Avoid patching symbols in the extension module

news/685.bugfix.rst

@@ -0,0 +1 @@
+Fix some crashes caused by interposing symbols in memray itself

src/memray/_memray/elf_shenanigans.cpp

@@ -17,7 +17,8 @@ namespace {
 struct elf_patcher_context_t
 {
     bool restore_original;
-    std::set<std::string> patched;
+    std::set<std::string>& patched;
+    const std::string& self_so_name;
 };
 
 }  // namespace
@@ -172,10 +173,10 @@ phdrs_callback(dl_phdr_info* info, [[maybe_unused]] size_t size, void* data) noe
     }
 
     if (strstr(info->dlpi_name, "/ld-linux") || strstr(info->dlpi_name, "/ld-musl")
-        || strstr(info->dlpi_name, "linux-vdso.so.1"))
+        || strstr(info->dlpi_name, "linux-vdso.so.1")
+        || strstr(info->dlpi_name, context.self_so_name.c_str()))
     {
         // Avoid chaos by not overwriting the symbols in the linker.
-        // TODO: Don't override the symbols in our shared library!
         return 0;
     }
 
@@ -198,14 +199,14 @@ phdrs_callback(dl_phdr_info* info, [[maybe_unused]] size_t size, void* data) noe
 void
 SymbolPatcher::overwrite_symbols() noexcept
 {
-    elf_patcher_context_t context{false, symbols};
+    elf_patcher_context_t context{false, symbols, self_so_name};
     dl_iterate_phdr(&phdrs_callback, (void*)&context);
 }
 
 void
 SymbolPatcher::restore_symbols() noexcept
 {
-    elf_patcher_context_t context{true, symbols};
+    elf_patcher_context_t context{true, symbols, self_so_name};
     dl_iterate_phdr(&phdrs_callback, (void*)&context);
 }
 

src/memray/_memray/linker_shenanigans.h

@@ -3,14 +3,27 @@
 #include <set>
 #include <string>
 
+#include <dlfcn.h>
+
 namespace memray::linker {
 
+static void
+_dummy(void){};
+
 class SymbolPatcher
 {
   private:
     std::set<std::string> symbols;
+    std::string self_so_name = "_memray.cpython-";
 
   public:
+    SymbolPatcher()
+    {
+        Dl_info info;
+        if (dladdr((void*)&_dummy, &info)) {
+            self_so_name = info.dli_fname;
+        }
+    }
     void overwrite_symbols() noexcept;
     void restore_symbols() noexcept;
 };