[CRIU] [PATCHv3 3/4] cr-exec: initialize kdat.{task_size, has_compat_sigreturn} on criu exec

[Dmitry Safonov]

For `criu exec` we are searching for a place for syscall injection.
While searching for a VMA with PROT_EXEC and with needed size,
we check that VMA is lower than task_size.
The callpath for it is:
cr_exec => parasite_prep_ctl => get_vma_by_ip

Firstly, I thought to omit kdat.task_size checking if it's not inited:
> if (vma_area->e->start >= kdat.task_size && kdat.task_size)
but I think it's a hack then a proper solution.
Besides, this code still can choose VMA over task_size on ARM
and try to inject syscall there (IIRC, ARM has kernel-mapped
VMA in that area).

So, lets init kdat.task_size for `criu exec`.
Also lets init kdat.has_compat_sigreturn so we could exec into
compatible applications.

Cc: Christopher Covington <cov at codeaurora.org>
Cc: Andrew Vagin <avagin at virtuozzo.com>
Cc: Cyrill Gorcunov <gorcunov at openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
---
 criu/cr-exec.c         |  6 ++++++
 criu/include/kerndat.h |  1 +
 criu/kerndat.c         | 11 +++++++++++
 3 files changed, 18 insertions(+)

diff --git a/criu/cr-exec.c b/criu/cr-exec.c
index e8177388686b..42fb90f60123 100644
--- a/criu/cr-exec.c
+++ b/criu/cr-exec.c
@@ -7,6 +7,7 @@
 #include "vma.h"
 #include "log.h"
 #include "util.h"
+#include "kerndat.h"
 
 struct syscall_exec_desc {
 	char *name;
@@ -125,6 +126,11 @@ int cr_exec(int pid, char **opt)
 		goto out;
 	}
 
+	if (kerndat_init_cr_exec()) {
+		pr_err("Failed to init kerndat\n");
+		goto out;
+	}
+
 	if (seize_catch_task(pid))
 		goto out;
 
diff --git a/criu/include/kerndat.h b/criu/include/kerndat.h
index e1bf7ad043c6..0a5cd4bfac57 100644
--- a/criu/include/kerndat.h
+++ b/criu/include/kerndat.h
@@ -12,6 +12,7 @@ struct stat;
 
 extern int kerndat_init(void);
 extern int kerndat_init_rst(void);
+extern int kerndat_init_cr_exec(void);
 extern int kerndat_get_dirty_track(void);
 extern int kerndat_fdinfo_has_lock(void);
 extern int kerndat_loginuid(bool only_dump);
diff --git a/criu/kerndat.c b/criu/kerndat.c
index 07f848e7bae0..04a355ba4505 100644
--- a/criu/kerndat.c
+++ b/criu/kerndat.c
@@ -521,3 +521,14 @@ int kerndat_init_rst(void)
 
 	return ret;
 }
+
+int kerndat_init_cr_exec(void)
+{
+	int ret;
+
+	ret = get_task_size();
+	if (!ret)
+		ret = kerndat_compat_restore();
+
+	return ret;
+}
-- 
2.9.0