From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Tue, 13 Oct 2020 18:55:33 +0000 (-0400)
Subject: Fix: lttng-ctl: erroneous uses of LTTNG_PACKED
X-Git-Tag: v2.13.0-rc1~464
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=7bd95aee4660c6419a4a65429fc27754481e7e90;p=lttng-tools.git

Fix: lttng-ctl: erroneous uses of LTTNG_PACKED

The LTTNG_PACKED macro uses gcc attributes to indicate that a structure
should be packed. Hence, this macro obeys the same rules as the gcc
attribute.

Various mis-uses of the LTTNG_PACKED macros may result in structure not
being packed:
  - The LTTNG_PACKED macro should always be placed _before_ an identifier
    when a structure is declared in-place.
  - Adding LTTNG_PACKED at the definition site has no effect if the
    structure was declared elsewhere.

Those mis-uses cause issues when mixing the bitness (32/64) of the
session daemon and liblttng-ctl.

Outstanding issues include the following structures that are not
tagged as LTTNG_PACKED:
  - struct lttng_event
  - struct lttng_channel
  - struct lttng_event_context

Unfortunately, those structures are exposed by the public API and
can't be tagged as being "packed". Doing so would break the ABI
of liblttng-ctl.

These structures should be packed/unpacked explicitly.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I095dc0dffc6bf9e15dc7a7ec797958a5780ef150
---

diff --git a/include/lttng/session-internal.h b/include/lttng/session-internal.h
index b263377de..305c3f5f5 100644
--- a/include/lttng/session-internal.h
+++ b/include/lttng/session-internal.h
@@ -15,7 +15,7 @@ struct lttng_session_extended {
 	struct {
 		uint64_t value;
 		uint8_t is_set;
-	} creation_time LTTNG_PACKED;
+	} LTTNG_PACKED creation_time;
 } LTTNG_PACKED;
 
 #endif /* LTTNG_SESSION_INTERNAL_H */
diff --git a/include/lttng/snapshot-internal.h b/include/lttng/snapshot-internal.h
index 8012a1e4e..78c741349 100644
--- a/include/lttng/snapshot-internal.h
+++ b/include/lttng/snapshot-internal.h
@@ -11,6 +11,7 @@
 #include <limits.h>
 #include <stdint.h>
 #include <lttng/constant.h>
+#include <common/macros.h>
 
 /*
  * Object used for the snapshot API. This is opaque to the public library.
@@ -33,7 +34,7 @@ struct lttng_snapshot_output {
 	char ctrl_url[PATH_MAX];
 	/* Destination of the output. See lttng(1) for URL format. */
 	char data_url[PATH_MAX];
-};
+} LTTNG_PACKED;
 
 /*
  * Snapshot output list object opaque to the user.
diff --git a/src/common/sessiond-comm/sessiond-comm.h b/src/common/sessiond-comm/sessiond-comm.h
index c15a26f88..fca331fe7 100644
--- a/src/common/sessiond-comm/sessiond-comm.h
+++ b/src/common/sessiond-comm/sessiond-comm.h
@@ -283,7 +283,7 @@ struct lttcomm_session_msg {
 		/* Event data */
 		struct {
 			char channel_name[LTTNG_SYMBOL_NAME_LEN];
-			struct lttng_event event LTTNG_PACKED;
+			struct lttng_event event;
 			/* Length of following filter expression. */
 			uint32_t expression_len;
 			/* Length of following bytecode for filter. */
@@ -302,7 +302,7 @@ struct lttcomm_session_msg {
 		} LTTNG_PACKED enable;
 		struct {
 			char channel_name[LTTNG_SYMBOL_NAME_LEN];
-			struct lttng_event event LTTNG_PACKED;
+			struct lttng_event event;
 			/* Length of following filter expression. */
 			uint32_t expression_len;
 			/* Length of following bytecode for filter. */
@@ -316,14 +316,13 @@ struct lttcomm_session_msg {
 		} LTTNG_PACKED disable;
 		/* Create channel */
 		struct {
-			struct lttng_channel chan LTTNG_PACKED;
-			/* struct lttng_channel_extended is already packed. */
+			struct lttng_channel chan;
 			struct lttng_channel_extended extended;
 		} LTTNG_PACKED channel;
 		/* Context */
 		struct {
 			char channel_name[LTTNG_SYMBOL_NAME_LEN];
-			struct lttng_event_context ctx LTTNG_PACKED;
+			struct lttng_event_context ctx;
 			uint32_t provider_name_len;
 			uint32_t context_name_len;
 		} LTTNG_PACKED context;
@@ -342,18 +341,18 @@ struct lttcomm_session_msg {
 			uint32_t size;
 		} LTTNG_PACKED uri;
 		struct {
-			struct lttng_snapshot_output output LTTNG_PACKED;
+			struct lttng_snapshot_output output;
 		} LTTNG_PACKED snapshot_output;
 		struct {
 			uint32_t wait;
-			struct lttng_snapshot_output output LTTNG_PACKED;
+			struct lttng_snapshot_output output;
 		} LTTNG_PACKED snapshot_record;
 		struct {
 			uint32_t nb_uri;
 			unsigned int timer_interval;	/* usec */
 		} LTTNG_PACKED session_live;
 		struct {
-			struct lttng_save_session_attr attr; /* struct already packed */
+			struct lttng_save_session_attr attr;
 		} LTTNG_PACKED save_session;
 		struct {
 			char shm_path[PATH_MAX];