tashaboot: arm64 bootloaderHEADmain

holy shit it's here, Tashaboot, based from arm arm, enjoy
reading this masterpiece

Signed-off-by: Bradley Morgan <brads@mainlining.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/arch/arm64/lib/system.c b/arch/arm64/lib/system.c
new file mode 100644
index 0000000..25af2bf
--- /dev/null
+++ b/arch/arm64/lib/system.c
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * system.c - system power control, the PSCI SYSTEM_OFF and
+ * SYSTEM_RESET backends. off parks the core in WFI forever, the
+ * manual's low power entry (D1-2255). reset drives the PE reset
+ * domain: RMR_EL2 reset request with the system reset bit, RR bit 1,
+ * followed by a barrier pair so the request retires before anything
+ * else observes the core.
+ *
+ * On real hardware a SoC also needs a watchdog or PMIC write for a
+ * full board reset, that is board territory, the arch part is this.
+ *
+ * Copyright (C) 2026 Bradley Morgan <brads@mainlining.org>
+ */
+
+#include <debug.h>
+#include <stdint.h>
+
+void tb_system_off(void)
+{
+	dprintf(ALWAYS, "system off\n");
+
+	for (;;) {
+		asm volatile("wfi");
+	}
+}
+
+void tb_system_reset(void)
+{
+	uint64_t rmr;
+	uint64_t el;
+	register uint64_t r0 asm("x0") = 0x84000008;
+	register uint64_t r1 asm("x1") = 0;
+	register uint64_t r2 asm("x2") = 0;
+	register uint64_t r3 asm("x3") = 0;
+
+	dprintf(ALWAYS, "system reset\n");
+
+	/*
+	 * the firmware conduit first, PSCI SYSTEM_RESET through
+	 * the machine's own monitor. this is the only legal way
+	 * up from EL1: RMR_EL1 is undefined on hardware that
+	 * implements a higher exception level, the access traps
+	 * and the machine never resets.
+	 */
+	asm volatile("smc #0"
+		     : "+r"(r0), "+r"(r1), "+r"(r2), "+r"(r3));
+
+	/*
+	 * no monitor answered, or it refused. ask the reset
+	 * domain directly from a level that may write it.
+	 */
+	asm volatile("mrs %0, CurrentEL" : "=r" (el));
+	el >>= 2;
+
+	if (el >= 2) {
+		asm volatile("mrs %0, rmr_el2" : "=r" (rmr));
+		rmr |= (1 << 1);	/* RR, request reset */
+		asm volatile(
+			"msr	rmr_el2, %0\n"
+			"dsb	sy\n"
+			"isb\n"
+			:: "r" (rmr));
+	}
+
+	/* nothing worked, park */
+	for (;;) {
+		asm volatile("wfi");
+	}
+}