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-rw-r--r--arch/powerpc/include/asm/head-64.h172
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diff --git a/arch/powerpc/include/asm/head-64.h b/arch/powerpc/include/asm/head-64.h
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+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_POWERPC_HEAD_64_H
+#define _ASM_POWERPC_HEAD_64_H
+
+#include <asm/cache.h>
+
+#ifdef __ASSEMBLY__
+/*
+ * We can't do CPP stringification and concatination directly into the section
+ * name for some reason, so these macros can do it for us.
+ */
+.macro define_ftsec name
+ .section ".head.text.\name\()","ax",@progbits
+.endm
+.macro define_data_ftsec name
+ .section ".head.data.\name\()","a",@progbits
+.endm
+.macro use_ftsec name
+ .section ".head.text.\name\()","ax",@progbits
+.endm
+
+/*
+ * Fixed (location) sections are used by opening fixed sections and emitting
+ * fixed section entries into them before closing them. Multiple fixed sections
+ * can be open at any time.
+ *
+ * Each fixed section created in a .S file must have corresponding linkage
+ * directives including location, added to arch/powerpc/kernel/vmlinux.lds.S
+ *
+ * For each fixed section, code is generated into it in the order which it
+ * appears in the source. Fixed section entries can be placed at a fixed
+ * location within the section using _LOCATION postifx variants. These must
+ * be ordered according to their relative placements within the section.
+ *
+ * OPEN_FIXED_SECTION(section_name, start_address, end_address)
+ * FIXED_SECTION_ENTRY_BEGIN(section_name, label1)
+ *
+ * USE_FIXED_SECTION(section_name)
+ * label3:
+ * li r10,128
+ * mv r11,r10
+
+ * FIXED_SECTION_ENTRY_BEGIN_LOCATION(section_name, label2, start_address, size)
+ * FIXED_SECTION_ENTRY_END_LOCATION(section_name, label2, start_address, size)
+ * CLOSE_FIXED_SECTION(section_name)
+ *
+ * ZERO_FIXED_SECTION can be used to emit zeroed data.
+ *
+ * Troubleshooting:
+ * - If the build dies with "Error: attempt to move .org backwards" at
+ * CLOSE_FIXED_SECTION() or elsewhere, there may be something
+ * unexpected being added there. Remove the '. = x_len' line, rebuild, and
+ * check what is pushing the section down.
+ * - If the build dies in linking, check arch/powerpc/tools/head_check.sh
+ * comments.
+ * - If the kernel crashes or hangs in very early boot, it could be linker
+ * stubs at the start of the main text.
+ */
+
+#define OPEN_FIXED_SECTION(sname, start, end) \
+ sname##_start = (start); \
+ sname##_end = (end); \
+ sname##_len = (end) - (start); \
+ define_ftsec sname; \
+ . = 0x0; \
+start_##sname:
+
+/*
+ * .linker_stub_catch section is used to catch linker stubs from being
+ * inserted in our .text section, above the start_text label (which breaks
+ * the ABS_ADDR calculation). See kernel/vmlinux.lds.S and tools/head_check.sh
+ * for more details. We would prefer to just keep a cacheline (0x80), but
+ * 0x100 seems to be how the linker aligns branch stub groups.
+ */
+#ifdef CONFIG_LD_HEAD_STUB_CATCH
+#define OPEN_TEXT_SECTION(start) \
+ .section ".linker_stub_catch","ax",@progbits; \
+linker_stub_catch: \
+ . = 0x4; \
+ text_start = (start) + 0x100; \
+ .section ".text","ax",@progbits; \
+ .balign 0x100; \
+start_text:
+#else
+#define OPEN_TEXT_SECTION(start) \
+ text_start = (start); \
+ .section ".text","ax",@progbits; \
+ . = 0x0; \
+start_text:
+#endif
+
+#define ZERO_FIXED_SECTION(sname, start, end) \
+ sname##_start = (start); \
+ sname##_end = (end); \
+ sname##_len = (end) - (start); \
+ define_data_ftsec sname; \
+ . = 0x0; \
+ . = sname##_len;
+
+#define USE_FIXED_SECTION(sname) \
+ use_ftsec sname;
+
+#define USE_TEXT_SECTION() \
+ .text
+
+#define CLOSE_FIXED_SECTION(sname) \
+ USE_FIXED_SECTION(sname); \
+ . = sname##_len; \
+end_##sname:
+
+
+#define __FIXED_SECTION_ENTRY_BEGIN(sname, name, __align) \
+ USE_FIXED_SECTION(sname); \
+ .balign __align; \
+ .global name; \
+name:
+
+#define FIXED_SECTION_ENTRY_BEGIN(sname, name) \
+ __FIXED_SECTION_ENTRY_BEGIN(sname, name, IFETCH_ALIGN_BYTES)
+
+#define FIXED_SECTION_ENTRY_BEGIN_LOCATION(sname, name, start, size) \
+ USE_FIXED_SECTION(sname); \
+ name##_start = (start); \
+ .if ((start) % (size) != 0); \
+ .error "Fixed section exception vector misalignment"; \
+ .endif; \
+ .if ((size) != 0x20) && ((size) != 0x80) && ((size) != 0x100) && ((size) != 0x1000); \
+ .error "Fixed section exception vector bad size"; \
+ .endif; \
+ .if (start) < sname##_start; \
+ .error "Fixed section underflow"; \
+ .abort; \
+ .endif; \
+ . = (start) - sname##_start; \
+ .global name; \
+name:
+
+#define FIXED_SECTION_ENTRY_END_LOCATION(sname, name, start, size) \
+ .if (start) + (size) > sname##_end; \
+ .error "Fixed section overflow"; \
+ .abort; \
+ .endif; \
+ .if (. - name > (start) + (size) - name##_start); \
+ .error "Fixed entry overflow"; \
+ .abort; \
+ .endif; \
+ . = ((start) + (size) - sname##_start); \
+
+
+/*
+ * These macros are used to change symbols in other fixed sections to be
+ * absolute or related to our current fixed section.
+ *
+ * - DEFINE_FIXED_SYMBOL / FIXED_SYMBOL_ABS_ADDR is used to find the
+ * absolute address of a symbol within a fixed section, from any section.
+ *
+ * - ABS_ADDR is used to find the absolute address of any symbol, from within
+ * a fixed section.
+ */
+// define label as being _in_ sname
+#define DEFINE_FIXED_SYMBOL(label, sname) \
+ label##_absolute = (label - start_ ## sname + sname ## _start)
+
+#define FIXED_SYMBOL_ABS_ADDR(label) \
+ (label##_absolute)
+
+// find label from _within_ sname
+#define ABS_ADDR(label, sname) (label - start_ ## sname + sname ## _start)
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_POWERPC_HEAD_64_H */