[master] 11a50e7 umem: test-load libumem in a separate namespace in the management process

[Nils Goroll]

commit 11a50e7944fe3ae69e649204b9b6683b92d2e463
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Apr 4 09:21:11 2018 +0200

    umem: test-load libumem in a separate namespace in the management process
    
    libumem's atfork handler will redefine malloc() and friends so if we
    load it in the manager, we cannot confine its use to the stevedore

diff --git a/bin/varnishd/storage/storage_umem.c b/bin/varnishd/storage/storage_umem.c
index acb291a..7464a19 100644
--- a/bin/varnishd/storage/storage_umem.c
+++ b/bin/varnishd/storage/storage_umem.c
@@ -41,6 +41,7 @@
 #include <stdlib.h>
 #include <umem.h>
 #include <dlfcn.h>
+#include <link.h>
 
 #include "storage/storage.h"
 #include "storage/storage_simple.h"
@@ -262,7 +263,8 @@ smu_init(struct stevedore *parent, int ac, char * const *av)
 
 	/* Check if these load in the management process. */
 	(void) dlerror();
-	if ((libumem_hndl = dlopen("libumem.so", RTLD_NOW)) == NULL)
+	libumem_hndl = dlmopen(LM_ID_NEWLM, "libumem.so", RTLD_LAZY);
+	if (libumem_hndl == NULL)
 		ARGV_ERR("(-sumem) cannot open libumem.so: %s", dlerror());
 
 #define DLSYM_UMEM(fptr,sym)						\
@@ -282,6 +284,9 @@ smu_init(struct stevedore *parent, int ac, char * const *av)
 
 #undef DLSYM_UMEM
 
+	AZ(dlclose(libumem_hndl));
+	libumem_hndl = NULL;
+
 	e = VNUM_2bytes(av[0], &u, 0);
 	if (e != NULL)
 		ARGV_ERR("(-sumem) size \"%s\": %s\n", av[0], e);