From: Martin Quinson <martin.quinson@ens-rennes.fr>
Date: Fri, 22 Jul 2022 21:24:27 +0000 (+0200)
Subject: Another attempt at PRELOADing mmalloc (WIP)
X-Git-Tag: v3.32~135
X-Git-Url: http://bilbo.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/commitdiff_plain/8a3175c8d73996d77d1d06f85941bc60f5a9cf17

Another attempt at PRELOADing mmalloc (WIP)

Try to have mmalloc both in the simgrid library (for the regular use)
and also as an external library that can be LD_PRELOADed before
sthread too.

We'll have two copies of the library when actually preloading it in
sthread, but in this case, we use dlsym(RTDL_NEXT) to find the first
loaded symbol in memory to have only one mheap in the process.

It still segfault when launching a sthread code within simgrid-mc as
follows:
   bin/simgrid-mc --cfg=model-check/setenv:LD_PRELOAD=lib/libsgmalloc.so:lib/libsthread.soexamples/sthread/pthread-mutex-simple
but at least it should fix the breakage found on FreeBSD.
---

diff --git a/src/mc/api.cpp b/src/mc/api.cpp
index ce024e6e62..e097a37de8 100644
--- a/src/mc/api.cpp
+++ b/src/mc/api.cpp
@@ -37,18 +37,10 @@ simgrid::mc::Exploration* Api::initialize(char** argv, const std::unordered_map<
     int i = 1;
     while (argv[i] != nullptr && argv[i][0] == '-')
       i++;
-    if (env.find("LD_PRELOAD") == env.end())
-      setenv("LD_PRELOAD", "libsgmalloc.so", 1);
 
     for (auto const& [key, val] : env) {
-      if (key == "LD_PRELOAD") {
-        auto v2 = std::string("libsgmalloc.so:") + val;
-        XBT_INFO("setenv '%s'='%s'", key.c_str(), v2.c_str());
-        setenv(key.c_str(), v2.c_str(), 1);
-      } else {
-        XBT_INFO("setenv '%s'='%s'", key.c_str(), val.c_str());
-        setenv(key.c_str(), val.c_str(), 1);
-      }
+      XBT_INFO("setenv '%s'='%s'", key.c_str(), val.c_str());
+      setenv(key.c_str(), val.c_str(), 1);
     }
     xbt_assert(argv[i] != nullptr,
                "Unable to find a binary to exec on the command line. Did you only pass config flags?");
diff --git a/src/xbt/mmalloc/mm_interface.c b/src/xbt/mmalloc/mm_interface.c
index 28534b08fb..5f03243556 100644
--- a/src/xbt/mmalloc/mm_interface.c
+++ b/src/xbt/mmalloc/mm_interface.c
@@ -51,9 +51,3 @@ size_t mmalloc_get_bytes_used_remote(size_t heaplimit, const malloc_info* heapin
   }
   return bytes;
 }
-
-__attribute__((weak)) xbt_mheap_t mmalloc_get_current_heap(void)
-{
-  fprintf(stderr, "Fake mmalloc_get_current_heap()\n");
-  return NULL;
-}
\ No newline at end of file
diff --git a/src/xbt/mmalloc/mm_module.c b/src/xbt/mmalloc/mm_module.c
index d8b53599ac..37f301b1d7 100644
--- a/src/xbt/mmalloc/mm_module.c
+++ b/src/xbt/mmalloc/mm_module.c
@@ -193,15 +193,23 @@ static void mmalloc_fork_child(void)
 xbt_mheap_t mmalloc_preinit(void)
 {
   if (__mmalloc_default_mdp == NULL) {
-    if (!mmalloc_pagesize)
-      mmalloc_pagesize = getpagesize();
-    unsigned long mask    = ~((unsigned long)mmalloc_pagesize - 1);
-    void *addr = (void*)(((unsigned long)sbrk(0) + HEAP_OFFSET) & mask);
-    __mmalloc_default_mdp = xbt_mheap_new(addr, XBT_MHEAP_OPTION_MEMSET);
-
-    // atfork mandated at least on FreeBSD, or simgrid-mc will fail to fork the verified app
-    int res = pthread_atfork(mmalloc_fork_prepare, mmalloc_fork_parent, mmalloc_fork_child);
-    mmalloc_assert(res == 0, "pthread_atfork() failed: return value %d", res);
+    xbt_mheap_t (*other)(void) = dlsym(RTLD_NEXT, "mmalloc_preinit");
+    if (other != NULL) { // This is the second time that this module is loaded, let's use the other one
+      __mmalloc_default_mdp = other();
+      //      fprintf(stderr, "Reuse the other mmalloc_init\n");
+    } else {
+      //      fprintf(stderr, "New mmalloc_init\n");
+
+      if (!mmalloc_pagesize)
+        mmalloc_pagesize = getpagesize();
+      unsigned long mask    = ~((unsigned long)mmalloc_pagesize - 1);
+      void* addr            = (void*)(((unsigned long)sbrk(0) + HEAP_OFFSET) & mask);
+      __mmalloc_default_mdp = xbt_mheap_new(addr, XBT_MHEAP_OPTION_MEMSET);
+
+      // atfork mandated at least on FreeBSD, or simgrid-mc will fail to fork the verified app
+      int res = pthread_atfork(mmalloc_fork_prepare, mmalloc_fork_parent, mmalloc_fork_child);
+      mmalloc_assert(res == 0, "pthread_atfork() failed: return value %d", res);
+    }
   }
   mmalloc_assert(__mmalloc_default_mdp != NULL, "__mmalloc_default_mdp cannot be NULL");
 
diff --git a/tools/cmake/DefinePackages.cmake b/tools/cmake/DefinePackages.cmake
index 813d8292de..ae045cefa4 100644
--- a/tools/cmake/DefinePackages.cmake
+++ b/tools/cmake/DefinePackages.cmake
@@ -289,6 +289,7 @@ set(XBT_SRC
 
 if(HAVE_MMALLOC)
   set(SGMALLOC_SRC src/xbt/mmalloc/mm.c)
+  set(XBT_SRC      ${XBT_SRC} src/xbt/mmalloc/mm.c)
 else()
   set(EXTRA_DIST ${EXTRA_DIST} src/xbt/mmalloc/mm.c)
 endif()