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![Frederic Weisbecker](/assets/img/avatar_default.png)
This adds a new trace event internal flag that allows them to be used in perf by non privileged users in case of task bound tracing. This is desired for syscalls tracepoint because they don't leak global system informations, like some other tracepoints. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Jason Baron <jbaron@redhat.com>
216 lines
4.7 KiB
C
216 lines
4.7 KiB
C
/*
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* trace event based perf event profiling/tracing
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*
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* Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
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* Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
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*/
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#include "trace.h"
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static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];
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/*
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* Force it to be aligned to unsigned long to avoid misaligned accesses
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* suprises
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*/
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typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
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perf_trace_t;
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/* Count the events in use (per event id, not per instance) */
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static int total_ref_count;
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static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
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struct perf_event *p_event)
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{
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/* No tracing, just counting, so no obvious leak */
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if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
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return 0;
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/* Some events are ok to be traced by non-root users... */
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if (p_event->attach_state == PERF_ATTACH_TASK) {
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if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
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return 0;
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}
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/*
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* ...otherwise raw tracepoint data can be a severe data leak,
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* only allow root to have these.
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*/
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if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
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return -EPERM;
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return 0;
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}
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static int perf_trace_event_init(struct ftrace_event_call *tp_event,
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struct perf_event *p_event)
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{
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struct hlist_head __percpu *list;
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int ret;
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int cpu;
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ret = perf_trace_event_perm(tp_event, p_event);
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if (ret)
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return ret;
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p_event->tp_event = tp_event;
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if (tp_event->perf_refcount++ > 0)
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return 0;
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ret = -ENOMEM;
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list = alloc_percpu(struct hlist_head);
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if (!list)
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goto fail;
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for_each_possible_cpu(cpu)
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INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
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tp_event->perf_events = list;
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if (!total_ref_count) {
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char __percpu *buf;
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int i;
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for (i = 0; i < PERF_NR_CONTEXTS; i++) {
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buf = (char __percpu *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail;
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perf_trace_buf[i] = buf;
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}
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}
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ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);
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if (ret)
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goto fail;
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total_ref_count++;
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return 0;
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fail:
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if (!total_ref_count) {
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int i;
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for (i = 0; i < PERF_NR_CONTEXTS; i++) {
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free_percpu(perf_trace_buf[i]);
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perf_trace_buf[i] = NULL;
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}
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}
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if (!--tp_event->perf_refcount) {
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free_percpu(tp_event->perf_events);
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tp_event->perf_events = NULL;
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}
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return ret;
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}
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int perf_trace_init(struct perf_event *p_event)
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{
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struct ftrace_event_call *tp_event;
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int event_id = p_event->attr.config;
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int ret = -EINVAL;
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mutex_lock(&event_mutex);
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list_for_each_entry(tp_event, &ftrace_events, list) {
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if (tp_event->event.type == event_id &&
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tp_event->class && tp_event->class->reg &&
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try_module_get(tp_event->mod)) {
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ret = perf_trace_event_init(tp_event, p_event);
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if (ret)
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module_put(tp_event->mod);
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break;
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}
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}
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mutex_unlock(&event_mutex);
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return ret;
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}
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int perf_trace_add(struct perf_event *p_event, int flags)
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{
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struct ftrace_event_call *tp_event = p_event->tp_event;
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struct hlist_head __percpu *pcpu_list;
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struct hlist_head *list;
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pcpu_list = tp_event->perf_events;
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if (WARN_ON_ONCE(!pcpu_list))
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return -EINVAL;
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if (!(flags & PERF_EF_START))
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p_event->hw.state = PERF_HES_STOPPED;
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list = this_cpu_ptr(pcpu_list);
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hlist_add_head_rcu(&p_event->hlist_entry, list);
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return 0;
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}
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void perf_trace_del(struct perf_event *p_event, int flags)
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{
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hlist_del_rcu(&p_event->hlist_entry);
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}
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void perf_trace_destroy(struct perf_event *p_event)
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{
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struct ftrace_event_call *tp_event = p_event->tp_event;
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int i;
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mutex_lock(&event_mutex);
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if (--tp_event->perf_refcount > 0)
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goto out;
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tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);
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/*
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* Ensure our callback won't be called anymore. The buffers
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* will be freed after that.
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*/
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tracepoint_synchronize_unregister();
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free_percpu(tp_event->perf_events);
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tp_event->perf_events = NULL;
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if (!--total_ref_count) {
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for (i = 0; i < PERF_NR_CONTEXTS; i++) {
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free_percpu(perf_trace_buf[i]);
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perf_trace_buf[i] = NULL;
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}
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}
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out:
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module_put(tp_event->mod);
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mutex_unlock(&event_mutex);
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}
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__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
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struct pt_regs *regs, int *rctxp)
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{
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struct trace_entry *entry;
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unsigned long flags;
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char *raw_data;
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int pc;
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BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
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pc = preempt_count();
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*rctxp = perf_swevent_get_recursion_context();
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if (*rctxp < 0)
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return NULL;
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raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
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/* zero the dead bytes from align to not leak stack to user */
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memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
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entry = (struct trace_entry *)raw_data;
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local_save_flags(flags);
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tracing_generic_entry_update(entry, flags, pc);
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entry->type = type;
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return raw_data;
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}
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EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
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