tools/wmi: add a sample for dell smbios communication over WMI

This application uses the character device /dev/wmi/dell-smbios
to perform SMBIOS communications from userspace.

It offers demonstrations of a few simple tasks:
 - Running a class/select command
 - Querying a token value
 - Activating a token

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

tools/wmi/Makefile

@@ -0,0 +1,18 @@
+PREFIX ?= /usr
+SBINDIR ?= sbin
+INSTALL ?= install
+CFLAGS += -D__EXPORTED_HEADERS__ -I../../include/uapi -I../../include
+CC = $(CROSS_COMPILE)gcc
+
+TARGET = dell-smbios-example
+
+all: $(TARGET)
+
+%: %.c
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
+
+clean:
+	$(RM) $(TARGET)
+
+install: dell-smbios-example
+	$(INSTALL) -D -m 755 $(TARGET) $(DESTDIR)$(PREFIX)/$(SBINDIR)/$(TARGET)

tools/wmi/dell-smbios-example.c

@@ -0,0 +1,210 @@
+/*
+ *  Sample application for SMBIOS communication over WMI interface
+ *  Performs the following:
+ *  - Simple cmd_class/cmd_select lookup for TPM information
+ *  - Simple query of known tokens and their values
+ *  - Simple activation of a token
+ *
+ *  Copyright (C) 2017 Dell, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+/* if uapi header isn't installed, this might not yet exist */
+#ifndef __packed
+#define __packed __attribute__((packed))
+#endif
+#include <linux/wmi.h>
+
+/* It would be better to discover these using udev, but for a simple
+ * application they're hardcoded
+ */
+static const char *ioctl_devfs = "/dev/wmi/dell-smbios";
+static const char *token_sysfs =
+			"/sys/bus/platform/devices/dell-smbios.0/tokens";
+
+static void show_buffer(struct dell_wmi_smbios_buffer *buffer)
+{
+	printf("Call: %x/%x [%x,%x,%x,%x]\nResults: [%8x,%8x,%8x,%8x]\n",
+	buffer->std.cmd_class, buffer->std.cmd_select,
+	buffer->std.input[0], buffer->std.input[1],
+	buffer->std.input[2], buffer->std.input[3],
+	buffer->std.output[0], buffer->std.output[1],
+	buffer->std.output[2], buffer->std.output[3]);
+}
+
+static int run_wmi_smbios_cmd(struct dell_wmi_smbios_buffer *buffer)
+{
+	int fd;
+	int ret;
+
+	fd = open(ioctl_devfs, O_NONBLOCK);
+	ret = ioctl(fd, DELL_WMI_SMBIOS_CMD, buffer);
+	close(fd);
+	return ret;
+}
+
+static int find_token(__u16 token, __u16 *location, __u16 *value)
+{
+	char location_sysfs[60];
+	char value_sysfs[57];
+	char buf[4096];
+	FILE *f;
+	int ret;
+
+	ret = sprintf(value_sysfs, "%s/%04x_value", token_sysfs, token);
+	if (ret < 0) {
+		printf("sprintf value failed\n");
+		return 2;
+	}
+	f = fopen(value_sysfs, "rb");
+	if (!f) {
+		printf("failed to open %s\n", value_sysfs);
+		return 2;
+	}
+	fread(buf, 1, 4096, f);
+	fclose(f);
+	*value = (__u16) strtol(buf, NULL, 16);
+
+	ret = sprintf(location_sysfs, "%s/%04x_location", token_sysfs, token);
+	if (ret < 0) {
+		printf("sprintf location failed\n");
+		return 1;
+	}
+	f = fopen(location_sysfs, "rb");
+	if (!f) {
+		printf("failed to open %s\n", location_sysfs);
+		return 2;
+	}
+	fread(buf, 1, 4096, f);
+	fclose(f);
+	*location = (__u16) strtol(buf, NULL, 16);
+
+	if (*location)
+		return 0;
+	return 2;
+}
+
+static int token_is_active(__u16 *location, __u16 *cmpvalue,
+			   struct dell_wmi_smbios_buffer *buffer)
+{
+	int ret;
+
+	buffer->std.cmd_class = CLASS_TOKEN_READ;
+	buffer->std.cmd_select = SELECT_TOKEN_STD;
+	buffer->std.input[0] = *location;
+	ret = run_wmi_smbios_cmd(buffer);
+	if (ret != 0 || buffer->std.output[0] != 0)
+		return ret;
+	ret = (buffer->std.output[1] == *cmpvalue);
+	return ret;
+}
+
+static int query_token(__u16 token, struct dell_wmi_smbios_buffer *buffer)
+{
+	__u16 location;
+	__u16 value;
+	int ret;
+
+	ret = find_token(token, &location, &value);
+	if (ret != 0) {
+		printf("unable to find token %04x\n", token);
+		return 1;
+	}
+	return token_is_active(&location, &value, buffer);
+}
+
+static int activate_token(struct dell_wmi_smbios_buffer *buffer,
+		   __u16 token)
+{
+	__u16 location;
+	__u16 value;
+	int ret;
+
+	ret = find_token(token, &location, &value);
+	if (ret != 0) {
+		printf("unable to find token %04x\n", token);
+		return 1;
+	}
+	buffer->std.cmd_class = CLASS_TOKEN_WRITE;
+	buffer->std.cmd_select = SELECT_TOKEN_STD;
+	buffer->std.input[0] = location;
+	buffer->std.input[1] = 1;
+	ret = run_wmi_smbios_cmd(buffer);
+	return ret;
+}
+
+static int query_buffer_size(__u64 *buffer_size)
+{
+	FILE *f;
+
+	f = fopen(ioctl_devfs, "rb");
+	if (!f)
+		return -EINVAL;
+	fread(buffer_size, sizeof(__u64), 1, f);
+	fclose(f);
+	return EXIT_SUCCESS;
+}
+
+int main(void)
+{
+	struct dell_wmi_smbios_buffer *buffer;
+	int ret;
+	__u64 value = 0;
+
+	ret = query_buffer_size(&value);
+	if (ret == EXIT_FAILURE || !value) {
+		printf("Unable to read buffer size\n");
+		goto out;
+	}
+	printf("Detected required buffer size %lld\n", value);
+
+	buffer = malloc(value);
+	if (buffer == NULL) {
+		printf("failed to alloc memory for ioctl\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+	buffer->length = value;
+
+	/* simple SMBIOS call for looking up TPM info */
+	buffer->std.cmd_class = CLASS_FLASH_INTERFACE;
+	buffer->std.cmd_select = SELECT_FLASH_INTERFACE;
+	buffer->std.input[0] = 2;
+	ret = run_wmi_smbios_cmd(buffer);
+	if (ret) {
+		printf("smbios ioctl failed: %d\n", ret);
+		ret = EXIT_FAILURE;
+		goto out;
+	}
+	show_buffer(buffer);
+
+	/* query some tokens */
+	ret = query_token(CAPSULE_EN_TOKEN, buffer);
+	printf("UEFI Capsule enabled token is: %d\n", ret);
+	ret = query_token(CAPSULE_DIS_TOKEN, buffer);
+	printf("UEFI Capsule disabled token is: %d\n", ret);
+
+	/* activate UEFI capsule token if disabled */
+	if (ret) {
+		printf("Enabling UEFI capsule token");
+		if (activate_token(buffer, CAPSULE_EN_TOKEN)) {
+			printf("activate failed\n");
+			ret = -1;
+			goto out;
+		}
+	}
+	ret = EXIT_SUCCESS;
+out:
+	free(buffer);
+	return ret;
+}