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  */
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  */
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