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-rw-r--r--include/linux/ftrace_event.h34
1 files changed, 0 insertions, 34 deletions
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 06c6faa9e5cc..28672e87e910 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -571,40 +571,6 @@ do { \
571 __trace_printk(ip, fmt, ##args); \ 571 __trace_printk(ip, fmt, ##args); \
572} while (0) 572} while (0)
573 573
574/**
575 * tracepoint_string - register constant persistent string to trace system
576 * @str - a constant persistent string that will be referenced in tracepoints
577 *
578 * If constant strings are being used in tracepoints, it is faster and
579 * more efficient to just save the pointer to the string and reference
580 * that with a printf "%s" instead of saving the string in the ring buffer
581 * and wasting space and time.
582 *
583 * The problem with the above approach is that userspace tools that read
584 * the binary output of the trace buffers do not have access to the string.
585 * Instead they just show the address of the string which is not very
586 * useful to users.
587 *
588 * With tracepoint_string(), the string will be registered to the tracing
589 * system and exported to userspace via the debugfs/tracing/printk_formats
590 * file that maps the string address to the string text. This way userspace
591 * tools that read the binary buffers have a way to map the pointers to
592 * the ASCII strings they represent.
593 *
594 * The @str used must be a constant string and persistent as it would not
595 * make sense to show a string that no longer exists. But it is still fine
596 * to be used with modules, because when modules are unloaded, if they
597 * had tracepoints, the ring buffers are cleared too. As long as the string
598 * does not change during the life of the module, it is fine to use
599 * tracepoint_string() within a module.
600 */
601#define tracepoint_string(str) \
602 ({ \
603 static const char *___tp_str __tracepoint_string = str; \
604 ___tp_str; \
605 })
606#define __tracepoint_string __attribute__((section("__tracepoint_str")))
607
608#ifdef CONFIG_PERF_EVENTS 574#ifdef CONFIG_PERF_EVENTS
609struct perf_event; 575struct perf_event;
610 576