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  * To prevent the compiler from emitting GOT-indirected (and thus absolute)
11  * references to the section markers, override their visibility as 'hidden'
12  */
13 #pragma GCC visibility push(hidden)
14 #include <asm/sections.h>
15 #pragma GCC visibility pop
16 
17 #include <linux/efi.h>
18 #include <asm/efi.h>
19 #include <asm/memory.h>
20 #include <asm/sysreg.h>
21 
22 #include "efistub.h"
23 
24 efi_status_t check_platform_features(void)
25 {
26 	u64 tg;
27 
28 	/* UEFI mandates support for 4 KB granularity, no need to check */
29 	if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
30 		return EFI_SUCCESS;
31 
32 	tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
33 	if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
34 		if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
35 			pr_efi_err("This 64 KB granular kernel is not supported by your CPU\n");
36 		else
37 			pr_efi_err("This 16 KB granular kernel is not supported by your CPU\n");
38 		return EFI_UNSUPPORTED;
39 	}
40 	return EFI_SUCCESS;
41 }
42 
43 efi_status_t handle_kernel_image(unsigned long *image_addr,
44 				 unsigned long *image_size,
45 				 unsigned long *reserve_addr,
46 				 unsigned long *reserve_size,
47 				 unsigned long dram_base,
48 				 efi_loaded_image_t *image)
49 {
50 	efi_status_t status;
51 	unsigned long kernel_size, kernel_memsize = 0;
52 	void *old_image_addr = (void *)*image_addr;
53 	unsigned long preferred_offset;
54 	u64 phys_seed = 0;
55 
56 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
57 		if (!nokaslr()) {
58 			status = efi_get_random_bytes(sizeof(phys_seed),
59 						      (u8 *)&phys_seed);
60 			if (status == EFI_NOT_FOUND) {
61 				pr_efi("EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
62 			} else if (status != EFI_SUCCESS) {
63 				pr_efi_err("efi_get_random_bytes() failed\n");
64 				return status;
65 			}
66 		} else {
67 			pr_efi("KASLR disabled on kernel command line\n");
68 		}
69 	}
70 
71 	/*
72 	 * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
73 	 * a 2 MB aligned base, which itself may be lower than dram_base, as
74 	 * long as the resulting offset equals or exceeds it.
75 	 */
76 	preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
77 	if (preferred_offset < dram_base)
78 		preferred_offset += MIN_KIMG_ALIGN;
79 
80 	kernel_size = _edata - _text;
81 	kernel_memsize = kernel_size + (_end - _edata);
82 
83 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
84 		/*
85 		 * If CONFIG_DEBUG_ALIGN_RODATA is not set, produce a
86 		 * displacement in the interval [0, MIN_KIMG_ALIGN) that
87 		 * doesn't violate this kernel's de-facto alignment
88 		 * constraints.
89 		 */
90 		u32 mask = (MIN_KIMG_ALIGN - 1) & ~(EFI_KIMG_ALIGN - 1);
91 		u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
92 			     (phys_seed >> 32) & mask : TEXT_OFFSET;
93 
94 		/*
95 		 * With CONFIG_RANDOMIZE_TEXT_OFFSET=y, TEXT_OFFSET may not
96 		 * be a multiple of EFI_KIMG_ALIGN, and we must ensure that
97 		 * we preserve the misalignment of 'offset' relative to
98 		 * EFI_KIMG_ALIGN so that statically allocated objects whose
99 		 * alignment exceeds PAGE_SIZE appear correctly aligned in
100 		 * memory.
101 		 */
102 		offset |= TEXT_OFFSET % EFI_KIMG_ALIGN;
103 
104 		/*
105 		 * If KASLR is enabled, and we have some randomness available,
106 		 * locate the kernel at a randomized offset in physical memory.
107 		 */
108 		*reserve_size = kernel_memsize + offset;
109 		status = efi_random_alloc(*reserve_size,
110 					  MIN_KIMG_ALIGN, reserve_addr,
111 					  (u32)phys_seed);
112 
113 		*image_addr = *reserve_addr + offset;
114 	} else {
115 		/*
116 		 * Else, try a straight allocation at the preferred offset.
117 		 * This will work around the issue where, if dram_base == 0x0,
118 		 * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
119 		 * address of the allocation to be mistaken for a FAIL return
120 		 * value or a NULL pointer). It will also ensure that, on
121 		 * platforms where the [dram_base, dram_base + TEXT_OFFSET)
122 		 * interval is partially occupied by the firmware (like on APM
123 		 * Mustang), we can still place the kernel at the address
124 		 * 'dram_base + TEXT_OFFSET'.
125 		 */
126 		if (*image_addr == preferred_offset)
127 			return EFI_SUCCESS;
128 
129 		*image_addr = *reserve_addr = preferred_offset;
130 		*reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
131 
132 		status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
133 				     EFI_LOADER_DATA,
134 				     *reserve_size / EFI_PAGE_SIZE,
135 				     (efi_physical_addr_t *)reserve_addr);
136 	}
137 
138 	if (status != EFI_SUCCESS) {
139 		*reserve_size = kernel_memsize + TEXT_OFFSET;
140 		status = efi_low_alloc(*reserve_size,
141 				       MIN_KIMG_ALIGN, reserve_addr);
142 
143 		if (status != EFI_SUCCESS) {
144 			pr_efi_err("Failed to relocate kernel\n");
145 			*reserve_size = 0;
146 			return status;
147 		}
148 		*image_addr = *reserve_addr + TEXT_OFFSET;
149 	}
150 	memcpy((void *)*image_addr, old_image_addr, kernel_size);
151 
152 	return EFI_SUCCESS;
153 }
154