torvalds/linux

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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.
 */

#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;
}