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 */
25static 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
97fail:
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 */
111int 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