1 files changed, 248 insertions, 0 deletions
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
new file mode 100644
index 000000000..85443b5d1
--- /dev/null
+++ b/arch/arm/kernel/stacktrace.c
@@ -0,0 +1,248 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/export.h>
+#include <linux/kprobes.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/stacktrace.h>
+
+#include <asm/sections.h>
+#include <asm/stacktrace.h>
+#include <asm/traps.h>
+
+#include "reboot.h"
+
+#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
+/*
+ * Unwind the current stack frame and store the new register values in the
+ * structure passed as argument. Unwinding is equivalent to a function return,
+ * hence the new PC value rather than LR should be used for backtrace.
+ *
+ * With framepointer enabled, a simple function prologue looks like this:
+ *	mov	ip, sp
+ *	stmdb	sp!, {fp, ip, lr, pc}
+ *	sub	fp, ip, #4
+ *
+ * A simple function epilogue looks like this:
+ *	ldm	sp, {fp, sp, pc}
+ *
+ * When compiled with clang, pc and sp are not pushed. A simple function
+ * prologue looks like this when built with clang:
+ *
+ *	stmdb	{..., fp, lr}
+ *	add	fp, sp, #x
+ *	sub	sp, sp, #y
+ *
+ * A simple function epilogue looks like this when built with clang:
+ *
+ *	sub	sp, fp, #x
+ *	ldm	{..., fp, pc}
+ *
+ *
+ * Note that with framepointer enabled, even the leaf functions have the same
+ * prologue and epilogue, therefore we can ignore the LR value in this case.
+ */
+
+extern unsigned long call_with_stack_end;
+
+static int frame_pointer_check(struct stackframe *frame)
+{
+	unsigned long high, low;
+	unsigned long fp = frame->fp;
+	unsigned long pc = frame->pc;
+
+	/*
+	 * call_with_stack() is the only place we allow SP to jump from one
+	 * stack to another, with FP and SP pointing to different stacks,
+	 * skipping the FP boundary check at this point.
+	 */
+	if (pc >= (unsigned long)&call_with_stack &&
+			pc < (unsigned long)&call_with_stack_end)
+		return 0;
+
+	/* only go to a higher address on the stack */
+	low = frame->sp;
+	high = ALIGN(low, THREAD_SIZE);
+
+	/* check current frame pointer is within bounds */
+#ifdef CONFIG_CC_IS_CLANG
+	if (fp < low + 4 || fp > high - 4)
+		return -EINVAL;
+#else
+	if (fp < low + 12 || fp > high - 4)
+		return -EINVAL;
+#endif
+
+	return 0;
+}
+
+int notrace unwind_frame(struct stackframe *frame)
+{
+	unsigned long fp = frame->fp;
+
+	if (frame_pointer_check(frame))
+		return -EINVAL;
+
+	/*
+	 * When we unwind through an exception stack, include the saved PC
+	 * value into the stack trace.
+	 */
+	if (frame->ex_frame) {
+		struct pt_regs *regs = (struct pt_regs *)frame->sp;
+
+		/*
+		 * We check that 'regs + sizeof(struct pt_regs)' (that is,
+		 * &regs[1]) does not exceed the bottom of the stack to avoid
+		 * accessing data outside the task's stack. This may happen
+		 * when frame->ex_frame is a false positive.
+		 */
+		if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))
+			return -EINVAL;
+
+		frame->pc = regs->ARM_pc;
+		frame->ex_frame = false;
+		return 0;
+	}
+
+	/* restore the registers from the stack frame */
+#ifdef CONFIG_CC_IS_CLANG
+	frame->sp = frame->fp;
+	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
+	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 4));
+#else
+	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 12));
+	frame->sp = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 8));
+	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 4));
+#endif
+#ifdef CONFIG_KRETPROBES
+	if (is_kretprobe_trampoline(frame->pc))
+		frame->pc = kretprobe_find_ret_addr(frame->tsk,
+					(void *)frame->fp, &frame->kr_cur);
+#endif
+
+	if (in_entry_text(frame->pc))
+		frame->ex_frame = true;
+
+	return 0;
+}
+#endif
+
+void notrace walk_stackframe(struct stackframe *frame,
+		     int (*fn)(struct stackframe *, void *), void *data)
+{
+	while (1) {
+		int ret;
+
+		if (fn(frame, data))
+			break;
+		ret = unwind_frame(frame);
+		if (ret < 0)
+			break;
+	}
+}
+EXPORT_SYMBOL(walk_stackframe);
+
+#ifdef CONFIG_STACKTRACE
+struct stack_trace_data {
+	struct stack_trace *trace;
+	unsigned int no_sched_functions;
+	unsigned int skip;
+};
+
+static int save_trace(struct stackframe *frame, void *d)
+{
+	struct stack_trace_data *data = d;
+	struct stack_trace *trace = data->trace;
+	unsigned long addr = frame->pc;
+
+	if (data->no_sched_functions && in_sched_functions(addr))
+		return 0;
+	if (data->skip) {
+		data->skip--;
+		return 0;
+	}
+
+	trace->entries[trace->nr_entries++] = addr;
+	return trace->nr_entries >= trace->max_entries;
+}
+
+/* This must be noinline to so that our skip calculation works correctly */
+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;
+
+	data.trace = trace;
+	data.skip = trace->skip;
+	data.no_sched_functions = nosched;
+
+	if (tsk != current) {
+#ifdef CONFIG_SMP
+		/*
+		 * What guarantees do we have here that 'tsk' is not
+		 * running on another CPU?  For now, ignore it as we
+		 * can't guarantee we won't explode.
+		 */
+		return;
+#else
+		frame.fp = thread_saved_fp(tsk);
+		frame.sp = thread_saved_sp(tsk);
+		frame.lr = 0;		/* recovered from the stack */
+		frame.pc = thread_saved_pc(tsk);
+#endif
+	} else {
+		/* We don't want this function nor the caller */
+		data.skip += 2;
+		frame.fp = (unsigned long)__builtin_frame_address(0);
+		frame.sp = current_stack_pointer;
+		frame.lr = (unsigned long)__builtin_return_address(0);
+here:
+		frame.pc = (unsigned long)&&here;
+	}
+#ifdef CONFIG_KRETPROBES
+	frame.kr_cur = NULL;
+	frame.tsk = tsk;
+#endif
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+	frame.ex_frame = false;
+#endif
+
+	walk_stackframe(&frame, save_trace, &data);
+}
+
+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;
+
+	frame.fp = regs->ARM_fp;
+	frame.sp = regs->ARM_sp;
+	frame.lr = regs->ARM_lr;
+	frame.pc = regs->ARM_pc;
+#ifdef CONFIG_KRETPROBES
+	frame.kr_cur = NULL;
+	frame.tsk = current;
+#endif
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+	frame.ex_frame = in_entry_text(frame.pc);
+#endif
+
+	walk_stackframe(&frame, save_trace, &data);
+}
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+	__save_stack_trace(tsk, trace, 1);
+}
+EXPORT_SYMBOL(save_stack_trace_tsk);
+
+void save_stack_trace(struct stack_trace *trace)
+{
+	__save_stack_trace(current, trace, 0);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+#endif