path: root/arch/arm64/kernel/stacktrace.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Stack tracing support
 *
 * Copyright (C) 2012 ARM Ltd.
 */
#include <linux/kernel.h>
#include <linux/efi.h>
#include <linux/export.h>
#include <linux/filter.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/efi.h>
#include <asm/irq.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>

enum kunwind_source {
	KUNWIND_SOURCE_UNKNOWN,
	KUNWIND_SOURCE_FRAME,
	KUNWIND_SOURCE_CALLER,
	KUNWIND_SOURCE_TASK,
	KUNWIND_SOURCE_REGS_PC,
};

union unwind_flags {
	unsigned long	all;
	struct {
		unsigned long	fgraph : 1,
				kretprobe : 1;
	};
};

/*
 * Kernel unwind state
 *
 * @common:      Common unwind state.
 * @task:        The task being unwound.
 * @graph_idx:   Used by ftrace_graph_ret_addr() for optimized stack unwinding.
 * @kr_cur:      When KRETPROBES is selected, holds the kretprobe instance
 *               associated with the most recently encountered replacement lr
 *               value.
 */
struct kunwind_state {
	struct unwind_state common;
	struct task_struct *task;
	int graph_idx;
#ifdef CONFIG_KRETPROBES
	struct llist_node *kr_cur;
#endif
	enum kunwind_source source;
	union unwind_flags flags;
	struct pt_regs *regs;
};

static __always_inline void
kunwind_init(struct kunwind_state *state,
	     struct task_struct *task)
{
	unwind_init_common(&state->common);
	state->task = task;
	state->source = KUNWIND_SOURCE_UNKNOWN;
	state->flags.all = 0;
	state->regs = NULL;
}

/*
 * Start an unwind from a pt_regs.
 *
 * The unwind will begin at the PC within the regs.
 *
 * The regs must be on a stack currently owned by the calling task.
 */
static __always_inline void
kunwind_init_from_regs(struct kunwind_state *state,
		       struct pt_regs *regs)
{
	kunwind_init(state, current);

	state->regs = regs;
	state->common.fp = regs->regs[29];
	state->common.pc = regs->pc;
	state->source = KUNWIND_SOURCE_REGS_PC;
}

/*
 * Start an unwind from a caller.
 *
 * The unwind will begin at the caller of whichever function this is inlined
 * into.
 *
 * The function which invokes this must be noinline.
 */
static __always_inline void
kunwind_init_from_caller(struct kunwind_state *state)
{
	kunwind_init(state, current);

	state->common.fp = (unsigned long)__builtin_frame_address(1);
	state->common.pc = (unsigned long)__builtin_return_address(0);
	state->source = KUNWIND_SOURCE_CALLER;
}

/*
 * Start an unwind from a blocked task.
 *
 * The unwind will begin at the blocked tasks saved PC (i.e. the caller of
 * cpu_switch_to()).
 *
 * The caller should ensure the task is blocked in cpu_switch_to() for the
 * duration of the unwind, or the unwind will be bogus. It is never valid to
 * call this for the current task.
 */
static __always_inline void
kunwind_init_from_task(struct kunwind_state *state,
		       struct task_struct *task)
{
	kunwind_init(state, task);

	state->common.fp = thread_saved_fp(task);
	state->common.pc = thread_saved_pc(task);
	state->source = KUNWIND_SOURCE_TASK;
}

static __always_inline int
kunwind_recover_return_address(struct kunwind_state *state)
{
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	if (state->task->ret_stack &&
	    (state->common.pc == (unsigned long)return_to_handler)) {
		unsigned long orig_pc;
		orig_pc = ftrace_graph_ret_addr(state->task, &state->graph_idx,
						state->common.pc,
						(void *)state->common.fp);
		if (state->common.pc == orig_pc) {
			WARN_ON_ONCE(state->task == current);
			return -EINVAL;
		}
		state->common.pc = orig_pc;
		state->flags.fgraph = 1;
	}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

#ifdef CONFIG_KRETPROBES
	if (is_kretprobe_trampoline(state->common.pc)) {
		unsigned long orig_pc;
		orig_pc = kretprobe_find_ret_addr(state->task,
						  (void *)state->common.fp,
						  &state->kr_cur);
		if (!orig_pc)
			return -EINVAL;
		state->common.pc = orig_pc;
		state->flags.kretprobe = 1;
	}
#endif /* CONFIG_KRETPROBES */

	return 0;
}

static __always_inline
int kunwind_next_regs_pc(struct kunwind_state *state)
{
	struct stack_info *info;
	unsigned long fp = state->common.fp;
	struct pt_regs *regs;

	regs = container_of((u64 *)fp, struct pt_regs, stackframe.record.fp);

	info = unwind_find_stack(&state->common, (unsigned long)regs, sizeof(*regs));
	if (!info)
		return -EINVAL;

	unwind_consume_stack(&state->common, info, (unsigned long)regs,
			     sizeof(*regs));

	state->regs = regs;
	state->common.pc = regs->pc;
	state->common.fp = regs->regs[29];
	state->regs = NULL;
	state->source = KUNWIND_SOURCE_REGS_PC;
	return 0;
}

static __always_inline int
kunwind_next_frame_record_meta(struct kunwind_state *state)
{
	struct task_struct *tsk = state->task;
	unsigned long fp = state->common.fp;
	struct frame_record_meta *meta;
	struct stack_info *info;

	info = unwind_find_stack(&state->common, fp, sizeof(*meta));
	if (!info)
		return -EINVAL;

	meta = (struct frame_record_meta *)fp;
	switch (READ_ONCE(meta->type)) {
	case FRAME_META_TYPE_FINAL:
		if (meta == &task_pt_regs(tsk)->stackframe)
			return -ENOENT;
		WARN_ON_ONCE(tsk == current);
		return -EINVAL;
	case FRAME_META_TYPE_PT_REGS:
		return kunwind_next_regs_pc(state);
	default:
		WARN_ON_ONCE(tsk == current);
		return -EINVAL;
	}
}

static __always_inline int
kunwind_next_frame_record(struct kunwind_state *state)
{
	unsigned long fp = state->common.fp;
	struct frame_record *record;
	struct stack_info *info;
	unsigned long new_fp, new_pc;

	if (fp & 0x7)
		return -EINVAL;

	info = unwind_find_stack(&state->common, fp, sizeof(*record));
	if (!info)
		return -EINVAL;

	record = (struct frame_record *)fp;
	new_fp = READ_ONCE(record->fp);
	new_pc = READ_ONCE(record->lr