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 
18 efi_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  */
43 static bool check_image_region(u64 base, u64 size)
44 {
45 	unsigned long map_size, desc_size, buff_size;
46 	efi_memory_desc_t *memory_map;
47 	struct efi_boot_memmap map;
48 	efi_status_t status;
49 	bool ret = false;
50 	int map_offset;
51 
52 	map.map =	&memory_map;
53 	map.map_size =	&map_size;
54 	map.desc_size =	&desc_size;
55 	map.desc_ver =	NULL;
56 	map.key_ptr =	NULL;
57 	map.buff_size =	&buff_size;
58 
59 	status = efi_get_memory_map(&map);
60 	if (status != EFI_SUCCESS)
61 		return false;
62 
63 	for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
64 		efi_memory_desc_t *md = (void *)memory_map + map_offset;
65 		u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
66 
67 		/*
68 		 * Find the region that covers base, and return whether
69 		 * it covers base+size bytes.
70 		 */
71 		if (base >= md->phys_addr && base < end) {
72 			ret = (base + size) <= end;
73 			break;
74 		}
75 	}
76 
77 	efi_bs_call(free_pool, memory_map);
78 
79 	return ret;
80 }
81 
82 efi_status_t handle_kernel_image(unsigned long *image_addr,
83 				 unsigned long *image_size,
84 				 unsigned long *reserve_addr,
85 				 unsigned long *reserve_size,
86 				 efi_loaded_image_t *image)
87 {
88 	efi_status_t status;
89 	unsigned long kernel_size, kernel_memsize = 0;
90 	u32 phys_seed = 0;
91 
92 	/*
93 	 * Although relocatable kernels can fix up the misalignment with
94 	 * respect to MIN_KIMG_ALIGN, the resulting virtual text addresses are
95 	 * subtly out of sync with those recorded in the vmlinux when kaslr is
96 	 * disabled but the image required relocation anyway. Therefore retain
97 	 * 2M alignment if KASLR was explicitly disabled, even if it was not
98 	 * going to be activated to begin with.
99 	 */
100 	u64 min_kimg_align = efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
101 
102 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
103 		if (!efi_nokaslr) {
104 			status = efi_get_random_bytes(sizeof(phys_seed),
105 						      (u8 *)&phys_seed);
106 			if (status == EFI_NOT_FOUND) {
107 				efi_info("EFI_RNG_PROTOCOL unavailable\n");
108 				efi_nokaslr = true;
109 			} else if (status != EFI_SUCCESS) {
110 				efi_err("efi_get_random_bytes() failed (0x%lx)\n",
111 					status);
112 				efi_nokaslr = true;
113 			}
114 		} else {
115 			efi_info("KASLR disabled on kernel command line\n");
116 		}
117 	}
118 
119 	if (image->image_base != _text)
120 		efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
121 
122 	if (!IS_ALIGNED((u64)_text, SEGMENT_ALIGN))
123 		efi_err("FIRMWARE BUG: kernel image not aligned on %dk boundary\n",
124 			SEGMENT_ALIGN >> 10);
125 
126 	kernel_size = _edata - _text;
127 	kernel_memsize = kernel_size + (_end - _edata);
128 	*reserve_size = kernel_memsize;
129 
130 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
131 		/*
132 		 * If KASLR is enabled, and we have some randomness available,
133 		 * locate the kernel at a randomized offset in physical memory.
134 		 */
135 		status = efi_random_alloc(*reserve_size, min_kimg_align,
136 					  reserve_addr, phys_seed);
137 		if (status != EFI_SUCCESS)
138 			efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
139 	} else {
140 		status = EFI_OUT_OF_RESOURCES;
141 	}
142 
143 	if (status != EFI_SUCCESS) {
144 		if (!check_image_region((u64)_text, kernel_memsize)) {
145 			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
146 		} else if (IS_ALIGNED((u64)_text, min_kimg_align)) {
147 			/*
148 			 * Just execute from wherever we were loaded by the
149 			 * UEFI PE/COFF loader if the alignment is suitable.
150 			 */
151 			*image_addr = (u64)_text;
152 			*reserve_size = 0;
153 			return EFI_SUCCESS;
154 		}
155 
156 		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
157 						    ULONG_MAX, min_kimg_align);
158 
159 		if (status != EFI_SUCCESS) {
160 			efi_err("Failed to relocate kernel\n");
161 			*reserve_size = 0;
162 			return status;
163 		}
164 	}
165 
166 	*image_addr = *reserve_addr;
167 	memcpy((void *)*image_addr, _text, kernel_size);
168 
169 	return EFI_SUCCESS;
170 }
171