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@kernel.org>
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
21 static int da_command_address;
22 static int da_command_code;
23 static struct smi_buffer smi_buf;
24 static struct calling_interface_buffer *buffer;
25 static struct platform_device *platform_device;
26 static DEFINE_MUTEX(smm_mutex);
27
parse_da_table(const struct dmi_header * dm)28 static void parse_da_table(const struct dmi_header *dm)
29 {
30 struct calling_interface_structure *table =
31 container_of(dm, struct calling_interface_structure, header);
32
33 /* 4 bytes of table header, plus 7 bytes of Dell header, plus at least
34 * 6 bytes of entry
35 */
36 if (dm->length < 17)
37 return;
38
39 da_command_address = table->cmdIOAddress;
40 da_command_code = table->cmdIOCode;
41 }
42
find_cmd_address(const struct dmi_header * dm,void * dummy)43 static void find_cmd_address(const struct dmi_header *dm, void *dummy)
44 {
45 switch (dm->type) {
46 case 0xda: /* Calling interface */
47 parse_da_table(dm);
48 break;
49 }
50 }
51
dell_smbios_smm_call(struct calling_interface_buffer * input)52 static int dell_smbios_smm_call(struct calling_interface_buffer *input)
53 {
54 struct smi_cmd command;
55 size_t size;
56
57 size = sizeof(struct calling_interface_buffer);
58 command.magic = SMI_CMD_MAGIC;
59 command.command_address = da_command_address;
60 command.command_code = da_command_code;
61 command.ebx = smi_buf.dma;
62 command.ecx = 0x42534931;
63
64 mutex_lock(&smm_mutex);
65 memcpy(buffer, input, size);
66 dcdbas_smi_request(&command);
67 memcpy(input, buffer, size);
68 mutex_unlock(&smm_mutex);
69 return 0;
70 }
71
72 /* When enabled this indicates that SMM won't work */
test_wsmt_enabled(void)73 static bool test_wsmt_enabled(void)
74 {
75 struct calling_interface_token *wsmt;
76
77 /* if token doesn't exist, SMM will work */
78 wsmt = dell_smbios_find_token(WSMT_EN_TOKEN);
79 if (!wsmt)
80 return false;
81
82 /* If token exists, try to access over SMM but set a dummy return.
83 * - If WSMT disabled it will be overwritten by SMM
84 * - If WSMT enabled then dummy value will remain
85 */
86 buffer->cmd_class = CLASS_TOKEN_READ;
87 buffer->cmd_select = SELECT_TOKEN_STD;
88 memset(buffer, 0, sizeof(struct calling_interface_buffer));
89 buffer->input[0] = wsmt->location;
90 buffer->output[0] = 99;
91 dell_smbios_smm_call(buffer);
92 if (buffer->output[0] == 99)
93 return true;
94
95 return false;
96 }
97
init_dell_smbios_smm(void)98 int init_dell_smbios_smm(void)
99 {
100 int ret;
101 /*
102 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
103 * is passed to SMI handler.
104 */
105 ret = dcdbas_smi_alloc(&smi_buf, PAGE_SIZE);
106 if (ret)
107 return ret;
108 buffer = (void *)smi_buf.virt;
109
110 dmi_walk(find_cmd_address, NULL);
111
112 if (test_wsmt_enabled()) {
113 pr_debug("Disabling due to WSMT enabled\n");
114 ret = -ENODEV;
115 goto fail_wsmt;
116 }
117
118 platform_device = platform_device_alloc("dell-smbios", 1);
119 if (!platform_device) {
120 ret = -ENOMEM;
121 goto fail_platform_device_alloc;
122 }
123
124 ret = platform_device_add(platform_device);
125 if (ret)
126 goto fail_platform_device_add;
127
128 ret = dell_smbios_register_device(&platform_device->dev,
129 &dell_smbios_smm_call);
130 if (ret)
131 goto fail_register;
132
133 return 0;
134
135 fail_register:
136 platform_device_del(platform_device);
137
138 fail_platform_device_add:
139 platform_device_put(platform_device);
140
141 fail_wsmt:
142 fail_platform_device_alloc:
143 dcdbas_smi_free(&smi_buf);
144 return ret;
145 }
146
exit_dell_smbios_smm(void)147 void exit_dell_smbios_smm(void)
148 {
149 if (platform_device) {
150 dell_smbios_unregister_device(&platform_device->dev);
151 platform_device_unregister(platform_device);
152 dcdbas_smi_free(&smi_buf);
153 }
154 }
155