[PATCH v2 5/7] stacktrace: introduce snprint_stack_trace for buffer output

[Joonsoo Kim]

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
so so new function, snprint_stack_trace(), is needed.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
 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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