| 1 | // SPDX-License-Identifier: MIT |
| 2 | /* |
| 3 | * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 4 | */ |
| 5 | |
| 6 | #include <side/trace.h> |
| 7 | #include <string.h> |
| 8 | |
| 9 | #include "tracer.h" |
| 10 | #include "rcu.h" |
| 11 | |
| 12 | /* Top 8 bits reserved for kernel tracer use. */ |
| 13 | #define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000 |
| 14 | #define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000 |
| 15 | |
| 16 | /* Allow 2^24 tracer callbacks to be registered on an event. */ |
| 17 | #define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFF |
| 18 | |
| 19 | static struct side_rcu_gp_state rcu_gp; |
| 20 | |
| 21 | /* |
| 22 | * Lazy initialization for early use within library constructors. |
| 23 | */ |
| 24 | static bool initialized; |
| 25 | |
| 26 | static pthread_mutex_t side_lock = PTHREAD_MUTEX_INITIALIZER; |
| 27 | |
| 28 | static |
| 29 | void side_init(void) |
| 30 | __attribute__((constructor)); |
| 31 | |
| 32 | /* |
| 33 | * The empty callback has a NULL function callback pointer, which stops |
| 34 | * iteration on the array of callbacks immediately. |
| 35 | */ |
| 36 | const struct side_callback side_empty_callback; |
| 37 | |
| 38 | void side_call(const struct side_event_description *desc, const struct side_arg_vec_description *sav_desc) |
| 39 | { |
| 40 | const struct side_callback *side_cb; |
| 41 | unsigned int rcu_period; |
| 42 | |
| 43 | if (side_unlikely(!initialized)) |
| 44 | side_init(); |
| 45 | if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) { |
| 46 | printf("ERROR: unexpected variadic event description\n"); |
| 47 | abort(); |
| 48 | } |
| 49 | if (side_unlikely(*desc->enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { |
| 50 | // TODO: call kernel write. |
| 51 | } |
| 52 | if (side_unlikely(!(*desc->enabled & SIDE_EVENT_ENABLED_USER_MASK))) |
| 53 | return; |
| 54 | |
| 55 | //TODO: replace tracer_call by rcu iteration on list of registered callbacks |
| 56 | tracer_call(desc, sav_desc, NULL); |
| 57 | |
| 58 | rcu_period = side_rcu_read_begin(&rcu_gp); |
| 59 | for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++) |
| 60 | side_cb->u.call(desc, sav_desc, side_cb->priv); |
| 61 | side_rcu_read_end(&rcu_gp, rcu_period); |
| 62 | } |
| 63 | |
| 64 | void side_call_variadic(const struct side_event_description *desc, |
| 65 | const struct side_arg_vec_description *sav_desc, |
| 66 | const struct side_arg_dynamic_event_struct *var_struct) |
| 67 | { |
| 68 | const struct side_callback *side_cb; |
| 69 | unsigned int rcu_period; |
| 70 | |
| 71 | if (side_unlikely(!initialized)) |
| 72 | side_init(); |
| 73 | if (side_unlikely(*desc->enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { |
| 74 | // TODO: call kernel write. |
| 75 | } |
| 76 | if (side_unlikely(!(*desc->enabled & SIDE_EVENT_ENABLED_USER_MASK))) |
| 77 | return; |
| 78 | |
| 79 | //TODO: replace tracer_call by rcu iteration on list of registered callbacks |
| 80 | tracer_call_variadic(desc, sav_desc, var_struct, NULL); |
| 81 | |
| 82 | rcu_period = side_rcu_read_begin(&rcu_gp); |
| 83 | for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++) |
| 84 | side_cb->u.call_variadic(desc, sav_desc, var_struct, side_cb->priv); |
| 85 | side_rcu_read_end(&rcu_gp, rcu_period); |
| 86 | } |
| 87 | |
| 88 | static |
| 89 | const struct side_callback *side_tracer_callback_lookup( |
| 90 | const struct side_event_description *desc, |
| 91 | void (*call)(), void *priv) |
| 92 | { |
| 93 | const struct side_callback *cb; |
| 94 | |
| 95 | for (cb = desc->callbacks; cb->u.call != NULL; cb++) { |
| 96 | if (cb->u.call == call && cb->priv == priv) |
| 97 | return cb; |
| 98 | } |
| 99 | return NULL; |
| 100 | } |
| 101 | |
| 102 | static |
| 103 | int _side_tracer_callback_register(struct side_event_description *desc, |
| 104 | void (*call)(), void *priv) |
| 105 | { |
| 106 | struct side_callback *old_cb, *new_cb; |
| 107 | int ret = SIDE_ERROR_OK; |
| 108 | uint32_t old_nr_cb; |
| 109 | |
| 110 | if (!call) |
| 111 | return SIDE_ERROR_INVAL; |
| 112 | pthread_mutex_lock(&side_lock); |
| 113 | old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK; |
| 114 | if (old_nr_cb == SIDE_EVENT_ENABLED_USER_MASK) { |
| 115 | ret = SIDE_ERROR_INVAL; |
| 116 | goto unlock; |
| 117 | } |
| 118 | /* Reject duplicate (call, priv) tuples. */ |
| 119 | if (side_tracer_callback_lookup(desc, call, priv)) { |
| 120 | ret = SIDE_ERROR_EXIST; |
| 121 | goto unlock; |
| 122 | } |
| 123 | old_cb = (struct side_callback *) desc->callbacks; |
| 124 | /* old_nr_cb + 1 (new cb) + 1 (NULL) */ |
