user_namespace详解（1）

user_namespace
struct user_namespace init_user_ns = {
 .uid_map = {
  .nr_extents = 1,
  .extent[0] = {
   .first = 0,
   .lower_first = 0,
   .count = 4294967295U,
  },
 },
 .gid_map = {
  .nr_extents = 1,
  .extent[0] = {
   .first = 0,
   .lower_first = 0,
   .count = 4294967295U,
  },
 },
 .projid_map = {
  .nr_extents = 1,
  .extent[0] = {
   .first = 0,
   .lower_first = 0,
   .count = 4294967295U,
  },
 },
 .count = ATOMIC_INIT(3),
 .owner = GLOBAL_ROOT_UID,
 .group = GLOBAL_ROOT_GID,
 .proc_inum = PROC_USER_INIT_INO,
};

struct cred init_cred = {
 .usage   = ATOMIC_INIT(4),
#ifdef CONFIG_DEBUG_CREDENTIALS
 .subscribers  = ATOMIC_INIT(2),
 .magic   = CRED_MAGIC,
#endif
 .uid   = GLOBAL_ROOT_UID,
 .gid   = GLOBAL_ROOT_GID,
 .suid   = GLOBAL_ROOT_UID,
 .sgid   = GLOBAL_ROOT_GID,
 .euid   = GLOBAL_ROOT_UID,
 .egid   = GLOBAL_ROOT_GID,
 .fsuid   = GLOBAL_ROOT_UID,
 .fsgid   = GLOBAL_ROOT_GID,
 .securebits  = SECUREBITS_DEFAULT,
 .cap_inheritable = CAP_EMPTY_SET,
 .cap_permitted  = CAP_FULL_SET,
 .cap_effective  = CAP_FULL_SET,
 .cap_bset  = CAP_FULL_SET,
 .user   = INIT_USER,
 .user_ns  = &init_user_ns,
 .group_info  = &init_groups,
};