arm64: Move console stack display code to stacktrace.c

Currently the code for displaying a stack trace on the console is located
in traps.c rather than stacktrace.c, using the unwinding code that is in
stacktrace.c. This can be confusing and make the code hard to find since
such output is often referred to as a stack trace which might mislead the
unwary. Due to this and since traps.c doesn't interact with this code
except for via the public interfaces move the code to stacktrace.c to
make it easier to find.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200921122341.11280-1-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 804d076b02cb..fa56af1a59c3 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -132,6 +132,71 @@ void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 }
 NOKPROBE_SYMBOL(walk_stackframe);
 
+static void dump_backtrace_entry(unsigned long where, const char *loglvl)
+{
+	printk("%s %pS\n", loglvl, (void *)where);
+}
+
+void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+		    const char *loglvl)
+{
+	struct stackframe frame;
+	int skip = 0;
+
+	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+
+	if (regs) {
+		if (user_mode(regs))
+			return;
+		skip = 1;
+	}
+
+	if (!tsk)
+		tsk = current;
+
+	if (!try_get_task_stack(tsk))
+		return;
+
+	if (tsk == current) {
+		start_backtrace(&frame,
+				(unsigned long)__builtin_frame_address(0),
+				(unsigned long)dump_backtrace);
+	} else {
+		/*
+		 * task blocked in __switch_to
+		 */
+		start_backtrace(&frame,
+				thread_saved_fp(tsk),
+				thread_saved_pc(tsk));
+	}
+
+	printk("%sCall trace:\n", loglvl);
+	do {
+		/* skip until specified stack frame */
+		if (!skip) {
+			dump_backtrace_entry(frame.pc, loglvl);
+		} else if (frame.fp == regs->regs[29]) {
+			skip = 0;
+			/*
+			 * Mostly, this is the case where this function is
+			 * called in panic/abort. As exception handler's
+			 * stack frame does not contain the corresponding pc
+			 * at which an exception has taken place, use regs->pc
+			 * instead.
+			 */
+			dump_backtrace_entry(regs->pc, loglvl);
+		}
+	} while (!unwind_frame(tsk, &frame));
+
+	put_task_stack(tsk);
+}
+
+void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
+{
+	dump_backtrace(NULL, tsk, loglvl);
+	barrier();
+}
+
 #ifdef CONFIG_STACKTRACE
 
 void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,