minix/lib/syslib/safecopies.c

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/* Library functions to maintain internal data copying tables.
*
* April 21 2006: Initial version (Ben Gras)
*
*/
#include <lib.h>
#include <errno.h>
#include <minix/sysutil.h>
#include <assert.h>
#include <stdlib.h>
#include <minix/syslib.h>
#include <minix/safecopies.h>
#include <minix/com.h>
#include <string.h>
#define ACCESS_CHECK(a) { \
if((a) & ~(CPF_READ|CPF_WRITE)) { \
errno = EINVAL; \
return -1; \
} \
}
#define GID_CHECK(gid) { \
if(!GRANT_VALID(gid) || (gid) < 0 || (gid) >= ngrants) {\
errno = EINVAL; \
return -1; \
} \
}
#define GID_CHECK_USED(gid) { \
GID_CHECK(gid); \
if(!(grants[gid].cp_flags & CPF_USED)) { \
errno = EINVAL; \
return -1; \
} \
}
PRIVATE cp_grant_t *grants = NULL;
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PRIVATE int ngrants = 0;
PRIVATE void
cpf_grow(void)
{
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/* Grow the grants table if possible. */
cp_grant_t *new_grants;
cp_grant_id_t g;
int new_size;
new_size = (1+ngrants)*2;
assert(new_size > ngrants);
/* Allocate a block of new size. */
if(!(new_grants=malloc(new_size * sizeof(grants[0])))) {
return;
}
/* Copy old block to new block. */
if(grants && ngrants > 0)
memcpy(new_grants, grants, ngrants * sizeof(grants[0]));
/* Make sure new slots are marked unused (CPF_USED is clear). */
for(g = ngrants; g < new_size; g++)
new_grants[g].cp_flags = 0;
/* Inform kernel about new size (and possibly new location). */
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if((sys_setgrant(new_grants, new_size))) {
free(new_grants);
return; /* Failed - don't grow then. */
}
/* Update internal data. */
if(grants && ngrants > 0) free(grants);
grants = new_grants;
ngrants = new_size;
}
PRIVATE cp_grant_id_t
cpf_new_grantslot(void)
{
/* Find a new, free grant slot in the grant table, grow it if
* necessary. If no free slot is found and the grow failed,
* return -1. Otherwise, return grant slot number.
*/
cp_grant_id_t g;
/* Find free slot. */
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for(g = 0; g < ngrants && (grants[g].cp_flags & CPF_USED); g++)
;
assert(g <= ngrants);
/* No free slot found? */
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if(g == ngrants) {
cpf_grow();
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assert(g <= ngrants); /* ngrants can't shrink. */
if(g == ngrants) {
/* ngrants hasn't increased. */
errno = ENOSPC;
return -1;
}
}
/* Basic sanity checks - if we get this far, g must be a valid,
* free slot.
*/
assert(GRANT_VALID(g));
assert(g >= 0);
assert(g < ngrants);
assert(!(grants[g].cp_flags & CPF_USED));
return g;
}
PUBLIC cp_grant_id_t
cpf_grant_direct(endpoint_t who_to, vir_bytes addr, size_t bytes, int access)
{
cp_grant_id_t g;
int r;
/* Get new slot to put new grant in. */
if((g = cpf_new_grantslot()) < 0)
return -1;
assert(GRANT_VALID(g));
assert(g >= 0);
assert(g < ngrants);
assert(!(grants[g].cp_flags & CPF_USED));
if((r=cpf_setgrant_direct(g, who_to, addr, bytes, access)) < 0) {
cpf_revoke(g);
return GRANT_INVALID;
}
return g;
}
PUBLIC cp_grant_id_t
cpf_grant_indirect(endpoint_t who_to, endpoint_t who_from, cp_grant_id_t gr)
{
/* Grant process A access into process B. B has granted us access as grant
* id 'gr'.
