch32_continuation;
diff --git a/ddprof-lib/src/main/cpp/safeAccess.h b/ddprof-lib/src/main/cpp/safeAccess.h
index 921cfa49..1f8b27c0 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.h
+++ b/ddprof-lib/src/main/cpp/safeAccess.h
@@ -38,7 +38,7 @@ class SafeAccess {
     return SafeFetch32_impl(ptr, errorValue);
   }
 
-  static bool handle_safefetch(int sig, uintptr_t pc, void* context);
+  static bool handle_safefetch(int sig, void* context);
 
   NOINLINE NOADDRSANITIZE __attribute__((aligned(16))) static void *load(void **ptr) {
     return *ptr;
diff --git a/ddprof-lib/src/test/cpp/safefetch_ut.cpp b/ddprof-lib/src/test/cpp/safefetch_ut.cpp
new file mode 100644
index 00000000..4e36b862
--- /dev/null
+++ b/ddprof-lib/src/test/cpp/safefetch_ut.cpp
@@ -0,0 +1,51 @@
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <signal.h>
+
+#include "safeAccess.h"
+#include "os.h"
+
+
+static void (*orig_segvHandler)(int signo, siginfo_t *siginfo, void *ucontext);
+static void (*orig_busHandler)(int signo, siginfo_t *siginfo, void *ucontext);
+
+
+void signal_handle_wrapper(int signo, siginfo_t* siginfo, void* context) {
+  if (!SafeAccess::handle_safefetch(signo, context)) {
+    if (signo == SIGBUS) {
+       orig_busHandler(signo, siginfo, context);
+    } else if (signo == SIGSEGV) {
+       orig_segvHandler(signo, siginfo, context);
+    }
+  }
+}
+
+class SafeFetchTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+       orig_segvHandler = OS::replaceSigsegvHandler(signal_handle_wrapper);
+       orig_busHandler = OS::replaceSigbusHandler(signal_handle_wrapper);
+    }
+
+    void TearDown() override {
+       OS::replaceSigsegvHandler(orig_segvHandler);
+       OS::replaceSigbusHandler(orig_busHandler);
+    }
+};
+
+
+TEST_F(SafeFetchTest, validAccess) {
+  int i = 42;
+  int* p = &i;
+  int res = SafeAccess::safeFetch32(p, -1);
+  EXPECT_EQ(res, i);
+}
+
+
+TEST_F(SafeFetchTest, invalidAccess) {
+  int* p = nullptr;
+  int res = SafeAccess::safeFetch32(p, -1);
+  EXPECT_EQ(res, -1);
+  res = SafeAccess::safeFetch32(p, -2);
+  EXPECT_EQ(res, -2);
+}

From ab1b644898a45f9fa3d20a42350a94be69a4e4d0 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Wed, 16 Jul 2025 11:14:24 -0400
Subject: [PATCH 06/15] Fix safefetch handler

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index c803cd3f..a764ab36 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -38,7 +38,7 @@ bool SafeAccess::handle_safefetch(int sig, void* context) {
   uintptr_t pc = uc->context_pc;
   if ((sig == SIGSEGV || sig == SIGBUS) && uc != nullptr) {
     if (pc == (uintptr_t)_SafeFetch32_fault) {
-      uc->context_pc == (uintptr_t)_SafeFetch32_continuation;
+      uc->context_pc = (uintptr_t)_SafeFetch32_continuation;
       return true;
     }
   }

From bef720017229118acbf2c6391150b48377a6b6f0 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Wed, 16 Jul 2025 11:42:48 -0400
Subject: [PATCH 07/15] context_pc for aarch64 Linux

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index a764ab36..c30f0834 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -20,14 +20,18 @@
 #include <ucontext.h>
 
 #ifdef __APPLE__
-    #if defined(__x86_64)
+    #if defined(__x86_64__)
       #define context_pc context_rip
     #elif defined(__aarch64__)
       #define DU3_PREFIX(s, m) __ ## s.__ ## m
       #define context_pc uc_mcontext->DU3_PREFIX(ss,pc)
     #endif
 #else
-   #define context_pc uc_mcontext.gregs[REG_RIP]
+    #if defined(__x86_64__)
+      #define context_pc uc_mcontext.gregs[REG_RIP]
+    #elif defined(__aarch64__)
+      #define context_pc uc_mcontext.gregs[_REG_ELR]
+    #endif
 #endif
 
 extern "C" char _SafeFetch32_continuation[] __attribute__ ((visibility ("hidden")));

