change the design to hooking of __cxa_get_globals(), so that we don't…

… need to switch exception state
alibaba · Nov 5, 2024 · cedd27a · cedd27a
1 parent f51192b
commit cedd27a
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Showing 2 changed files with 39 additions and 23 deletions.
diff --git a/thread/test/test.cpp b/thread/test/test.cpp
@@ -405,14 +405,22 @@ TEST(Perf, ThreadSwitchWithStandaloneTSUpdater)
     return;
 }
 
+inline int std_uncaught_exceptions() {
+#if __cplusplus > 201700L
+    return std::uncaught_exceptions();
+#else
+    return std::uncaught_exception();
+#endif
+}
+
 TEST(exception, switch)
 {
     class Foo {
     public:
         ~Foo() {
-            LOG_INFO("before thread_yield():", VALUE(std::uncaught_exceptions()));
+            LOG_INFO("before thread_yield():", VALUE(std_uncaught_exceptions()));
             photon::thread_yield();
-            LOG_INFO("after  thread_yield():", VALUE(std::uncaught_exceptions()));
+            LOG_INFO("after  thread_yield():", VALUE(std_uncaught_exceptions()));
         }
     };
 
@@ -429,8 +437,8 @@ TEST(exception, switch)
     bool quit = false;
     auto th = photon::thread_create11([&](){
         while(!quit) {
-            LOG_INFO(VALUE(std::uncaught_exceptions()));
-            EXPECT_EQ(std::uncaught_exceptions(), 0);
+            LOG_INFO(VALUE(std_uncaught_exceptions()));
+            EXPECT_EQ(std_uncaught_exceptions(), 0);
             try {
                 throw 3.1415926f;
             } catch(...) { }

diff --git a/thread/thread.cpp b/thread/thread.cpp
@@ -31,6 +31,7 @@ limitations under the License.
 #include <thread>
 #include <mutex>
 #include <condition_variable>
+#include <dlfcn.h>
 
 #ifdef _WIN64
 #include <processthreadsapi.h>
@@ -197,6 +198,7 @@ namespace photon
         size_t stack_size;
 // offset 96B
         condition_variable cond;            /* used for join */
+        uint64_t __gh_globals[2] = {0};
 
         enum shift {
             joinable = 0,
@@ -649,20 +651,33 @@ namespace photon
     }
 
     static void _photon_thread_die(thread* th) asm("_photon_thread_die");
-    struct __cxa_eh_globals
-    {
-        void *	caughtExceptions;
-        unsigned int	uncaughtExceptions;
+    struct __cxa_eh_globals {
+        void* caughtExceptions;
+        unsigned int uncaughtExceptions;
     };
-
-    extern "C" __cxa_eh_globals* __cxa_get_globals (void);
-
-    static void* cxa_get_globals() asm("cxa_get_globals");
-
-    static __attribute__((used))
-    void* cxa_get_globals() {
-        return __cxa_get_globals();
+    inline void install_hook(void* target, void* hook) {
+        auto page = (uint64_t)target & ~4095UL;
+        int ret = mprotect((void*)page, 4096, PROT_READ | PROT_WRITE | PROT_EXEC);
+        assert(ret == 0); (void)ret;
+        *(uint16_t*)((char*)target + 0) = 0xb848; // movabs imm64 to rax
+        *(uint64_t*)((char*)target + 2) = (uint64_t)hook;
+        *(uint16_t*)((char*)target + 10) = 0xe0ff; // jmp *rax
     }
+    inline void* install_hook(const char* sym, void* hook) {
+        auto addr = dlsym(RTLD_DEFAULT, sym);
+        assert(addr);
+        install_hook(addr, hook);
+        return addr;
+    }
+    static __cxa_eh_globals* cxa_get_globals (void) {
+        thread_local __cxa_eh_globals eh = {0};
+        return !CURRENT ? &eh : (__cxa_eh_globals*) CURRENT->__gh_globals;
+    }
+    __attribute__((constructor))
+    static void install_eh_globals_hook() {
+        install_hook("__cxa_get_globals", (void*)&cxa_get_globals);
+    }
+
 
 #if defined(__x86_64__)
 #if !defined(_WIN64)
@@ -826,11 +841,6 @@ R"(
 
 DEF_ASM_FUNC(_photon_thread_stub)
 R"(
-        sub sp, sp, #16
-        bl  cxa_get_globals
-        add sp, sp, #16
-        str xzr, [x0, #0x0]
-        str wzr, [x0, #0x8]
         ldp x0, x1, [x29, #0x40] //; load arg, start into x0, x1
         str xzr, [x29, #0x40]    //; set arg as 0
         blr x1                   //; start(x0)
@@ -847,7 +857,6 @@ R"(
 
     inline void switch_context(thread* from, thread* to) {
         prepare_switch(from, to);
-        auto exception_state = *__cxa_get_globals();
         auto _t_ = to->stack.pointer_ref();
         register auto f asm("x0") = from->stack.pointer_ref();
         register auto t asm("x1") = _t_;
@@ -862,7 +871,6 @@ R"(
                      // Corouptable register, may change ,should save
                      "x9", "x10", "x11", "x12", "x13", "x14", "x15", "x16",
                      "x17", "x18");
-        *__cxa_get_globals() = exception_state;
     }
 
     inline void switch_context_defer(thread* from, thread* to,