1 /*
2  * Copyright (C) 2013, 2014 Linaro Ltd;  <roy.franz@linaro.org>
3  *
4  * This file implements the EFI boot stub for the arm64 kernel.
5  * Adapted from ARM version by Mark Salter <msalter@redhat.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  */
12 #include <linux/efi.h>
13 #include <asm/efi.h>
14 #include <asm/sections.h>
15 #include <asm/sysreg.h>
16 
17 #include "efistub.h"
18 
19 extern bool __nokaslr;
20 
21 efi_status_t check_platform_features(efi_system_table_t *sys_table_arg)
22 {
23 	u64 tg;
24 
25 	/* UEFI mandates support for 4 KB granularity, no need to check */
26 	if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
27 		return EFI_SUCCESS;
28 
29 	tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
30 	if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
31 		if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
32 			pr_efi_err(sys_table_arg, "This 64 KB granular kernel is not supported by your CPU\n");
33 		else
34 			pr_efi_err(sys_table_arg, "This 16 KB granular kernel is not supported by your CPU\n");
35 		return EFI_UNSUPPORTED;
36 	}
37 	return EFI_SUCCESS;
38 }
39 
40 efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
41 				 unsigned long *image_addr,
42 				 unsigned long *image_size,
43 				 unsigned long *reserve_addr,
44 				 unsigned long *reserve_size,
45 				 unsigned long dram_base,
46 				 efi_loaded_image_t *image)
47 {
48 	efi_status_t status;
49 	unsigned long kernel_size, kernel_memsize = 0;
50 	void *old_image_addr = (void *)*image_addr;
51 	unsigned long preferred_offset;
52 	u64 phys_seed = 0;
53 
54 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
55 		if (!__nokaslr) {
56 			status = efi_get_random_bytes(sys_table_arg,
57 						      sizeof(phys_seed),
58 						      (u8 *)&phys_seed);
59 			if (status == EFI_NOT_FOUND) {
60 				pr_efi(sys_table_arg, "EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
61 			} else if (status != EFI_SUCCESS) {
62 				pr_efi_err(sys_table_arg, "efi_get_random_bytes() failed\n");
63 				return status;
64 			}
65 		} else {
66 			pr_efi(sys_table_arg, "KASLR disabled on kernel command line\n");
67 		}
68 	}
69 
70 	/*
71 	 * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
72 	 * a 2 MB aligned base, which itself may be lower than dram_base, as
73 	 * long as the resulting offset equals or exceeds it.
74 	 */
75 	preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
76 	if (preferred_offset < dram_base)
77 		preferred_offset += MIN_KIMG_ALIGN;
78 
79 	kernel_size = _edata - _text;
80 	kernel_memsize = kernel_size + (_end - _edata);
81 
82 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
83 		/*
84 		 * If CONFIG_DEBUG_ALIGN_RODATA is not set, produce a
85 		 * displacement in the interval [0, MIN_KIMG_ALIGN) that
86 		 * is a multiple of the minimal segment alignment (SZ_64K)
87 		 */
88 		u32 mask = (MIN_KIMG_ALIGN - 1) & ~(SZ_64K - 1);
89 		u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
90 			     (phys_seed >> 32) & mask : TEXT_OFFSET;
91 
92 		/*
93 		 * If KASLR is enabled, and we have some randomness available,
94 		 * locate the kernel at a randomized offset in physical memory.
95 		 */
96 		*reserve_size = kernel_memsize + offset;
97 		status = efi_random_alloc(sys_table_arg, *reserve_size,
98 					  MIN_KIMG_ALIGN, reserve_addr,
99 					  (u32)phys_seed);
100 
101 		*image_addr = *reserve_addr + offset;
102 	} else {
103 		/*
104 		 * Else, try a straight allocation at the preferred offset.
105 		 * This will work around the issue where, if dram_base == 0x0,
106 		 * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
107 		 * address of the allocation to be mistaken for a FAIL return
108 		 * value or a NULL pointer). It will also ensure that, on
109 		 * platforms where the [dram_base, dram_base + TEXT_OFFSET)
110 		 * interval is partially occupied by the firmware (like on APM
111 		 * Mustang), we can still place the kernel at the address
112 		 * 'dram_base + TEXT_OFFSET'.
113 		 */
114 		if (*image_addr == preferred_offset)
115 			return EFI_SUCCESS;
116 
117 		*image_addr = *reserve_addr = preferred_offset;
118 		*reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
119 
120 		status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
121 					EFI_LOADER_DATA,
122 					*reserve_size / EFI_PAGE_SIZE,
123 					(efi_physical_addr_t *)reserve_addr);
124 	}
125 
126 	if (status != EFI_SUCCESS) {
127 		*reserve_size = kernel_memsize + TEXT_OFFSET;
128 		status = efi_low_alloc(sys_table_arg, *reserve_size,
129 				       MIN_KIMG_ALIGN, reserve_addr);
130 
131 		if (status != EFI_SUCCESS) {
132 			pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
133 			*reserve_size = 0;
134 			return status;
135 		}
136 		*image_addr = *reserve_addr + TEXT_OFFSET;
137 	}
138 	memcpy((void *)*image_addr, old_image_addr, kernel_size);
139 
140 	return EFI_SUCCESS;
141 }
142