From aca18b73bfd47f9fd2cf0dcac3fce06e1d7cdace Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Wed, 16 Jul 2025 11:50:23 -0400
Subject: [PATCH 08/15] fix

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index c30f0834..b3567a92 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -30,7 +30,7 @@
     #if defined(__x86_64__)
       #define context_pc uc_mcontext.gregs[REG_RIP]
     #elif defined(__aarch64__)
-      #define context_pc uc_mcontext.gregs[_REG_ELR]
+      #define context_pc uc_mcontext.regs[_REG_ELR]
     #endif
 #endif
 

From 8ac912ee0aa5a98b70a273ff2235b9afe56d4a0b Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Wed, 16 Jul 2025 13:55:00 -0400
Subject: [PATCH 09/15] Fix

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index b3567a92..90379913 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -30,7 +30,7 @@
     #if defined(__x86_64__)
       #define context_pc uc_mcontext.gregs[REG_RIP]
     #elif defined(__aarch64__)
-      #define context_pc uc_mcontext.regs[_REG_ELR]
+      #define context_pc uc_mcontext.regs[REG_ELR]
     #endif
 #endif
 

From 8d20ad6b7d449a72b542c59c2e479ec0bdb0c8a4 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Wed, 16 Jul 2025 15:01:48 -0400
Subject: [PATCH 10/15] fix

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index 90379913..ff5aa5c1 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -30,7 +30,7 @@
     #if defined(__x86_64__)
       #define context_pc uc_mcontext.gregs[REG_RIP]
     #elif defined(__aarch64__)
-      #define context_pc uc_mcontext.regs[REG_ELR]
+      #define context_pc uc_mcontext.pc
     #endif
 #endif
 

From 33261bcefbc38e26d70cd67f33995e1dee5c5fb6 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Thu, 17 Jul 2025 12:24:34 -0400
Subject: [PATCH 11/15] Use inline assembly

---
 ddprof-lib/build.gradle                   | 43 ---------------
 ddprof-lib/gtest/build.gradle             |  7 +--
 ddprof-lib/src/main/assembler/safefetch.S | 64 ----------------------
 ddprof-lib/src/main/cpp/safeAccess.cpp    | 67 +++++++++++++++++++++--
 ddprof-lib/src/main/cpp/safeAccess.h      |  5 +-
 5 files changed, 67 insertions(+), 119 deletions(-)
 delete mode 100644 ddprof-lib/src/main/assembler/safefetch.S

diff --git a/ddprof-lib/build.gradle b/ddprof-lib/build.gradle
index 773ecb01..b25ffc57 100644
--- a/ddprof-lib/build.gradle
+++ b/ddprof-lib/build.gradle
@@ -516,19 +516,15 @@ tasks.whenTaskAdded { task ->
             onlyIf {
               config.active
             }
-
             group = 'build'
             description = "Link the ${config.name} build of the library"
             source = fileTree("$buildDir/obj/main/${config.name}")
-            source.from(file("${projectDir}/build/obj/main/asm/assembly.o"))
 
             linkedFile = file("$buildDir/lib/main/${config.name}/${osIdentifier()}/${archIdentifier()}/libjavaProfiler.${os().isLinux() ? 'so' : 'dylib'}")
             def compileTask = tasks.findByName("compileLib${config.name.capitalize()}".toString())
             if (compileTask != null) {
               dependsOn compileTask
             }
-            def asmTask = tasks.findByName("asm")
-            dependsOn asmTask
             linkerArgs.addAll(config.linkerArgs)
             toolChain = task.toolChain
             targetPlatform = task.targetPlatform
@@ -609,45 +605,6 @@ tasks.register('javadocJar', Jar) {
   from javadoc.destinationDir
 }
 
