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| 1 | /* |
| 2 | * trace event based perf event profiling/tracing |
| 3 | * |
| 4 | * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com> |
| 5 | * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com> |
| 6 | */ |
| 7 | |
| 8 | #include <linux/module.h> |
| 9 | #include <linux/kprobes.h> |
| 10 | #include "trace.h" |
| 11 | |
| 12 | static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS]; |
| 13 | |
| 14 | /* |
| 15 | * Force it to be aligned to unsigned long to avoid misaligned accesses |
| 16 | * suprises |
| 17 | */ |
| 18 | typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)]) |
| 19 | perf_trace_t; |
| 20 | |
| 21 | /* Count the events in use (per event id, not per instance) */ |
| 22 | static int total_ref_count; |
| 23 | |
| 24 | static int perf_trace_event_perm(struct ftrace_event_call *tp_event, |
| 25 | struct perf_event *p_event) |
| 26 | { |
| 27 | /* No tracing, just counting, so no obvious leak */ |
| 28 | if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW)) |
| 29 | return 0; |
| 30 | |
| 31 | /* Some events are ok to be traced by non-root users... */ |
| 32 | if (p_event->attach_state == PERF_ATTACH_TASK) { |
| 33 | if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY) |
| 34 | return 0; |
| 35 | } |
| 36 | |
| 37 | /* |
| 38 | * ...otherwise raw tracepoint data can be a severe data leak, |
| 39 | * only allow root to have these. |
| 40 | */ |
| 41 | if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN)) |
| 42 | return -EPERM; |
| 43 | |
| 44 | return 0; |
| 45 | } |
| 46 | |
| 47 | static int perf_trace_event_init(struct ftrace_event_call *tp_event, |
| 48 | struct perf_event *p_event) |
| 49 | { |
| 50 | struct hlist_head __percpu *list; |
| 51 | int ret; |
| 52 | int cpu; |
| 53 | |
| 54 | ret = perf_trace_event_perm(tp_event, p_event); |
| 55 | if (ret) |
| 56 | return ret; |
| 57 | |
| 58 | p_event->tp_event = tp_event; |
| 59 | if (tp_event->perf_refcount++ > 0) |
| 60 | return 0; |
| 61 | |
| 62 | ret = -ENOMEM; |
| 63 | |
| 64 | list = alloc_percpu(struct hlist_head); |
| 65 | if (!list) |
| 66 | goto fail; |
| 67 | |
| 68 | for_each_possible_cpu(cpu) |
| 69 | INIT_HLIST_HEAD(per_cpu_ptr(list, cpu)); |
| 70 | |
| 71 | tp_event->perf_events = list; |
| 72 | |
| 73 | if (!total_ref_count) { |
| 74 | char __percpu *buf; |
| 75 | int i; |
| 76 | |
| 77 | for (i = 0; i < PERF_NR_CONTEXTS; i++) { |
| 78 | buf = (char __percpu *)alloc_percpu(perf_trace_t); |
| 79 | if (!buf) |
| 80 | goto fail; |
| 81 | |
| 82 | perf_trace_buf[i] = buf; |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER); |
| 87 | if (ret) |
| 88 | goto fail; |
| 89 | |
| 90 | total_ref_count++; |
| 91 | return 0; |
| 92 | |
| 93 | fail: |
| 94 | if (!total_ref_count) { |
| 95 | int i; |
| 96 | |
| 97 | for (i = 0; i < PERF_NR_CONTEXTS; i++) { |
| 98 | free_percpu(perf_trace_buf[i]); |
| 99 | perf_trace_buf[i] = NULL; |
| 100 | } |
| 101 | } |
| 102 | |
| 103 | if (!--tp_event->perf_refcount) { |
| 104 | free_percpu(tp_event->perf_events); |
| 105 | tp_event->perf_events = NULL; |
| 106 | } |
| 107 | |
| 108 | return ret; |
| 109 | } |
| 110 | |
| 111 | int perf_trace_init(struct perf_event *p_event) |
| 112 | { |
| 113 | struct ftrace_event_call *tp_event; |
| 114 | int event_id = p_event->attr.config; |
