sdk/include/platform/sunburst/platform-early_boot.inc - 3p/cheriot-rtos - Git at Google

 	// The shadow memory may not be zeroed, ensure it is before we start or
 	// random capability loads will fail.
 	li         a0, SUNBURST_SHADOW_BASE
 	cspecialr  ca4, mtdc
 	csetaddr   ca0, ca4, a0
 	li         a1, SUNBURST_SHADOW_BASE + SUNBURST_SHADOW_SIZE
 	cjal       .Lfill_block
	// The shadow memory may not be zeroed, ensure it is before we start or
	// random capability loads will fail.
	li a0, SUNBURST_SHADOW_BASE
	cspecialr ca4, mtdc
	csetaddr ca0, ca4, a0
	li a1, SUNBURST_SHADOW_BASE + SUNBURST_SHADOW_SIZE
	cjal .Lfill_block