| 125 | new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback)); |
| 126 | if (!new_cb) { |
| 127 | ret = SIDE_ERROR_NOMEM; |
| 128 | goto unlock; |
| 129 | } |
| 130 | memcpy(new_cb, old_cb, old_nr_cb); |
| 131 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) |
| 132 | new_cb[old_nr_cb].u.call_variadic = call; |
| 133 | else |
| 134 | new_cb[old_nr_cb].u.call = call; |
| 135 | new_cb[old_nr_cb].priv = priv; |
| 136 | side_rcu_assign_pointer(desc->callbacks, new_cb); |
| 137 | side_rcu_wait_grace_period(&rcu_gp); |
| 138 | if (old_nr_cb) |
| 139 | free(old_cb); |
| 140 | /* Increment concurrently with kernel setting the top bits. */ |
| 141 | (void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED); |
| 142 | unlock: |
| 143 | pthread_mutex_unlock(&side_lock); |
| 144 | return ret; |
| 145 | } |
| 146 | |
| 147 | int side_tracer_callback_register(struct side_event_description *desc, |
| 148 | void (*call)(const struct side_event_description *desc, |
| 149 | const struct side_arg_vec_description *sav_desc, |
| 150 | void *priv), |
| 151 | void *priv) |
| 152 | { |
| 153 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) |
| 154 | return SIDE_ERROR_INVAL; |
| 155 | return _side_tracer_callback_register(desc, call, priv); |
| 156 | } |
| 157 | |
| 158 | int side_tracer_callback_variadic_register(struct side_event_description *desc, |
| 159 | void (*call_variadic)(const struct side_event_description *desc, |
| 160 | const struct side_arg_vec_description *sav_desc, |
| 161 | const struct side_arg_dynamic_event_struct *var_struct, |
| 162 | void *priv), |
| 163 | void *priv) |
| 164 | { |
| 165 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) |
| 166 | return SIDE_ERROR_INVAL; |
| 167 | return _side_tracer_callback_register(desc, call_variadic, priv); |
| 168 | } |
| 169 | |
| 170 | int _side_tracer_callback_unregister(struct side_event_description *desc, |
| 171 | void (*call)(), void *priv) |
| 172 | { |
| 173 | struct side_callback *old_cb, *new_cb; |
| 174 | const struct side_callback *cb_pos; |
| 175 | uint32_t pos_idx; |
| 176 | int ret = SIDE_ERROR_OK; |
| 177 | uint32_t old_nr_cb; |
| 178 | |
| 179 | if (!call) |
| 180 | return SIDE_ERROR_INVAL; |
| 181 | pthread_mutex_lock(&side_lock); |
| 182 | cb_pos = side_tracer_callback_lookup(desc, call, priv); |
| 183 | if (!cb_pos) { |
| 184 | ret = SIDE_ERROR_NOENT; |
| 185 | goto unlock; |
| 186 | } |
| 187 | old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK; |
| 188 | old_cb = (struct side_callback *) desc->callbacks; |
| 189 | if (old_nr_cb == 1) { |
| 190 | new_cb = (struct side_callback *) &side_empty_callback; |
| 191 | } else { |
| 192 | pos_idx = cb_pos - desc->callbacks; |
| 193 | /* Remove entry at pos_idx. */ |
| 194 | /* old_nr_cb - 1 (removed cb) + 1 (NULL) */ |
| 195 | new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback)); |
| 196 | if (!new_cb) { |
| 197 | ret = SIDE_ERROR_NOMEM; |
| 198 | goto unlock; |
| 199 | } |
| 200 | memcpy(new_cb, old_cb, pos_idx); |
| 201 | memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1); |
| 202 | } |
| 203 | side_rcu_assign_pointer(desc->callbacks, new_cb); |
| 204 | side_rcu_wait_grace_period(&rcu_gp); |
| 205 | free(old_cb); |
| 206 | /* Decrement concurrently with kernel setting the top bits. */ |
| 207 | (void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED); |
| 208 | unlock: |
| 209 | pthread_mutex_unlock(&side_lock); |
| 210 | return ret; |
| 211 | } |
| 212 | |
| 213 | int side_tracer_callback_unregister(struct side_event_description *desc, |
| 214 | void (*call)(const struct side_event_description *desc, |
| 215 | const struct side_arg_vec_description *sav_desc, |
| 216 | void *priv), |
| 217 | void *priv) |
| 218 | { |
| 219 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) |
| 220 | return SIDE_ERROR_INVAL; |
| 221 | return _side_tracer_callback_unregister(desc, call, priv); |
| 222 | } |
| 223 | |
| 224 | int side_tracer_callback_variadic_unregister(struct side_event_description *desc, |
| 225 | void (*call_variadic)(const struct side_event_description *desc, |
| 226 | const struct side_arg_vec_description *sav_desc, |
| 227 | const struct side_arg_dynamic_event_struct *var_struct, |
| 228 | void *priv), |
| 229 | void *priv) |
| 230 | { |
| 231 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) |
| 232 | return SIDE_ERROR_INVAL; |
| 233 | return _side_tracer_callback_unregister(desc, call_variadic, priv); |
| 234 | } |
| 235 | |
| 236 | static |
| 237 | void side_init(void) |
| 238 | { |
| 239 | if (initialized) |
| 240 | return; |
| 241 | side_rcu_gp_init(&rcu_gp); |
| 242 | initialized = true; |
| 243 | } |