x86: stackprotector: mix TSC to the boot canary

#ifndef _ASM_STACKPROTECTOR_H

#define _ASM_STACKPROTECTOR_H 1

#include <asm/tsc.h>

/*

 * Initialize the stackprotector canary value.

 *

 */

static __always_inline void boot_init_stack_canary(void)

{

	u64 canary;

	u64 tsc;

	/*

	 * If we're the non-boot CPU, nothing set the PDA stack

	 * canary up for us - and if we are the boot CPU we have

	 * a 0 stack canary. This is a good place for updating

	 * it, as we wont ever return from this function (so the

	 * invalid canaries already on the stack wont ever

	 * trigger):

	 * trigger).

	 *

	 * We both use the random pool and the current TSC as a source

	 * of randomness. The TSC only matters for very early init,

	 * there it already has some randomness on most systems. Later

	 * on during the bootup the random pool has true entropy too.

	 */

	current->stack_canary = get_random_int();

	write_pda(stack_canary, current->stack_canary);

	get_random_bytes(&canary, sizeof(canary));

	tsc = __native_read_tsc();

	canary += tsc + (tsc << 32UL);

	current->stack_canary = canary;

	write_pda(stack_canary, canary);

}

#endif