-tasks.register('asm', Exec) {
-  group = 'build'
-
-  def arch
-  if (archIdentifier() == 'x64') {
-    arch = '-D__x86_64__'
-  } else {
-    arch = '-D__aarch64__'
-  }
-
-  def os
-  if (osIdentifier() == 'macos') {
-    os = '-D__APPLE__'
-  } else {
-    os = '-D__LINUX__'
-  }
-  def asmDir = file("${projectDir}/src/main/assembler")
-  if (!asmDir.exists()) {
-    // no assembler files found, skipping
-    return
-  }
-
-  doLast {
-    // Ensure the output directory exists
-    file("${projectDir}/build/obj/main/asm").mkdirs()
-  }
-
-  // collect all assembler files and compile them
-  workingDir asmDir
-  inputs.files fileTree("${projectDir}/src/main/assembler") {
-    include '**/*.S'
-  }
-  def asmFiles = inputs.files.collect { it.absolutePath }
-  outputs.dir "${projectDir}/build/obj/main/asm"
-  // use gcc to compile assembler files
-  commandLine 'gcc', arch, os, '-c', '-x', 'assembler-with-cpp',
-  *asmFiles, '-o', "${projectDir}/build/obj/main/asm/assembly.o"
-}
-
 tasks.register('scanBuild', Exec) {
   workingDir "${projectDir}/src/test/make"
   commandLine 'scan-build'
diff --git a/ddprof-lib/gtest/build.gradle b/ddprof-lib/gtest/build.gradle
index 1792aefd..d2604ff8 100644
--- a/ddprof-lib/gtest/build.gradle
+++ b/ddprof-lib/gtest/build.gradle
@@ -154,10 +154,7 @@ tasks.whenTaskAdded { task ->
             group = 'verification'
             description = "Run all Google Tests for the ${config.name} build of the library"
           }
-          def libProject = project(':ddprof-lib')
-          def asmTask = libProject.tasks.findByName("asm")
-
-          libProject.file("src/test/cpp/").eachFile {
+          project(':ddprof-lib').file("src/test/cpp/").eachFile {
 
             def testFile = it
             def testName = it.name.substring(0, it.name.lastIndexOf('.'))
@@ -170,7 +167,6 @@ tasks.whenTaskAdded { task ->
               group = 'build'
               description = "Link the Google Test for the ${config.name} build of the library"
               source = fileTree("$buildDir/obj/gtest/${config.name}/${testName}")
-              source.from(file("${rootDir}/ddprof-lib/build/obj/main/asm/assembly.o"))
               linkedFile = binary
               if (config.name != 'release') {
                 // linking the gtests using the minimizing release flags is making gtest unhappy
@@ -187,7 +183,6 @@ tasks.whenTaskAdded { task ->
               libs = task.libs
               inputs.files source
               outputs.file linkedFile
-              dependsOn asmTask
             }
             def gtestExecuteTask = tasks.register("gtest${config.name.capitalize()}_${testName}", Exec) {
               onlyIf {
diff --git a/ddprof-lib/src/main/assembler/safefetch.S b/ddprof-lib/src/main/assembler/safefetch.S
deleted file mode 100644
index 5e66d385..00000000
--- a/ddprof-lib/src/main/assembler/safefetch.S
+++ /dev/null
@@ -1,64 +0,0 @@
-#ifdef __APPLE__
-  # macOS prefixes symbols with _
-  #define SYMBOL(s) _ ## s
-
-  #define DECLARE_FUNC(func) \
-    .globl SYMBOL(func) %% \
-    .private_extern SYMBOL(func) %% \
-    SYMBOL(func)
-#else
-  #define SYMBOL(s) s
-
-  #define DECLARE_FUNC(func) \
-    .globl func ; \
-    .hidden func ; \
-    .type func, %function ; \
-    func
-#endif // __APPLE__
-
-#if defined(__x86_64__)
-    .text
-
-    # Support for int SafeFetch32(int* address, int defaultval);
-    #
-    #  %rdi : address
-    #  %esi : defaultval
-DECLARE_FUNC(SafeFetch32_impl):
-DECLARE_FUNC(_SafeFetch32_fault):
-    movl (%rdi), %eax       # load target value, may fault
-    ret
-DECLARE_FUNC(_SafeFetch32_continuation):
-    movl %esi, %eax         # return default
-    ret
-
-#elif defined(__aarch64__)
-#ifdef __APPLE__
-    # Support for int SafeFetch32(int* address, int defaultval);
-    #
-    #  x0 : address
-    #  w1 : defaultval
-
-    # needed to align function start to 4 byte
-    .align  6
-DECLARE_FUNC(SafeFetch32_impl):
-DECLARE_FUNC(_SafeFetch32_fault):
-    ldr      w0, [x0]
-    ret
-DECLARE_FUNC(_SafeFetch32_continuation):
-    mov      x0, x1
-    ret
-#else
-    # Support for int SafeFetch32(int* address, int defaultval);
-    #
-    #  x0 : address
-    #  x1 : defaultval
-DECLARE_FUNC(SafeFetch32_impl):
-DECLARE_FUNC(_SafeFetch32_fault):
-    ldr      w0, [x0]
-    ret
-DECLARE_FUNC(_SafeFetch32_continuation):
-    mov      x0, x1
-    ret
-#endif // __APPLE__
-
-#endif
diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index ff5aa5c1..9aa1eda9 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -34,15 +34,74 @@
     #endif
 #endif
 
