/* 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