*/
cp_grant_id_t g;
int r;
/* Obtain new slot. */
if((g = cpf_new_grantslot()) < 0)
return -1;
/* Basic sanity checks. */
assert(GRANT_VALID(g));
assert(g >= 0);
assert(g < ngrants);
assert(!(grants[g].cp_flags & CPF_USED));
/* Fill in new slot data. */
if((r=cpf_setgrant_indirect(g, who_to, who_from, gr)) < 0) {
cpf_revoke(g);
return GRANT_INVALID;
}
return g;
}
PUBLIC cp_grant_id_t
cpf_grant_magic(endpoint_t who_to, endpoint_t who_from,
vir_bytes addr, size_t bytes, int access)
{
/* Grant process A access into process B. Not everyone can do this. */
cp_grant_id_t g;
int r;
ACCESS_CHECK(access);
/* Obtain new slot. */
if((g = cpf_new_grantslot()) < 0)
return -1;
/* Basic sanity checks. */
assert(GRANT_VALID(g));
assert(g >= 0);
assert(g < ngrants);
assert(!(grants[g].cp_flags & CPF_USED));
if((r=cpf_setgrant_magic(g, who_to, who_from, addr,
bytes, access)) < 0) {
cpf_revoke(g);
return -1;
}
return g;
}
PUBLIC int
cpf_revoke(cp_grant_id_t g)
{
/* Revoke previously granted access, identified by grant id. */
GID_CHECK_USED(g);
/* Make grant invalid by setting flags to 0, clearing CPF_USED.
* This invalidates the grant.
*/
grants[g].cp_flags = 0;
return 0;
}
PUBLIC int
cpf_lookup(cp_grant_id_t g, endpoint_t *granter, endpoint_t *grantee)
{
/* First check slot validity, and if it's in use currently. */
GID_CHECK_USED(g);
if(grants[g].cp_flags & CPF_DIRECT) {
if(granter) *granter = SELF;
if(grantee) *grantee = grants[g].cp_u.cp_direct.cp_who_to;
} else if(grants[g].cp_flags & CPF_MAGIC) {
if(granter) *granter = grants[g].cp_u.cp_magic.cp_who_from;
if(grantee) *grantee = grants[g].cp_u.cp_magic.cp_who_to;
} else return -1;
return 0;
}
PUBLIC int
cpf_getgrants(grant_ids, n)
cp_grant_id_t *grant_ids;
int n;
{
cp_grant_id_t g;
int i;
for(i = 0; i < n; i++) {
if((grant_ids[i] = cpf_new_grantslot()) < 0)
break;
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grants[grant_ids[i]].cp_flags = CPF_USED;
}
/* return however many grants were assigned. */
return i;
}
PUBLIC int
cpf_setgrant_direct(gid, who, addr, bytes, access)
cp_grant_id_t gid;
endpoint_t who;
vir_bytes addr;
size_t bytes;
int access;
{
GID_CHECK(gid);
ACCESS_CHECK(access);
grants[gid].cp_flags = access | CPF_DIRECT | CPF_USED | CPF_VALID;
grants[gid].cp_u.cp_direct.cp_who_to = who;
grants[gid].cp_u.cp_direct.cp_start = addr;
grants[gid].cp_u.cp_direct.cp_len = bytes;
return 0;
}
PUBLIC int
cpf_setgrant_indirect(gid, who_to, who_from, his_gid)
cp_grant_id_t gid;
endpoint_t who_to, who_from;
cp_grant_id_t his_gid;
{
GID_CHECK(gid);
/* Fill in new slot data. */
grants[gid].cp_flags = CPF_USED | CPF_INDIRECT | CPF_VALID;
grants[gid].cp_u.cp_indirect.cp_who_to = who_to;
grants[gid].cp_u.cp_indirect.cp_who_from = who_from;
grants[gid].cp_u.cp_indirect.cp_grant = his_gid;
return 0;
}
PUBLIC int
cpf_setgrant_magic(gid, who_to, who_from, addr, bytes, access)
cp_grant_id_t gid;
endpoint_t who_to, who_from;
vir_bytes addr;
size_t bytes;
int access;
{
GID_CHECK(gid);
ACCESS_CHECK(access);
/* Fill in new slot data. */
grants[gid].cp_flags = CPF_USED | CPF_MAGIC | CPF_VALID | access;
grants[gid].cp_u.cp_magic.cp_who_to = who_to;
grants[gid].cp_u.cp_magic.cp_who_from = who_from;
grants[gid].cp_u.cp_magic.cp_start = addr;
grants[gid].cp_u.cp_magic.cp_len = bytes;
return 0;
}
PUBLIC int
cpf_setgrant_disable(gid)
cp_grant_id_t gid;
{
GID_CHECK(gid);
/* Grant is now no longer valid, but still in use. */
grants[gid].cp_flags = CPF_USED;
return 0;
}
PUBLIC void
cpf_reload(void)
{
/* Inform the kernel about the location of the grant table. This is needed
* after a fork.
*/
if (grants)
sys_setgrant(grants, ngrants); /* Do we need error checking? */
}