[RFC v6 4/8] stacktrace, stackdepot: Add sprintf_end()-like variants of functions

[Alejandro Colomar]

Cc: Kees Cook <kees@xxxxxxxxxx>
Cc: Christopher Bazley <chris.bazley.wg14@xxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Alejandro Colomar <alx@xxxxxxxxxx>
---
 include/linux/stackdepot.h | 13 +++++++++++++
 include/linux/stacktrace.h |  3 +++
 kernel/stacktrace.c        | 28 ++++++++++++++++++++++++++++
 lib/stackdepot.c           | 13 +++++++++++++
 4 files changed, 57 insertions(+)

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index 2cc21ffcdaf9..76182e874f67 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -219,6 +219,19 @@ void stack_depot_print(depot_stack_handle_t stack);
 int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
 		       int spaces);
 
+/**
+ * stack_depot_sprint_end - Print a stack trace from stack depot into a buffer
+ *
+ * @handle:	Stack depot handle returned from stack_depot_save()
+ * @p:		Pointer to the print buffer
+ * @end:	Pointer to one past the last element in the buffer
+ * @spaces:	Number of leading spaces to print
+ *
+ * Return:	Pointer to trailing '\0'; or NULL on truncation
+ */
+char *stack_depot_sprint_end(depot_stack_handle_t handle, char *p,
+                             const char end[0], int spaces);
+
 /**
  * stack_depot_put - Drop a reference to a stack trace from stack depot
  *
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 97455880ac41..79ada795d479 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -67,6 +67,9 @@ void stack_trace_print(const unsigned long *trace, unsigned int nr_entries,
 		       int spaces);
 int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
 			unsigned int nr_entries, int spaces);
+char *stack_trace_sprint_end(char *p, const char end[0],
+			     const unsigned long *entries,
+			     unsigned int nr_entries, int spaces);
 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
 			      unsigned int skipnr);
 unsigned int stack_trace_save_tsk(struct task_struct *task,
diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index afb3c116da91..f389647d8e44 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -70,6 +70,34 @@ int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
 }
 EXPORT_SYMBOL_GPL(stack_trace_snprint);
 
+/**
+ * stack_trace_sprint_end - Print the entries in the stack trace into a buffer
+ * @p:		Pointer to the print buffer
+ * @end:	Pointer to one past the last element in the buffer
+ * @entries:	Pointer to storage array
+ * @nr_entries:	Number of entries in the storage array
+ * @spaces:	Number of leading spaces to print
+ *
+ * Return: Pointer to the trailing '\0'; or NULL on truncation.
+ */
+char *stack_trace_sprint_end(char *p, const char end[0],
+			  const unsigned long *entries, unsigned int nr_entries,
+			  int spaces)
+{
+	unsigned int i;
+
+	if (WARN_ON(!entries))
+		return 0;
+
+	for (i = 0; i < nr_entries; i++) {
+		p = sprintf_end(p, end, "%*c%pS\n", 1 + spaces, ' ',
+			     (void *)entries[i]);
+	}
+
+	return p;
+}
+EXPORT_SYMBOL_GPL(stack_trace_sprint_end);
+
 #ifdef CONFIG_ARCH_STACKWALK
 
 struct stacktrace_cookie {
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 73d7b50924ef..48e5c0ff37e8 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -771,6 +771,19 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
 }
 EXPORT_SYMBOL_GPL(stack_depot_snprint);
 
+char *stack_depot_sprint_end(depot_stack_handle_t handle, char *p,
+			     const char end[0], int spaces)
+{
+	unsigned long *entries;
+	unsigned int nr_entries;
+
+	nr_entries = stack_depot_fetch(handle, &entries);
+	return nr_entries ?
+		stack_trace_sprint_end(p, end, entries, nr_entries, spaces)
+		: sprintf_end(p, end, "");
+}
+EXPORT_SYMBOL_GPL(stack_depot_sprint_end);
+
 depot_stack_handle_t __must_check stack_depot_set_extra_bits(
 			depot_stack_handle_t handle, unsigned int extra_bits)
 {
-- 
2.50.0