x86, bts, ftrace: a BTS ftrace plug-in prototype

Impact: add new ftrace plugin

A prototype for a BTS ftrace plug-in.

The tracer collects branch trace in a cyclic buffer for each cpu.

The tracer is not configurable and the trace for each snapshot is
appended when doing cat /debug/tracing/trace.

This is a proof of concept that will be extended with future patches
to become a (hopefully) useful tool.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 9cbf7761f498..620feadff67a 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -28,6 +28,9 @@ config HAVE_DYNAMIC_FTRACE
 config HAVE_FTRACE_MCOUNT_RECORD
         bool
 
+config HAVE_HW_BRANCH_TRACER
+        bool
+
 config TRACER_MAX_TRACE
         bool
 
@@ -233,6 +236,14 @@ config STACK_TRACER
 
           Say N if unsure.
 
+config BTS_TRACER
+        depends on HAVE_HW_BRANCH_TRACER
+        bool "Trace branches"
+        select TRACING
+        help
+          This tracer records all branches on the system in a circular
+          buffer giving access to the last N branches for each cpu.
+
 config DYNAMIC_FTRACE
         bool "enable/disable ftrace tracepoints dynamically"
         depends on FUNCTION_TRACER