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Subject[PATCH v3 5/8] stacktrace: introduce snprint_stack_trace for buffer output
Date
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.

v3:
fix potential buffer overflow case
make snprint_stack_trace() return generated string length rather than
printed string length like as snprint* functions semantic.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
include/linux/stacktrace.h | 5 +++++
kernel/stacktrace.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+)

diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 115b570..669045a 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -1,6 +1,8 @@
#ifndef __LINUX_STACKTRACE_H
#define __LINUX_STACKTRACE_H

+#include <linux/types.h>
+
struct task_struct;
struct pt_regs;

@@ -20,6 +22,8 @@ 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, size_t size,
+ struct stack_trace *trace, int spaces);

#ifdef CONFIG_USER_STACKTRACE_SUPPORT
extern void save_stack_trace_user(struct stack_trace *trace);
@@ -32,6 +36,7 @@ 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, size, trace, spaces) do { } while (0)
#endif

#endif
diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 00fe55c..b6e4c16 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
--
1.7.9.5


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