1 files changed, 221 insertions, 0 deletions
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
new file mode 100644
index 000000000..c445828ec
--- /dev/null
+++ b/arch/arm64/kernel/stacktrace.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Stack tracing support
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ */
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/ftrace.h>
+#include <linux/kprobes.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/stacktrace.h>
+
+#include <asm/irq.h>
+#include <asm/pointer_auth.h>
+#include <asm/stack_pointer.h>
+#include <asm/stacktrace.h>
+
+/*
+ * AArch64 PCS assigns the frame pointer to x29.
+ *
+ * A simple function prologue looks like this:
+ * 	sub	sp, sp, #0x10
+ *   	stp	x29, x30, [sp]
+ *	mov	x29, sp
+ *
+ * A simple function epilogue looks like this:
+ *	mov	sp, x29
+ *	ldp	x29, x30, [sp]
+ *	add	sp, sp, #0x10
+ */
+
+/*
+ * Unwind from one frame record (A) to the next frame record (B).
+ *
+ * We terminate early if the location of B indicates a malformed chain of frame
+ * records (e.g. a cycle), determined based on the location and fp value of A
+ * and the location (but not the fp value) of B.
+ */
+int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
+{
+	unsigned long fp = frame->fp;
+	struct stack_info info;
+
+	if (fp & 0xf)
+		return -EINVAL;
+
+	if (!tsk)
+		tsk = current;
+
+	if (!on_accessible_stack(tsk, fp, &info))
+		return -EINVAL;
+
+	if (test_bit(info.type, frame->stacks_done))
+		return -EINVAL;
+
+	/*
+	 * As stacks grow downward, any valid record on the same stack must be
+	 * at a strictly higher address than the prior record.
+	 *
+	 * Stacks can nest in several valid orders, e.g.
+	 *
+	 * TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL
+	 * TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW
+	 *
+	 * ... but the nesting itself is strict. Once we transition from one
+	 * stack to another, it's never valid to unwind back to that first
+	 * stack.
+	 */
+	if (info.type == frame->prev_type) {
+		if (fp <= frame->prev_fp)
+			return -EINVAL;
+	} else {
+		set_bit(frame->prev_type, frame->stacks_done);
+	}
+
+	/*
+	 * Record this frame record's values and location. The prev_fp and
+	 * prev_type are only meaningful to the next unwind_frame() invocation.
+	 */
+	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
+	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
+	frame->prev_fp = fp;
+	frame->prev_type = info.type;
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	if (tsk->ret_stack &&
+		(ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) {
+		struct ftrace_ret_stack *ret_stack;
+		/*
+		 * This is a case where function graph tracer has
+		 * modified a return address (LR) in a stack frame
+		 * to hook a function return.
+		 * So replace it to an original value.
+		 */
+		ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);
+		if (WARN_ON_ONCE(!ret_stack))
+			return -EINVAL;
+		frame->pc = ret_stack->ret;
+	}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+	frame->pc = ptrauth_strip_insn_pac(frame->pc);
+
+	/*
+	 * Frames created upon entry from EL0 have NULL FP and PC values, so
+	 * don't bother reporting these. Frames created by __noreturn functions
+	 * might have a valid FP even if PC is bogus, so only terminate where
+	 * both are NULL.
+	 */
+	if (!frame->fp && !frame->pc)
+		return -EINVAL;
+
+	return 0;
+}
+NOKPROBE_SYMBOL(unwind_frame);
+
+void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
+			     bool (*fn)(void *, unsigned long), void *data)
+{
+	while (1) {
+		int ret;
+
+		if (!fn(data, frame->pc))
+			break;
+		ret = unwind_frame(tsk, frame);
+		if (ret < 0)
+			break;
+	}
+}
+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
+
+noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
+			      void *cookie, struct task_struct *task,
+			      struct pt_regs *regs)
+{
+	struct stackframe frame;
+
+	if (regs)
+		start_backtrace(&frame, regs->regs[29], regs->pc);
+	else if (task == current)
+		start_backtrace(&frame,
+				(unsigned long)__builtin_frame_address(1),
+				(unsigned long)__builtin_return_address(0));
+	else
+		start_backtrace(&frame, thread_saved_fp(task),
+				thread_saved_pc(task));
+
+	walk_stackframe(task, &frame, consume_entry, cookie);
+}
+
+#endif