1 /* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */ 2 // NOLINTNEXTLINE(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp) 3 #define _GNU_SOURCE 4 #include <libpldm/instance-id.h> 5 #include <libpldm/pldm.h> 6 7 #include <errno.h> 8 #include <fcntl.h> 9 #include <stdlib.h> 10 #include <sys/stat.h> 11 #include <unistd.h> 12 13 #define BIT(i) (1UL << (i)) 14 15 #define PLDM_TID_MAX 256 16 #define PLDM_INST_ID_MAX 32 17 18 /* We need to track our allocations explicitly due to OFD lock merging/splitting 19 */ 20 struct pldm_tid_state { 21 pldm_instance_id_t prev; 22 uint32_t allocations; 23 }; 24 25 struct pldm_instance_db { 26 struct pldm_tid_state state[PLDM_TID_MAX]; 27 int lock_db_fd; 28 }; 29 30 static inline int iid_next(pldm_instance_id_t cur) 31 { 32 return (cur + 1) % PLDM_INST_ID_MAX; 33 } 34 35 LIBPLDM_ABI_STABLE 36 int pldm_instance_db_init(struct pldm_instance_db **ctx, const char *dbpath) 37 { 38 struct pldm_instance_db *l_ctx; 39 struct stat statbuf; 40 int rc; 41 42 /* Make sure the provided pointer was initialised to NULL. In the future 43 * if we stabilise the ABI and expose the struct definition the caller 44 * can potentially pass a valid pointer to a struct they've allocated 45 */ 46 if (!ctx || *ctx) { 47 return -EINVAL; 48 } 49 50 /* Ensure the underlying file is sized for properly managing allocations 51 */ 52 rc = stat(dbpath, &statbuf); 53 if (rc < 0) { 54 return -EINVAL; 55 } 56 57 if (statbuf.st_size < 58 ((off_t)(PLDM_TID_MAX) * (off_t)(PLDM_INST_ID_MAX))) { 59 return -EINVAL; 60 } 61 62 l_ctx = calloc(1, sizeof(struct pldm_instance_db)); 63 if (!l_ctx) { 64 return -ENOMEM; 65 } 66 67 /* Initialise previous ID values so the next one is zero */ 68 for (int i = 0; i < PLDM_TID_MAX; i++) { 69 l_ctx->state[i].prev = 31; 70 } 71 72 /* Lock database may be read-only, either by permissions or mountpoint 73 */ 74 l_ctx->lock_db_fd = open(dbpath, O_RDONLY | O_CLOEXEC); 75 if (l_ctx->lock_db_fd < 0) { 76 free(l_ctx); 77 return -errno; 78 } 79 *ctx = l_ctx; 80 81 return 0; 82 } 83 84 LIBPLDM_ABI_STABLE 85 int pldm_instance_db_init_default(struct pldm_instance_db **ctx) 86 { 87 return pldm_instance_db_init(ctx, 88 "/usr/share/libpldm/instance-db/default"); 89 } 90 91 LIBPLDM_ABI_STABLE 92 int pldm_instance_db_destroy(struct pldm_instance_db *ctx) 93 { 94 if (!ctx) { 95 return 0; 96 } 97 close(ctx->lock_db_fd); 98 free(ctx); 99 return 0; 100 } 101 102 LIBPLDM_ABI_STABLE 103 int pldm_instance_id_alloc(struct pldm_instance_db *ctx, pldm_tid_t tid, 104 pldm_instance_id_t *iid) 105 { 106 static const struct flock cfls = { 107 .l_type = F_RDLCK, 108 .l_whence = SEEK_SET, 109 .l_len = 1, 110 }; 111 static const struct flock cflx = { 112 .l_type = F_WRLCK, 113 .l_whence = SEEK_SET, 114 .l_len = 1, 115 }; 116 uint8_t l_iid; 117 118 if (!iid) { 119 return -EINVAL; 120 } 121 122 l_iid = ctx->state[tid].prev; 123 if (l_iid >= PLDM_INST_ID_MAX) { 124 return -EPROTO; 125 } 126 127 while ((l_iid = iid_next(l_iid)) != ctx->state[tid].prev) { 128 struct flock flop; 129 off_t loff; 130 int rc; 131 132 /* Have we already allocated this instance ID? */ 133 if (ctx->state[tid].allocations & BIT(l_iid)) { 134 continue; 135 } 136 137 /* Derive the instance ID offset in the lock database */ 138 loff = tid * PLDM_INST_ID_MAX + l_iid; 139 140 /* Reserving the TID's IID. Done via a shared lock */ 141 flop = cfls; 142 flop.l_start = loff; 143 rc = fcntl(ctx->lock_db_fd, F_OFD_SETLK, &flop); 144 if (rc < 0) { 145 if (errno == EAGAIN || errno == EINTR) { 146 return -EAGAIN; 147 } 148 return -EPROTO; 149 } 150 151 /* 152 * If we *may* promote the lock to exclusive then this IID is 153 * only reserved by us. This is now our allocated IID. 154 * 155 * If we *may not* promote the lock to exclusive then this IID 156 * is also reserved on another file descriptor. Move on to the 157 * next IID index. 158 * 159 * Note that we cannot actually *perform* the promotion in 160 * practice because this is prevented by the lock database being 161 * opened O_RDONLY. 162 */ 163 flop = cflx; 164 flop.l_start = loff; 165 rc = fcntl(ctx->lock_db_fd, F_OFD_GETLK, &flop); 166 if (rc < 0) { 167 if (errno == EAGAIN || errno == EINTR) { 168 return -EAGAIN; 169 } 170 return -EPROTO; 171 } 172 173 /* F_UNLCK is the type of the lock if we could successfully 174 * promote it to F_WRLCK */ 175 if (flop.l_type == F_UNLCK) { 176 ctx->state[tid].prev = l_iid; 177 ctx->state[tid].allocations |= BIT(l_iid); 178 *iid = l_iid; 179 return 0; 180 } 181 if (flop.l_type != F_RDLCK) { 182 return -EPROTO; 183 } 184 } 185 186 /* Failed to allocate an IID after a full loop. Make the caller try 187 * again */ 188 return -EAGAIN; 189 } 190 191 LIBPLDM_ABI_STABLE 192 int pldm_instance_id_free(struct pldm_instance_db *ctx, pldm_tid_t tid, 193 pldm_instance_id_t iid) 194 { 195 static const struct flock cflu = { 196 .l_type = F_UNLCK, 197 .l_whence = SEEK_SET, 198 .l_len = 1, 199 }; 200 struct flock flop; 201 int rc; 202 203 /* Trying to free an instance ID that is not currently allocated */ 204 if (!(ctx->state[tid].allocations & BIT(iid))) { 205 return -EINVAL; 206 } 207 208 flop = cflu; 209 flop.l_start = tid * PLDM_INST_ID_MAX + iid; 210 rc = fcntl(ctx->lock_db_fd, F_OFD_SETLK, &flop); 211 if (rc < 0) { 212 if (errno == EAGAIN || errno == EINTR) { 213 return -EAGAIN; 214 } 215 return -EPROTO; 216 } 217 218 /* Mark the instance ID as no-longer allocated */ 219 ctx->state[tid].allocations &= ~BIT(iid); 220 221 return 0; 222 } 223