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#include <linux/linkage.h> 18 19/* 20 * The lowest address on tsk's stack which we can plausibly erase. 21 */ 22static __always_inline unsigned long 23stackleak_task_low_bound(const struct task_struct *tsk) 24{ 25 /* 26 * The lowest unsigned long on the task stack contains STACK_END_MAGIC, 27 * which we must not corrupt. 28 */ 29 return (unsigned long)end_of_stack(tsk) + sizeof(unsigned long); 30} 31 32/* 33 * The address immediately after the highest address on tsk's stack which we 34 * can plausibly erase. 35 */ 36static __always_inline unsigned long 37stackleak_task_high_bound(const struct task_struct *tsk) 38{ 39 /* 40 * The task's pt_regs lives at the top of the task stack and will be 41 * overwritten by exception entry, so there's no need to erase them. 42 */ 43 return (unsigned long)task_pt_regs(tsk); 44} 45 46/* 47 * Find the address immediately above the poisoned region of the stack, where 48 * that region falls between 'low' (inclusive) and 'high' (exclusive). 49 */ 50static __always_inline unsigned long 51stackleak_find_top_of_poison(const unsigned long low, const unsigned long high) 52{ 53 const unsigned int depth = STACKLEAK_SEARCH_DEPTH / sizeof(unsigned long); 54 unsigned int poison_count = 0; 55 unsigned long poison_high = high; 56 unsigned long sp = high; 57 58 while (sp > low && poison_count < depth) { 59 sp -= sizeof(unsigned long); 60 61 if (*(unsigned long *)sp == STACKLEAK_POISON) { 62 poison_count++; 63 } else { 64 poison_count = 0; 65 poison_high = sp; 66 } 67 } 68 69 return poison_high; 70} 71 72static inline void stackleak_task_init(struct task_struct *t) 73{ 74 t->lowest_stack = stackleak_task_low_bound(t); 75# ifdef CONFIG_STACKLEAK_METRICS 76 t->prev_lowest_stack = t->lowest_stack; 77# endif 78} 79 80asmlinkage void noinstr stackleak_erase(void); 81asmlinkage void noinstr stackleak_erase_on_task_stack(void); 82asmlinkage void noinstr stackleak_erase_off_task_stack(void); 83void __no_caller_saved_registers noinstr stackleak_track_stack(void); 84 85#else /* !CONFIG_GCC_PLUGIN_STACKLEAK */ 86static inline void stackleak_task_init(struct task_struct *t) { } 87#endif 88 89#endif 90