wrapper/linker: __cxa_demangle from linker

We want to use android's libstdc++, so we need to pass __cxa_demangle
from linker.

3 files changed, 29 insertions, 8 deletions

diff --git a/src/linker/linker.c b/src/linker/linker.c
index b5b782d..f91316c 100644
--- a/src/linker/linker.c
+++ b/src/linker/linker.c
@@ -1271,10 +1271,16 @@ soinfo *apkenv_find_library(const char *name, const bool try_glibc)
     }
 
     TRACE("[ %5d '%s' has not been loaded yet.  Locating...]\n", apkenv_pid, name);
-    si = apkenv_load_library(name, try_glibc);
-    if(si == NULL)
+    if (!(si = apkenv_load_library(name, try_glibc)) || !(si = apkenv_init_library(si)))
         return NULL;
-    return apkenv_init_library(si);
+
+    if (!strstr(bname, "libstdc++.so")) {
+        Elf32_Sym *sym = apkenv_lookup_in_library(si, "__cxa_demangle");
+        if (sym && ELF32_ST_BIND(sym->st_info) == STB_GLOBAL && sym->st_shndx != 0)
+            wrapper_set_cpp_demangler((void*)(intptr_t)(sym->st_value + si->base));
+    }
+
+    return si;
 }
 
 /* TODO:
diff --git a/src/wrapper/wrapper.c b/src/wrapper/wrapper.c
index 2d61519..51d17a6 100644
--- a/src/wrapper/wrapper.c
+++ b/src/wrapper/wrapper.c
@@ -2,11 +2,10 @@
 #include <stdio.h>
 #include <stdarg.h>
 #include <stdbool.h>
-#include <stdint.h>
 #include <stddef.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#include <dlfcn.h>
 #include <assert.h>
 #include <sys/mman.h>
 #include "verbose.h"
@@ -61,17 +60,33 @@ trace(const char *const symbol)
         char *demangled;
         static __thread char *data;
         static __thread size_t size;
+        static __thread bool skip_trace;
+
+        // Avoid infinite recursion and tracing calls made by __cxa_demangle.fun
+        if (skip_trace)
+            return;
+
+        skip_trace = true;
         if ((demangled = __cxa_demangle.fun(symbol, data, &size, &status))) {
             data = (data != demangled ? demangled : data);
             verbose("trace: %s", demangled);
             return;
         }
+        skip_trace = false;
     }
 
     verbose("trace: %s", symbol);
 }
 #endif
 
+void
+wrapper_set_cpp_demangler(void *function)
+{
+#ifdef WRAPPER_TRACE
+    __cxa_demangle.ptr = function;
+#endif
+}
+
 void*
 wrapper_create(const char *const symbol, void *function)
 {
@@ -83,9 +98,6 @@ wrapper_create(const char *const symbol, void *function)
     }
 
 #ifdef WRAPPER_TRACE
-    if (!__cxa_demangle.ptr)
-        __cxa_demangle.ptr = dlsym(RTLD_DEFAULT, "__cxa_demangle");
-
     const size_t sz = &wrapper_end - &wrapper_start;
     unsigned char *fun = mmap(NULL, sz, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
     assert(fun != MAP_FAILED);
diff --git a/src/wrapper/wrapper.h b/src/wrapper/wrapper.h
index c75ef33..c28c71e 100644
--- a/src/wrapper/wrapper.h
+++ b/src/wrapper/wrapper.h
@@ -2,3 +2,6 @@
 
 void*
 wrapper_create(const char *const symbol, void *function);
+
+void
+wrapper_set_cpp_demangler(void *function);