[CRIU] [PATCH 2/5] seize: Reorder struct proc_status_creds

[Kirill Tkhai]

Time goes, and new fields are being implemented
in /proc/[pid]/status file. Some of them may be
variable len, e.g. NSpid and friends.

Next patches will allow struct seize_task_status
be extensible to confirm the time challenges. So,
in this case simple comparation in creds_dumpable()
won't work, as we're interested in currently known
fields there.

The patch reorders struct proc_status_creds and
places proc_status_creds::s before uncompared fields.
This will allow to continue use memcpy() to compare
the data from beginning of struct proc_status_creds
to proc_status_creds::s::seccomp_mode.

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 criu/include/proc_parse.h |    7 +++----
 criu/seize.c              |    5 ++++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/criu/include/proc_parse.h b/criu/include/proc_parse.h
index d67ac5e56..91f2adb51 100644
--- a/criu/include/proc_parse.h
+++ b/criu/include/proc_parse.h
@@ -73,17 +73,16 @@ struct seccomp_info {
 #define PROC_CAP_SIZE	2
 
 struct proc_status_creds {
-	struct seize_task_status s;
-
 	unsigned int uids[4];
 	unsigned int gids[4];
 
 	u32			last_filter;
 
 	/*
-	 * Keep them at the end of structure
-	 * for fast comparison reason.
+	 * Keep them at the end of structure for fast comparison
+	 * reason (see creds_dumpable()); and place s before caps.
 	 */
+	struct seize_task_status s;
 	u32			cap_inh[PROC_CAP_SIZE];
 	u32			cap_prm[PROC_CAP_SIZE];
 	u32			cap_eff[PROC_CAP_SIZE];
diff --git a/criu/seize.c b/criu/seize.c
index eda4e8a27..5727b8ff8 100644
--- a/criu/seize.c
+++ b/criu/seize.c
@@ -629,7 +629,10 @@ static inline bool thread_collected(struct pstree_item *i, pid_t tid)
 static bool creds_dumpable(struct proc_status_creds *parent,
 				struct proc_status_creds *child)
 {
-	const size_t size = offsetof(struct proc_status_creds, cap_inh);
+	/* From beginning of struct to proc_status_creds::s::seccomp_mode */
+	const size_t size = ((unsigned long)&parent->s.seccomp_mode) -
+			    ((unsigned long)parent) +
+			    sizeof(parent->s.seccomp_mode);
 
 	/*
 	 * The comparison rules are the following