[PATCH v2] xtensa: improve stack dumping

[Max Filippov <jcmvbkbc@gmail.com>]

Calculate printable stack size and use print_hex_dump instead of
opencoding it.
Make size of stack dump configurable.
Drop extra newline output in show_trace as its output format does not
depend on CONFIG_KALLSYMS.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
Changes v1->v2:
- use print_hex_dump.

 arch/xtensa/Kconfig.debug  |  7 +++++++
 arch/xtensa/kernel/traps.c | 24 ++++++++----------------
 2 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/arch/xtensa/Kconfig.debug b/arch/xtensa/Kconfig.debug
index 39de98e20018..83cc8d12fa0e 100644
--- a/arch/xtensa/Kconfig.debug
+++ b/arch/xtensa/Kconfig.debug
@@ -31,3 +31,10 @@ config S32C1I_SELFTEST
 	  It is easy to make wrong hardware configuration, this test should catch it early.
 
 	  Say 'N' on stable hardware.
+
+config PRINT_STACK_DEPTH
+	int "Stack depth to print" if DEBUG_KERNEL
+	default 64
+	help
+	  This option allows you to set the stack depth that the kernel
+	  prints in stack traces.
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 4a6c495ce9b6..fe090ab1cab8 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -491,32 +491,24 @@ void show_trace(struct task_struct *task, unsigned long *sp)
 
 	pr_info("Call Trace:\n");
 	walk_stackframe(sp, show_trace_cb, NULL);
-#ifndef CONFIG_KALLSYMS
-	pr_cont("\n");
-#endif
 }
 
-static int kstack_depth_to_print = 24;
+static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
 
 void show_stack(struct task_struct *task, unsigned long *sp)
 {
-	int i = 0;
-	unsigned long *stack;
+	size_t len;
 
 	if (!sp)
 		sp = stack_pointer(task);
-	stack = sp;
 
-	pr_info("Stack:\n");
+	len = min((-(unsigned long)sp) & (THREAD_SIZE - 4),
+		  kstack_depth_to_print * 4ul);
 
-	for (i = 0; i < kstack_depth_to_print; i++) {
-		if (kstack_end(sp))
-			break;
-		pr_cont(" %08lx", *sp++);
-		if (i % 8 == 7)
-			pr_cont("\n");
-	}
-	show_trace(task, stack);
+	pr_info("Stack:\n");
+	print_hex_dump(KERN_INFO, " ", DUMP_PREFIX_NONE, 32, 4,
+		       sp, len, false);
+	show_trace(task, sp);
 }
 
 DEFINE_SPINLOCK(die_lock);
-- 
2.20.1