restore: add arch_prctl mapping compatible vDSO

Map here instead of park before unmap.
TODO: need to check that mapped size is smaller than x86_64 vDSO.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/cr-restore.c

@@ -2957,6 +2957,7 @@ static int sigreturn_restore(pid_t pid, struct task_restore_args *task_args, uns
 	if (core->tc->has_seccomp_mode)
 		task_args->seccomp_mode = core->tc->seccomp_mode;
 
+	task_args->compatible_mode = core_is_compat(core);
 	/*
 	 * Arguments for task restoration.
 	 */

criu/include/parasite-vdso.h

@@ -80,12 +80,14 @@ static inline bool is_vdso_mark(void *addr)
 }
 
 extern int vdso_do_park(struct vdso_symtable *sym_rt, unsigned long park_at, unsigned long park_size);
+int vdso_map_compat(unsigned long map_at);
 extern int vdso_proxify(char *who, struct vdso_symtable *sym_rt,
 			unsigned long vdso_rt_parked_at, size_t index,
 			VmaEntry *vmas, size_t nr_vmas);
 
 #else /* CONFIG_VDSO */
 #define vdso_do_park(sym_rt, park_at, park_size)		(0)
+#define vdso_map_compat(map_at)					(0)
 
 #endif /* CONFIG_VDSO */
 

criu/include/restorer.h

@@ -174,6 +174,8 @@ struct task_restore_args {
 
 	int				seccomp_mode;
 
+	bool				compatible_mode;
+
 #ifdef CONFIG_VDSO
 	unsigned long			vdso_rt_size;
 	struct vdso_symtable		vdso_sym_rt;		/* runtime vdso symbols */

criu/pie/parasite-vdso.c

@@ -68,6 +68,26 @@ int vdso_do_park(struct vdso_symtable *sym_rt, unsigned long park_at, unsigned l
 	return ret;
 }
 
+#ifdef CONFIG_X86_64
+#ifndef ARCH_MAP_VDSO_32
+# define ARCH_MAP_VDSO_32	0x2002
+#endif
+int vdso_map_compat(unsigned long map_at)
+{
+	int ret;
+
+	pr_debug("Mapping compatible vDSO at %lx\n", map_at);
+
+	ret = sys_arch_prctl(ARCH_MAP_VDSO_32, map_at);
+	return ret;
+}
+#else
+int vdso_map_compat(unsigned long map_at)
+{
+	return 0;
+}
+#endif
+
 int vdso_proxify(char *who, struct vdso_symtable *sym_rt,
 		 unsigned long vdso_rt_parked_at, size_t index,
 		 VmaEntry *vmas, size_t nr_vmas)

criu/pie/restorer.c

@@ -1087,13 +1087,23 @@ long __export_restore_task(struct task_restore_args *args)
 
 	pr_info("Switched to the restorer %d\n", my_pid);
 
-	if (vdso_do_park(&args->vdso_sym_rt, args->vdso_rt_parked_at, vdso_rt_size))
-		goto core_restore_end;
+	if (!args->compatible_mode) {
+		/* Compatible vDSO will be mapped, not moved */
+		if (vdso_do_park(&args->vdso_sym_rt,
+				args->vdso_rt_parked_at, vdso_rt_size))
+			goto core_restore_end;
+	}
 
 	if (unmap_old_vmas((void *)args->premmapped_addr, args->premmapped_len,
 				bootstrap_start, bootstrap_len, args->task_size))
 		goto core_restore_end;
 
+	if (args->compatible_mode) {
+		/* Map compatible vdso */
+		if (vdso_map_compat(args->vdso_rt_parked_at))
+			goto core_restore_end;
+	}
+
 	/* Shift private vma-s to the left */
 	for (i = 0; i < args->vmas_n; i++) {
 		vma_entry = args->vmas + i;