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-rw-r--r--include/linux/stackleak.h55
1 files changed, 54 insertions, 1 deletions
diff --git a/include/linux/stackleak.h b/include/linux/stackleak.h
index ccaab2043fcd..c36e7a3b45e7 100644
--- a/include/linux/stackleak.h
+++ b/include/linux/stackleak.h
@@ -15,9 +15,62 @@
#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 = (unsigned long)end_of_stack(t) + sizeof(unsigned long);
+ t->lowest_stack = stackleak_task_low_bound(t);
# ifdef CONFIG_STACKLEAK_METRICS
t->prev_lowest_stack = t->lowest_stack;
# endif