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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Common arm64 stack unwinder code.
*
* To implement a new arm64 stack unwinder:
* 1) Include this header
*
* 2) Provide implementations for the following functions:
* on_overflow_stack(): Returns true if SP is on the overflow
* stack.
* on_accessible_stack(): Returns true is SP is on any accessible
* stack.
* unwind_next(): Performs validation checks on the frame
* pointer, and transitions unwind_state
* to the next frame.
*
* See: arch/arm64/include/asm/stacktrace.h for reference
* implementations.
*
* Copyright (C) 2012 ARM Ltd.
*/
#ifndef __ASM_STACKTRACE_COMMON_H
#define __ASM_STACKTRACE_COMMON_H
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/kprobes.h>
#include <linux/types.h>
enum stack_type {
STACK_TYPE_UNKNOWN,
STACK_TYPE_TASK,
STACK_TYPE_IRQ,
STACK_TYPE_OVERFLOW,
STACK_TYPE_SDEI_NORMAL,
STACK_TYPE_SDEI_CRITICAL,
STACK_TYPE_HYP,
__NR_STACK_TYPES
};
struct stack_info {
unsigned long low;
unsigned long high;
enum stack_type type;
};
/*
* A snapshot of a frame record or fp/lr register values, along with some
* accounting information necessary for robust unwinding.
*
* @fp: The fp value in the frame record (or the real fp)
* @pc: The lr value in the frame record (or the real lr)
*
* @stacks_done: Stacks which have been entirely unwound, for which it is no
* longer valid to unwind to.
*
* @prev_fp: The fp that pointed to this frame record, or a synthetic value
* of 0. This is used to ensure that within a stack, each
* subsequent frame record is at an increasing address.
* @prev_type: The type of stack this frame record was on, or a synthetic
* value of STACK_TYPE_UNKNOWN. This is used to detect a
* transition from one stack to another.
*
* @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
* associated with the most recently encountered replacement lr
* value.
*
* @task: The task being unwound.
*/
struct unwind_state {
unsigned long fp;
unsigned long pc;
DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);
unsigned long prev_fp;
enum stack_type prev_type;
#ifdef CONFIG_KRETPROBES
struct llist_node *kr_cur;
#endif
struct task_struct *task;
};
static inline bool on_stack(unsigned long sp, unsigned long size,
unsigned long low, unsigned long high,
enum stack_type type, struct stack_info *info)
{
if (!low)
return false;
if (sp < low || sp + size < sp || sp + size > high)
return false;
if (info) {
info->low = low;
info->high = high;
info->type = type;
}
return true;
}
static inline void unwind_init_common(struct unwind_state *state,
struct task_struct *task)
{
state->task = task;
#ifdef CONFIG_KRETPROBES
state->kr_cur = NULL;
#endif
/*
* Prime the first unwind.
*
* In unwind_next() we'll check that the FP points to a valid stack,
* which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
* treated as a transition to whichever stack that happens to be. The
* prev_fp value won't be used, but we set it to 0 such that it is
* definitely not an accessible stack address.
*/
bitmap_zero(state->stacks_done, __NR_STACK_TYPES);
state->prev_fp = 0;
state->prev_type = STACK_TYPE_UNKNOWN;
}
/*
* stack_trace_translate_fp_fn() - Translates a non-kernel frame pointer to
* a kernel address.
*
* @fp: the frame pointer to be updated to its kernel address.
* @type: the stack type associated with frame pointer @fp
*
* Returns true and success and @fp is updated to the corresponding
* kernel virtual address; otherwise returns false.
*/
typedef bool (*stack_trace_translate_fp_fn)(unsigned long *fp,
enum stack_type type);
/*
* on_accessible_stack_fn() - Check whether a stack range is on any
* of the possible stacks.
*
* @tsk: task whose stack is being unwound
* @sp: stack address being checked
* @size: size of the stack range being checked
* @info: stack unwinding context
*/
typedef bool (*on_accessible_stack_fn)(const struct task_struct *tsk,
unsigned long sp, unsigned long size,
struct stack_info *info);
static inline int unwind_next_common(struct unwind_state *state,
struct stack_info *info,
on_accessible_stack_fn accessible,
stack_trace_translate_fp_fn translate_fp)
{
unsigned long fp = state->fp, kern_fp = fp;
struct task_struct *tsk = state->task;
if (fp & 0x7)
return -EINVAL;
if (!accessible(tsk, fp, 16, info))
return -EINVAL;
if (test_bit(info->type, state->stacks_done))
return -EINVAL;
/*
* If fp is not from the current address space perform the necessary
* translation before dereferencing it to get the next fp.
*/
if (translate_fp && !translate_fp(&kern_fp, info->type))
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
* HYP -> 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 == state->prev_type) {
if (fp <= state->prev_fp)
return -EINVAL;
} else {
__set_bit(state->prev_type, state->stacks_done);
}
/*
* Record this frame record's values and location. The prev_fp and
* prev_type are only meaningful to the next unwind_next() invocation.
*/
state->fp = READ_ONCE(*(unsigned long *)(kern_fp));
state->pc = READ_ONCE(*(unsigned long *)(kern_fp + 8));
state->prev_fp = fp;
state->prev_type = info->type;
return 0;
}
#endif /* __ASM_STACKTRACE_COMMON_H */
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