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#include <kmi/canary.h>
#include <kmi/mem.h>
/**
* @file canary.c
* Kernel stack canary implementation.
*/
/** Typedef for canary value type. */
typedef uint32_t canary_t;
/** Canary magic value. */
static const canary_t canary = 0xb00b1e5;
/**
* Helper for calculating the canary location of \p t.
*
* @param t \ref tcb to calculate canary position of.
* @return Pointer to canary location, that is bottom of stack.
* \todo This assumes that all stacks grow downwards. Unlikely to ever be
* ported to a platform that doesn't abide by this, but keep it in mind anyway.
*/
static canary_t *get_canary(struct tcb *t)
{
size_t s = order_size(KERNEL_STACK_PAGE_ORDER);
return (canary_t *)align_down((uintptr_t)t, s);
}
void set_canary(struct tcb *t)
{
canary_t *c = get_canary(t);
*c = canary;
}
bool check_canary(struct tcb *t)
{
canary_t *c = get_canary(t);
return *c != canary;
}
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