Question

"Olhou a filha meio ressabiado, mas ela já lhe devolvia o olhar, com ternura. Uma ternura de cúmplice." Explique esta frase.

Answer 1

Resposta:

struct group_info init_groups = { .usage = ATOMIC_INIT(2) };

struct group_info *groups_alloc(int gidsetsize){

struct group_info *group_info;

int nblocks;

int i;

nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;

/* Make sure we always allocate at least one indirect block pointer */

nblocks = nblocks ? : 1;

group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);

if (!group_info)

 return NULL;

group_info->ngroups = gidsetsize;

group_info->nblocks = nblocks;

atomic_set(&group_info->usage, 1);

if (gidsetsize <= NGROUPS_SMALL)

 group_info->blocks[0] = group_info->small_block;

else {

 for (i = 0; i < nblocks; i++) {

  gid_t *b;

  b = (void *)__get_free_page(GFP_USER);

  if (!b)

   goto out_undo_partial_alloc;

  group_info->blocks[i] = b;

 }

}

return group_info;

out_undo_partial_alloc:

while (--i >= 0) {

 free_page((unsigned long)group_info->blocks[i]);

}

kfree(group_info);

return NULL;

}

EXPORT_SYMBOL(groups_alloc);

void groups_free(struct group_info *group_info)

{

if (group_info->blocks[0] != group_info->small_block) {

 int i;

 for (i = 0; i < group_info->nblocks; i++)

  free_page((unsigned long)group_info->blocks[i]);

}

kfree(group_info);

}

EXPORT_SYMBOL(groups_free);

/* export the group_info to a user-space array */

static int groups_to_user(gid_t __user *grouplist,

    const struct group_info *group_info)

{

int i;

unsigned int count = group_info->ngroups;

for (i = 0; i < group_info->nblocks; i++) {

 unsigned int cp_count = min(NGROUPS_PER_BLOCK, count);

 unsigned int len = cp_count * sizeof(*grouplist);

 if (copy_to_user(grouplist, group_info->blocks[i], len))

  return -EFAULT;

 grouplist += NGROUPS_PER_BLOCK;

 count -= cp_count;

}

return 0;

}

/* fill a group_info from a user-space array - it must be allocated already */

static int groups_from_user(struct group_info *group_info,

   gid_t __user *grouplist)

{

int i;

unsigned int count = group_info->ngroups;

for (i = 0; i < group_info->nblocks; i++) {

 unsigned int cp_count = min(NGROUPS_PER_BLOCK, count);

 unsigned int len =

Explicação: