[RFC PATCH 4/5] stacktrace: support snprint

[Joonsoo Kim <iamjoonsoo.kim@lge.com>]

Current stacktrace only have the function for console output.
page_owner that will be introduced in following patch needs to print
the output of stacktrace into the buffer for our own output format. Also,
it needs to print message to debugfs output buffer, so new function,
snprint is needed.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
 include/linux/stacktrace.h |    3 +++
 kernel/stacktrace.c        |   24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 115b570..5948c67 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -20,6 +20,8 @@ extern void save_stack_trace_tsk(struct task_struct *tsk,
 				struct stack_trace *trace);
 
 extern void print_stack_trace(struct stack_trace *trace, int spaces);
+extern int  snprint_stack_trace(char *buf, int buf_len,
+				struct stack_trace *trace, int spaces);
 
 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
 extern void save_stack_trace_user(struct stack_trace *trace);
@@ -32,6 +34,7 @@ extern void save_stack_trace_user(struct stack_trace *trace);
 # define save_stack_trace_tsk(tsk, trace)		do { } while (0)
 # define save_stack_trace_user(trace)			do { } while (0)
 # define print_stack_trace(trace, spaces)		do { } while (0)
+# define snprint_stack_trace(buf, len, trace, spaces)	do { } while (0)
 #endif
 
 #endif
diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 00fe55c..61088ff 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -25,6 +25,30 @@ void print_stack_trace(struct stack_trace *trace, int spaces)
 }
 EXPORT_SYMBOL_GPL(print_stack_trace);
 
+int snprint_stack_trace(char *buf, int buf_len, struct stack_trace *trace,
+			int spaces)
+{
+	int i, printed;
+	unsigned long ip;
+	int ret = 0;
+
+	if (WARN_ON(!trace->entries))
+		return 0;
+
+	for (i = 0; i < trace->nr_entries && buf_len; i++) {
+		ip = trace->entries[i];
+		printed = snprintf(buf, buf_len, "%*c[<%p>] %pS\n",
+				1 + spaces, ' ', (void *) ip, (void *) ip);
+
+		buf_len -= printed;
+		ret += printed;
+		buf += printed;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(snprint_stack_trace);
+
 /*
  * Architectures that do not implement save_stack_trace_tsk or
  * save_stack_trace_regs get this weak alias and a once-per-bootup warning
-- 
1.7.9.5

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