fac23fe4be
The current feature section logic only supports nop'ing out code, this means if you want to choose at runtime between instruction sequences, one or both cases will have to execute the nop'ed out contents of the other section, eg: BEGIN_FTR_SECTION or 1,1,1 END_FTR_SECTION_IFSET(FOO) BEGIN_FTR_SECTION or 2,2,2 END_FTR_SECTION_IFCLR(FOO) and the resulting code will be either, or 1,1,1 nop or, nop or 2,2,2 For small code segments this is fine, but for larger code blocks and in performance criticial code segments, it would be nice to avoid the nops. This commit starts to implement logic to allow the following: BEGIN_FTR_SECTION or 1,1,1 FTR_SECTION_ELSE or 2,2,2 ALT_FTR_SECTION_END_IFSET(FOO) and the resulting code will be: or 1,1,1 or, or 2,2,2 We achieve this by extending the existing FTR macros. The current feature section semantic just becomes a special case, ie. if the else case is empty we nop out the default case. The key limitation is that the size of the else case must be less than or equal to the size of the default case. If the else case is smaller the remainder of the section is nop'ed. We let the linker put the else case code in with the rest of the text, so that relative branches from the else case are more likley to link, this has the disadvantage that we can't free the unused else cases. This commit introduces the required macro and linker script changes, but does not enable the patching of the alternative sections. We also need to update two hand-made section entries in reg.h and timex.h Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Paul Mackerras <paulus@samba.org>
117 lines
4.1 KiB
C
117 lines
4.1 KiB
C
#ifndef __ASM_POWERPC_FEATURE_FIXUPS_H
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#define __ASM_POWERPC_FEATURE_FIXUPS_H
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/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#ifdef __ASSEMBLY__
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/*
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* Feature section common macros
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*
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* Note that the entries now contain offsets between the table entry
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* and the code rather than absolute code pointers in order to be
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* useable with the vdso shared library. There is also an assumption
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* that values will be negative, that is, the fixup table has to be
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* located after the code it fixes up.
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*/
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#if defined(CONFIG_PPC64) && !defined(__powerpc64__)
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/* 64 bits kernel, 32 bits code (ie. vdso32) */
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#define FTR_ENTRY_LONG .llong
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#define FTR_ENTRY_OFFSET .long 0xffffffff; .long
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#else
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/* 64 bit kernel 64 bit code, or 32 bit kernel 32 bit code */
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#define FTR_ENTRY_LONG PPC_LONG
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#define FTR_ENTRY_OFFSET PPC_LONG
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#endif
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#define START_FTR_SECTION(label) label##1:
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#define FTR_SECTION_ELSE_NESTED(label) \
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label##2: \
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.pushsection __ftr_alt_##label,"a"; \
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.align 2; \
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label##3:
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#define MAKE_FTR_SECTION_ENTRY(msk, val, label, sect) \
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label##4: \
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.popsection; \
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.pushsection sect,"a"; \
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.align 3; \
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label##5: \
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FTR_ENTRY_LONG msk; \
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FTR_ENTRY_LONG val; \
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FTR_ENTRY_OFFSET label##1b-label##5b; \
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FTR_ENTRY_OFFSET label##2b-label##5b; \
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FTR_ENTRY_OFFSET label##3b-label##5b; \
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FTR_ENTRY_OFFSET label##4b-label##5b; \
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.popsection;
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/* CPU feature dependent sections */
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#define BEGIN_FTR_SECTION_NESTED(label) START_FTR_SECTION(label)
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#define BEGIN_FTR_SECTION START_FTR_SECTION(97)
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#define END_FTR_SECTION_NESTED(msk, val, label) \
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FTR_SECTION_ELSE_NESTED(label) \
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MAKE_FTR_SECTION_ENTRY(msk, val, label, __ftr_fixup)
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#define END_FTR_SECTION(msk, val) \
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END_FTR_SECTION_NESTED(msk, val, 97)
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#define END_FTR_SECTION_IFSET(msk) END_FTR_SECTION((msk), (msk))
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#define END_FTR_SECTION_IFCLR(msk) END_FTR_SECTION((msk), 0)
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/* CPU feature sections with alternatives, use BEGIN_FTR_SECTION to start */
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#define FTR_SECTION_ELSE FTR_SECTION_ELSE_NESTED(97)
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#define ALT_FTR_SECTION_END_NESTED(msk, val, label) \
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MAKE_FTR_SECTION_ENTRY(msk, val, label, __ftr_fixup)
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#define ALT_FTR_SECTION_END_NESTED_IFSET(msk, label) \
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ALT_FTR_SECTION_END_NESTED(msk, msk, label)
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#define ALT_FTR_SECTION_END_NESTED_IFCLR(msk, label) \
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ALT_FTR_SECTION_END_NESTED(msk, 0, label)
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#define ALT_FTR_SECTION_END(msk, val) \
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ALT_FTR_SECTION_END_NESTED(msk, val, 97)
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#define ALT_FTR_SECTION_END_IFSET(msk) \
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ALT_FTR_SECTION_END_NESTED_IFSET(msk, 97)
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#define ALT_FTR_SECTION_END_IFCLR(msk) \
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ALT_FTR_SECTION_END_NESTED_IFCLR(msk, 97)
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/* Firmware feature dependent sections */
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#define BEGIN_FW_FTR_SECTION_NESTED(label) START_FTR_SECTION(label)
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#define BEGIN_FW_FTR_SECTION START_FTR_SECTION(97)
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#define END_FW_FTR_SECTION_NESTED(msk, val, label) \
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FTR_SECTION_ELSE_NESTED(label) \
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MAKE_FTR_SECTION_ENTRY(msk, val, label, __fw_ftr_fixup)
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#define END_FW_FTR_SECTION(msk, val) \
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END_FW_FTR_SECTION_NESTED(msk, val, 97)
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#define END_FW_FTR_SECTION_IFSET(msk) END_FW_FTR_SECTION((msk), (msk))
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#define END_FW_FTR_SECTION_IFCLR(msk) END_FW_FTR_SECTION((msk), 0)
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/* Firmware feature sections with alternatives */
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#define FW_FTR_SECTION_ELSE_NESTED(label) FTR_SECTION_ELSE_NESTED(label)
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#define FW_FTR_SECTION_ELSE FTR_SECTION_ELSE_NESTED(97)
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#define ALT_FW_FTR_SECTION_END_NESTED(msk, val, label) \
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MAKE_FTR_SECTION_ENTRY(msk, val, label, __fw_ftr_fixup)
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#define ALT_FW_FTR_SECTION_END_NESTED_IFSET(msk, label) \
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ALT_FW_FTR_SECTION_END_NESTED(msk, msk, label)
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#define ALT_FW_FTR_SECTION_END_NESTED_IFCLR(msk, label) \
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ALT_FW_FTR_SECTION_END_NESTED(msk, 0, label)
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#define ALT_FW_FTR_SECTION_END(msk, val) \
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ALT_FW_FTR_SECTION_END_NESTED(msk, val, 97)
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#define ALT_FW_FTR_SECTION_END_IFSET(msk) \
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ALT_FW_FTR_SECTION_END_NESTED_IFSET(msk, 97)
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#define ALT_FW_FTR_SECTION_END_IFCLR(msk) \
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ALT_FW_FTR_SECTION_END_NESTED_IFCLR(msk, 97)
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_POWERPC_FEATURE_FIXUPS_H */
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