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 | */ |
21 | static __always_inline unsigned long |
22 | stackleak_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 | */ |
35 | static __always_inline unsigned long |
36 | stackleak_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 | */ |
49 | static __always_inline unsigned long |
50 | stackleak_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 | |
71 | static 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 */ |
80 | static inline void stackleak_task_init(struct task_struct *t) { } |
81 | #endif |
82 | |
83 | #endif |
84 | |