-extern "C" char _SafeFetch32_continuation[] __attribute__ ((visibility ("hidden")));
-extern "C" char _SafeFetch32_fault[] __attribute__ ((visibility ("hidden")));
+#if defined(__x86_64__)
+  #ifdef __APPLE__
+    asm(R"(
+        .globl _safefetch32_impl
+        .private_extern _safefetch32_impl
+        _safefetch32_impl:
+            movl (%rdi), %eax
+            ret
+        .globl _safefetch32_continuation
+        .private_extern _safefetch32_continuation
+        _safefetch32_continuation:
+            movl %esi, %eax
+            ret
+    )");
+  #else
+    asm(R"(
+        .globl safefetch32_impl
+        .hidden safefetch32_impl
+        .type safefetch32_imp, %function
+        safefetch32_impl:
+            movl (%rdi), %eax
+            ret
+        .globl safefetch32_continuation
+        .hidden safefetch32_continuation
+        .type safefetch32_continuation, %function
+        safefetch32_continuation:
+            movl %esi, %eax
+            ret
+    )");
+  #endif // __APPLE__
+#elif defined(__aarch64__)
+  #ifdef __APPLE__
+    asm(R"(
+        .globl _safefetch32_impl
+        .private_extern _safefetch32_impl
+        _safefetch32_impl:
+            ldr      w0, [x0]
+            ret
+        .globl _safefetch32_continuation
+        .private_extern _safefetch32_continuation
+        _safefetch32_continuation:
+            mov      x0, x1
+            ret
+    )");
+  #else
+    asm(R"(
+        .globl safefetch32_impl
+        .hidden safefetch32_impl
+        .type safefetch32_impl, %function
+        safefetch32_impl:
+            ldr      w0, [x0]
+            ret
+        .globl safefetch32_continuation
+        .hidden safefetch32_continuation
+        .type safefetch32_continuation, %function
+        safefetch32_continuation:
+            mov      x0, x1
+            ret
+    )");
+  #endif
+#endif
 
 bool SafeAccess::handle_safefetch(int sig, void* context) {
   ucontext_t* uc = (ucontext_t*)context;
   uintptr_t pc = uc->context_pc;
   if ((sig == SIGSEGV || sig == SIGBUS) && uc != nullptr) {
-    if (pc == (uintptr_t)_SafeFetch32_fault) {
-      uc->context_pc = (uintptr_t)_SafeFetch32_continuation;
+    if (pc == (uintptr_t)safefetch32_impl) {
+      uc->context_pc = (uintptr_t)safefetch32_continuation;
       return true;
     }
   }
diff --git a/ddprof-lib/src/main/cpp/safeAccess.h b/ddprof-lib/src/main/cpp/safeAccess.h
index 1f8b27c0..19e83beb 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.h
+++ b/ddprof-lib/src/main/cpp/safeAccess.h
@@ -22,7 +22,8 @@
 #include <cassert>
 #include <stdint.h>
 
-extern "C" int SafeFetch32_impl(int* adr, int errValue);
+extern "C" int safefetch32_impl(int* adr, int errValue);
+extern "C" int safefetch32_continuation(int* adr, int errValue);
 
 #ifdef __clang__
 #define NOINLINE __attribute__((noinline))
@@ -35,7 +36,7 @@ class SafeAccess {
 public:
 
   static inline int safeFetch32(int* ptr, int errorValue) {
-    return SafeFetch32_impl(ptr, errorValue);
+    return safefetch32_impl(ptr, errorValue);
   }
 
   static bool handle_safefetch(int sig, void* context);

