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, 67 insertions, 0 deletions

diff --git a/arch/arm64/kernel/exceptions.c b/arch/arm64/kernel/exceptions.c
new file mode 100644
index 0000000..7b40690
--- /dev/null
+++ b/arch/arm64/kernel/exceptions.c
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * exceptions.c - report an abort through the console before parking,
+ * so a firmware handoff bug says why it died instead of hanging quiet.
+ * ESR/FAR decode follows armv8 DDI 0487, the EC and ISS fields.
+ *
+ * Copyright (C) 2026 Bradley Morgan <brads@mainlining.org>
+ */
+
+#include <stdint.h>
+#include <debug.h>
+
+struct exc_frame {
+	uint64_t esr;
+	uint64_t far;
+	uint64_t lr;
+};
+
+/*
+ * exception class from ESR, bits 31:26. the classes a bootloader can
+ * actually hit with any frequency.
+ */
+static const char *exc_class_str(uint64_t esr)
+{
+	switch (esr >> 26) {
+	case 0x04:	return "data abort, lower EL";
+	case 0x05:	return "data abort, same EL";
+	case 0x25:	return "data abort, same EL";
+	case 0x08:	return "stack pointer misaligned";
+	case 0x11:	return "instruction abort, same EL";
+	case 0x16:	return "SError";
+	case 0x1a:	return "unhandled exception";
+	case 0x22:	return "pc alignment fault";
+	case 0x24:	return "unknown trap";
+	case 0x26:	return "same EL exception return";
+	default:	return "unknown EC";
+	}
+}
+
+/*
+ * far is only meaningful for the abort and alignment classes, note it
+ * for those and skip it otherwise so the report does not mislead.
+ */
+static int exc_far_valid(uint64_t esr)
+{
+	switch (esr >> 26) {
+	case 0x04:
+	case 0x05:
+	case 0x25:
+	case 0x11:
+	case 0x22:
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+void exc_report(uint64_t esr, uint64_t far, uint64_t lr)
+{
+	dprintf(CRITICAL, "tashaboot: exception %s\n", exc_class_str(esr));
+	dprintf(CRITICAL, "esr %016llx lr %016llx\n",
+		(unsigned long long)esr, (unsigned long long)lr);
+	if (exc_far_valid(esr))
+		dprintf(CRITICAL, "far %016llx\n", (unsigned long long)far);
+
+	/* nothing recovers from an abort here, park after reporting */
+}