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) {
28 		if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
29 			pr_efi_err("This 64 KB granular kernel is not supported by your CPU\n");
30 		else
31 			pr_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 efi_status_t handle_kernel_image(unsigned long *image_addr,
38 				 unsigned long *image_size,
39 				 unsigned long *reserve_addr,
40 				 unsigned long *reserve_size,
41 				 unsigned long dram_base,
42 				 efi_loaded_image_t *image)
43 {
44 	efi_status_t status;
45 	unsigned long kernel_size, kernel_memsize = 0;
46 	unsigned long preferred_offset;
47 	u64 phys_seed = 0;
48 
49 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
50 		if (!nokaslr()) {
51 			status = efi_get_random_bytes(sizeof(phys_seed),
52 						      (u8 *)&phys_seed);
53 			if (status == EFI_NOT_FOUND) {
54 				pr_efi("EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
55 			} else if (status != EFI_SUCCESS) {
56 				pr_efi_err("efi_get_random_bytes() failed\n");
57 				return status;
58 			}
59 		} else {
60 			pr_efi("KASLR disabled on kernel command line\n");
61 		}
62 	}
63 
64 	/*
65 	 * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
66 	 * a 2 MB aligned base, which itself may be lower than dram_base, as
67 	 * long as the resulting offset equals or exceeds it.
68 	 */
69 	preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
70 	if (preferred_offset < dram_base)
71 		preferred_offset += MIN_KIMG_ALIGN;
72 
73 	kernel_size = _edata - _text;
74 	kernel_memsize = kernel_size + (_end - _edata);
75 
76 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
77 		/*
78 		 * Produce a displacement in the interval [0, MIN_KIMG_ALIGN)
79 		 * that doesn't violate this kernel's de-facto alignment
80 		 * constraints.
81 		 */
82 		u32 mask = (MIN_KIMG_ALIGN - 1) & ~(EFI_KIMG_ALIGN - 1);
83 		u32 offset = (phys_seed >> 32) & mask;
84 
85 		/*
86 		 * With CONFIG_RANDOMIZE_TEXT_OFFSET=y, TEXT_OFFSET may not
87 		 * be a multiple of EFI_KIMG_ALIGN, and we must ensure that
88 		 * we preserve the misalignment of 'offset' relative to
89 		 * EFI_KIMG_ALIGN so that statically allocated objects whose
90 		 * alignment exceeds PAGE_SIZE appear correctly aligned in
91 		 * memory.
92 		 */
93 		offset |= TEXT_OFFSET % EFI_KIMG_ALIGN;
94 
95 		/*
96 		 * If KASLR is enabled, and we have some randomness available,
97 		 * locate the kernel at a randomized offset in physical memory.
98 		 */
99 		*reserve_size = kernel_memsize + offset;
100 		status = efi_random_alloc(*reserve_size,
101 					  MIN_KIMG_ALIGN, reserve_addr,
102 					  (u32)phys_seed);
103 
104 		*image_addr = *reserve_addr + offset;
105 	} else {
106 		/*
107 		 * Else, try a straight allocation at the preferred offset.
108 		 * This will work around the issue where, if dram_base == 0x0,
109 		 * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
110 		 * address of the allocation to be mistaken for a FAIL return
111 		 * value or a NULL pointer). It will also ensure that, on
112 		 * platforms where the [dram_base, dram_base + TEXT_OFFSET)
113 		 * interval is partially occupied by the firmware (like on APM
114 		 * Mustang), we can still place the kernel at the address
115 		 * 'dram_base + TEXT_OFFSET'.
116 		 */
117 		*image_addr = (unsigned long)_text;
118 		if (*image_addr == preferred_offset)
119 			return EFI_SUCCESS;
120 
121 		*image_addr = *reserve_addr = preferred_offset;
122 		*reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
123 
124 		status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
125 				     EFI_LOADER_DATA,
126 				     *reserve_size / EFI_PAGE_SIZE,
127 				     (efi_physical_addr_t *)reserve_addr);
128 	}
129 
130 	if (status != EFI_SUCCESS) {
131 		*reserve_size = kernel_memsize + TEXT_OFFSET;
132 		status = efi_low_alloc(*reserve_size,
133 				       MIN_KIMG_ALIGN, reserve_addr);
134 
135 		if (status != EFI_SUCCESS) {
136 			pr_efi_err("Failed to relocate kernel\n");
137 			*reserve_size = 0;
138 			return status;
139 		}
140 		*image_addr = *reserve_addr + TEXT_OFFSET;
141 	}
142 
143 	if (image->image_base != _text)
144 		pr_efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
145 
146 	memcpy((void *)*image_addr, _text, kernel_size);
147 
148 	return EFI_SUCCESS;
149 }
150