async-profiler#747: Workaround for JDK-8307549

KindlingProject · Aug 2, 2023 · a852bdd · a852bdd
1 parent eb28799
commit a852bdd
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Showing 3 changed files with 30 additions and 2 deletions.
diff --git a/src/profiler.cpp b/src/profiler.cpp
@@ -800,14 +800,22 @@ void Profiler::trapHandler(int signo, siginfo_t* siginfo, void* ucontext) {
 void Profiler::segvHandler(int signo, siginfo_t* siginfo, void* ucontext) {
     StackFrame frame(ucontext);
 
-    uintptr_t length = SafeAccess::skipFaultInstruction(frame.pc());
+    uintptr_t length = SafeAccess::skipLoad(frame.pc());
     if (length > 0) {
         // Skip the fault instruction, as if it successfully loaded NULL
         frame.pc() += length;
         frame.retval() = 0;
         return;
     }
 
+    length = SafeAccess::skipLoad32(frame.pc());
+    if (length > 0) {
+        // Act as if the load returned default_value argument
+        frame.pc() += length;
+        frame.retval() = frame.arg1();
+        return;
+    }
+
     if (WX_MEMORY && Trap::isFaultInstruction(frame.pc())) {
         return;
     }

diff --git a/src/safeAccess.h b/src/safeAccess.h
@@ -35,7 +35,12 @@ class SafeAccess {
         return *ptr;
     }
 
-    static uintptr_t skipFaultInstruction(uintptr_t pc) {
+    NOINLINE __attribute__((aligned(16)))
+    static u32 load32(u32* ptr, u32 default_value) {
+        return *ptr;
+    }
+
+    static uintptr_t skipLoad(uintptr_t pc) {
         if ((pc - (uintptr_t)load) < 16) {
 #if defined(__x86_64__)
             return *(u16*)pc == 0x8b48 ? 3 : 0;  // mov rax, [reg]
@@ -51,6 +56,13 @@ class SafeAccess {
         }
         return 0;
     }
+
+    static uintptr_t skipLoad32(uintptr_t pc) {
+        if (WX_MEMORY && (pc - (uintptr_t)load32) < 16) {
+            return 4;
+        }
+        return 0;
+    }
 };
 
 #endif // _SAFEACCESS_H
diff --git a/src/vmEntry.cpp b/src/vmEntry.cpp
@@ -252,6 +252,14 @@ void VM::ready() {
 
     Profiler::setupSignalHandlers();
 
+    if (WX_MEMORY && hotspot_version() == 17) {
+        // Workaround for JDK-8307549
+        void** entry = (void**)VMStructs::libjvm()->findSymbol("_ZN12StubRoutines18_safefetch32_entryE");
+        if (entry != NULL) {
+            *entry = (void*)SafeAccess::load32;
+        }
+    }
+
     _libjava = getLibraryHandle("libjava.so");
 
     // Make sure we reload method IDs upon class retransformation