1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_STACKLEAK_H
3#define _LINUX_STACKLEAK_H
4
5#include <linux/sched.h>
6#include <linux/sched/task_stack.h>
7
8/*
9 * Check that the poison value points to the unused hole in the
10 * virtual memory map for your platform.
11 */
12#define STACKLEAK_POISON -0xBEEF
13#define STACKLEAK_SEARCH_DEPTH 128
14
15#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
16#include <asm/stacktrace.h>
17
18/*
19 * The lowest address on tsk's stack which we can plausibly erase.
20 */
21static __always_inline unsigned long
22stackleak_task_low_bound(const struct task_struct *tsk)
23{
24 /*
25 * The lowest unsigned long on the task stack contains STACK_END_MAGIC,
26 * which we must not corrupt.
27 */
28 return (unsigned long)end_of_stack(tsk) + sizeof(unsigned long);
29}
30
31/*
32 * The address immediately after the highest address on tsk's stack which we
33 * can plausibly erase.
34 */
35static __always_inline unsigned long
36stackleak_task_high_bound(const struct task_struct *tsk)
37{
38 /*
39 * The task's pt_regs lives at the top of the task stack and will be
40 * overwritten by exception entry, so there's no need to erase them.
41 */
42 return (unsigned long)task_pt_regs(tsk);
43}
44
45/*
46 * Find the address immediately above the poisoned region of the stack, where
47 * that region falls between 'low' (inclusive) and 'high' (exclusive).
48 */
49static __always_inline unsigned long
50stackleak_find_top_of_poison(const unsigned long low, const unsigned long high)
51{
52 const unsigned int depth = STACKLEAK_SEARCH_DEPTH / sizeof(unsigned long);
53 unsigned int poison_count = 0;
54 unsigned long poison_high = high;
55 unsigned long sp = high;
56
57 while (sp > low && poison_count < depth) {
58 sp -= sizeof(unsigned long);
59
60 if (*(unsigned long *)sp == STACKLEAK_POISON) {
61 poison_count++;
62 } else {
63 poison_count = 0;
64 poison_high = sp;
65 }
66 }
67
68 return poison_high;
69}
70
71static inline void stackleak_task_init(struct task_struct *t)
72{
73 t->lowest_stack = stackleak_task_low_bound(t);
74# ifdef CONFIG_STACKLEAK_METRICS
75 t->prev_lowest_stack = t->lowest_stack;
76# endif
77}
78
79#else /* !CONFIG_GCC_PLUGIN_STACKLEAK */
80static inline void stackleak_task_init(struct task_struct *t) { }
81#endif
82
83#endif
84

source code of linux/include/linux/stackleak.h