X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;ds=sidebyside;f=src%2Flib%2Flttng-ust-fd%2Flttng-ust-fd.c;fp=src%2Flib%2Flttng-ust-fd%2Flttng-ust-fd.c;h=0360b6f269a85eca5db049bacf258492b7c97249;hb=4b01076fea0f635af6af6762a8edce1be03e5d39;hp=d2ebcfbc38be862b6effffdc490f7a7d0ce968cb;hpb=9c3f3d0208bab524c94466b8cc6bb1dcbc4a906b;p=lttng-ust.git

diff --git a/src/lib/lttng-ust-fd/lttng-ust-fd.c b/src/lib/lttng-ust-fd/lttng-ust-fd.c
index d2ebcfbc..0360b6f2 100644
--- a/src/lib/lttng-ust-fd/lttng-ust-fd.c
+++ b/src/lib/lttng-ust-fd/lttng-ust-fd.c
@@ -21,6 +21,8 @@
 
 static int (*__lttng_ust_fd_plibc_close)(int fd) = NULL;
 static int (*__lttng_ust_fd_plibc_fclose)(FILE *stream) = NULL;
+static int (*__lttng_ust_fd_plibc_close_range)(unsigned int first,
+		unsigned int last, int flags) = NULL;
 
 /*
  * Use dlsym to find the original libc close() symbol and store it in
@@ -60,6 +62,24 @@ void *_lttng_ust_fd_init_plibc_fclose(void)
 	return __lttng_ust_fd_plibc_fclose;
 }
 
+/*
+ * Use dlsym to find the original libc close_range() symbol and store it
+ * in __lttng_ust_fd_plibc_close_range. The close_range symbol only
+ * appears in glibc 2.34, so it is considered optional.
+ */
+static
+void *_lttng_ust_fd_init_plibc_close_range(void)
+{
+	if (__lttng_ust_fd_plibc_close_range == NULL) {
+		__lttng_ust_fd_plibc_close_range = dlsym(RTLD_NEXT, "close_range");
+
+		if (__lttng_ust_fd_plibc_close_range == NULL)
+			__lttng_ust_fd_plibc_close_range = (void *) LTTNG_UST_DLSYM_FAILED_PTR;
+	}
+
+	return __lttng_ust_fd_plibc_close_range;
+}
+
 static
 void _lttng_ust_fd_ctor(void)
 	__attribute__((constructor));
@@ -75,6 +95,7 @@ void _lttng_ust_fd_ctor(void)
 	 */
 	(void) _lttng_ust_fd_init_plibc_close();
 	(void) _lttng_ust_fd_init_plibc_fclose();
+	(void) _lttng_ust_fd_init_plibc_close_range();
 }
 
 /*
@@ -127,6 +148,30 @@ int fclose(FILE *stream)
 			__lttng_ust_fd_plibc_fclose);
 }
 
+/*
+ * Override the libc close_range() symbol with our own, allowing
+ * applications to close arbitrary file descriptors. If the fd is owned
+ * by lttng-ust, return -1, errno=EBADF instead of closing it.
+ *
+ * If dlsym failed to find the original libc close_range() symbol,
+ * return -1, 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.
+ */
+int close_range(unsigned int first, unsigned int last, int flags)
+{
+	/*
+	 * We can't retry dlsym here since close is async-signal-safe.
+	 */
+	if (_lttng_ust_fd_init_plibc_close_range() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) {
+		errno = ENOSYS;
+		return -1;
+	}
+
+	return lttng_ust_safe_close_range_fd(first, last, flags, __lttng_ust_fd_plibc_close_range);
+}
+
 #if defined(__sun__) || defined(__FreeBSD__)
 /* Solaris and FreeBSD. */
 void closefrom(int lowfd)