BUG/MEDIUM: tools: avoid calling dlsym() in static builds (try 2)
The first approach in commit 288dc1d8e ("BUG/MEDIUM: tools: avoid calling
dlsym() in static builds") relied on dlopen() but on certain configs (at
least gcc-4.8+ld-2.27+glibc-2.17) it used to catch situations where it
ought not fail.
Let's have a second try on this using dladdr() instead. The variable was
renamed "build_is_static" as it's exactly what's being detected there.
We could even take it for reporting in -vv though that doesn't seem very
useful. At least the variable was made global to ease inspection via the
debugger, or in case it's useful later.
Now it properly detects a static build even with gcc-4.4+glibc-2.11.1 and
doesn't crash anymore.
(cherry picked from commit 5b3cd9561bdbf7bac7db04bafead76125f1458ae)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 1dbb19401536db79d394a39da5758838e483659d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit cf3050812faf628e1beda1dfbe9cabdb8f06f60a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/tools.c b/src/tools.c
index c381f21..da0c8d7 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -95,6 +95,9 @@
*/
THREAD_LOCAL unsigned int statistical_prng_state = 2463534242U;
+/* set to true if this is a static build */
+int build_is_static = 0;
+
/*
* unsigned long long ASCII representation
*
@@ -4826,22 +4829,25 @@
return ret;
}
-/* dlopen() support: 0=no/not yet checked, 1=ok */
-static int dlopen_usable = 0;
-
-/* Sets dlopen_usable to true if dlopen() works and is usable. We verify if
- * we're in a static build because some old glibcs used to crash in dlsym()
- * in this case.
+/* Sets build_is_static to true if we detect a static build. Some older glibcs
+ * tend to crash inside dlsym() in static builds, but tests show that at least
+ * dladdr() still works (and will fail to resolve anything of course). Thus we
+ * try to determine if we're on a static build to avoid calling dlsym() in this
+ * case.
*/
-void check_if_dlopen_usable()
+void check_if_static_build()
{
- /* dlopen(NULL) returns a handle to the main program or NULL
- * on static builds.
- */
- dlopen_usable = dlopen(NULL, RTLD_LAZY) ? 1 : 0;
+ Dl_info dli = { };
+ size_t size = 0;
+
+ /* Now let's try to be smarter */
+ if (!dladdr_and_size(&main, &dli, &size))
+ build_is_static = 1;
+ else
+ build_is_static = 0;
}
-INITCALL0(STG_PREPARE, check_if_dlopen_usable);
+INITCALL0(STG_PREPARE, check_if_static_build);
/* Tries to retrieve the address of the first occurrence symbol <name>.
* Note that NULL in return is not always an error as a symbol may have that
@@ -4852,7 +4858,7 @@
void *ptr = NULL;
#ifdef RTLD_DEFAULT
- if (dlopen_usable)
+ if (!build_is_static)
ptr = dlsym(RTLD_DEFAULT, name);
#endif
return ptr;
@@ -4868,7 +4874,7 @@
void *ptr = NULL;
#ifdef RTLD_NEXT
- if (dlopen_usable)
+ if (!build_is_static)
ptr = dlsym(RTLD_NEXT, name);
#endif
return ptr;