tracing/core: drop the old trace_printk() implementation in favour of trace_bprintk()

Impact: faster and lighter tracing

Now that we have trace_bprintk() which is faster and consume lesser
memory than trace_printk() and has the same purpose, we can now drop
the old implementation in favour of the binary one from trace_bprintk(),
which means we move all the implementation of trace_bprintk() to
trace_printk(), so the Api doesn't change except that we must now use
trace_seq_bprintk() to print the TRACE_PRINT entries.

Some changes result of this:

- Previously, trace_bprintk depended of a single tracer and couldn't
  work without. This tracer has been dropped and the whole implementation
  of trace_printk() (like the module formats management) is now integrated
  in the tracing core (comes with CONFIG_TRACING), though we keep the file
  trace_printk (previously trace_bprintk.c) where we can find the module
  management. Thus we don't overflow trace.c

- changes some parts to use trace_seq_bprintk() to print TRACE_PRINT entries.

- change a bit trace_printk/trace_vprintk macros to support non-builtin formats
  constants, and fix 'const' qualifiers warnings. But this is all transparent for
  developers.

- etc...

V2:

- Rebase against last changes
- Fix mispell on the changelog

V3:

- Rebase against last changes (moving trace_printk() to kernel.h)

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1236356510-8381-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 138 insertions, 0 deletions

diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
new file mode 100644
index 000000000000..a50aea22e929
--- /dev/null
+++ b/kernel/trace/trace_printk.c
@@ -0,0 +1,138 @@
+/*
+ * trace binary printk
+ *
+ * Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/ftrace.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/fs.h>
+#include <linux/marker.h>
+#include <linux/uaccess.h>
+
+#include "trace.h"
+
+#ifdef CONFIG_MODULES
+
+/*
+ * modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
+ * which are queued on trace_bprintk_fmt_list.
+ */
+static LIST_HEAD(trace_bprintk_fmt_list);
+
+/* serialize accesses to trace_bprintk_fmt_list */
+static DEFINE_MUTEX(btrace_mutex);
+
+struct trace_bprintk_fmt {
+        struct list_head list;
+        char fmt[0];
+};
+
+static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
+{
+        struct trace_bprintk_fmt *pos;
+        list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
+                if (!strcmp(pos->fmt, fmt))
+                        return pos;
+        }
+        return NULL;
+}
+
+static
+void hold_module_trace_bprintk_format(const char **start, const char **end)
+{
+        const char **iter;
+
+        mutex_lock(&btrace_mutex);
+        for (iter = start; iter < end; iter++) {
+                struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
+                if (tb_fmt) {
+                        *iter = tb_fmt->fmt;
+                        continue;
+                }
+
+                tb_fmt = kmalloc(offsetof(struct trace_bprintk_fmt, fmt)
+                                + strlen(*iter) + 1, GFP_KERNEL);
+                if (tb_fmt) {
+                        list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
+                        strcpy(tb_fmt->fmt, *iter);
+                        *iter = tb_fmt->fmt;
+                } else
+                        *iter = NULL;
+        }
+        mutex_unlock(&btrace_mutex);
+}
+
+static int module_trace_bprintk_format_notify(struct notifier_block *self,
+                unsigned long val, void *data)
+{
+        struct module *mod = data;
+        if (mod->num_trace_bprintk_fmt) {
+                const char **start = mod->trace_bprintk_fmt_start;
+                const char **end = start + mod->num_trace_bprintk_fmt;
+
+                if (val == MODULE_STATE_COMING)
+                        hold_module_trace_bprintk_format(start, end);
+        }
+        return 0;
+}
+
+#else /* !CONFIG_MODULES */
+__init static int
+module_trace_bprintk_format_notify(struct notifier_block *self,
+                unsigned long val, void *data)
+{
+        return 0;
+}
+#endif /* CONFIG_MODULES */
+
+
+__initdata_or_module static
+struct notifier_block module_trace_bprintk_format_nb = {
+        .notifier_call = module_trace_bprintk_format_notify,
+};
+
+int __trace_printk(unsigned long ip, const char *fmt, ...)
+ {
+        int ret;
+        va_list ap;
+
+        if (unlikely(!fmt))
+                return 0;
+
+        if (!(trace_flags & TRACE_ITER_PRINTK))
+                return 0;
+
+        va_start(ap, fmt);
+        ret = trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
+        va_end(ap);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(__trace_printk);
+
+int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
+ {
+        if (unlikely(!fmt))
+                return 0;
+
+        if (!(trace_flags & TRACE_ITER_PRINTK))
+                return 0;
+
+        return trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
+}
+EXPORT_SYMBOL_GPL(__ftrace_vprintk);
+
+
+static __init int init_trace_printk(void)
+{
+        return register_module_notifier(&module_trace_bprintk_format_nb);
+}
+
+early_initcall(init_trace_printk);