riscv/efi_stub: Fix get_boot_hartid_from_fdt() return value

The get_boot_hartid_from_fdt() function currently returns U32_MAX
for failure case which is not correct because U32_MAX is a valid
hartid value. This patch fixes the issue by returning error code.

Cc: <stable@vger.kernel.org>
Fixes: d707174 ("RISC-V: Add EFI stub support.")
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: vlsunil

drivers/firmware/efi/libstub/riscv-stub.c

@@ -25,31 +25,34 @@ typedef void __noreturn (*jump_kernel_func)(unsigned int, unsigned long);
 
 static u32 hartid;
 
-static u32 get_boot_hartid_from_fdt(void)
+static int get_boot_hartid_from_fdt(void)
 {
 	const void *fdt;
 	int chosen_node, len;
 	const fdt32_t *prop;
 
 	fdt = get_efi_config_table(DEVICE_TREE_GUID);
 	if (!fdt)
-		return U32_MAX;
+		return -EINVAL;
 
 	chosen_node = fdt_path_offset(fdt, "/chosen");
 	if (chosen_node < 0)
-		return U32_MAX;
+		return -EINVAL;
 
 	prop = fdt_getprop((void *)fdt, chosen_node, "boot-hartid", &len);
 	if (!prop || len != sizeof(u32))
-		return U32_MAX;
+		return -EINVAL;
 
-	return fdt32_to_cpu(*prop);
+	hartid = fdt32_to_cpu(*prop);
+	return 0;
 }
 
 efi_status_t check_platform_features(void)
 {
-	hartid = get_boot_hartid_from_fdt();
-	if (hartid == U32_MAX) {
+	int ret;
+
+	ret = get_boot_hartid_from_fdt();
+	if (ret) {
 		efi_err("/chosen/boot-hartid missing or invalid!\n");
 		return EFI_UNSUPPORTED;
 	}