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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_STACKLEAK_H
#define _LINUX_STACKLEAK_H
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
/*
* Check that the poison value points to the unused hole in the
* virtual memory map for your platform.
*/
#define STACKLEAK_POISON -0xBEEF
#define STACKLEAK_SEARCH_DEPTH 128
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
#include <asm/stacktrace.h>
/*
* The lowest address on tsk's stack which we can plausibly erase.
*/
static __always_inline unsigned long
stackleak_task_low_bound(const struct task_struct *tsk)
{
/*
* The lowest unsigned long on the task stack contains STACK_END_MAGIC,
* which we must not corrupt.
*/
return (unsigned long)end_of_stack(tsk) + sizeof(unsigned long);
}
/*
* The address immediately after the highest address on tsk's stack which we
* can plausibly erase.
*/
static __always_inline unsigned long
stackleak_task_high_bound(const struct task_struct *tsk)
{
/*
* The task's pt_regs lives at the top of the task stack and will be
* overwritten by exception entry, so there's no need to erase them.
*/
return (unsigned long)task_pt_regs(tsk);
}
/*
* Find the address immediately above the poisoned region of the stack, where
* that region falls between 'low' (inclusive) and 'high' (exclusive).
*/
static __always_inline unsigned long
stackleak_find_top_of_poison(const unsigned long low, const unsigned long high)
{
const unsigned int depth = STACKLEAK_SEARCH_DEPTH / sizeof(unsigned long);
unsigned int poison_count = 0;
unsigned long poison_high = high;
unsigned long sp = high;
while (sp > low && poison_count < depth) {
sp -= sizeof(unsigned long);
if (*(unsigned long *)sp == STACKLEAK_POISON) {
poison_count++;
} else {
poison_count = 0;
poison_high = sp;
}
}
return poison_high;
}
static inline void stackleak_task_init(struct task_struct *t)
{
t->lowest_stack = stackleak_task_low_bound(t);
# ifdef CONFIG_STACKLEAK_METRICS
t->prev_lowest_stack = t->lowest_stack;
# endif
}
#else /* !CONFIG_GCC_PLUGIN_STACKLEAK */
static inline void stackleak_task_init(struct task_struct *t) { }
#endif
#endif
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