tracing/function-graph-tracer: annotate do_IRQ and smp_apic_timer_interrupt

Impact: move most important x86 irq entry-points to a separate subsection

Annotate do_IRQ and smp_apic_timer_interrupt to put them into the .irqentry.text
subsection. These function will so be recognized as hardirq entrypoints for the
function-graph-tracer. We could also annotate other irq entries but the others
are far less important but they can be added on request.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 11cac81eed08..44020f31bd81 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -377,6 +377,16 @@ struct ftrace_graph_ret {
  */
 #define __notrace_funcgraph             notrace
 
+/*
+ * We want to which function is an entrypoint of a hardirq.
+ * That will help us to put a signal on output.
+ */
+#define __irq_entry              __attribute__((__section__(".irqentry.text")))
+
+/* Limits of hardirq entrypoints */
+extern char __irqentry_text_start[];
+extern char __irqentry_text_end[];
+
 #define FTRACE_RETFUNC_DEPTH 50
 #define FTRACE_RETSTACK_ALLOC_SIZE 32
 /* Type of the callback handlers for tracing function graph*/
@@ -414,6 +424,7 @@ static inline void unpause_graph_tracing(void)
 #else
 
 #define __notrace_funcgraph
+#define __irq_entry
 
 static inline void ftrace_graph_init_task(struct task_struct *t) { }
 static inline void ftrace_graph_exit_task(struct task_struct *t) { }