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Subject[PATCH 4/7] tracing/function: Introduce persistent trace option
Date
This patch introduces 'func_ptrace' option, now available in
/sys/kernel/debug/tracing/options when function tracer
is selected.

The patch also adds some tiny code that calls back to pstore
to record the trace. The callback is no-op when PSTORE=n.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
kernel/trace/trace_functions.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index c7b0c6a..269627c 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -13,6 +13,7 @@
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
+#include <linux/pstore.h>
#include <linux/fs.h>

#include "trace.h"
@@ -74,6 +75,14 @@ function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
preempt_enable_notrace();
}

+/* Our two options */
+enum {
+ TRACE_FUNC_OPT_STACK = 0x1,
+ TRACE_FUNC_OPT_PSTORE = 0x2,
+};
+
+static struct tracer_flags func_flags;
+
static void
function_trace_call(unsigned long ip, unsigned long parent_ip)
{
@@ -97,6 +106,12 @@ function_trace_call(unsigned long ip, unsigned long parent_ip)
disabled = atomic_inc_return(&data->disabled);

if (likely(disabled == 1)) {
+ /*
+ * So far tracing doesn't support multiple buffers, so
+ * we make an explicit call for now.
+ */
+ if (unlikely(func_flags.val & TRACE_FUNC_OPT_PSTORE))
+ pstore_ftrace_call(ip, parent_ip);
pc = preempt_count();
trace_function(tr, ip, parent_ip, flags, pc);
}
@@ -158,15 +173,13 @@ static struct ftrace_ops trace_stack_ops __read_mostly =
.flags = FTRACE_OPS_FL_GLOBAL,
};

-/* Our two options */
-enum {
- TRACE_FUNC_OPT_STACK = 0x1,
-};
-
static struct tracer_opt func_opts[] = {
#ifdef CONFIG_STACKTRACE
{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
#endif
+#ifdef CONFIG_PSTORE_FTRACE
+ { TRACER_OPT(func_pstore, TRACE_FUNC_OPT_PSTORE) },
+#endif
{ } /* Always set a last empty entry */
};

@@ -219,6 +232,8 @@ static int func_set_flag(u32 old_flags, u32 bit, int set)

return 0;
}
+ if (bit == TRACE_FUNC_OPT_PSTORE)
+ return 0;

return -EINVAL;
}
--
1.7.10.4


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