1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2013, 2014 Linaro Ltd;  <roy.franz@linaro.org>
4 *
5 * This file implements the EFI boot stub for the arm64 kernel.
6 * Adapted from ARM version by Mark Salter <msalter@redhat.com>
7 */
8
9
10#include <linux/efi.h>
11#include <asm/efi.h>
12#include <asm/memory.h>
13#include <asm/sections.h>
14#include <asm/sysreg.h>
15
16#include "efistub.h"
17
18efi_status_t check_platform_features(void)
19{
20	u64 tg;
21
22	/* UEFI mandates support for 4 KB granularity, no need to check */
23	if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
24		return EFI_SUCCESS;
25
26	tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
27	if (tg < ID_AA64MMFR0_TGRAN_SUPPORTED_MIN || tg > ID_AA64MMFR0_TGRAN_SUPPORTED_MAX) {
28		if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
29			efi_err("This 64 KB granular kernel is not supported by your CPU\n");
30		else
31			efi_err("This 16 KB granular kernel is not supported by your CPU\n");
32		return EFI_UNSUPPORTED;
33	}
34	return EFI_SUCCESS;
35}
36
37/*
38 * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail
39 * to provide space, and fail to zero it). Check for this condition by double
40 * checking that the first and the last byte of the image are covered by the
41 * same EFI memory map entry.
42 */
43static bool check_image_region(u64 base, u64 size)
44{
45	struct efi_boot_memmap *map;
46	efi_status_t status;
47	bool ret = false;
48	int map_offset;
49
50	status = efi_get_memory_map(&map, false);
51	if (status != EFI_SUCCESS)
52		return false;
53
54	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
55		efi_memory_desc_t *md = (void *)map->map + map_offset;
56		u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
57
58		/*
59		 * Find the region that covers base, and return whether
60		 * it covers base+size bytes.
61		 */
62		if (base >= md->phys_addr && base < end) {
63			ret = (base + size) <= end;
64			break;
65		}
66	}
67
68	efi_bs_call(free_pool, map);
69
70	return ret;
71}
72
73efi_status_t handle_kernel_image(unsigned long *image_addr,
74				 unsigned long *image_size,
75				 unsigned long *reserve_addr,
76				 unsigned long *reserve_size,
77				 efi_loaded_image_t *image)
78{
79	efi_status_t status;
80	unsigned long kernel_size, kernel_memsize = 0;
81	u32 phys_seed = 0;
82
83	/*
84	 * Although relocatable kernels can fix up the misalignment with
85	 * respect to MIN_KIMG_ALIGN, the resulting virtual text addresses are
86	 * subtly out of sync with those recorded in the vmlinux when kaslr is
87	 * disabled but the image required relocation anyway. Therefore retain
88	 * 2M alignment if KASLR was explicitly disabled, even if it was not
89	 * going to be activated to begin with.
90	 */
91	u64 min_kimg_align = efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
92
93	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
94		if (!efi_nokaslr) {
95			status = efi_get_random_bytes(sizeof(phys_seed),
96						      (u8 *)&phys_seed);
97			if (status == EFI_NOT_FOUND) {
98				efi_info("EFI_RNG_PROTOCOL unavailable, KASLR will be disabled\n");
99				efi_nokaslr = true;
100			} else if (status != EFI_SUCCESS) {
101				efi_err("efi_get_random_bytes() failed (0x%lx), KASLR will be disabled\n",
102					status);
103				efi_nokaslr = true;
104			}
105		} else {
106			efi_info("KASLR disabled on kernel command line\n");
107		}
108	}
109
110	if (image->image_base != _text)
111		efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
112
113	if (!IS_ALIGNED((u64)_text, SEGMENT_ALIGN))
114		efi_err("FIRMWARE BUG: kernel image not aligned on %dk boundary\n",
115			SEGMENT_ALIGN >> 10);
116
117	kernel_size = _edata - _text;
118	kernel_memsize = kernel_size + (_end - _edata);
119	*reserve_size = kernel_memsize;
120
121	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
122		/*
123		 * If KASLR is enabled, and we have some randomness available,
124		 * locate the kernel at a randomized offset in physical memory.
125		 */
126		status = efi_random_alloc(*reserve_size, min_kimg_align,
127					  reserve_addr, phys_seed);
128	} else {
129		status = EFI_OUT_OF_RESOURCES;
130	}
131
132	if (status != EFI_SUCCESS) {
133		if (!check_image_region((u64)_text, kernel_memsize)) {
134			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
135		} else if (IS_ALIGNED((u64)_text, min_kimg_align)) {
136			/*
137			 * Just execute from wherever we were loaded by the
138			 * UEFI PE/COFF loader if the alignment is suitable.
139			 */
140			*image_addr = (u64)_text;
141			*reserve_size = 0;
142			return EFI_SUCCESS;
143		}
144
145		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
146						    ULONG_MAX, min_kimg_align);
147
148		if (status != EFI_SUCCESS) {
149			efi_err("Failed to relocate kernel\n");
150			*reserve_size = 0;
151			return status;
152		}
153	}
154
155	*image_addr = *reserve_addr;
156	memcpy((void *)*image_addr, _text, kernel_size);
157
158	return EFI_SUCCESS;
159}
160