| 115 | int ret = -EINVAL; |
| 116 | |
| 117 | mutex_lock(&event_mutex); |
| 118 | list_for_each_entry(tp_event, &ftrace_events, list) { |
| 119 | if (tp_event->event.type == event_id && |
| 120 | tp_event->class && tp_event->class->reg && |
| 121 | try_module_get(tp_event->mod)) { |
| 122 | ret = perf_trace_event_init(tp_event, p_event); |
| 123 | if (ret) |
| 124 | module_put(tp_event->mod); |
| 125 | break; |
| 126 | } |
| 127 | } |
| 128 | mutex_unlock(&event_mutex); |
| 129 | |
| 130 | return ret; |
| 131 | } |
| 132 | |
| 133 | int perf_trace_add(struct perf_event *p_event, int flags) |
| 134 | { |
| 135 | struct ftrace_event_call *tp_event = p_event->tp_event; |
| 136 | struct hlist_head __percpu *pcpu_list; |
| 137 | struct hlist_head *list; |
| 138 | |
| 139 | pcpu_list = tp_event->perf_events; |
| 140 | if (WARN_ON_ONCE(!pcpu_list)) |
| 141 | return -EINVAL; |
| 142 | |
| 143 | if (!(flags & PERF_EF_START)) |
| 144 | p_event->hw.state = PERF_HES_STOPPED; |
| 145 | |
| 146 | list = this_cpu_ptr(pcpu_list); |
| 147 | hlist_add_head_rcu(&p_event->hlist_entry, list); |
| 148 | |
| 149 | return 0; |
| 150 | } |
| 151 | |
| 152 | void perf_trace_del(struct perf_event *p_event, int flags) |
| 153 | { |
| 154 | hlist_del_rcu(&p_event->hlist_entry); |
| 155 | } |
| 156 | |
| 157 | void perf_trace_destroy(struct perf_event *p_event) |
| 158 | { |
| 159 | struct ftrace_event_call *tp_event = p_event->tp_event; |
| 160 | int i; |
| 161 | |
| 162 | mutex_lock(&event_mutex); |
| 163 | if (--tp_event->perf_refcount > 0) |
| 164 | goto out; |
| 165 | |
| 166 | tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER); |
| 167 | |
| 168 | /* |
| 169 | * Ensure our callback won't be called anymore. The buffers |
| 170 | * will be freed after that. |
| 171 | */ |
| 172 | tracepoint_synchronize_unregister(); |
| 173 | |
| 174 | free_percpu(tp_event->perf_events); |
| 175 | tp_event->perf_events = NULL; |
| 176 | |
| 177 | if (!--total_ref_count) { |
| 178 | for (i = 0; i < PERF_NR_CONTEXTS; i++) { |
| 179 | free_percpu(perf_trace_buf[i]); |
| 180 | perf_trace_buf[i] = NULL; |
| 181 | } |
| 182 | } |
| 183 | out: |
| 184 | module_put(tp_event->mod); |
| 185 | mutex_unlock(&event_mutex); |
| 186 | } |
| 187 | |
| 188 | __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, |
| 189 | struct pt_regs *regs, int *rctxp) |
| 190 | { |
| 191 | struct trace_entry *entry; |
| 192 | unsigned long flags; |
| 193 | char *raw_data; |
| 194 | int pc; |
| 195 | |
| 196 | BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); |
| 197 | |
| 198 | pc = preempt_count(); |
| 199 | |
| 200 | *rctxp = perf_swevent_get_recursion_context(); |
| 201 | if (*rctxp < 0) |
| 202 | return NULL; |
| 203 | |
| 204 | raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]); |
| 205 | |
| 206 | /* zero the dead bytes from align to not leak stack to user */ |
| 207 | memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); |
| 208 | |
| 209 | entry = (struct trace_entry *)raw_data; |
| 210 | local_save_flags(flags); |
| 211 | tracing_generic_entry_update(entry, flags, pc); |
| 212 | entry->type = type; |
| 213 | |
| 214 | return raw_data; |
| 215 | } |
| 216 | EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); |
| 217 |
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