From 26da4ed5af6bc5cc6f7b94b7b9623e6ca8ed6f50 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Thu, 19 Sep 2024 00:56:33 +0100
Subject: [PATCH] Avoid patching symbols in the extension module

The fact that patching ourselves had not raised problems so far its
really an outstanding fact in this universe. Unfortunately seems that
with the latest toolchain + GCC there is something that causes memray to
point the d_original entry of the hooks pointing to itself, which should
never happen.

To fix this resiliently, avoid patching ourselves by getting our own
name in the extension module and then avoiding that shared object.

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>
---
 news/685.bugfix.rst                     |  1 +
 src/memray/_memray/elf_shenanigans.cpp  |  9 +++++----
 src/memray/_memray/linker_shenanigans.h | 14 ++++++++++++++
 3 files changed, 20 insertions(+), 4 deletions(-)
 create mode 100644 news/685.bugfix.rst

diff --git a/news/685.bugfix.rst b/news/685.bugfix.rst
new file mode 100644
index 0000000000..057c58427d
--- /dev/null
+++ b/news/685.bugfix.rst
@@ -0,0 +1 @@
+Fix some crashes caused by interposing symbols in memray itself
diff --git a/src/memray/_memray/elf_shenanigans.cpp b/src/memray/_memray/elf_shenanigans.cpp
index 997599ea74..c692f54842 100644
--- a/src/memray/_memray/elf_shenanigans.cpp
+++ b/src/memray/_memray/elf_shenanigans.cpp
@@ -18,6 +18,7 @@ struct elf_patcher_context_t
 {
     bool restore_original;
     std::set<std::string> patched;
+    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);
 }
 
diff --git a/src/memray/_memray/linker_shenanigans.h b/src/memray/_memray/linker_shenanigans.h
index 17ae39ff26..c1de88eab3 100644
--- a/src/memray/_memray/linker_shenanigans.h
+++ b/src/memray/_memray/linker_shenanigans.h
@@ -3,14 +3,28 @@
 #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;
+        }
+        printf("%s\n", self_so_name.c_str());
+    }
     void overwrite_symbols() noexcept;
     void restore_symbols() noexcept;
 };