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d72c4a36d7
The LLVM integrated assembler really does not like us reassigning things to the same label: <instantiation>:7:9: error: invalid reassignment of non-absolute variable 'fs_label' This happens across a bunch of platforms: https://github.com/ClangBuiltLinux/linux/issues/1043 https://github.com/ClangBuiltLinux/linux/issues/1008 https://github.com/ClangBuiltLinux/linux/issues/920 https://github.com/ClangBuiltLinux/linux/issues/1050 There is no hope of getting this fixed in LLVM (see https://github.com/ClangBuiltLinux/linux/issues/1043#issuecomment-641571200 and https://bugs.llvm.org/show_bug.cgi?id=47798#c1 ) so if we want to build with LLVM_IAS, we need to hack around it ourselves. For us the big problem comes from this: \#define USE_FIXED_SECTION(sname) \ fs_label = start_##sname; \ fs_start = sname##_start; \ use_ftsec sname; \#define USE_TEXT_SECTION() fs_label = start_text; \ fs_start = text_start; \ .text and in particular fs_label. This works around it by not setting those 'variables' and requiring that users of the variables instead track for themselves what section they are in. This isn't amazing, by any stretch, but it gets us further in the compilation. Note that even though users have to keep track of the section, using a wrong one produces an error with both binutils and llvm which prevents from using wrong section at the compile time: llvm error example: AS arch/powerpc/kernel/head_64.o <unknown>:0: error: Cannot represent a difference across sections make[3]: *** [/home/aik/p/kernels-llvm/llvm/scripts/Makefile.build:388: arch/powerpc/kernel/head_64.o] Error 1 binutils error example: /home/aik/p/kernels-llvm/llvm/arch/powerpc/kernel/exceptions-64s.S: Assembler messages: /home/aik/p/kernels-llvm/llvm/arch/powerpc/kernel/exceptions-64s.S:1974: Error: can't resolve `system_call_common' {.text section} - `start_r eal_vectors' {.head.text.real_vectors section} make[3]: *** [/home/aik/p/kernels-llvm/llvm/scripts/Makefile.build:388: arch/powerpc/kernel/head_64.o] Error 1 Signed-off-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211221055904.555763-5-aik@ozlabs.ru
172 lines
5.4 KiB
C
172 lines
5.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_HEAD_64_H
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#define _ASM_POWERPC_HEAD_64_H
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#include <asm/cache.h>
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#ifdef __ASSEMBLY__
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/*
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* We can't do CPP stringification and concatination directly into the section
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* name for some reason, so these macros can do it for us.
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*/
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.macro define_ftsec name
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.section ".head.text.\name\()","ax",@progbits
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.endm
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.macro define_data_ftsec name
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.section ".head.data.\name\()","a",@progbits
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.endm
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.macro use_ftsec name
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.section ".head.text.\name\()","ax",@progbits
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.endm
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/*
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* Fixed (location) sections are used by opening fixed sections and emitting
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* fixed section entries into them before closing them. Multiple fixed sections
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* can be open at any time.
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*
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* Each fixed section created in a .S file must have corresponding linkage
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* directives including location, added to arch/powerpc/kernel/vmlinux.lds.S
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*
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* For each fixed section, code is generated into it in the order which it
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* appears in the source. Fixed section entries can be placed at a fixed
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* location within the section using _LOCATION postifx variants. These must
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* be ordered according to their relative placements within the section.
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*
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* OPEN_FIXED_SECTION(section_name, start_address, end_address)
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* FIXED_SECTION_ENTRY_BEGIN(section_name, label1)
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*
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* USE_FIXED_SECTION(section_name)
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* label3:
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* li r10,128
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* mv r11,r10
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* FIXED_SECTION_ENTRY_BEGIN_LOCATION(section_name, label2, start_address, size)
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* FIXED_SECTION_ENTRY_END_LOCATION(section_name, label2, start_address, size)
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* CLOSE_FIXED_SECTION(section_name)
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*
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* ZERO_FIXED_SECTION can be used to emit zeroed data.
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*
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* Troubleshooting:
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* - If the build dies with "Error: attempt to move .org backwards" at
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* CLOSE_FIXED_SECTION() or elsewhere, there may be something
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* unexpected being added there. Remove the '. = x_len' line, rebuild, and
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* check what is pushing the section down.