From ca9c47b0caf7857fff5ae1cff62d76eb81ee9b51 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Thu, 17 Jul 2025 13:59:53 -0400
Subject: [PATCH 12/15] fix

---
 ddprof-lib/src/main/cpp/safeAccess.h     | 1 -
 ddprof-lib/src/test/cpp/safefetch_ut.cpp | 4 ++--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.h b/ddprof-lib/src/main/cpp/safeAccess.h
index 19e83beb..4030ffa0 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.h
+++ b/ddprof-lib/src/main/cpp/safeAccess.h
@@ -23,7 +23,6 @@
 #include <stdint.h>
 
 extern "C" int safefetch32_impl(int* adr, int errValue);
-extern "C" int safefetch32_continuation(int* adr, int errValue);
 
 #ifdef __clang__
 #define NOINLINE __attribute__((noinline))
diff --git a/ddprof-lib/src/test/cpp/safefetch_ut.cpp b/ddprof-lib/src/test/cpp/safefetch_ut.cpp
index 4e36b862..3519fa44 100644
--- a/ddprof-lib/src/test/cpp/safefetch_ut.cpp
+++ b/ddprof-lib/src/test/cpp/safefetch_ut.cpp
@@ -12,9 +12,9 @@ static void (*orig_busHandler)(int signo, siginfo_t *siginfo, void *ucontext);
 
 void signal_handle_wrapper(int signo, siginfo_t* siginfo, void* context) {
   if (!SafeAccess::handle_safefetch(signo, context)) {
-    if (signo == SIGBUS) {
+    if (signo == SIGBUS && orig_busHandler != nullptr) {
        orig_busHandler(signo, siginfo, context);
-    } else if (signo == SIGSEGV) {
+    } else if (signo == SIGSEGV && orig_segvHandler != nullptr) {
        orig_segvHandler(signo, siginfo, context);
     }
   }

From 66c69adb92a6672f3caeac9da5241103d99ca517 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Thu, 17 Jul 2025 14:06:13 -0400
Subject: [PATCH 13/15] Cleanup

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 44 ++++++++++++++------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index 9aa1eda9..411c4f3b 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -19,18 +19,20 @@
 #include <signal.h>
 #include <ucontext.h>
 
+extern "C" int safefetch32_cont(int* adr, int errValue);
+
 #ifdef __APPLE__
     #if defined(__x86_64__)
-      #define context_pc context_rip
+      #define current_pc context_rip
     #elif defined(__aarch64__)
       #define DU3_PREFIX(s, m) __ ## s.__ ## m
-      #define context_pc uc_mcontext->DU3_PREFIX(ss,pc)
+      #define current_pc uc_mcontext->DU3_PREFIX(ss,pc)
     #endif
 #else
     #if defined(__x86_64__)
-      #define context_pc uc_mcontext.gregs[REG_RIP]
+      #define current_pc uc_mcontext.gregs[REG_RIP]
     #elif defined(__aarch64__)
-      #define context_pc uc_mcontext.pc
+      #define current_pc uc_mcontext.pc
     #endif
 #endif
 
@@ -42,24 +44,25 @@
         _safefetch32_impl:
             movl (%rdi), %eax
             ret
-        .globl _safefetch32_continuation
-        .private_extern _safefetch32_continuation
-        _safefetch32_continuation:
+        .globl _safefetch32_cont
+        .private_extern _safefetch32_cont
+        _safefetch32_cont:
             movl %esi, %eax
             ret
     )");
   #else
     asm(R"(
+        .text
         .globl safefetch32_impl
         .hidden safefetch32_impl
         .type safefetch32_imp, %function
         safefetch32_impl:
             movl (%rdi), %eax
             ret
-        .globl safefetch32_continuation
-        .hidden safefetch32_continuation
-        .type safefetch32_continuation, %function
-        safefetch32_continuation:
+        .globl safefetch32_cont
+        .hidden safefetch32_cont
+        .type safefetch32_cont, %function
+        safefetch32_cont:
             movl %esi, %eax
             ret
     )");
@@ -72,24 +75,25 @@
         _safefetch32_impl:
             ldr      w0, [x0]
             ret
-        .globl _safefetch32_continuation
-        .private_extern _safefetch32_continuation
-        _safefetch32_continuation:
+        .globl _safefetch32_cont
+        .private_extern _safefetch32_cont
+        _safefetch32_cont:
             mov      x0, x1
             ret
     )");
   #else
     asm(R"(
+        .text
         .globl safefetch32_impl
         .hidden safefetch32_impl
         .type safefetch32_impl, %function
         safefetch32_impl:
             ldr      w0, [x0]
             ret
-        .globl safefetch32_continuation
-        .hidden safefetch32_continuation
-        .type safefetch32_continuation, %function
-        safefetch32_continuation:
+        .globl safefetch32_cont
+        .hidden safefetch32_cont
+        .type safefetch32_cont, %function
+        safefetch32_cont:
             mov      x0, x1
             ret
     )");
@@ -98,10 +102,10 @@
 
