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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/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)
*
* @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;
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)
{
state->stack = stackinfo_get_unknown();
}
/**
* unwind_find_stack() - Find the accessible stack which entirely contains an
* object.
*
* @state: the current unwind state.
* @sp: the base address of the object.
* @size: the size of the object.
*
* Return: a pointer to the relevant stack_info if found; NULL otherwise.
*/
static struct stack_info *unwind_find_stack(struct unwind_state *state,
unsigned long sp,
unsigned long size)
{
struct stack_info *info = &state->stack;
if (stackinfo_on_stack(info, sp, size))
return info;
for (int i = 0; i < state->nr_stacks; i++) {
info = &state->stacks[i];
if (stackinfo_on_stack(info, sp, size))
return info;
}
return NULL;
}
/**
* unwind_consume_stack() - Update stack boundaries so that future unwind steps
* cannot consume this object again.
*
* @state: the current unwind state.
* @info: the stack_info of the stack containing the object.
* @sp: the base address of the object.
* @size: the size of the object.
*
* Return: 0 upon success, an error code otherwise.
*/
static inline void unwind_consume_stack(struct unwind_state *state,
struct stack_info *info,
unsigned long sp,
unsigned long size)
{
struct stack_info tmp;
/*
* 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.
*
* Destroy the old stack info so that it cannot be found upon a
* subsequent transition. If the stack has not changed, we'll
* immediately restore the current stack info.
*
* 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.
*/
tmp = *info;
*info = stackinfo_get_unknown();
state->stack = tmp;
/*
* 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;
}
/**
* 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)
{
struct stack_info *info;
struct frame_record *record;
unsigned long fp = state->fp;
if (fp & 0x7)
return -EINVAL;
info = unwind_find_stack(state, fp, sizeof(*record));
if (!info)
return -EINVAL;
unwind_consume_stack(state, info, fp, sizeof(*record));
/*
* Record this frame record's values.
*/
record = (struct frame_record *)fp;
state->fp = READ_ONCE(record->fp);
state->pc = READ_ONCE(record->lr);
return 0;
}
#endif /* __ASM_STACKTRACE_COMMON_H */
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