cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

efivar.c (3360B)

      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[64];
    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}