arm64: stacktrace: Convert to ARCH_STACKWALK

Historically architectures have had duplicated code in their stack trace
implementations for filtering what gets traced. In order to avoid this
duplication some generic code has been provided using a new interface
arch_stack_walk(), enabled by selecting ARCH_STACKWALK in Kconfig, which
factors all this out into the generic stack trace code. Convert arm64
to use this common infrastructure.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/20200914153409.25097-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/Kconfig

@@ -29,6 +29,7 @@ config ARM64
 	select ARCH_HAS_SETUP_DMA_OPS
 	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_SET_MEMORY
+	select ARCH_STACKWALK
 	select ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE

arch/arm64/kernel/stacktrace.c

@@ -133,82 +133,23 @@ void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 NOKPROBE_SYMBOL(walk_stackframe);
 
 #ifdef CONFIG_STACKTRACE
-struct stack_trace_data {
-	struct stack_trace *trace;
-	unsigned int no_sched_functions;
-	unsigned int skip;
-};
 
-static bool save_trace(void *d, unsigned long addr)
+void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+		     struct task_struct *task, struct pt_regs *regs)
 {
-	struct stack_trace_data *data = d;
-	struct stack_trace *trace = data->trace;
-
-	if (data->no_sched_functions && in_sched_functions(addr))
-		return false;
-	if (data->skip) {
-		data->skip--;
-		return false;
-	}
-
-	trace->entries[trace->nr_entries++] = addr;
-
-	return trace->nr_entries >= trace->max_entries;
-}
-
-void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
-{
-	struct stack_trace_data data;
-	struct stackframe frame;
-
-	data.trace = trace;
-	data.skip = trace->skip;
-	data.no_sched_functions = 0;
-
-	start_backtrace(&frame, regs->regs[29], regs->pc);
-	walk_stackframe(current, &frame, save_trace, &data);
-}
-EXPORT_SYMBOL_GPL(save_stack_trace_regs);
-
-static noinline void __save_stack_trace(struct task_struct *tsk,
-	struct stack_trace *trace, unsigned int nosched)
-{
-	struct stack_trace_data data;
 	struct stackframe frame;
 
-	if (!try_get_task_stack(tsk))
-		return;
-
-	data.trace = trace;
-	data.skip = trace->skip;
-	data.no_sched_functions = nosched;
-
-	if (tsk != current) {
-		start_backtrace(&frame, thread_saved_fp(tsk),
-				thread_saved_pc(tsk));
-	} else {
-		/* We don't want this function nor the caller */
-		data.skip += 2;
+	if (regs)
+		start_backtrace(&frame, regs->regs[29], regs->pc);
+	else if (task == current)
 		start_backtrace(&frame,
 				(unsigned long)__builtin_frame_address(0),
-				(unsigned long)__save_stack_trace);
-	}
-
-	walk_stackframe(tsk, &frame, save_trace, &data);
+				(unsigned long)arch_stack_walk);
+	else
+		start_backtrace(&frame, thread_saved_fp(task),
+				thread_saved_pc(task));
 
-	put_task_stack(tsk);
-}
-
-void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
-{
-	__save_stack_trace(tsk, trace, 1);
-}
-EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
-
-void save_stack_trace(struct stack_trace *trace)
-{
-	__save_stack_trace(current, trace, 0);
+	walk_stackframe(task, &frame, consume_entry, cookie);
 }
 
-EXPORT_SYMBOL_GPL(save_stack_trace);
 #endif