stacktrace: introduce snprint_stack_trace for buffer output

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@lge.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Jungsoo Son <jungsoo.son@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 00fe55cc5a82..b6e4c16377c7 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -25,6 +25,38 @@ void print_stack_trace(struct stack_trace *trace, int spaces)
 }
 EXPORT_SYMBOL_GPL(print_stack_trace);
 
+int snprint_stack_trace(char *buf, size_t size,
+                        struct stack_trace *trace, int spaces)
+{
+        int i;
+        unsigned long ip;
+        int generated;
+        int total = 0;
+
+        if (WARN_ON(!trace->entries))
+                return 0;
+
+        for (i = 0; i < trace->nr_entries; i++) {
+                ip = trace->entries[i];
+                generated = snprintf(buf, size, "%*c[<%p>] %pS\n",
+                                1 + spaces, ' ', (void *) ip, (void *) ip);
+
+                total += generated;
+
+                /* Assume that generated isn't a negative number */
+                if (generated >= size) {
+                        buf += size;
+                        size = 0;
+                } else {
+                        buf += generated;
+                        size -= generated;
+                }
+        }
+
+        return total;
+}
+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