perf: Factorize trace events raw sample buffer operations

Introduce ftrace_perf_buf_prepare() and ftrace_perf_buf_submit() to
gather the common code that operates on raw events sampling buffer.
This cleans up redundant code between regular trace events, syscall
events and kprobe events.

Changelog v1->v2:
- Rename function name as per Masami and Frederic's suggestion
- Add __kprobes for ftrace_perf_buf_prepare() and make
  ftrace_perf_buf_submit() inline as per Masami's suggestion
- Export ftrace_perf_buf_prepare since modules will use it

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <4B60E92D.9000808@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 47 insertions, 5 deletions

diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index 9e25573242cf..f0d693005075 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -6,14 +6,12 @@
  */
 
 #include <linux/module.h>
+#include <linux/kprobes.h>
 #include "trace.h"
 
 
-char *perf_trace_buf;
-EXPORT_SYMBOL_GPL(perf_trace_buf);
-
-char *perf_trace_buf_nmi;
-EXPORT_SYMBOL_GPL(perf_trace_buf_nmi);
+static char *perf_trace_buf;
+static char *perf_trace_buf_nmi;
 
 typedef typeof(char [FTRACE_MAX_PROFILE_SIZE]) perf_trace_t ;
 
@@ -120,3 +118,47 @@ void ftrace_profile_disable(int event_id)
         }
         mutex_unlock(&event_mutex);
 }
+
+__kprobes void *ftrace_perf_buf_prepare(int size, unsigned short type,
+                                        int *rctxp, unsigned long *irq_flags)
+{
+        struct trace_entry *entry;
+        char *trace_buf, *raw_data;
+        int pc, cpu;
+
+        pc = preempt_count();
+
+        /* Protect the per cpu buffer, begin the rcu read side */
+        local_irq_save(*irq_flags);
+
+        *rctxp = perf_swevent_get_recursion_context();
+        if (*rctxp < 0)
+                goto err_recursion;
+
+        cpu = smp_processor_id();
+
+        if (in_nmi())
+                trace_buf = rcu_dereference(perf_trace_buf_nmi);
+        else
+                trace_buf = rcu_dereference(perf_trace_buf);
+
+        if (!trace_buf)
+                goto err;
+
+        raw_data = per_cpu_ptr(trace_buf, cpu);
+
+        /* zero the dead bytes from align to not leak stack to user */
+        *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
+
+        entry = (struct trace_entry *)raw_data;
+        tracing_generic_entry_update(entry, *irq_flags, pc);
+        entry->type = type;
+
+        return raw_data;
+err:
+        perf_swevent_put_recursion_context(*rctxp);
+err_recursion:
+        local_irq_restore(*irq_flags);
+        return NULL;
+}
+EXPORT_SYMBOL_GPL(ftrace_perf_buf_prepare);