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

   1 /*
   2  *  SMI methods for use with dell-smbios
   3  *
   4  *  Copyright (c) Red Hat <mjg@redhat.com>
   5  *  Copyright (c) 2014 Gabriele Mazzotta <gabriele.mzt@gmail.com>
   6  *  Copyright (c) 2014 Pali Rohár <pali.rohar@gmail.com>
   7  *  Copyright (c) 2017 Dell Inc.
   8  *
   9  *  This program is free software; you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License version 2 as
  11  *  published by the Free Software Foundation.
  12  */
  13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/dmi.h>
  16 #include <linux/gfp.h>
  17 #include <linux/io.h>
  18 #include <linux/module.h>
  19 #include <linux/mutex.h>
  20 #include <linux/platform_device.h>
  21 #include "../../firmware/dcdbas.h"
  22 #include "dell-smbios.h"
  23
  24 static int da_command_address;
  25 static int da_command_code;
  26 static struct calling_interface_buffer *buffer;
  27 static struct platform_device *platform_device;
  28 static DEFINE_MUTEX(smm_mutex);
  29
  30 static const struct dmi_system_id dell_device_table[] __initconst = {
  31         {
  32                 .ident = "Dell laptop",
  33                 .matches = {
  34                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
  35                         DMI_MATCH(DMI_CHASSIS_TYPE, "8"),
  36                 },
  37         },
  38         {
  39                 .matches = {
  40                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
  41                         DMI_MATCH(DMI_CHASSIS_TYPE, "9"), /*Laptop*/
  42                 },
  43         },
  44         {
  45                 .matches = {
  46                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
  47                         DMI_MATCH(DMI_CHASSIS_TYPE, "10"), /*Notebook*/
  48                 },
  49         },
  50         {
  51                 .ident = "Dell Computer Corporation",
  52                 .matches = {
  53                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
  54                         DMI_MATCH(DMI_CHASSIS_TYPE, "8"),
  55                 },
  56         },
  57         { }
  58 };
  59 MODULE_DEVICE_TABLE(dmi, dell_device_table);
  60
  61 static void parse_da_table(const struct dmi_header *dm)
  62 {
  63         struct calling_interface_structure *table =
  64                 container_of(dm, struct calling_interface_structure, header);
  65
  66         /* 4 bytes of table header, plus 7 bytes of Dell header, plus at least
  67          * 6 bytes of entry
  68          */
  69         if (dm->length < 17)
  70                 return;
  71
  72         da_command_address = table->cmdIOAddress;
  73         da_command_code = table->cmdIOCode;
  74 }
  75
  76 static void find_cmd_address(const struct dmi_header *dm, void *dummy)
  77 {
  78         switch (dm->type) {
  79         case 0xda: /* Calling interface */
  80                 parse_da_table(dm);
  81                 break;
  82         }
  83 }
  84
  85 static int dell_smbios_smm_call(struct calling_interface_buffer *input)
  86 {
  87         struct smi_cmd command;
  88         size_t size;
  89
  90         size = sizeof(struct calling_interface_buffer);
  91         command.magic = SMI_CMD_MAGIC;
  92         command.command_address = da_command_address;
  93         command.command_code = da_command_code;
  94         command.ebx = virt_to_phys(buffer);
  95         command.ecx = 0x42534931;
  96
  97         mutex_lock(&smm_mutex);
  98         memcpy(buffer, input, size);
  99         dcdbas_smi_request(&command);
 100         memcpy(input, buffer, size);
 101         mutex_unlock(&smm_mutex);
 102         return 0;
 103 }
 104
 105 /* When enabled this indicates that SMM won't work */
 106 static bool test_wsmt_enabled(void)
 107 {
 108         struct calling_interface_token *wsmt;
 109
 110         /* if token doesn't exist, SMM will work */
 111         wsmt = dell_smbios_find_token(WSMT_EN_TOKEN);
 112         if (!wsmt)
 113                 return false;
 114
 115         /* If token exists, try to access over SMM but set a dummy return.
 116          * - If WSMT disabled it will be overwritten by SMM
 117          * - If WSMT enabled then dummy value will remain
 118          */
 119         buffer->cmd_class = CLASS_TOKEN_READ;
 120         buffer->cmd_select = SELECT_TOKEN_STD;
 121         memset(buffer, 0, sizeof(struct calling_interface_buffer));
 122         buffer->input[0] = wsmt->location;
 123         buffer->output[0] = 99;
 124         dell_smbios_smm_call(buffer);
 125         if (buffer->output[0] == 99)
 126                 return true;
 127
 128         return false;
 129 }
 130
 131 int init_dell_smbios_smm(void)
 132 {
 133         int ret;
 134         /*
 135          * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
 136          * is passed to SMI handler.
 137          */
 138         buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
 139         if (!buffer)
 140                 return -ENOMEM;
 141
 142         dmi_walk(find_cmd_address, NULL);
 143
 144         if (test_wsmt_enabled()) {
 145                 pr_debug("Disabling due to WSMT enabled\n");
 146                 ret = -ENODEV;
 147                 goto fail_wsmt;
 148         }
 149
 150         platform_device = platform_device_alloc("dell-smbios", 1);
 151         if (!platform_device) {
 152                 ret = -ENOMEM;
 153                 goto fail_platform_device_alloc;
 154         }
 155
 156         ret = platform_device_add(platform_device);
 157         if (ret)
 158                 goto fail_platform_device_add;
 159
 160         ret = dell_smbios_register_device(&platform_device->dev,
 161                                           &dell_smbios_smm_call);
 162         if (ret)
 163                 goto fail_register;
 164
 165         return 0;
 166
 167 fail_register:
 168         platform_device_del(platform_device);
 169
 170 fail_platform_device_add:
 171         platform_device_put(platform_device);
 172
 173 fail_wsmt:
 174 fail_platform_device_alloc:
 175         free_page((unsigned long)buffer);
 176         return ret;
 177 }
 178
 179 void exit_dell_smbios_smm(void)
 180 {
 181         if (platform_device) {
 182                 dell_smbios_unregister_device(&platform_device->dev);
 183                 platform_device_unregister(platform_device);
 184                 free_page((unsigned long)buffer);
 185         }
 186 }