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 
91 	if (!IS_ALIGNED((u64)_text, SEGMENT_ALIGN))
92 		efi_err("FIRMWARE BUG: kernel image not aligned on %dk boundary\n",
93 			SEGMENT_ALIGN >> 10);
94 
95 	kernel_size = _edata - _text;
96 	kernel_codesize = __inittext_end - _text;
97 	kernel_memsize = kernel_size + (_end - _edata);
98 	*reserve_size = kernel_memsize;
99 
100 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
101 		/*
102 		 * If KASLR is enabled, and we have some randomness available,
103 		 * locate the kernel at a randomized offset in physical memory.
104 		 */
105 		status = efi_random_alloc(*reserve_size, min_kimg_align,
106 					  reserve_addr, phys_seed,
107 					  EFI_LOADER_CODE);
108 		if (status != EFI_SUCCESS)
109 			efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
110 	} else {
111 		status = EFI_OUT_OF_RESOURCES;
112 	}
113 
114 	if (status != EFI_SUCCESS) {
115 		if (!check_image_region((u64)_text, kernel_memsize)) {
116 			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
117 		} else if (IS_ALIGNED((u64)_text, min_kimg_align) &&
118 			   (u64)_end < EFI_ALLOC_LIMIT) {
119 			/*
120 			 * Just execute from wherever we were loaded by the
121 			 * UEFI PE/COFF loader if the placement is suitable.
122 			 */
123 			*image_addr = (u64)_text;
124 			*reserve_size = 0;
125 			return EFI_SUCCESS;
126 		}
127 
128 		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
129 						    ULONG_MAX, min_kimg_align,
130 						    EFI_LOADER_CODE);
131 
132 		if (status != EFI_SUCCESS) {
133 			efi_err("Failed to relocate kernel\n");
134 			*reserve_size = 0;
135 			return status;
136 		}
137 	}
138 
139 	*image_addr = *reserve_addr;
140 	memcpy((void *)*image_addr, _text, kernel_size);
141 	caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
142 
143 	return EFI_SUCCESS;
144 }
145 
146 asmlinkage void primary_entry(void);
147 
148 unsigned long primary_entry_offset(void)
149 {
150 	/*
151 	 * When built as part of the kernel, the EFI stub cannot branch to the
152 	 * kernel proper via the image header, as the PE/COFF header is
153 	 * strictly not part of the in-memory presentation of the image, only
154 	 * of the file representation. So instead, we need to jump to the
155 	 * actual entrypoint in the .text region of the image.
156 	 */
157 	return (char *)primary_entry - _text;
158 }
159