diff options
Diffstat (limited to 'include/linux/stackleak.h')
-rw-r--r-- | include/linux/stackleak.h | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/include/linux/stackleak.h b/include/linux/stackleak.h new file mode 100644 index 000000000..c36e7a3b4 --- /dev/null +++ b/include/linux/stackleak.h @@ -0,0 +1,83 @@ +/* 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 |