[RFC patch 18/41] stacktrace: Provide helpers for common stack trace operations

[Thomas Gleixner <tglx@linutronix.de>]

All operations with stack traces are based on struct stack_trace. That's a
horrible construct as the struct is a kitchen sink for input and
output. Quite some usage sites embed it into their own data structures
which creates weird indirections.

There is absolutely no point in doing so. For all use cases a storage array
and the number of valid stack trace entries in the array is sufficient.

Provide helper functions which avoid the struct stack_trace indirection so
the usage sites can be cleaned up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/stacktrace.h |   18 +++++
 kernel/stacktrace.c        |  137 ++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 140 insertions(+), 15 deletions(-)

--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -26,6 +26,24 @@ extern void print_stack_trace(struct sta
 extern int snprint_stack_trace(char *buf, size_t size,
 			struct stack_trace *trace, int spaces);
 
+extern void stack_trace_print(unsigned long *trace, unsigned int nr_entries,
+			      int spaces);
+extern int stack_trace_snprint(char *buf, size_t size, unsigned long *entries,
+			       unsigned int nr_entries, int spaces);
+extern unsigned int stack_trace_save(unsigned long *store, unsigned int size,
+				     unsigned int skipnr);
+extern unsigned int stack_trace_save_tsk(struct task_struct *task,
+					 unsigned long *store,
+					 unsigned int size,
+					 unsigned int skipnr);
+extern unsigned int stack_trace_save_regs(struct pt_regs *regs,
+					  unsigned long *store,
+					  unsigned int size,
+					  unsigned int skipnr);
+extern unsigned int stack_trace_save_user(unsigned long *store,
+					  unsigned int size,
+					  unsigned int skipnr);
+
 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
 extern void save_stack_trace_user(struct stack_trace *trace);
 #else
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -11,35 +11,52 @@
 #include <linux/kallsyms.h>
 #include <linux/stacktrace.h>
 
-void print_stack_trace(struct stack_trace *trace, int spaces)
+/**
+ * stack_trace_print - Print the entries in the stack trace
+ * @entries:	Pointer to storage array
+ * @nr_entries:	Number of entries in the storage array
+ * @spaces:	Number of leading spaces to print
+ */
+void stack_trace_print(unsigned long *entries, unsigned int nr_entries,
+		       int spaces)
 {
-	int i;
+	unsigned int i;
 
-	if (WARN_ON(!trace->entries))
+	if (WARN_ON(!entries))
 		return;
 
-	for (i = 0; i < trace->nr_entries; i++)
-		printk("%*c%pS\n", 1 + spaces, ' ', (void *)trace->entries[i]);
+	for (i = 0; i < nr_entries; i++)
+		printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
+}
+EXPORT_SYMBOL_GPL(stack_trace_print);
+
+void print_stack_trace(struct stack_trace *trace, int spaces)
+{
+	stack_trace_print(trace->entries, trace->nr_entries, spaces);
 }
 EXPORT_SYMBOL_GPL(print_stack_trace);
 
-int snprint_stack_trace(char *buf, size_t size,
-			struct stack_trace *trace, int spaces)
+/**
+ * stack_trace_snprint - Print the entries in the stack trace into a buffer
+ * @buf:	Pointer to the print buffer
+ * @size:	Size of the print buffer
+ * @entries:	Pointer to storage array
+ * @nr_entries:	Number of entries in the storage array
+ * @spaces:	Number of leading spaces to print
+ */
+int stack_trace_snprint(char *buf, size_t size, unsigned long *entries,
+			unsigned int nr_entries, int spaces)
 {
-	int i;
-	int generated;
-	int total = 0;
+	unsigned int generated, i, total = 0;
 
-	if (WARN_ON(!trace->entries))
+	if (WARN_ON(!entries))
 		return 0;
 
-	for (i = 0; i < trace->nr_entries; i++) {
+	for (i = 0; i < nr_entries; i++) {
 		generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
-				     (void *)trace->entries[i]);
+				     (void *)entries[i]);
 
 		total += generated;
-
-		/* Assume that generated isn't a negative number */
 		if (generated >= size) {
 			buf += size;
 			size = 0;
@@ -51,6 +68,14 @@ int snprint_stack_trace(char *buf, size_
 
 	return total;
 }
+EXPORT_SYMBOL_GPL(stack_trace_snprint);
+
+int snprint_stack_trace(char *buf, size_t size,
+			struct stack_trace *trace, int spaces)
+{
+	return stack_trace_snprint(buf, size, trace->entries,
+				   trace->nr_entries, spaces);
+}
 EXPORT_SYMBOL_GPL(snprint_stack_trace);
 
 /*
@@ -77,3 +102,85 @@ save_stack_trace_tsk_reliable(struct tas
 	WARN_ONCE(1, KERN_INFO "save_stack_tsk_reliable() not implemented yet.\n");
 	return -ENOSYS;
 }
+
+/**
+ * stack_trace_save - Save a stack trace into a storage array
+ * @store:	Pointer to storage array
+ * @size:	Size of the storage array
+ * @skipnr:	Number of entries to skip at the start of the stack trace
+ */
+unsigned int stack_trace_save(unsigned long *store, unsigned int size,
+			      unsigned int skipnr)
+{
+	struct stack_trace trace = {
+		.entries	= store,
+		.max_entries	= size,
+		.skip		= skipnr + 1,
+	};
+
+	save_stack_trace(&trace);
+	return trace.nr_entries;
+}
+EXPORT_SYMBOL_GPL(stack_trace_save);
+
+/**
+ * stack_trace_save_tsk - Save a task stack trace into a storage array
+ * @task:	The task to examine
+ * @store:	Pointer to storage array
+ * @size:	Size of the storage array
+ * @skipnr:	Number of entries to skip at the start of the stack trace
+ */
+unsigned int stack_trace_save_tsk(struct task_struct *task,
+				  unsigned long *store, unsigned int size,
+				  unsigned int skipnr)
+{
+	struct stack_trace trace = {
+		.entries	= store,
+		.max_entries	= size,
+		.skip		= skipnr + 1,
+	};
+
+	save_stack_trace_tsk(task, &trace);
+	return trace.nr_entries;
+}
+
+/**
+ * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
+ * @regs:	Pointer to pt_regs to examine
+ * @store:	Pointer to storage array
+ * @size:	Size of the storage array
+ * @skipnr:	Number of entries to skip at the start of the stack trace
+ */
+unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
+				   unsigned int size, unsigned int skipnr)
+{
+	struct stack_trace trace = {
+		.entries	= store,
+		.max_entries	= size,
+		.skip		= skipnr + 1,
+	};
+
+	save_stack_trace_regs(regs, &trace);
+	return trace.nr_entries;
+}
+
+#ifdef CONFIG_USER_STACKTRACE_SUPPORT
+/**
+ * stack_trace_save_user - Save a user space stack trace into a storage array
+ * @store:	Pointer to storage array
+ * @size:	Size of the storage array
+ * @skipnr:	Number of entries to skip at the start of the stack trace
+ */
+unsigned int stack_trace_save_user(unsigned long *store, unsigned int size,
+				   unsigned int skipnr)
+{
+	struct stack_trace trace = {
+		.entries	= store,
+		.max_entries	= size,
+		.skip		= skipnr + 1,
+	};
+
+	save_stack_trace_user(&trace);
+	return trace.nr_entries;
+}
+#endif