1 files changed, 128 insertions, 0 deletions
diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
new file mode 100644
index 000000000000..97a8415e3216
--- /dev/null
+++ b/kernel/unwind/user.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+* Generic interfaces for unwinding user space
+*/
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/unwind_user.h>
+#include <linux/uaccess.h>
+
+static const struct unwind_user_frame fp_frame = {
+	ARCH_INIT_USER_FP_FRAME
+};
+
+#define for_each_user_frame(state) \
+	for (unwind_user_start(state); !(state)->done; unwind_user_next(state))
+
+static int unwind_user_next_fp(struct unwind_user_state *state)
+{
+	const struct unwind_user_frame *frame = &fp_frame;
+	unsigned long cfa, fp, ra;
+	unsigned int shift;
+
+	if (frame->use_fp) {
+		if (state->fp < state->sp)
+			return -EINVAL;
+		cfa = state->fp;
+	} else {
+		cfa = state->sp;
+	}
+
+	/* Get the Canonical Frame Address (CFA) */
+	cfa += frame->cfa_off;
+
+	/* stack going in wrong direction? */
+	if (cfa <= state->sp)
+		return -EINVAL;
+
+	/* Make sure that the address is word aligned */
+	shift = sizeof(long) == 4 ? 2 : 3;
+	if (cfa & ((1 << shift) - 1))
+		return -EINVAL;
+
+	/* Find the Return Address (RA) */
+	if (get_user(ra, (unsigned long *)(cfa + frame->ra_off)))
+		return -EINVAL;
+
+	if (frame->fp_off && get_user(fp, (unsigned long __user *)(cfa + frame->fp_off)))
+		return -EINVAL;
+
+	state->ip = ra;
+	state->sp = cfa;
+	if (frame->fp_off)
+		state->fp = fp;
+	return 0;
+}
+
+static int unwind_user_next(struct unwind_user_state *state)
+{
+	unsigned long iter_mask = state->available_types;
+	unsigned int bit;
+
+	if (state->done)
+		return -EINVAL;
+
+	for_each_set_bit(bit, &iter_mask, NR_UNWIND_USER_TYPE_BITS) {
+		enum unwind_user_type type = BIT(bit);
+
+		state->current_type = type;
+		switch (type) {
+		case UNWIND_USER_TYPE_FP:
+			if (!unwind_user_next_fp(state))
+				return 0;
+			continue;
+		default:
+			WARN_ONCE(1, "Undefined unwind bit %d", bit);
+			break;
+		}
+		break;
+	}
+
+	/* No successful unwind method. */
+	state->current_type = UNWIND_USER_TYPE_NONE;
+	state->done = true;
+	return -EINVAL;
+}
+
+static int unwind_user_start(struct unwind_user_state *state)
+{
+	struct pt_regs *regs = task_pt_regs(current);
+
+	memset(state, 0, sizeof(*state));
+
+	if ((current->flags & PF_KTHREAD) || !user_mode(regs)) {
+		state->done = true;
+		return -EINVAL;
+	}
+
+	if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP))
+		state->available_types |= UNWIND_USER_TYPE_FP;
+
+	state->ip = instruction_pointer(regs);
+	state->sp = user_stack_pointer(regs);
+	state->fp = frame_pointer(regs);
+
+	return 0;
+}
+
+int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries)
+{
+	struct unwind_user_state state;
+
+	trace->nr = 0;
+
+	if (!max_entries)
+		return -EINVAL;
+
+	if (current->flags & PF_KTHREAD)
+		return 0;
+
+	for_each_user_frame(&state) {
+		trace->entries[trace->nr++] = state.ip;
+		if (trace->nr >= max_entries)
+			break;
+	}
+
+	return 0;
+}