1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Performance events callchain code, extracted from core.c: 4 * 5 * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de> 6 * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar 7 * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra 8 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com> 9 */ 10 11 #include <linux/perf_event.h> 12 #include <linux/slab.h> 13 #include <linux/sched/task_stack.h> 14 #include <linux/uprobes.h> 15 16 #include "internal.h" 17 18 struct callchain_cpus_entries { 19 struct rcu_head rcu_head; 20 struct perf_callchain_entry *cpu_entries[]; 21 }; 22 23 int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; 24 int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK; 25 26 static inline size_t perf_callchain_entry__sizeof(void) 27 { 28 return (sizeof(struct perf_callchain_entry) + 29 sizeof(__u64) * (sysctl_perf_event_max_stack + 30 sysctl_perf_event_max_contexts_per_stack)); 31 } 32 33 static DEFINE_PER_CPU(u8, callchain_recursion[PERF_NR_CONTEXTS]); 34 static atomic_t nr_callchain_events; 35 static DEFINE_MUTEX(callchain_mutex); 36 static struct callchain_cpus_entries *callchain_cpus_entries; 37 38 39 __weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, 40 struct pt_regs *regs) 41 { 42 } 43 44 __weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry, 45 struct pt_regs *regs) 46 { 47 } 48 49 static void release_callchain_buffers_rcu(struct rcu_head *head) 50 { 51 struct callchain_cpus_entries *entries; 52 int cpu; 53 54 entries = container_of(head, struct callchain_cpus_entries, rcu_head); 55 56 for_each_possible_cpu(cpu) 57 kfree(entries->cpu_entries[cpu]); 58 59 kfree(entries); 60 } 61 62 static void release_callchain_buffers(void) 63 { 64 struct callchain_cpus_entries *entries; 65 66 entries = callchain_cpus_entries; 67 RCU_INIT_POINTER(callchain_cpus_entries, NULL); 68 call_rcu(&entries->rcu_head, release_callchain_buffers_rcu); 69 } 70 71 static int alloc_callchain_buffers(void) 72 { 73 int cpu; 74 int size; 75 struct callchain_cpus_entries *entries; 76 77 /* 78 * We can't use the percpu allocation API for data that can be 79 * accessed from NMI. Use a temporary manual per cpu allocation 80 * until that gets sorted out. 81 */ 82 size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]); 83 84 entries = kzalloc(size, GFP_KERNEL); 85 if (!entries) 86 return -ENOMEM; 87 88 size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS; 89 90 for_each_possible_cpu(cpu) { 91 entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL, 92 cpu_to_node(cpu)); 93 if (!entries->cpu_entries[cpu]) 94 goto fail; 95 } 96 97 rcu_assign_pointer(callchain_cpus_entries, entries); 98 99 return 0; 100 101 fail: 102 for_each_possible_cpu(cpu) 103 kfree(entries->cpu_entries[cpu]); 104 kfree(entries); 105 106 return -ENOMEM; 107 } 108 109 int get_callchain_buffers(int event_max_stack) 110 { 111 int err = 0; 112 int count; 113 114 mutex_lock(&callchain_mutex); 115 116 count = atomic_inc_return(&nr_callchain_events); 117 if (WARN_ON_ONCE(count < 1)) { 118 err = -EINVAL; 119 goto exit; 120 } 121 122 /* 123 * If requesting per event more than the global cap, 124 * return a different error to help userspace figure 125 * this out. 126 * 127 * And also do it here so that we have &callchain_mutex held. 128 */ 129 if (event_max_stack > sysctl_perf_event_max_stack) { 130 err = -EOVERFLOW; 131 goto exit; 132 } 133 134 if (count == 1) 135 err = alloc_callchain_buffers(); 136 exit: 137 if (err) 138 atomic_dec(&nr_callchain_events); 139 140 mutex_unlock(&callchain_mutex); 141 142 return err; 143 } 144 145 void put_callchain_buffers(void) 146 { 147 if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) { 148 release_callchain_buffers(); 149 mutex_unlock(&callchain_mutex); 150 } 151 } 