forked from luck/tmp_suning_uos_patched
eb1e79611c
The trace event buffer used by perf to record raw sample events is typed as an array of char and may then not be aligned to 8 by alloc_percpu(). But we need it to be aligned to 8 in sparc64 because we cast this buffer into a random structure type built by the TRACE_EVENT() macro to store the traces. So if a random 64 bits field is accessed inside, it may be not under an expected good alignment. Use an array of long instead to force the appropriate alignment, and perform a compile time check to ensure the size in byte of the buffer is a multiple of sizeof(long) so that its actual size doesn't get shrinked under us. This fixes unaligned accesses reported while using perf lock in sparc 64. Suggested-by: David Miller <davem@davemloft.net> Suggested-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: David Miller <davem@davemloft.net> Cc: Steven Rostedt <rostedt@goodmis.org>
176 lines
3.7 KiB
C
176 lines
3.7 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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DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
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EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs);
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EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
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static char *perf_trace_buf;
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static char *perf_trace_buf_nmi;
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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_enable(struct ftrace_event_call *event)
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{
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char *buf;
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int ret = -ENOMEM;
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if (event->perf_refcount++ > 0)
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return 0;
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if (!total_ref_count) {
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail_buf;
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rcu_assign_pointer(perf_trace_buf, buf);
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail_buf_nmi;
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rcu_assign_pointer(perf_trace_buf_nmi, buf);
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}
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ret = event->perf_event_enable(event);
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if (!ret) {
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total_ref_count++;
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return 0;
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}
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fail_buf_nmi:
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if (!total_ref_count) {
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free_percpu(perf_trace_buf_nmi);
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free_percpu(perf_trace_buf);
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perf_trace_buf_nmi = NULL;
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perf_trace_buf = NULL;
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}
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fail_buf:
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event->perf_refcount--;
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return ret;
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}
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int perf_trace_enable(int event_id)
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{
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struct ftrace_event_call *event;
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int ret = -EINVAL;
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mutex_lock(&event_mutex);
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list_for_each_entry(event, &ftrace_events, list) {
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if (event->id == event_id && event->perf_event_enable &&
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try_module_get(event->mod)) {
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ret = perf_trace_event_enable(event);
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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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static void perf_trace_event_disable(struct ftrace_event_call *event)
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{
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char *buf, *nmi_buf;
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if (--event->perf_refcount > 0)
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return;
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event->perf_event_disable(event);
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if (!--total_ref_count) {
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buf = perf_trace_buf;
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rcu_assign_pointer(perf_trace_buf, NULL);
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nmi_buf = perf_trace_buf_nmi;
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rcu_assign_pointer(perf_trace_buf_nmi, NULL);
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/*
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* Ensure every events in profiling have finished before
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* releasing the buffers
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*/
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synchronize_sched();
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free_percpu(buf);
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free_percpu(nmi_buf);
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}
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}
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void perf_trace_disable(int event_id)
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{
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struct ftrace_event_call *event;
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mutex_lock(&event_mutex);
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list_for_each_entry(event, &ftrace_events, list) {
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if (event->id == event_id) {
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perf_trace_event_disable(event);
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module_put(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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}
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__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
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int *rctxp, unsigned long *irq_flags)
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{
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struct trace_entry *entry;
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char *trace_buf, *raw_data;
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int pc, cpu;
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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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/* Protect the per cpu buffer, begin the rcu read side */
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local_irq_save(*irq_flags);
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*rctxp = perf_swevent_get_recursion_context();
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if (*rctxp < 0)
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goto err_recursion;
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cpu = smp_processor_id();
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if (in_nmi())
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trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
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else
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trace_buf = rcu_dereference_sched(perf_trace_buf);
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if (!trace_buf)
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goto err;
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raw_data = per_cpu_ptr(trace_buf, cpu);
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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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tracing_generic_entry_update(entry, *irq_flags, pc);
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entry->type = type;
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return raw_data;
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err:
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perf_swevent_put_recursion_context(*rctxp);
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err_recursion:
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local_irq_restore(*irq_flags);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
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