restorer: refill symtable for rt-vdso

Otherwise, we still have parsed x86_64 vdso symtable.
After this:
  pie: 17917: vdso: Mapping compatible vDSO at 0x25000
  pie: 17917: vdso: Parsing at 0x25000 0x29000
  pie: 17917: Error (pie/util-vdso-elf32.c:87): vdso: Elf header magic m>
  pie: 17917: ismatch
  pie: 17917: vdso: Parsing at 0x26000 0x29000
  pie: 17917: Error (pie/util-vdso-elf32.c:87): vdso: Elf header magic m>
  pie: 17917: ismatch
  pie: 17917: vdso: Parsing at 0x27000 0x29000
  pie: 17917: vdso: PT_LOAD p_vaddr: 0x0
  pie: 17917: vdso: DT_HASH: 0xb4
  pie: 17917: vdso: DT_STRTAB: 0x1c0
  pie: 17917: vdso: DT_SYMTAB: 0x130
  pie: 17917: vdso: DT_STRSZ: 0x95
  pie: 17917: vdso: DT_SYMENT: 0x10
  pie: 17917: vdso: nbucket 0x3 nchain 0x9 bucket 0x270bc chain 0x270c8

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/include/parasite-vdso.h

@@ -80,14 +80,15 @@ 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_map_compat(unsigned long map_at, unsigned long park_size,
+		struct vdso_symtable *sym_rt);
 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, bool compat_vdso);
 
 #else /* CONFIG_VDSO */
 #define vdso_do_park(sym_rt, park_at, park_size)		(0)
-#define vdso_map_compat(map_at)					(0)
+#define vdso_map_compat(map_at, park_size, sym_rt)		(0)
 
 #endif /* CONFIG_VDSO */
 

criu/pie/parasite-vdso.c

@@ -72,18 +72,37 @@ int vdso_do_park(struct vdso_symtable *sym_rt, unsigned long park_at, unsigned l
 #ifndef ARCH_MAP_VDSO_32
 # define ARCH_MAP_VDSO_32	0x2002
 #endif
-int vdso_map_compat(unsigned long map_at)
+extern int vdso_fill_symtable_compat(uintptr_t mem, size_t size,
+		struct vdso_symtable *t);
+
+int vdso_map_compat(unsigned long map_at, unsigned long park_size,
+		struct vdso_symtable *sym_rt)
 {
+	unsigned long search_vdso;
 	int ret;
 
 	pr_debug("Mapping compatible vDSO at %lx\n", map_at);
 
 	ret = sys_arch_prctl(ARCH_MAP_VDSO_32, map_at);
+	if (ret)
+		return ret;
+
+	/*
+	 * We could map VVAR firstly, or VDSO.
+	 * Try to find VDSO pages in this couple of parking pages.
+	 */
+	for (search_vdso = map_at; search_vdso < map_at + park_size;
+			search_vdso += PAGE_SIZE)
+	{
+		ret = vdso_fill_symtable_compat(search_vdso,
+			map_at + park_size - search_vdso, sym_rt);
+		if (!ret)
+			return 0;
+	}
+	pr_err("Failed to parse a arch_prctl-mapped vDSO %d\n", ret);
 	return ret;
 }
 
-extern int vdso_fill_symtable_compat(uintptr_t mem, size_t size,
-		struct vdso_symtable *t);
 int __vdso_fill_symtable(uintptr_t mem, size_t size,
 		struct vdso_symtable *t, bool compat_vdso)
 {
@@ -93,7 +112,9 @@ int __vdso_fill_symtable(uintptr_t mem, size_t size,
 		return vdso_fill_symtable(mem, size, t);
 }
 #else
-int vdso_map_compat(unsigned long map_at)
+int vdso_map_compat(unsigned long __always_unused map_at,
+		unsigned long __always_unused park_size,
+		struct vdso_symtable __always_unused *sym_rt)
 {
 	return 0;
 }

criu/pie/restorer.c

@@ -1100,7 +1100,8 @@ long __export_restore_task(struct task_restore_args *args)
 
 	if (args->compatible_mode) {
 		/* Map compatible vdso */
-		if (vdso_map_compat(args->vdso_rt_parked_at))
+		if (vdso_map_compat(args->vdso_rt_parked_at,
+				vdso_rt_size, &args->vdso_sym_rt))
 			goto core_restore_end;
 	}