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