152 153 struct perf_callchain_entry *get_callchain_entry(int *rctx) 154 { 155 int cpu; 156 struct callchain_cpus_entries *entries; 157 158 *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion)); 159 if (*rctx == -1) 160 return NULL; 161 162 entries = rcu_dereference(callchain_cpus_entries); 163 if (!entries) { 164 put_recursion_context(this_cpu_ptr(callchain_recursion), *rctx); 165 return NULL; 166 } 167 168 cpu = smp_processor_id(); 169 170 return (((void *)entries->cpu_entries[cpu]) + 171 (*rctx * perf_callchain_entry__sizeof())); 172 } 173 174 void 175 put_callchain_entry(int rctx) 176 { 177 put_recursion_context(this_cpu_ptr(callchain_recursion), rctx); 178 } 179 180 static void fixup_uretprobe_trampoline_entries(struct perf_callchain_entry *entry, 181 int start_entry_idx) 182 { 183 #ifdef CONFIG_UPROBES 184 struct uprobe_task *utask = current->utask; 185 struct return_instance *ri; 186 __u64 *cur_ip, *last_ip, tramp_addr; 187 188 if (likely(!utask || !utask->return_instances)) 189 return; 190 191 cur_ip = &entry->ip[start_entry_idx]; 192 last_ip = &entry->ip[entry->nr - 1]; 193 ri = utask->return_instances; 194 tramp_addr = uprobe_get_trampoline_vaddr(); 195 196 /* 197 * If there are pending uretprobes for the current thread, they are 198 * recorded in a list inside utask->return_instances; each such 199 * pending uretprobe replaces traced user function's return address on 200 * the stack, so when stack trace is captured, instead of seeing 201 * actual function's return address, we'll have one or many uretprobe 202 * trampoline addresses in the stack trace, which are not helpful and 203 * misleading to users. 204 * So here we go over the pending list of uretprobes, and each 205 * encountered trampoline address is replaced with actual return 206 * address. 207 */ 208 while (ri && cur_ip <= last_ip) { 209 if (*cur_ip == tramp_addr) { 210 *cur_ip = ri->orig_ret_vaddr; 211 ri = ri->next; 212 } 213 cur_ip++; 214 } 215 #endif 216 } 217 218 struct perf_callchain_entry * 219 get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, 220 u32 max_stack, bool crosstask, bool add_mark) 221 { 222 struct perf_callchain_entry *entry; 223 struct perf_callchain_entry_ctx ctx; 224 int rctx, start_entry_idx; 225 226 entry = get_callchain_entry(&rctx); 227 if (!entry) 228 return NULL; 229 230 ctx.entry = entry; 231 ctx.max_stack = max_stack; 232 ctx.nr = entry->nr = init_nr; 233 ctx.contexts = 0; 234 ctx.contexts_maxed = false; 235 236 if (kernel && !user_mode(regs)) { 237 if (add_mark) 238 perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); 239 perf_callchain_kernel(&ctx, regs); 240 } 241 242 if (user) { 243 if (!user_mode(regs)) { 244 if (current->mm) 245 regs = task_pt_regs(current); 246 else 247 regs = NULL; 248 } 249 250 if (regs) { 251 if (crosstask) 252 goto exit_put; 253 254 if (add_mark) 255 perf_callchain_store_context(&ctx, PERF_CONTEXT_USER); 256 257 start_entry_idx = entry->nr; 258 perf_callchain_user(&ctx, regs); 259 fixup_uretprobe_trampoline_entries(entry, start_entry_idx); 260 } 261 } 262 263 exit_put: 264 put_callchain_entry(rctx); 265 266 return entry; 267 } 268 269 /* 270 * Used for sysctl_perf_event_max_stack and 271 * sysctl_perf_event_max_contexts_per_stack. 272 */ 273 int perf_event_max_stack_handler(const struct ctl_table *table, int write, 274 void *buffer, size_t *lenp, loff_t *ppos) 275 { 276 int *value = table->data; 277 int new_value = *value, ret; 278 struct ctl_table new_table = *table; 279 280 new_table.data = &new_value; 281 ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos); 282 if (ret || !write) 283 return ret; 284 285 mutex_lock(&callchain_mutex); 286 if (atomic_read(&nr_callchain_events)) 287 ret = -EBUSY; 288 else 289 *value = new_value; 290 291 mutex_unlock(&callchain_mutex); 292 293 return ret; 294 } 295