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* - If the build dies in linking, check arch/powerpc/tools/head_check.sh
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* comments.
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* - If the kernel crashes or hangs in very early boot, it could be linker
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* stubs at the start of the main text.
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*/
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#define OPEN_FIXED_SECTION(sname, start, end) \
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sname##_start = (start); \
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sname##_end = (end); \
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sname##_len = (end) - (start); \
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define_ftsec sname; \
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. = 0x0; \
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start_##sname:
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/*
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* .linker_stub_catch section is used to catch linker stubs from being
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* inserted in our .text section, above the start_text label (which breaks
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* the ABS_ADDR calculation). See kernel/vmlinux.lds.S and tools/head_check.sh
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* for more details. We would prefer to just keep a cacheline (0x80), but
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* 0x100 seems to be how the linker aligns branch stub groups.
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*/
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#ifdef CONFIG_LD_HEAD_STUB_CATCH
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#define OPEN_TEXT_SECTION(start) \
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.section ".linker_stub_catch","ax",@progbits; \
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linker_stub_catch: \
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. = 0x4; \
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text_start = (start) + 0x100; \
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.section ".text","ax",@progbits; \
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.balign 0x100; \
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start_text:
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#else
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#define OPEN_TEXT_SECTION(start) \
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text_start = (start); \
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.section ".text","ax",@progbits; \
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. = 0x0; \
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start_text:
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#endif
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#define ZERO_FIXED_SECTION(sname, start, end) \
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sname##_start = (start); \
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sname##_end = (end); \
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sname##_len = (end) - (start); \
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define_data_ftsec sname; \
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. = 0x0; \
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. = sname##_len;
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#define USE_FIXED_SECTION(sname) \
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use_ftsec sname;
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#define USE_TEXT_SECTION() \
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.text
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#define CLOSE_FIXED_SECTION(sname) \
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USE_FIXED_SECTION(sname); \
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. = sname##_len; \
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end_##sname:
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#define __FIXED_SECTION_ENTRY_BEGIN(sname, name, __align) \
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USE_FIXED_SECTION(sname); \
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.balign __align; \
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.global name; \
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name:
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#define FIXED_SECTION_ENTRY_BEGIN(sname, name) \
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__FIXED_SECTION_ENTRY_BEGIN(sname, name, IFETCH_ALIGN_BYTES)
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#define FIXED_SECTION_ENTRY_BEGIN_LOCATION(sname, name, start, size) \
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USE_FIXED_SECTION(sname); \
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name##_start = (start); \
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.if ((start) % (size) != 0); \
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.error "Fixed section exception vector misalignment"; \
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.endif; \
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.if ((size) != 0x20) && ((size) != 0x80) && ((size) != 0x100) && ((size) != 0x1000); \
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.error "Fixed section exception vector bad size"; \
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.endif; \
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.if (start) < sname##_start; \
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.error "Fixed section underflow"; \
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.abort; \
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.endif; \
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. = (start) - sname##_start; \
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.global name; \
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name:
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#define FIXED_SECTION_ENTRY_END_LOCATION(sname, name, start, size) \
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.if (start) + (size) > sname##_end; \
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.error "Fixed section overflow"; \
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.abort; \
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.endif; \
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.if (. - name > (start) + (size) - name##_start); \
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.error "Fixed entry overflow"; \
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.abort; \
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.endif; \
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. = ((start) + (size) - sname##_start); \
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/*
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* These macros are used to change symbols in other fixed sections to be
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* absolute or related to our current fixed section.
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*
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* - DEFINE_FIXED_SYMBOL / FIXED_SYMBOL_ABS_ADDR is used to find the
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* absolute address of a symbol within a fixed section, from any section.
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*
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* - ABS_ADDR is used to find the absolute address of any symbol, from within
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* a fixed section.
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*/
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// define label as being _in_ sname
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#define DEFINE_FIXED_SYMBOL(label, sname) \
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label##_absolute = (label - start_ ## sname + sname ## _start)
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#define FIXED_SYMBOL_ABS_ADDR(label) \
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(label##_absolute)
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// find label from _within_ sname
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#define ABS_ADDR(label, sname) (label - start_ ## sname + sname ## _start)
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_POWERPC_HEAD_64_H */
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