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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Common arm64 stack unwinder code.
*
* See: arch/arm64/kernel/stacktrace.c for the reference implementation.
*
* Copyright (C) 2012 ARM Ltd.
*/
#ifndef __ASM_STACKTRACE_COMMON_H
#define __ASM_STACKTRACE_COMMON_H
#include <linux/kprobes.h>
#include <linux/types.h>
struct stack_info {
unsigned long low;
unsigned long high;
};
/**
* struct unwind_state - state used 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)
*
* @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
* associated with the most recently encountered replacement lr
* value.
*
* @task: The task being unwound.
*
* @stack: The stack currently being unwound.
* @stacks: An array of stacks which can be unwound.
* @nr_stacks: The number of stacks in @stacks.
*/
struct unwind_state {
unsigned long fp;
unsigned long pc;
#ifdef CONFIG_KRETPROBES
struct llist_node *kr_cur;
#endif
struct task_struct *task;
struct stack_info stack;
struct stack_info *stacks;
int nr_stacks;
};
static inline struct stack_info stackinfo_get_unknown(void)
{
return (struct stack_info) {
.low = 0,
.high = 0,
};
}
static inline bool stackinfo_on_stack(const struct stack_info *info,
unsigned long sp, unsigned long size)
{
if (!info->low)
return false;
if (sp < info->low || sp + size < sp || sp + size > info->high)
return false;
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
state->stack = stackinfo_get_unknown();
}
static struct stack_info *unwind_find_next_stack(const struct unwind_state *state,
unsigned long sp,
unsigned long size)
{
for (int i = 0; i < state->nr_stacks; i++) {
struct stack_info *info = &state->stacks[i];
if (stackinfo_on_stack(info, sp, size))
return info;
}
return NULL;
}
/**
* unwind_consume_stack() - Check if an object is on an accessible stack,
* updating stack boundaries so that future unwind steps cannot consume this
* object again.
*
* @state: the current unwind state.
* @sp: the base address of the object.
* @size: the size of the object.
*
* Return: 0 upon success, an error code otherwise.
*/
static inline int unwind_consume_stack(struct unwind_state *state,
unsigned long sp,
unsigned long size)
{
struct stack_info *next;
if (stackinfo_on_stack(&state->stack, sp, size))
goto found;
next = unwind_find_next_stack(state, sp, size);
if (!next)
return -EINVAL;
/*
* Stack transitions are strictly one-way, and once we've
* transitioned from one stack to another, it's never valid to
* unwind back to the old stack.
*
* Remove the current stack from the list of stacks so that it cannot
* be found on a subsequent transition.
*
* Note that stacks can nest in several valid orders, e.g.
*
* TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL
* TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW
* HYP -> OVERFLOW
*
* ... so we do not check the specific order of stack
* transitions.
*/
state->stack = *next;
*next = stackinfo_get_unknown();
found:
/*
* Future unwind steps can only consume stack above this frame record.
* Update the current stack to start immediately above it.
*/
state->stack.low = sp + size;
return 0;
}
/**
* unwind_next_frame_record() - Unwind to the next frame record.
*
* @state: the current unwind state.
*
* Return: 0 upon success, an error code otherwise.
*/
static inline int
unwind_next_frame_record(struct unwind_state *state)
{
unsigned long fp = state->fp;
int err;
if (fp & 0x7)
return -EINVAL;
err = unwind_consume_stack(state, fp, 16);
if (err)
return err;
/*
* Record this frame record's values.
*/
state->fp = READ_ONCE(*(unsigned long *)(fp));
state->pc = READ_ONCE(*(unsigned long *)(fp + 8));
return 0;
}
#endif /* __ASM_STACKTRACE_COMMON_H */
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