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
21static int da_command_address;
22static int da_command_code;
23static struct smi_buffer smi_buf;
24static struct calling_interface_buffer *buffer;
25static struct platform_device *platform_device;
26static DEFINE_MUTEX(smm_mutex);
27
28static 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
43static 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
52static 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 */
73static 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
98int 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
135fail_register:
136	platform_device_del(platform_device);
137
138fail_platform_device_add:
139	platform_device_put(platform_device);
140
141fail_wsmt:
142fail_platform_device_alloc:
143	dcdbas_smi_free(&smi_buf);
144	return ret;
145}
146
147void 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