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 
15 #include "efistub.h"
16 
17 /*
18  * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail
19  * to provide space, and fail to zero it). Check for this condition by double
20  * checking that the first and the last byte of the image are covered by the
21  * same EFI memory map entry.
22  */
23 static bool check_image_region(u64 base, u64 size)
24 {
25 	struct efi_boot_memmap *map;
26 	efi_status_t status;
27 	bool ret = false;
28 	int map_offset;
29 
30 	status = efi_get_memory_map(&map, false);
31 	if (status != EFI_SUCCESS)
32 		return false;
33 
34 	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
35 		efi_memory_desc_t *md = (void *)map->map + map_offset;
36 		u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
37 
38 		/*
39 		 * Find the region that covers base, and return whether
40 		 * it covers base+size bytes.
41 		 */
42 		if (base >= md->phys_addr && base < end) {
43 			ret = (base + size) <= end;
44 			break;
45 		}
46 	}
47 
48 	efi_bs_call(free_pool, map);
49 
50 	return ret;
51 }
52 
53 efi_status_t handle_kernel_image(unsigned long *image_addr,
54 				 unsigned long *image_size,
55 				 unsigned long *reserve_addr,
56 				 unsigned long *reserve_size,
57 				 efi_loaded_image_t *image,
58 				 efi_handle_t image_handle)
59 {
60 	efi_status_t status;
61 	unsigned long kernel_size, kernel_codesize, kernel_memsize;
62 	u32 phys_seed = 0;
63 	u64 min_kimg_align = efi_get_kimg_min_align();
64 
65 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
66 		efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID;
67 		void *p;
68 
69 		if (efi_nokaslr) {
70 			efi_info("KASLR disabled on kernel command line\n");
71 		} else if (efi_bs_call(handle_protocol, image_handle,
72 				       &li_fixed_proto, &p) == EFI_SUCCESS) {
73 			efi_info("Image placement fixed by loader\n");
74 		} else {
75 			status = efi_get_random_bytes(sizeof(phys_seed),
76 						      (u8 *)&phys_seed);
77 			if (status == EFI_NOT_FOUND) {
78 				efi_info("EFI_RNG_PROTOCOL unavailable\n");
79 				efi_nokaslr = true;
80 			} else if (status != EFI_SUCCESS) {
81 				efi_err("efi_get_random_bytes() failed (0x%lx)\n",
82 					status);
83 				efi_nokaslr = true;
84 			}
85 		}
86 	}
87 
88 	if (image->image_base != _text) {
89 		efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
90 		image->image_base = _text;
91 	}
92 
93 	if (!IS_ALIGNED((u64)_text, SEGMENT_ALIGN))
94 		efi_err("FIRMWARE BUG: kernel image not aligned on %dk boundary\n",
95 			SEGMENT_ALIGN >> 10);
96 
97 	kernel_size = _edata - _text;
98 	kernel_codesize = __inittext_end - _text;
99 	kernel_memsize = kernel_size + (_end - _edata);
100 	*reserve_size = kernel_memsize;
101 
102 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
103 		/*
104 		 * If KASLR is enabled, and we have some randomness available,
105 		 * locate the kernel at a randomized offset in physical memory.
106 		 */
107 		status = efi_random_alloc(*reserve_size, min_kimg_align,
108 					  reserve_addr, phys_seed,
109 					  EFI_LOADER_CODE, EFI_ALLOC_LIMIT);
110 		if (status != EFI_SUCCESS)
111 			efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
112 	} else {
113 		status = EFI_OUT_OF_RESOURCES;
114 	}
115 
116 	if (status != EFI_SUCCESS) {
117 		if (!check_image_region((u64)_text, kernel_memsize)) {
118 			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
119 		} else if (IS_ALIGNED((u64)_text, min_kimg_align) &&
120 			   (u64)_end < EFI_ALLOC_LIMIT) {
121 			/*
122 			 * Just execute from wherever we were loaded by the
123 			 * UEFI PE/COFF loader if the placement is suitable.
124 			 */
125 			*image_addr = (u64)_text;
126 			*reserve_size = 0;
127 			return EFI_SUCCESS;
128 		}
129 
130 		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
131 						    ULONG_MAX, min_kimg_align,
132 						    EFI_LOADER_CODE);
133 
134 		if (status != EFI_SUCCESS) {
135 			efi_err("Failed to relocate kernel\n");
136 			*reserve_size = 0;
137 			return status;
138 		}
139 	}
140 
141 	*image_addr = *reserve_addr;
142 	memcpy((void *)*image_addr, _text, kernel_size);
143 	caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
144 	efi_remap_image(*image_addr, *reserve_size, kernel_codesize);
145 
146 	return EFI_SUCCESS;
147 }
148 
149 asmlinkage void primary_entry(void);
150 
151 unsigned long primary_entry_offset(void)
152 {
153 	/*
154 	 * When built as part of the kernel, the EFI stub cannot branch to the
155 	 * kernel proper via the image header, as the PE/COFF header is
156 	 * strictly not part of the in-memory presentation of the image, only
157 	 * of the file representation. So instead, we need to jump to the
158 	 * actual entrypoint in the .text region of the image.
159 	 */
160 	return (char *)primary_entry - _text;
161 }
162