Fix dlopen directory lookup behavior

lib/interpose.c

@@ -76,8 +76,6 @@ static void *(*real_aligned_alloc)(size_t, size_t) = NULL;
 static int (*real_posix_memalign)(void **, size_t, size_t) = NULL;
 
 /* Dynamic loader functions. */
-static void *(*real_dlopen)(const char *, int) = NULL;
-static void *(*real_dlmopen)(Lmid_t, const char *, int) = NULL;
 static int (*real_dlclose)(void *) = NULL;
 static int (*real_dladdr)(const void *, Dl_info *) = NULL;
 static int (*real_dladdr1)(const void *, Dl_info *, void **, int) = NULL;
@@ -268,24 +266,12 @@ __ulp_asunsafe_begin(void)
 
   bool ok = true;
 
-  real_dlopen = dlsym(RTLD_NEXT, "dlopen");
-  real_dlmopen = dlsym(RTLD_NEXT, "dlmopen");
   real_dlclose = dlsym(RTLD_NEXT, "dlclose");
   real_dladdr = dlsym(RTLD_NEXT, "dladdr");
   real_dladdr1 = dlsym(RTLD_NEXT, "dladdr1");
   real_dlinfo = dlsym(RTLD_NEXT, "dlinfo");
 
   /* Check if we got the symbols we need from libdl.  */
-  if (!real_dlopen) {
-    set_libpulp_error_state_with_reason(ENOLIBDL, "unable to find function `dlopen`.");
-    ok = false;
-  }
-
-  if (!real_dlmopen) {
-    set_libpulp_error_state_with_reason(ENOLIBDL, "unable to find function `dlmopen`.");
-    ok = false;
-  }
-
   if (!real_dlclose) {
     set_libpulp_error_state_with_reason(ENOLIBDL, "unable to find function `dlclose`.");
     ok = false;
@@ -567,38 +553,6 @@ posix_memalign(void **memptr, size_t alignment, size_t size)
   return result;
 }
 
-void *
-dlopen(const char *filename, int flags)
-{
-  void *result;
-
-  if (real_dlopen == NULL) {
-    __ulp_asunsafe_begin();
-  }
-
-  __sync_fetch_and_add(&flag, 1);
-  result = real_dlopen(filename, flags);
-  __sync_fetch_and_sub(&flag, 1);
-
-  return result;
-}
-
-void *
-dlmopen(Lmid_t nsid, const char *file, int mode)
-{
-  void *result;
-
-  if (real_dlmopen == NULL) {
-    __ulp_asunsafe_begin();
-  }
-
-  __sync_fetch_and_add(&flag, 1);
-  result = real_dlmopen(nsid, file, mode);
-  __sync_fetch_and_sub(&flag, 1);
-
-  return result;
-}
-
 int
 dlclose(void *handle)
 {

tests/Makefile.am

@@ -478,7 +478,8 @@ check_PROGRAMS = \
   insn_queue \
   chroot \
   visibility \
-  notes
+  notes \
+  dlopen
 
 numserv_SOURCES = numserv.c
 numserv_LDADD = libdozens.la libhundreds.la
@@ -648,6 +649,11 @@ notes_DEPENDENCIES = notes.ld $(POST_PROCESS) $(METADATA)
 
 EXTRA_DIST += notes.ld
 
+dlopen_SOURCES = dlopen.c
+dlopen_CFLAGS = $(AM_CFLAGS)
+dlsym_LDADD = -lpthread -ldl -lrt
+dlsym_DEPENDENCIES = libhundreds.la
+
 TESTS = \
   numserv.py \
   numserv_bsymbolic.py \
@@ -707,7 +713,8 @@ TESTS = \
   textrel.py \
   seccomp_disable.py \
   run_libc.py \
-  glibc_private.py
+  glibc_private.py \
+  dlopen.py
 
 XFAIL_TESTS = \
   blocked.py \

tests/dlopen.c

@@ -0,0 +1,40 @@
+/*
+ *  libpulp - User-space Livepatching Library
+ *
+ *  Copyright (C) 2025 SUSE Software Solutions GmbH
+ *
+ *  This file is part of libpulp.
+ *
+ *  libpulp is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  libpulp is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with libpulp.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <dlfcn.h>
+#include <unistd.h>
+
+int main()
+{
+  void *handle = dlopen(".libs/libhundreds.so", RTLD_NOW | RTLD_GLOBAL);
+  if (!handle) {
+    printf("Failed to load libhundreds.so: %s\n", dlerror());
+    return 1;
+  }
+  int (*hundred)(void) = dlsym(handle, "hundred");
+  do {
+    printf("hundred: %d\n", hundred());
+    sleep(1);
+  } while (1);
+
+  return 0;
+}

tests/dlopen.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+
+#   libpulp - User-space Livepatching Library
+#
+#   Copyright (C) 2025 SUSE Software Solutions GmbH
+#
+#   This file is part of libpulp.
+#
+#   libpulp is free software; you can redistribute it and/or
+#   modify it under the terms of the GNU Lesser General Public
+#   License as published by the Free Software Foundation; either
+#   version 2.1 of the License, or (at your option) any later version.
+#
+#   libpulp is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#   Lesser General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with libpulp.  If not, see <http://www.gnu.org/licenses/>.
+
+import testsuite
+
+child = testsuite.spawn(testsuite.testname)
+
+child.expect('100', reject='Failed to load libhundreds.so')
+
+child.close(force=True)
+exit(0)