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\()","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 /* __ASSEMBLY__ */
171
172#endif	/* _ASM_POWERPC_HEAD_64_H */
173