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