ASAN fixes

Use same trick as dlopen to support siglongjmp bypass.

src/julia.h

@@ -2285,15 +2285,9 @@ void (ijl_longjmp)(jmp_buf _Buf, int _Value);
 #define jl_setjmp_name "sigsetjmp"
 #endif
 #define jl_setjmp(a,b) sigsetjmp(a,b)
-#if defined(_COMPILER_ASAN_ENABLED_) && __GLIBC__
-// Bypass the ASAN longjmp wrapper - we're unpoisoning the stack ourselves.
-#if !__GLIBC_PREREQ(2, 34)
-JL_DLLIMPORT int __attribute__ ((nothrow)) (__libc_siglongjmp)(jl_jmp_buf buf, int val);
-#define jl_longjmp(a,b) __libc_siglongjmp(a,b)
-#else
-// This broke with glibc 2.34, where the __libc_siglongjmp symbol was removed
-#define jl_longjmp(a,b) siglongjmp(a,b)
-#endif
+#if defined(_COMPILER_ASAN_ENABLED_) && defined(__GLIBC__)
+extern void (*real_siglongjmp)(jmp_buf _Buf, int _Value);
+#define jl_longjmp(a,b) real_siglongjmp(a,b)
 #else
 #define jl_longjmp(a,b) siglongjmp(a,b)
 #endif

src/task.c

@@ -42,6 +42,13 @@ extern "C" {
 #endif
 
 #if defined(_COMPILER_ASAN_ENABLED_)
+#if __GLIBC__
+#include <dlfcn.h>
+// Bypass the ASAN longjmp wrapper - we are unpoisoning the stack ourselves,
+// since ASAN normally unpoisons far too much.
+// c.f. interceptor in jl_dlopen as well
+void (*real_siglongjmp)(jmp_buf _Buf, int _Value) = NULL;
+#endif
 static inline void sanitizer_start_switch_fiber(jl_ptls_t ptls, jl_task_t *from, jl_task_t *to) {
     if (to->copy_stack)
         __sanitizer_start_switch_fiber(&from->ctx.asan_fake_stack, (char*)ptls->stackbase-ptls->stacksize, ptls->stacksize);
@@ -1226,6 +1233,17 @@ void jl_init_tasks(void) JL_GC_DISABLED
         exit(1);
     }
 #endif
+#if defined(_COMPILER_ASAN_ENABLED_) && __GLIBC__
+    void *libc_handle = dlopen("libc.so.6", RTLD_NOW | RTLD_NOLOAD);
+    if (libc_handle) {
+        *(void**)&real_siglongjmp = dlsym(libc_handle, "siglongjmp");
+        dlclose(libc_handle);
+    }
+    if (real_siglongjmp == NULL) {
+        jl_safe_printf("failed to get real siglongjmp\n");
+        exit(1);
+    }
+#endif
 }
 
 #if defined(_COMPILER_ASAN_ENABLED_)