Fix: lazily dlopen 2.12 lttng-ust from liblttng-ust-fd.so symbol overrides

[lttng-ust.git] / src / lib / lttng-ust-fd / lttng-ust-fd.c

diff --git a/src/lib/lttng-ust-fd/lttng-ust-fd.c b/src/lib/lttng-ust-fd/lttng-ust-fd.c
index c58ebdb71bf084316bae330febfa0e0ee4d0c81b..af208a9852dbf03e9442140d6089c9f18472d110 100644 (file)
--- a/src/lib/lttng-ust-fd/lttng-ust-fd.c
+++ b/src/lib/lttng-ust-fd/lttng-ust-fd.c
@@ -16,6 +16,7 @@
 
 #include "common/macros.h"
 #include "common/ust-fd.h"
+#include "lib/lttng-ust-common/fd-tracker.h"
 
 #define LTTNG_UST_DLSYM_FAILED_PTR 0x1
 
@@ -60,25 +61,44 @@ void *_lttng_ust_fd_init_plibc_fclose(void)
        return __lttng_ust_fd_plibc_fclose;
 }
 
-static
-void _lttng_ust_fd_ctor(void)
-       __attribute__((constructor));
-static
-void _lttng_ust_fd_ctor(void)
-{
 #if !defined(LTTNG_UST_CUSTOM_UPGRADE_CONFLICTING_SYMBOLS)
-       void *handle = NULL;
 
+static void *lttng_ust_2_12_handle;
+
+static
+void lttng_ust_init_close_chaining(void)
+{
+       if (lttng_ust_2_12_handle)
+               return;
        /*
         * Load ust-2.12 in the global symbol namespace.
         */
-       handle = dlopen("liblttng-ust.so.0", RTLD_GLOBAL | RTLD_NOW);
-       if (!handle) {
+       lttng_ust_2_12_handle = dlopen("liblttng-ust.so.0", RTLD_GLOBAL | RTLD_NOW);
+       if (!lttng_ust_2_12_handle) {
                fprintf(stderr, "liblttng-ust-fd.so.1: Failed to dlopen liblttng-ust.so.0: %s\n", dlerror());
                abort();
        }
+       /*
+        * Initialize the function pointers to the ust 2.12 symbols in
+        * the constructor since close() has to stay async-signal-safe
+        * and as such, we can't call dlsym() in the override functions.
+        */
+       (void) lttng_ust_safe_close_fd_init();
+       (void) lttng_ust_safe_fclose_stream_init();
+}
+#else
+static
+void lttng_ust_init_close_chaining(void) { }
 #endif
 
+static
+void _lttng_ust_fd_ctor(void)
+       __attribute__((constructor));
+static
+void _lttng_ust_fd_ctor(void)
+{
+       lttng_ust_init_close_chaining();
+
        lttng_ust_common_ctor();
 
        /*
@@ -99,10 +119,13 @@ void _lttng_ust_fd_ctor(void)
  * errno=ENOSYS.
  *
  * There is a short window before the library constructor has executed where
- * this wrapper could call dlsym() and thus not be async-signal-safe.
+ * this wrapper could call dlsym() and dlopen() and thus not be
+ * async-signal-safe.
  */
 int close(int fd)
 {
+       lttng_ust_init_close_chaining();
+
        /*
         * We can't retry dlsym here since close is async-signal-safe.
         */
@@ -131,6 +154,8 @@ int close(int fd)
  */
 int fclose(FILE *stream)
 {
+       lttng_ust_init_close_chaining();
+
        if (_lttng_ust_fd_init_plibc_fclose() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) {
                errno = ENOSYS;
                return -1;
@@ -141,6 +166,9 @@ int fclose(FILE *stream)
 }
 
 #if defined(__sun__) || defined(__FreeBSD__)
+
+#error "Custom upgrade branch does not support Solaris/FreeBSD closefrom"
+
 /* Solaris and FreeBSD. */
 void closefrom(int lowfd)
 {
@@ -151,6 +179,9 @@ void closefrom(int lowfd)
        (void) lttng_ust_safe_closefrom_fd(lowfd, __lttng_ust_fd_plibc_close);
 }
 #elif defined(__NetBSD__) || defined(__OpenBSD__)
+
+#error "Custom upgrade branch does not support NetBSD/OpenBSD closefrom"
+
 /* NetBSD and OpenBSD. */
 int closefrom(int lowfd)
 {