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/*******************************************************************************
 * DESCRIPTION   : Stack protect function
 ******************************************************************************/
 /******************************************************************************
 * @file          stack_protect.c
 * - Version      : 0.01
 * @brief         Check for Stack Smashing Attacks.
 * .
 *****************************************************************************/
/******************************************************************************
 * History : DD.MM.YYYY Version  Description
 *         : 31.01.2023 0.01     First Release
 *****************************************************************************/

#include <stdint.h>
#include <log.h>

/* Specify fixed canary value as reference implementation. */
#define CANARY_VAL              (0xB9DFF6A0U)

#define STACK_PROTECT_ENABLE    (1U)

/* Save canary to __stack_chk_guard. */
extern uintptr_t __stack_chk_guard;
__attribute__((section(".canary"))) uintptr_t __stack_chk_guard;

/* Prototype */
extern void __ghs_set_stack_chk_guard(void);
#if (STACK_PROTECT == STACK_PROTECT_ENABLE)
extern void __stack_chk_fail(void);
static inline uintptr_t *__ghs_get_stack_chk_guard_address(void);
#endif

void __ghs_set_stack_chk_guard(void)
{
#if (STACK_PROTECT == STACK_PROTECT_ENABLE)
    /* Initialize the stack canary before any code that may require a stack canary. */
    /* So don't add valiables larger than 8-bytes to this function.                 */
    /* Don't call function that uses stack canaries from this function.             */
    /* If customize CANARY_VAL to random value, don't allow the function            */
    /* to be inlined or this function may require a canary.                         */

    *__ghs_get_stack_chk_guard_address() = (uintptr_t)CANARY_VAL;

#endif
}
/* End of function __ghs_set_stack_chk_guard(void) */

#if (STACK_PROTECT == STACK_PROTECT_ENABLE)
static inline uintptr_t *__ghs_get_stack_chk_guard_address(void)
{
    /* Don't modify this function. */
    return &__stack_chk_guard;
}
/* End of function __ghs_get_stack_chk_guard_address(void) */

void __stack_chk_fail(void)
{
    ERROR("Stack smashing detected\n");
    panic;
}
/* End of function __stack_chk_fail(void) */
#endif /* (STACK_PROTECT == STACK_PROTECT_ENABLE) */