X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=libringbuffer%2Fshm.c;h=c10e58a23cc281fb06128c93d16697efc2d0b019;hb=dda4784f1d19fa0426cbaae0738c054ee4d39cba;hp=563903877f5eb59a62409ce32662a8bd6f7600bd;hpb=a88038977008704e88544601cef0291b138f8387;p=lttng-ust.git

diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 56390387..c10e58a2 100644
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -13,7 +13,12 @@
 #include <sys/stat.h>	/* For mode constants */
 #include <fcntl.h>	/* For O_* constants */
 #include <assert.h>
-#include <ust/align.h>
+#include <stdio.h>
+#include <signal.h>
+#include <dirent.h>
+#include <lttng/align.h>
+#include <helper.h>
+#include <limits.h>
 
 struct shm_object_table *shm_object_table_create(size_t max_nb_obj)
 {
@@ -28,9 +33,11 @@ struct shm_object_table *shm_object_table_create(size_t max_nb_obj)
 struct shm_object *shm_object_table_append(struct shm_object_table *table,
 					   size_t memory_map_size)
 {
-	int shmfd, waitfd[2], ret, i;
+	int shmfd, waitfd[2], ret, i, sigblocked = 0;
 	struct shm_object *obj;
 	char *memory_map;
+	char tmp_name[NAME_MAX] = "/ust-shm-tmp-XXXXXX";
+	sigset_t all_sigs, orig_sigs;
 
 	if (table->allocated_len >= table->size)
 		return NULL;
@@ -59,6 +66,19 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 
 	/* shm_fd: create shm */
 
+	/*
+	 * Theoretically, we could leak a shm if the application crashes
+	 * between open and unlink. Disable signals on this thread for
+	 * increased safety against this scenario.
+	 */
+	sigfillset(&all_sigs);
+	ret = pthread_sigmask(SIG_BLOCK, &all_sigs, &orig_sigs);
+	if (ret == -1) {
+		PERROR("pthread_sigmask");
+		goto error_pthread_sigmask;
+	}
+	sigblocked = 1;
+
 	/*
 	 * Allocate shm, and immediately unlink its shm oject, keeping
 	 * only the file descriptor as a reference to the object. If it
@@ -67,30 +87,35 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 	 * We specifically do _not_ use the / at the beginning of the
 	 * pathname so that some OS implementations can keep it local to
 	 * the process (POSIX leaves this implementation-defined).
-	 * Ignore the shm_unlink errors, because we handle leaks that
-	 * could occur by applications crashing between shm_open and
-	 * shm_unlink by unlinking the shm before every open. Therefore,
-	 * we can only leak one single shm (and only if the application
-	 * crashes between shm_open and the following shm_unlink).
 	 */
 	do {
-		ret = shm_unlink("ust-shm-tmp");
-		if (ret < 0 && errno != ENOENT) {
-			PERROR("shm_unlink");
-			goto error_shm_unlink;
+		/*
+		 * Using mktemp filename with O_CREAT | O_EXCL open
+		 * flags.
+		 */
+		mktemp(tmp_name);
+		if (tmp_name[0] == '\0') {
+			PERROR("mktemp");
+			goto error_shm_open;
 		}
-		shmfd = shm_open("ust-shm-tmp",
+		shmfd = shm_open(tmp_name,
 				 O_CREAT | O_EXCL | O_RDWR, 0700);
-	} while (shmfd < 0 && errno == EEXIST);
+	} while (shmfd < 0 && (errno == EEXIST || errno == EACCES));
 	if (shmfd < 0) {
 		PERROR("shm_open");
 		goto error_shm_open;
 	}
-	ret = shm_unlink("ust-shm-tmp");
+	ret = shm_unlink(tmp_name);
 	if (ret < 0 && errno != ENOENT) {
 		PERROR("shm_unlink");
 		goto error_shm_release;
 	}
+	sigblocked = 0;
+	ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
+	if (ret == -1) {
+		PERROR("pthread_sigmask");
+		goto error_sigmask_release;
+	}
 	ret = ftruncate(shmfd, memory_map_size);
 	if (ret) {
 		PERROR("ftruncate");
@@ -115,13 +140,20 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 error_mmap:
 error_ftruncate:
 error_shm_release:
+error_sigmask_release:
 	ret = close(shmfd);
 	if (ret) {
 		PERROR("close");
 		assert(0);
 	}
-error_shm_unlink:
 error_shm_open:
+	if (sigblocked) {
+		ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
+		if (ret == -1) {
+			PERROR("pthread_sigmask");
+		}
+	}
+error_pthread_sigmask:
 error_fcntl:
 	for (i = 0; i < 2; i++) {
 		ret = close(waitfd[i]);
@@ -135,22 +167,61 @@ error_pipe:
 	
 }
 
+struct shm_object *shm_object_table_append_shadow(struct shm_object_table *table,
+			int shm_fd, int wait_fd, size_t memory_map_size)
+{
+	struct shm_object *obj;
+	char *memory_map;
+
+	if (table->allocated_len >= table->size)
+		return NULL;
+	obj = &table->objects[table->allocated_len];
+
+	/* wait_fd: set read end of the pipe. */
+	obj->wait_fd[0] = wait_fd;
+	obj->wait_fd[1] = -1;	/* write end is unset. */
+	obj->shm_fd = shm_fd;
+
+	/* memory_map: mmap */
+	memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE,
+			  MAP_SHARED, shm_fd, 0);
+	if (memory_map == MAP_FAILED) {
+		PERROR("mmap");
+		goto error_mmap;
+	}
+	obj->memory_map = memory_map;
+	obj->memory_map_size = memory_map_size;
+	obj->allocated_len = memory_map_size;
+	obj->index = table->allocated_len++;
+
+	return obj;
+
+error_mmap:
+	return NULL;
+}
+
 static
 void shmp_object_destroy(struct shm_object *obj)
 {
 	int ret, i;
 
-        ret = munmap(obj->memory_map, obj->memory_map_size);
-        if (ret) {
-                PERROR("umnmap");
-                assert(0);
-        }
-	ret = close(obj->shm_fd);
-	if (ret) {
-		PERROR("close");
-		assert(0);
+	if (!obj->is_shadow) {
+		ret = munmap(obj->memory_map, obj->memory_map_size);
+		if (ret) {
+			PERROR("umnmap");
+			assert(0);
+		}
+	}
+	if (obj->shm_fd >= 0) {
+		ret = close(obj->shm_fd);
+		if (ret) {
+			PERROR("close");
+			assert(0);
+		}
 	}
 	for (i = 0; i < 2; i++) {
+		if (obj->wait_fd[i] < 0)
+			continue;
 		ret = close(obj->wait_fd[i]);
 		if (ret) {
 			PERROR("close");