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 __ASSEMBLER__
  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\()","ax",@progbits
 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;						\
 66start_##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;		\
 78linker_stub_catch:						\
 79	. = 0x4;						\
 80	text_start = (start) + 0x100;				\
 81	.section ".text","ax",@progbits;			\
 82	.balign 0x100;						\
 83start_text:
 84#else
 85#define OPEN_TEXT_SECTION(start)				\
 86	text_start = (start);					\
 87	.section ".text","ax",@progbits;			\
 88	. = 0x0;						\
 89start_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	use_ftsec sname;
102
103#define USE_TEXT_SECTION()					\
104	.text
105
106#define CLOSE_FIXED_SECTION(sname)				\
107	USE_FIXED_SECTION(sname);				\
108	. = sname##_len;					\
109end_##sname:
110
111
112#define __FIXED_SECTION_ENTRY_BEGIN(sname, name, __align)	\
113	USE_FIXED_SECTION(sname);				\
114	.balign __align;					\
115	.global name;						\
116name:
117
118#define FIXED_SECTION_ENTRY_BEGIN(sname, name)			\
119	__FIXED_SECTION_ENTRY_BEGIN(sname, name, IFETCH_ALIGN_BYTES)
120
121#define FIXED_SECTION_ENTRY_BEGIN_LOCATION(sname, name, start, size) \
122	USE_FIXED_SECTION(sname);				\
123	name##_start = (start);					\
124	.if ((start) % (size) != 0);				\
125	.error "Fixed section exception vector misalignment";	\
126	.endif;							\
127	.if ((size) != 0x20) && ((size) != 0x80) && ((size) != 0x100) && ((size) != 0x1000); \
128	.error "Fixed section exception vector bad size";	\
129	.endif;							\
130	.if (start) < sname##_start;				\
131	.error "Fixed section underflow";			\
132	.abort;							\
133	.endif;							\
134	. = (start) - sname##_start;				\
135	.global name;						\
136name:
137
138#define FIXED_SECTION_ENTRY_END_LOCATION(sname, name, start, size) \
139	.if (start) + (size) > sname##_end;			\
140	.error "Fixed section overflow";			\
141	.abort;							\
142	.endif;							\
143	.if (. - name > (start) + (size) - name##_start);	\
144	.error "Fixed entry overflow";				\
145	.abort;							\
146	.endif;							\
147	. = ((start) + (size) - sname##_start);			\
148
149
150/*
151 * These macros are used to change symbols in other fixed sections to be
152 * absolute or related to our current fixed section.
153 *
154 * - DEFINE_FIXED_SYMBOL / FIXED_SYMBOL_ABS_ADDR is used to find the
155 *   absolute address of a symbol within a fixed section, from any section.
156 *
157 * - ABS_ADDR is used to find the absolute address of any symbol, from within
158 *   a fixed section.
159 */
160// define label as being _in_ sname
161#define DEFINE_FIXED_SYMBOL(label, sname) \
162	label##_absolute = (label - start_ ## sname + sname ## _start)
163
164#define FIXED_SYMBOL_ABS_ADDR(label)				\
165	(label##_absolute)
166
167// find label from _within_ sname
168#define ABS_ADDR(label, sname) (label - start_ ## sname + sname ## _start)
169
170#endif /* __ASSEMBLER__ */
171
172#endif	/* _ASM_POWERPC_HEAD_64_H */