LXR linux/drivers/platform/x86/dell-smbios-smm.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  SMI methods for use with dell-smbios
   4 *
   5 *  Copyright (c) Red Hat <mjg@redhat.com>
   6 *  Copyright (c) 2014 Gabriele Mazzotta <gabriele.mzt@gmail.com>
   7 *  Copyright (c) 2014 Pali Rohár <pali.rohar@gmail.com>
   8 *  Copyright (c) 2017 Dell Inc.
   9 */
  10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12#include <linux/dmi.h>
  13#include <linux/gfp.h>
  14#include <linux/io.h>
  15#include <linux/module.h>
  16#include <linux/mutex.h>
  17#include <linux/platform_device.h>
  18#include "dcdbas.h"
  19#include "dell-smbios.h"
  20
  21static int da_command_address;
  22static int da_command_code;
  23static struct calling_interface_buffer *buffer;
  24static struct platform_device *platform_device;
  25static DEFINE_MUTEX(smm_mutex);
  26
  27static const struct dmi_system_id dell_device_table[] __initconst = {
  28        {
  29                .ident = "Dell laptop",
  30                .matches = {
  31                        DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
  32                        DMI_MATCH(DMI_CHASSIS_TYPE, "8"),
  33                },
  34        },
  35        {
  36                .matches = {
  37                        DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
  38                        DMI_MATCH(DMI_CHASSIS_TYPE, "9"), /*Laptop*/
  39                },
  40        },
  41        {
  42                .matches = {
  43                        DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
  44                        DMI_MATCH(DMI_CHASSIS_TYPE, "10"), /*Notebook*/
  45                },
  46        },
  47        {
  48                .ident = "Dell Computer Corporation",
  49                .matches = {
  50                        DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
  51                        DMI_MATCH(DMI_CHASSIS_TYPE, "8"),
  52                },
  53        },
  54        { }
  55};
  56MODULE_DEVICE_TABLE(dmi, dell_device_table);
  57
  58static void parse_da_table(const struct dmi_header *dm)
  59{
  60        struct calling_interface_structure *table =
  61                container_of(dm, struct calling_interface_structure, header);
  62
  63        /* 4 bytes of table header, plus 7 bytes of Dell header, plus at least
  64         * 6 bytes of entry
  65         */
  66        if (dm->length < 17)
  67                return;
  68
  69        da_command_address = table->cmdIOAddress;
  70        da_command_code = table->cmdIOCode;
  71}
  72
  73static void find_cmd_address(const struct dmi_header *dm, void *dummy)
  74{
  75        switch (dm->type) {
  76        case 0xda: /* Calling interface */
  77                parse_da_table(dm);
  78                break;
  79        }
  80}
  81
  82static int dell_smbios_smm_call(struct calling_interface_buffer *input)
  83{
  84        struct smi_cmd command;
  85        size_t size;
  86
  87        size = sizeof(struct calling_interface_buffer);
  88        command.magic = SMI_CMD_MAGIC;
  89        command.command_address = da_command_address;
  90        command.command_code = da_command_code;
  91        command.ebx = virt_to_phys(buffer);
  92        command.ecx = 0x42534931;
  93
  94        mutex_lock(&smm_mutex);
  95        memcpy(buffer, input, size);
  96        dcdbas_smi_request(&command);
  97        memcpy(input, buffer, size);
  98        mutex_unlock(&smm_mutex);
  99        return 0;
 100}
 101
 102/* When enabled this indicates that SMM won't work */
 103static bool test_wsmt_enabled(void)
 104{
 105        struct calling_interface_token *wsmt;
 106
 107        /* if token doesn't exist, SMM will work */
 108        wsmt = dell_smbios_find_token(WSMT_EN_TOKEN);
 109        if (!wsmt)
 110                return false;
 111
 112        /* If token exists, try to access over SMM but set a dummy return.
 113         * - If WSMT disabled it will be overwritten by SMM
 114         * - If WSMT enabled then dummy value will remain
 115         */
 116        buffer->cmd_class = CLASS_TOKEN_READ;
 117        buffer->cmd_select = SELECT_TOKEN_STD;
 118        memset(buffer, 0, sizeof(struct calling_interface_buffer));
 119        buffer->input[0] = wsmt->location;
 120        buffer->output[0] = 99;
 121        dell_smbios_smm_call(buffer);
 122        if (buffer->output[0] == 99)
 123                return true;
 124
 125        return false;
 126}
 127
 128int init_dell_smbios_smm(void)
 129{
 130        int ret;
 131        /*
 132         * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
 133         * is passed to SMI handler.
 134         */
 135        buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
 136        if (!buffer)
 137                return -ENOMEM;
 138
 139        dmi_walk(find_cmd_address, NULL);
 140
 141        if (test_wsmt_enabled()) {
 142                pr_debug("Disabling due to WSMT enabled\n");
 143                ret = -ENODEV;
 144                goto fail_wsmt;
 145        }
 146
 147        platform_device = platform_device_alloc("dell-smbios", 1);
 148        if (!platform_device) {
 149                ret = -ENOMEM;
 150                goto fail_platform_device_alloc;
 151        }
 152
 153        ret = platform_device_add(platform_device);
 154        if (ret)
 155                goto fail_platform_device_add;
 156
 157        ret = dell_smbios_register_device(&platform_device->dev,
 158                                          &dell_smbios_smm_call);
 159        if (ret)
 160                goto fail_register;
 161
 162        return 0;
 163
 164fail_register:
 165        platform_device_del(platform_device);
 166
 167fail_platform_device_add:
 168        platform_device_put(platform_device);
 169
 170fail_wsmt:
 171fail_platform_device_alloc:
 172        free_page((unsigned long)buffer);
 173        return ret;
 174}
 175
 176void exit_dell_smbios_smm(void)
 177{
 178        if (platform_device) {
 179                dell_smbios_unregister_device(&platform_device->dev);
 180                platform_device_unregister(platform_device);
 181                free_page((unsigned long)buffer);
 182        }
 183}
 184