tracing: infrastructure for supporting binary record

Impact: save on memory for tracing

Current tracers are typically using a struct(like struct ftrace_entry,
struct ctx_switch_entry, struct special_entr etc...)to record a binary
event. These structs can only record a their own kind of events.
A new kind of tracer need a new struct and a lot of code too handle it.

So we need a generic binary record for events. This infrastructure
is for this purpose.

[fweisbec@gmail.com: rebase against latest -tip, make it safe while sched
tracing as reported by Steven Rostedt]

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1236356510-8381-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 56 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e6144acf2b75..ff53509e19f8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3792,6 +3792,62 @@ int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
 }
 EXPORT_SYMBOL_GPL(__ftrace_vprintk);
 
+/**
+ * trace_vbprintk - write binary msg to tracing buffer
+ *
+ * Caller must insure @fmt are valid when msg is in tracing buffer.
+ */
+int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
+{
+        static DEFINE_SPINLOCK(trace_buf_lock);
+        static u32 trace_buf[TRACE_BUF_SIZE];
+
+        struct ring_buffer_event *event;
+        struct trace_array *tr = &global_trace;
+        struct trace_array_cpu *data;
+        struct bprintk_entry *entry;
+        unsigned long flags;
+        int resched;
+        int cpu, len = 0, size, pc;
+
+        if (tracing_disabled || !trace_bprintk_enable)
+                return 0;
+
+        pc = preempt_count();
+        resched = ftrace_preempt_disable();
+        cpu = raw_smp_processor_id();
+        data = tr->data[cpu];
+
+        if (unlikely(atomic_read(&data->disabled)))
+                goto out;
+
+        spin_lock_irqsave(&trace_buf_lock, flags);
+        len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);
+
+        if (len > TRACE_BUF_SIZE || len < 0)
+                goto out_unlock;
+
+        size = sizeof(*entry) + sizeof(u32) * len;
+        event = trace_buffer_lock_reserve(tr, TRACE_BPRINTK, size, flags, pc);
+        if (!event)
+                goto out_unlock;
+        entry = ring_buffer_event_data(event);
+        entry->ip                       = ip;
+        entry->fmt                      = fmt;
+
+        memcpy(entry->buf, trace_buf, sizeof(u32) * len);
+        ring_buffer_unlock_commit(tr->buffer, event);
+
+out_unlock:
+        spin_unlock_irqrestore(&trace_buf_lock, flags);
+
+out:
+        ftrace_preempt_enable(resched);
+
+        return len;
+}
+EXPORT_SYMBOL_GPL(trace_vbprintk);
+
 static int trace_panic_handler(struct notifier_block *this,
                                unsigned long event, void *unused)
 {