arch/arm64/kernel/image.h

   1 /*
   2  * Linker script macros to generate Image header fields.
   3  *
   4  * Copyright (C) 2014 ARM Ltd.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 #ifndef __ASM_IMAGE_H
  19 #define __ASM_IMAGE_H
  20
  21 #ifndef LINKER_SCRIPT
  22 #error This file should only be included in vmlinux.lds.S
  23 #endif
  24
  25 /*
  26  * There aren't any ELF relocations we can use to endian-swap values known only
  27  * at link time (e.g. the subtraction of two symbol addresses), so we must get
  28  * the linker to endian-swap certain values before emitting them.
  29  *
  30  * Note that, in order for this to work when building the ELF64 PIE executable
  31  * (for KASLR), these values should not be referenced via R_AARCH64_ABS64
  32  * relocations, since these are fixed up at runtime rather than at build time
  33  * when PIE is in effect. So we need to split them up in 32-bit high and low
  34  * words.
  35  */
  36 #ifdef CONFIG_CPU_BIG_ENDIAN
  37 #define DATA_LE32(data)                         \
  38         ((((data) & 0x000000ff) << 24) |        \
  39          (((data) & 0x0000ff00) << 8)  |        \
  40          (((data) & 0x00ff0000) >> 8)  |        \
  41          (((data) & 0xff000000) >> 24))
  42 #else
  43 #define DATA_LE32(data) ((data) & 0xffffffff)
  44 #endif
  45
  46 #define DEFINE_IMAGE_LE64(sym, data)                            \
  47         sym##_lo32 = DATA_LE32((data) & 0xffffffff);            \
  48         sym##_hi32 = DATA_LE32((data) >> 32)
  49
  50 #ifdef CONFIG_CPU_BIG_ENDIAN
  51 #define __HEAD_FLAG_BE          1
  52 #else
  53 #define __HEAD_FLAG_BE          0
  54 #endif
  55
  56 #define __HEAD_FLAG_PAGE_SIZE   ((PAGE_SHIFT - 10) / 2)
  57
  58 #define __HEAD_FLAG_PHYS_BASE   1
  59
  60 #define __HEAD_FLAGS            ((__HEAD_FLAG_BE << 0) |        \
  61                                  (__HEAD_FLAG_PAGE_SIZE << 1) | \
  62                                  (__HEAD_FLAG_PHYS_BASE << 3))
  63
  64 /*
  65  * These will output as part of the Image header, which should be little-endian
  66  * regardless of the endianness of the kernel. While constant values could be
  67  * endian swapped in head.S, all are done here for consistency.
  68  */
  69 #define HEAD_SYMBOLS                                            \
  70         DEFINE_IMAGE_LE64(_kernel_size_le, _end - _text);       \
  71         DEFINE_IMAGE_LE64(_kernel_offset_le, TEXT_OFFSET);      \
  72         DEFINE_IMAGE_LE64(_kernel_flags_le, __HEAD_FLAGS);
  73
  74 #ifdef CONFIG_EFI
  75
  76 /*
  77  * Prevent the symbol aliases below from being emitted into the kallsyms
  78  * table, by forcing them to be absolute symbols (which are conveniently
  79  * ignored by scripts/kallsyms) rather than section relative symbols.
  80  * The distinction is only relevant for partial linking, and only for symbols
  81  * that are defined within a section declaration (which is not the case for
  82  * the definitions below) so the resulting values will be identical.
  83  */
  84 #define KALLSYMS_HIDE(sym)      ABSOLUTE(sym)
  85
  86 /*
  87  * The EFI stub has its own symbol namespace prefixed by __efistub_, to
  88  * isolate it from the kernel proper. The following symbols are legally
  89  * accessed by the stub, so provide some aliases to make them accessible.
  90  * Only include data symbols here, or text symbols of functions that are
  91  * guaranteed to be safe when executed at another offset than they were
  92  * linked at. The routines below are all implemented in assembler in a
  93  * position independent manner
  94  */
  95 __efistub_memcmp                = KALLSYMS_HIDE(__pi_memcmp);
  96 __efistub_memchr                = KALLSYMS_HIDE(__pi_memchr);
  97 __efistub_memcpy                = KALLSYMS_HIDE(__pi_memcpy);
  98 __efistub_memmove               = KALLSYMS_HIDE(__pi_memmove);
  99 __efistub_memset                = KALLSYMS_HIDE(__pi_memset);
 100 __efistub_strlen                = KALLSYMS_HIDE(__pi_strlen);
 101 __efistub_strnlen               = KALLSYMS_HIDE(__pi_strnlen);
 102 __efistub_strcmp                = KALLSYMS_HIDE(__pi_strcmp);
 103 __efistub_strncmp               = KALLSYMS_HIDE(__pi_strncmp);
 104 __efistub___flush_dcache_area   = KALLSYMS_HIDE(__pi___flush_dcache_area);
 105
 106 #ifdef CONFIG_KASAN
 107 __efistub___memcpy              = KALLSYMS_HIDE(__pi_memcpy);
 108 __efistub___memmove             = KALLSYMS_HIDE(__pi_memmove);
 109 __efistub___memset              = KALLSYMS_HIDE(__pi_memset);
 110 #endif
 111
 112 __efistub__text                 = KALLSYMS_HIDE(_text);
 113 __efistub__end                  = KALLSYMS_HIDE(_end);
 114 __efistub__edata                = KALLSYMS_HIDE(_edata);
 115
 116 #endif
 117
 118 #endif /* __ASM_IMAGE_H */