platform/x86/intel/ifs: Read IFS firmware image

Driver probe routine allocates structure to communicate status
and parameters between functions in the driver. Also call
load_ifs_binary() to load the scan image file.

There is a separate scan image file for each processor family,
model, stepping combination. This is read from the static path:

  /lib/firmware/intel/ifs/{ff-mm-ss}.scan

Step 1 in loading is to generate the correct path and use
request_firmware_direct() to load into memory.

Subsequent patches will use the IFS MSR interfaces to copy
the image to BIOS reserved memory and validate the SHA256
checksums.
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Co-developed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220506225410.1652287-6-tony.luck@intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/intel/ifs/Makefile

 obj-$(CONFIG_INTEL_IFS)		+= intel_ifs.o
 
-intel_ifs-objs			:= core.o
+intel_ifs-objs			:= core.o load.o

drivers/platform/x86/intel/ifs/core.c

@@ -6,6 +6,8 @@
 
 #include <asm/cpu_device_id.h>
 
+#include "ifs.h"
+
 #define X86_MATCH(model)				\
 	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(INTEL, 6,	\
 		INTEL_FAM6_##model, X86_FEATURE_CORE_CAPABILITIES, NULL)
@@ -16,6 +18,17 @@ static const struct x86_cpu_id ifs_cpu_ids[] __initconst = {
 };
 MODULE_DEVICE_TABLE(x86cpu, ifs_cpu_ids);
 
+static struct ifs_device ifs_device = {
+	.data = {
+		.integrity_cap_bit = MSR_INTEGRITY_CAPS_PERIODIC_BIST_BIT,
+	},
+	.misc = {
+		.name = "intel_ifs_0",
+		.nodename = "intel_ifs/0",
+		.minor = MISC_DYNAMIC_MINOR,
+	},
+};
+
 static int __init ifs_init(void)
 {
 	const struct x86_cpu_id *m;
@@ -34,11 +47,18 @@ static int __init ifs_init(void)
 	if (rdmsrl_safe(MSR_INTEGRITY_CAPS, &msrval))
 		return -ENODEV;
 
-	return 0;
+	if ((msrval & BIT(ifs_device.data.integrity_cap_bit)) &&
+	    !misc_register(&ifs_device.misc)) {
+		ifs_load_firmware(ifs_device.misc.this_device);
+		return 0;
+	}
+
+	return -ENODEV;
 }
 
 static void __exit ifs_exit(void)
 {
+	misc_deregister(&ifs_device.misc);
 }
 
 module_init(ifs_init);

drivers/platform/x86/intel/ifs/ifs.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright(c) 2022 Intel Corporation. */
+
+#ifndef _IFS_H_
+#define _IFS_H_
+
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+
+/**
+ * struct ifs_data - attributes related to intel IFS driver
+ * @integrity_cap_bit: MSR_INTEGRITY_CAPS bit enumerating this test
+ */
+struct ifs_data {
+	int	integrity_cap_bit;
+};
+
+struct ifs_device {
+	struct ifs_data data;
+	struct miscdevice misc;
+};
+
+void ifs_load_firmware(struct device *dev);
+
+#endif

drivers/platform/x86/intel/ifs/load.c

+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2022 Intel Corporation. */
+
+#include <linux/firmware.h>
+
+#include "ifs.h"
+
+/*
+ * Load ifs image. Before loading ifs module, the ifs image must be located
+ * in /lib/firmware/intel/ifs and named as {family/model/stepping}.{testname}.
+ */
+void ifs_load_firmware(struct device *dev)
+{
+	const struct firmware *fw;
+	char scan_path[32];
+	int ret;
+
+	snprintf(scan_path, sizeof(scan_path), "intel/ifs/%02x-%02x-%02x.scan",
+		 boot_cpu_data.x86, boot_cpu_data.x86_model, boot_cpu_data.x86_stepping);
+
+	ret = request_firmware_direct(&fw, scan_path, dev);
+	if (ret) {
+		dev_err(dev, "ifs file %s load failed\n", scan_path);
+		return;
+	}
+
+	release_firmware(fw);
+}