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 calling_interface_buffer *buffer;
24 static struct platform_device *platform_device;
25 static DEFINE_MUTEX(smm_mutex);
26
parse_da_table(const struct dmi_header * dm)27 static void parse_da_table(const struct dmi_header *dm)
28 {
29 struct calling_interface_structure *table =
30 container_of(dm, struct calling_interface_structure, header);
31
32 /* 4 bytes of table header, plus 7 bytes of Dell header, plus at least
33 * 6 bytes of entry
34 */
35 if (dm->length < 17)
36 return;
37
38 da_command_address = table->cmdIOAddress;
39 da_command_code = table->cmdIOCode;
40 }
41
find_cmd_address(const struct dmi_header * dm,void * dummy)42 static void find_cmd_address(const struct dmi_header *dm, void *dummy)
43 {
44 switch (dm->type) {
45 case 0xda: /* Calling interface */
46 parse_da_table(dm);
47 break;
48 }
49 }
50
dell_smbios_smm_call(struct calling_interface_buffer * input)51 static int dell_smbios_smm_call(struct calling_interface_buffer *input)
52 {
53 struct smi_cmd command;
54 size_t size;
55
56 size = sizeof(struct calling_interface_buffer);
57 command.magic = SMI_CMD_MAGIC;
58 command.command_address = da_command_address;
59 command.command_code = da_command_code;
60 command.ebx = virt_to_phys(buffer);
61 command.ecx = 0x42534931;
62
63 mutex_lock(&smm_mutex);
64 memcpy(buffer, input, size);
65 dcdbas_smi_request(&command);
66 memcpy(input, buffer, size);
67 mutex_unlock(&smm_mutex);
68 return 0;
69 }
70
71 /* When enabled this indicates that SMM won't work */
test_wsmt_enabled(void)72 static bool test_wsmt_enabled(void)
73 {
74 struct calling_interface_token *wsmt;
75
76 /* if token doesn't exist, SMM will work */
77 wsmt = dell_smbios_find_token(WSMT_EN_TOKEN);
78 if (!wsmt)
79 return false;
80
81 /* If token exists, try to access over SMM but set a dummy return.
82 * - If WSMT disabled it will be overwritten by SMM
83 * - If WSMT enabled then dummy value will remain
84 */
85 buffer->cmd_class = CLASS_TOKEN_READ;
86 buffer->cmd_select = SELECT_TOKEN_STD;
87 memset(buffer, 0, sizeof(struct calling_interface_buffer));
88 buffer->input[0] = wsmt->location;
89 buffer->output[0] = 99;
90 dell_smbios_smm_call(buffer);
91 if (buffer->output[0] == 99)
92 return true;
93
94 return false;
95 }
96
init_dell_smbios_smm(void)97 int init_dell_smbios_smm(void)
98 {
99 int ret;
100 /*
101 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
102 * is passed to SMI handler.
103 */
104 buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
105 if (!buffer)
106 return -ENOMEM;
107
108 dmi_walk(find_cmd_address, NULL);
109
110 if (test_wsmt_enabled()) {
111 pr_debug("Disabling due to WSMT enabled\n");
112 ret = -ENODEV;
113 goto fail_wsmt;
114 }
115
116 platform_device = platform_device_alloc("dell-smbios", 1);
117 if (!platform_device) {
118 ret = -ENOMEM;
119 goto fail_platform_device_alloc;
120 }
121
122 ret = platform_device_add(platform_device);
123 if (ret)
124 goto fail_platform_device_add;
125
126 ret = dell_smbios_register_device(&platform_device->dev,
127 &dell_smbios_smm_call);
128 if (ret)
129 goto fail_register;
130
131 return 0;
132
133 fail_register:
134 platform_device_del(platform_device);
135
136 fail_platform_device_add:
137 platform_device_put(platform_device);
138
139 fail_wsmt:
140 fail_platform_device_alloc:
141 free_page((unsigned long)buffer);
142 return ret;
143 }
144
exit_dell_smbios_smm(void)145 void exit_dell_smbios_smm(void)
146 {
147 if (platform_device) {
148 dell_smbios_unregister_device(&platform_device->dev);
149 platform_device_unregister(platform_device);
150 free_page((unsigned long)buffer);
151 }
152 }
153
