On 08/30/2017 11:25 AM, Ziqian SUN (Zamir) wrote:
From: "Ziqian SUN (Zamir)" <z...@redhat.com>
The mmiotrace tracer cannot be enabled with ftrace=mmiotrace in
kernel commandline. With this patch, a trace_noboot_tracer_list
is implemented and will be checked during system boot. If the
tracer declares itself as not for boot up, system will print out
a message and continue booting.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=196557
Signed-off-by: Ziqian SUN (Zamir) <z...@redhat.com>
---
kernel/trace/trace.c | 35 ++++++++++++++++++++++++++++++++++-
kernel/trace/trace.h | 11 +++++++++++
kernel/trace/trace_mmiotrace.c | 4 ++++
3 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 44004d8..aba774d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -319,6 +319,34 @@ void trace_free_pid_list(struct trace_pid_list *pid_list)
kfree(pid_list);
}
+/*struct list_head trace_noboot_tracer_list;*/
Just realized this commented line is no longer needed. I will send out
v2 to remove it.
+struct mutex trace_noboot_tracer_lock;
+
+DEFINE_MUTEX(trace_noboot_tracer_lock);
+LIST_HEAD(trace_noboot_tracer_list);
+
+void trace_noboot_tracer_put(struct tracer_noboot *noboot_tracer)
+{
+ mutex_lock(&trace_noboot_tracer_lock);
+ list_add(&noboot_tracer->list, &trace_noboot_tracer_list);
+ mutex_unlock(&trace_noboot_tracer_lock);
+}
+
+bool trace_noboot_tracer_find(const char *str)
+{
+ mutex_lock(&trace_noboot_tracer_lock);
+ struct tracer_noboot *ptr = NULL;
+
+ list_for_each_entry(ptr, &trace_noboot_tracer_list, list) {
+ if (strcmp(ptr->name, str) == 0) {
+ mutex_unlock(&trace_noboot_tracer_lock);
+ return true;
+ }
+ }
+ mutex_unlock(&trace_noboot_tracer_lock);
+ return false;
+}
+
/**
* trace_find_filtered_pid - check if a pid exists in a filtered_pid list
* @filtered_pids: The list of pids to check
@@ -1641,8 +1669,13 @@ int __init register_tracer(struct tracer *type)
if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE))
goto out_unlock;
+ /* If the tracer should not be enabled by kernel parameter */
+ if (trace_noboot_tracer_find(type->name)) {
+ pr_warn("Tracer '%s' cannot be enabled during boot\n",
type->name);
+ goto out_unlock;
+ }
+
printk(KERN_INFO "Starting tracer '%s'\n", type->name);
- /* Do we want this tracer to start on bootup? */
tracing_set_tracer(&global_trace, type->name);
default_bootup_tracer = NULL;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 490ba22..23bc668 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -502,6 +502,17 @@ enum {
TRACE_IRQ_BIT,
};
+/*
+ * For tracer that cannot be enabled during boot time.
+ */
+
+struct tracer_noboot {
+ const char *name;
+ struct list_head list;
+};
+
+void trace_noboot_tracer_put(struct tracer_noboot *noboot_tracer);
+
#define trace_recursion_set(bit) do { (current)->trace_recursion |=
(1<<(bit)); } while (0)
#define trace_recursion_clear(bit) do { (current)->trace_recursion &=
~(1<<(bit)); } while (0)
#define trace_recursion_test(bit) ((current)->trace_recursion &
(1<<(bit)))
diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index cd7480d..06aa0a5 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -286,6 +286,10 @@ static enum print_line_t mmio_print_line(struct
trace_iterator *iter)
__init static int init_mmio_trace(void)
{
+ struct tracer_noboot mmio_notrace;
+
+ mmio_notrace.name = "mmiotrace";
+ trace_noboot_tracer_put(&mmio_notrace);
return register_tracer(&mmio_tracer);
}
device_initcall(init_mmio_trace);
--
Ziqian SUN (Zamir)
Red Hat Software (Beijing) Co.,Ltd
