blob: 7b6de87bf101f771647f426af005df51a3dfd86e [file] [log] [blame]
/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
// NOLINTNEXTLINE(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp)
#define _GNU_SOURCE
#include <libpldm/instance-id.h>
#include <libpldm/pldm.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#define BIT(i) (1UL << (i))
#define PLDM_TID_MAX 256
#define PLDM_INST_ID_MAX 32
/* We need to track our allocations explicitly due to OFD lock merging/splitting
*/
struct pldm_tid_state {
pldm_instance_id_t prev;
uint32_t allocations;
};
struct pldm_instance_db {
struct pldm_tid_state state[PLDM_TID_MAX];
int lock_db_fd;
};
static inline int iid_next(pldm_instance_id_t cur)
{
return (cur + 1) % PLDM_INST_ID_MAX;
}
LIBPLDM_ABI_STABLE
int pldm_instance_db_init(struct pldm_instance_db **ctx, const char *dbpath)
{
struct pldm_instance_db *l_ctx;
struct stat statbuf;
int rc;
/* Make sure the provided pointer was initialised to NULL. In the future
* if we stabilise the ABI and expose the struct definition the caller
* can potentially pass a valid pointer to a struct they've allocated
*/
if (!ctx || *ctx) {
return -EINVAL;
}
/* Ensure the underlying file is sized for properly managing allocations
*/
rc = stat(dbpath, &statbuf);
if (rc < 0) {
return -EINVAL;
}
if (statbuf.st_size <
((off_t)(PLDM_TID_MAX) * (off_t)(PLDM_INST_ID_MAX))) {
return -EINVAL;
}
l_ctx = calloc(1, sizeof(struct pldm_instance_db));
if (!l_ctx) {
return -ENOMEM;
}
/* Initialise previous ID values so the next one is zero */
for (int i = 0; i < PLDM_TID_MAX; i++) {
l_ctx->state[i].prev = 31;
}
/* Lock database may be read-only, either by permissions or mountpoint
*/
l_ctx->lock_db_fd = open(dbpath, O_RDONLY | O_CLOEXEC);
if (l_ctx->lock_db_fd < 0) {
free(l_ctx);
return -errno;
}
*ctx = l_ctx;
return 0;
}
LIBPLDM_ABI_STABLE
int pldm_instance_db_init_default(struct pldm_instance_db **ctx)
{
return pldm_instance_db_init(ctx,
"/usr/share/libpldm/instance-db/default");
}
LIBPLDM_ABI_STABLE
int pldm_instance_db_destroy(struct pldm_instance_db *ctx)
{
if (!ctx) {
return 0;
}
close(ctx->lock_db_fd);
free(ctx);
return 0;
}
LIBPLDM_ABI_STABLE
int pldm_instance_id_alloc(struct pldm_instance_db *ctx, pldm_tid_t tid,
pldm_instance_id_t *iid)
{
static const struct flock cfls = {
.l_type = F_RDLCK,
.l_whence = SEEK_SET,
.l_len = 1,
};
static const struct flock cflx = {
.l_type = F_WRLCK,
.l_whence = SEEK_SET,
.l_len = 1,
};
uint8_t l_iid;
if (!iid) {
return -EINVAL;
}
l_iid = ctx->state[tid].prev;
if (l_iid >= PLDM_INST_ID_MAX) {
return -EPROTO;
}
while ((l_iid = iid_next(l_iid)) != ctx->state[tid].prev) {
struct flock flop;
off_t loff;
int rc;
/* Have we already allocated this instance ID? */
if (ctx->state[tid].allocations & BIT(l_iid)) {
continue;
}
/* Derive the instance ID offset in the lock database */
loff = tid * PLDM_INST_ID_MAX + l_iid;
/* Reserving the TID's IID. Done via a shared lock */
flop = cfls;
flop.l_start = loff;
rc = fcntl(ctx->lock_db_fd, F_OFD_SETLK, &flop);
if (rc < 0) {
if (errno == EAGAIN || errno == EINTR) {
return -EAGAIN;
}
return -EPROTO;
}
/*
* If we *may* promote the lock to exclusive then this IID is
* only reserved by us. This is now our allocated IID.
*
* If we *may not* promote the lock to exclusive then this IID
* is also reserved on another file descriptor. Move on to the
* next IID index.
*
* Note that we cannot actually *perform* the promotion in
* practice because this is prevented by the lock database being
* opened O_RDONLY.
*/
flop = cflx;
flop.l_start = loff;
rc = fcntl(ctx->lock_db_fd, F_OFD_GETLK, &flop);
if (rc < 0) {
if (errno == EAGAIN || errno == EINTR) {
return -EAGAIN;
}
return -EPROTO;
}
/* F_UNLCK is the type of the lock if we could successfully
* promote it to F_WRLCK */
if (flop.l_type == F_UNLCK) {
ctx->state[tid].prev = l_iid;
ctx->state[tid].allocations |= BIT(l_iid);
*iid = l_iid;
return 0;
}
if (flop.l_type != F_RDLCK) {
return -EPROTO;
}
}
/* Failed to allocate an IID after a full loop. Make the caller try
* again */
return -EAGAIN;
}
LIBPLDM_ABI_STABLE
int pldm_instance_id_free(struct pldm_instance_db *ctx, pldm_tid_t tid,
pldm_instance_id_t iid)
{
static const struct flock cflu = {
.l_type = F_UNLCK,
.l_whence = SEEK_SET,
.l_len = 1,
};
struct flock flop;
int rc;
/* Trying to free an instance ID that is not currently allocated */
if (!(ctx->state[tid].allocations & BIT(iid))) {
return -EINVAL;
}
flop = cflu;
flop.l_start = tid * PLDM_INST_ID_MAX + iid;
rc = fcntl(ctx->lock_db_fd, F_OFD_SETLK, &flop);
if (rc < 0) {
if (errno == EAGAIN || errno == EINTR) {
return -EAGAIN;
}
return -EPROTO;
}
/* Mark the instance ID as no-longer allocated */
ctx->state[tid].allocations &= ~BIT(iid);
return 0;
}