 bool SafeAccess::handle_safefetch(int sig, void* context) {
   ucontext_t* uc = (ucontext_t*)context;
-  uintptr_t pc = uc->context_pc;
+  uintptr_t pc = uc->current_pc;
   if ((sig == SIGSEGV || sig == SIGBUS) && uc != nullptr) {
     if (pc == (uintptr_t)safefetch32_impl) {
-      uc->context_pc = (uintptr_t)safefetch32_continuation;
+      uc->current_pc = (uintptr_t)safefetch32_cont;
       return true;
     }
   }

From ca37ca6b1408f4d16b6df41ac05d90b4e88f4cf1 Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Thu, 17 Jul 2025 14:18:06 -0400
Subject: [PATCH 14/15] formatting

---
 ddprof-lib/build.gradle | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/ddprof-lib/build.gradle b/ddprof-lib/build.gradle
index b25ffc57..51438cbc 100644
--- a/ddprof-lib/build.gradle
+++ b/ddprof-lib/build.gradle
@@ -519,7 +519,6 @@ tasks.whenTaskAdded { task ->
             group = 'build'
             description = "Link the ${config.name} build of the library"
             source = fileTree("$buildDir/obj/main/${config.name}")
-
             linkedFile = file("$buildDir/lib/main/${config.name}/${osIdentifier()}/${archIdentifier()}/libjavaProfiler.${os().isLinux() ? 'so' : 'dylib'}")
             def compileTask = tasks.findByName("compileLib${config.name.capitalize()}".toString())
             if (compileTask != null) {
@@ -605,13 +604,15 @@ tasks.register('javadocJar', Jar) {
   from javadoc.destinationDir
 }
 
+
+
 tasks.register('scanBuild', Exec) {
   workingDir "${projectDir}/src/test/make"
   commandLine 'scan-build'
   args "-o", "${projectDir}/build/reports/scan-build",
-  "--force-analyze-debug-code",
-  "--use-analyzer", "/usr/bin/clang++",
-  "make", "-j4",  "clean", "all"
+    "--force-analyze-debug-code",
+    "--use-analyzer", "/usr/bin/clang++",
+    "make", "-j4",  "clean", "all"
 }
 
 tasks.withType(Test) {

From 1c299c4353a3a4de1db8373ac85efbf34f5fec7a Mon Sep 17 00:00:00 2001
From: Zhengyu Gu <zhengyu.gu@datadoghq.com>
Date: Fri, 18 Jul 2025 09:10:02 -0400
Subject: [PATCH 15/15] add comment

---
 ddprof-lib/src/main/cpp/safeAccess.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/ddprof-lib/src/main/cpp/safeAccess.cpp b/ddprof-lib/src/main/cpp/safeAccess.cpp
index 411c4f3b..2fea8de3 100644
--- a/ddprof-lib/src/main/cpp/safeAccess.cpp
+++ b/ddprof-lib/src/main/cpp/safeAccess.cpp
@@ -36,6 +36,13 @@ extern "C" int safefetch32_cont(int* adr, int errValue);
     #endif
 #endif
 
+/**
+ Loading a 32-bit value from specific address, the errValue will be returned
+ if the address is invalid.
+ The load is protected by the 'handle_safefetch` signal handler, who sets next `pc`
+ to `safefetch32_cont`, upon returning from signal handler, `safefetch32_cont` returns `errValue`
+ **/
+
 #if defined(__x86_64__)
   #ifdef __APPLE__
     asm(R"(