arch/powerpc/include/asm/head-64.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_POWERPC_HEAD_64_H
   3 #define _ASM_POWERPC_HEAD_64_H
   4
   5 #include <asm/cache.h>
   6
   7 #ifdef __ASSEMBLY__
   8 /*
   9  * We can't do CPP stringification and concatination directly into the section
  10  * name for some reason, so these macros can do it for us.
  11  */
  12 .macro define_ftsec name
  13         .section ".head.text.\name\()","ax",@progbits
  14 .endm
  15 .macro define_data_ftsec name
  16         .section ".head.data.\name\()","a",@progbits
  17 .endm
  18 .macro use_ftsec name
  19         .section ".head.text.\name\()"
  20 .endm
  21
  22 /*
  23  * Fixed (location) sections are used by opening fixed sections and emitting
  24  * fixed section entries into them before closing them. Multiple fixed sections
  25  * can be open at any time.
  26  *
  27  * Each fixed section created in a .S file must have corresponding linkage
  28  * directives including location, added to  arch/powerpc/kernel/vmlinux.lds.S
  29  *
  30  * For each fixed section, code is generated into it in the order which it
  31  * appears in the source.  Fixed section entries can be placed at a fixed
  32  * location within the section using _LOCATION postifx variants. These must
  33  * be ordered according to their relative placements within the section.
  34  *
  35  * OPEN_FIXED_SECTION(section_name, start_address, end_address)
  36  * FIXED_SECTION_ENTRY_BEGIN(section_name, label1)
  37  *
  38  * USE_FIXED_SECTION(section_name)
  39  * label3:
  40  *     li  r10,128
  41  *     mv  r11,r10
  42
  43  * FIXED_SECTION_ENTRY_BEGIN_LOCATION(section_name, label2, start_address, size)
  44  * FIXED_SECTION_ENTRY_END_LOCATION(section_name, label2, start_address, size)
  45  * CLOSE_FIXED_SECTION(section_name)
  46  *
  47  * ZERO_FIXED_SECTION can be used to emit zeroed data.
  48  *
  49  * Troubleshooting:
  50  * - If the build dies with "Error: attempt to move .org backwards" at
  51  *   CLOSE_FIXED_SECTION() or elsewhere, there may be something
  52  *   unexpected being added there. Remove the '. = x_len' line, rebuild, and
  53  *   check what is pushing the section down.
  54  * - If the build dies in linking, check arch/powerpc/tools/head_check.sh
  55  *   comments.
  56  * - If the kernel crashes or hangs in very early boot, it could be linker
  57  *   stubs at the start of the main text.
  58  */
  59
  60 #define OPEN_FIXED_SECTION(sname, start, end)                   \
  61         sname##_start = (start);                                \
  62         sname##_end = (end);                                    \
  63         sname##_len = (end) - (start);                          \
  64         define_ftsec sname;                                     \
  65         . = 0x0;                                                \
  66 start_##sname:
  67
  68 /*
  69  * .linker_stub_catch section is used to catch linker stubs from being
  70  * inserted in our .text section, above the start_text label (which breaks
  71  * the ABS_ADDR calculation). See kernel/vmlinux.lds.S and tools/head_check.sh
  72  * for more details. We would prefer to just keep a cacheline (0x80), but
  73  * 0x100 seems to be how the linker aligns branch stub groups.
  74  */
  75 #ifdef CONFIG_LD_HEAD_STUB_CATCH
  76 #define OPEN_TEXT_SECTION(start)                                \
  77         .section ".linker_stub_catch","ax",@progbits;           \
  78 linker_stub_catch:                                              \
  79         . = 0x4;                                                \
  80         text_start = (start) + 0x100;                           \
  81         .section ".text","ax",@progbits;                        \
  82         .balign 0x100;                                          \
  83 start_text:
  84 #else
  85 #define OPEN_TEXT_SECTION(start)                                \
  86         text_start = (start);                                   \
  87         .section ".text","ax",@progbits;                        \
  88         . = 0x0;                                                \
  89 start_text:
  90 #endif
  91
  92 #define ZERO_FIXED_SECTION(sname, start, end)                   \
  93         sname##_start = (start);                                \
  94         sname##_end = (end);                                    \
  95         sname##_len = (end) - (start);                          \
  96         define_data_ftsec sname;                                \
  97         . = 0x0;                                                \
  98         . = sname##_len;
  99
 100 #define USE_FIXED_SECTION(sname)                                \
 101         fs_label = start_##sname;                               \
 102         fs_start = sname##_start;                               \
 103         use_ftsec sname;
 104
 105 #define USE_TEXT_SECTION()                                      \
 106         fs_label = start_text;                                  \
 107         fs_start = text_start;                                  \
 108         .text
 109
 110 #define CLOSE_FIXED_SECTION(sname)                              \
 111         USE_FIXED_SECTION(sname);                               \
 112         . = sname##_len;                                        \
 113 end_##sname:
 114
 115
 116 #define __FIXED_SECTION_ENTRY_BEGIN(sname, name, __align)       \
 117         USE_FIXED_SECTION(sname);                               \
 118         .balign __align;                                        \
 119         .global name;                                           \
 120 name:
 121
 122 #define FIXED_SECTION_ENTRY_BEGIN(sname, name)                  \
 123         __FIXED_SECTION_ENTRY_BEGIN(sname, name, IFETCH_ALIGN_BYTES)
 124
 125 #define FIXED_SECTION_ENTRY_BEGIN_LOCATION(sname, name, start, size) \
 126         USE_FIXED_SECTION(sname);                               \
 127         name##_start = (start);                                 \
 128         .if ((start) % (size) != 0);                            \
 129         .error "Fixed section exception vector misalignment";   \
 130         .endif;                                                 \
 131         .if ((size) != 0x20) && ((size) != 0x80) && ((size) != 0x100); \
 132         .error "Fixed section exception vector bad size";       \
 133         .endif;                                                 \
 134         .if (start) < sname##_start;                            \
 135         .error "Fixed section underflow";                       \
 136         .abort;                                                 \
 137         .endif;                                                 \
 138         . = (start) - sname##_start;                            \
 139         .global name;                                           \
 140 name:
 141
 142 #define FIXED_SECTION_ENTRY_END_LOCATION(sname, name, start, size) \
 143         .if (start) + (size) > sname##_end;                     \
 144         .error "Fixed section overflow";                        \
 145         .abort;                                                 \
 146         .endif;                                                 \
 147         .if (. - name > (start) + (size) - name##_start);       \
 148         .error "Fixed entry overflow";                          \
 149         .abort;                                                 \
 150         .endif;                                                 \
 151         . = ((start) + (size) - sname##_start);                 \
 152
 153
 154 /*
 155  * These macros are used to change symbols in other fixed sections to be
 156  * absolute or related to our current fixed section.
 157  *
 158  * - DEFINE_FIXED_SYMBOL / FIXED_SYMBOL_ABS_ADDR is used to find the
 159  *   absolute address of a symbol within a fixed section, from any section.
 160  *
 161  * - ABS_ADDR is used to find the absolute address of any symbol, from within
 162  *   a fixed section.
 163  */
 164 #define DEFINE_FIXED_SYMBOL(label)                              \
 165         label##_absolute = (label - fs_label + fs_start)
 166
 167 #define FIXED_SYMBOL_ABS_ADDR(label)                            \
 168         (label##_absolute)
 169
 170 #define ABS_ADDR(label) (label - fs_label + fs_start)
 171
 172 #endif /* __ASSEMBLY__ */
 173
 174 #endif  /* _ASM_POWERPC_HEAD_64_H */