1 // SPDX-License-Identifier: GPL-2.0 or BSD-3-Clause
2 /*
3 * Copyright(c) 2015, 2016 Intel Corporation.
4 */
5
6 #include <linux/string.h>
7 #include <linux/string_helpers.h>
8
9 #include "efivar.h"
10
11 /* GUID for HFI1 variables in EFI */
12 #define HFI1_EFIVAR_GUID EFI_GUID(0xc50a953e, 0xa8b2, 0x42a6, \
13 0xbf, 0x89, 0xd3, 0x33, 0xa6, 0xe9, 0xe6, 0xd4)
14 /* largest EFI data size we expect */
15 #define EFI_DATA_SIZE 4096
16
17 /*
18 * Read the named EFI variable. Return the size of the actual data in *size
19 * and a kmalloc'ed buffer in *return_data. The caller must free the
20 * data. It is guaranteed that *return_data will be NULL and *size = 0
21 * if this routine fails.
22 *
23 * Return 0 on success, -errno on failure.
24 */
read_efi_var(const char * name,unsigned long * size,void ** return_data)25 static int read_efi_var(const char *name, unsigned long *size,
26 void **return_data)
27 {
28 efi_status_t status;
29 efi_char16_t *uni_name;
30 efi_guid_t guid;
31 unsigned long temp_size;
32 void *temp_buffer;
33 void *data;
34 int i;
35 int ret;
36
37 /* set failure return values */
38 *size = 0;
39 *return_data = NULL;
40
41 if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
42 return -EOPNOTSUPP;
43
44 uni_name = kcalloc(strlen(name) + 1, sizeof(efi_char16_t), GFP_KERNEL);
45 temp_buffer = kzalloc(EFI_DATA_SIZE, GFP_KERNEL);
46
47 if (!uni_name || !temp_buffer) {
48 ret = -ENOMEM;
49 goto fail;
50 }
51
52 /* input: the size of the buffer */
53 temp_size = EFI_DATA_SIZE;
54
55 /* convert ASCII to unicode - it is a 1:1 mapping */
56 for (i = 0; name[i]; i++)
57 uni_name[i] = name[i];
58
59 /* need a variable for our GUID */
60 guid = HFI1_EFIVAR_GUID;
61
62 /* call into EFI runtime services */
63 status = efi.get_variable(
64 uni_name,
65 &guid,
66 NULL,
67 &temp_size,
68 temp_buffer);
69
70 /*
71 * It would be nice to call efi_status_to_err() here, but that
72 * is in the EFIVAR_FS code and may not be compiled in.
73 * However, even that is insufficient since it does not cover
74 * EFI_BUFFER_TOO_SMALL which could be an important return.
75 * For now, just split out success or not found.
76 */
77 ret = status == EFI_SUCCESS ? 0 :
78 status == EFI_NOT_FOUND ? -ENOENT :
79 -EINVAL;
80 if (ret)
81 goto fail;
82
83 /*
84 * We have successfully read the EFI variable into our
85 * temporary buffer. Now allocate a correctly sized
86 * buffer.
87 */
88 data = kmemdup(temp_buffer, temp_size, GFP_KERNEL);
89 if (!data) {
90 ret = -ENOMEM;
91 goto fail;
92 }
93
94 *size = temp_size;
95 *return_data = data;
96
97 fail:
98 kfree(uni_name);
99 kfree(temp_buffer);
100
101 return ret;
102 }
103
104 /*
105 * Read an HFI1 EFI variable of the form:
106 * <PCIe address>-<kind>
107 * Return an kalloc'ed array and size of the data.
108 *
109 * Returns 0 on success, -errno on failure.
110 */
read_hfi1_efi_var(struct hfi1_devdata * dd,const char * kind,unsigned long * size,void ** return_data)111 int read_hfi1_efi_var(struct hfi1_devdata *dd, const char *kind,
112 unsigned long *size, void **return_data)
113 {
114 char prefix_name[64];
115 char name[128];
116 int result;
117
118 /* create a common prefix */
119 snprintf(prefix_name, sizeof(prefix_name), "%04x:%02x:%02x.%x",
120 pci_domain_nr(dd->pcidev->bus),
121 dd->pcidev->bus->number,
122 PCI_SLOT(dd->pcidev->devfn),
123 PCI_FUNC(dd->pcidev->devfn));
124 snprintf(name, sizeof(name), "%s-%s", prefix_name, kind);
125 result = read_efi_var(name, size, return_data);
126
127 /*
128 * If reading the lowercase EFI variable fail, read the uppercase
129 * variable.
130 */
131 if (result) {
132 string_upper(prefix_name, prefix_name);
133 snprintf(name, sizeof(name), "%s-%s", prefix_name, kind);
134 result = read_efi_var(name, size, return_data);
135 }
136
137 return result;
138 }
139