lib: sbi: implement SBI FWFT extension

The SBI FWFT extension defines a set of function that can be called
to control the configuration of some platform features (misaligned
trap delegation, etc). This patch implements sbi_fwft_set() and
sbi_fwft_get() as defined in the specification [1].

Link: https://lists.riscv.org/g/tech-prs/message/924 [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/sbi/sbi_ecall_fwft.c

@@ -0,0 +1,49 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024 Rivos Inc.
+ *
+ * Authors:
+ *   Clément Léger <cleger@rivosinc.com>
+ */
+
+#include <sbi/sbi_ecall.h>
+#include <sbi/sbi_ecall_interface.h>
+#include <sbi/sbi_error.h>
+#include <sbi/sbi_fwft.h>
+#include <sbi/sbi_trap.h>
+
+static int sbi_ecall_fwft_handler(unsigned long extid, unsigned long funcid,
+				 struct sbi_trap_regs *regs,
+				 struct sbi_ecall_return *out)
+{
+	int ret = 0;
+
+	switch (funcid) {
+	case SBI_EXT_FWFT_SET:
+		ret = sbi_fwft_set(regs->a0, regs->a1, regs->a2);
+		break;
+	case SBI_EXT_FWFT_GET:
+		ret = sbi_fwft_get(regs->a0, &out->value);
+		break;
+	default:
+		ret = SBI_ENOTSUPP;
+		break;
+	}
+
+	return ret;
+}
+
+struct sbi_ecall_extension ecall_fwft;
+
+static int sbi_ecall_fwft_register_extensions(void)
+{
+	return sbi_ecall_register_extension(&ecall_fwft);
+}
+
+struct sbi_ecall_extension ecall_fwft = {
+	.extid_start = SBI_EXT_FWFT,
+	.extid_end = SBI_EXT_FWFT,
+	.register_extensions = sbi_ecall_fwft_register_extensions,
+	.handle = sbi_ecall_fwft_handler,
+};