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e6ed91fd07
clang fails to handle ".if" statements in inline assembly which are heavily used in the alternatives code. To work around this remove this code, and enforce that users of alternatives must specify original and alternative instruction sequences which have identical sizes. Add a compile time check with two ".org" statements similar to arm64. In result not only clang can handle this, but also quite a lot of code can be removed. Acked-by: Vasily Gorbik <gor@linux.ibm.com> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://github.com/ClangBuiltLinux/linux/issues/1356 Link: https://lore.kernel.org/r/20220511120532.2228616-3-hca@linux.ibm.com Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
120 lines
4 KiB
C
120 lines
4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_S390_ALTERNATIVE_H
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#define _ASM_S390_ALTERNATIVE_H
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#ifndef __ASSEMBLY__
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#include <linux/types.h>
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#include <linux/stddef.h>
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#include <linux/stringify.h>
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struct alt_instr {
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s32 instr_offset; /* original instruction */
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s32 repl_offset; /* offset to replacement instruction */
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u16 facility; /* facility bit set for replacement */
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u8 instrlen; /* length of original instruction */
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} __packed;
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void apply_alternative_instructions(void);
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void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
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/*
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* +---------------------------------+
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* |661: |662:
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* | oldinstr |
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* +---------------------------------+
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*
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* .altinstr_replacement section
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* +---------------------------------+
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* |6641: |6651:
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* | alternative instr 1 |
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* +---------------------------------+
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* |6642: |6652:
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* | alternative instr 2 |
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* +---------------------------------+
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*
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* .altinstructions section
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* +---------------------------------+
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* | alt_instr entries for each |
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* | alternative instr |
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* +---------------------------------+
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*/
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#define b_altinstr(num) "664"#num
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#define e_altinstr(num) "665"#num
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#define oldinstr_len "662b-661b"
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#define altinstr_len(num) e_altinstr(num)"b-"b_altinstr(num)"b"
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#define OLDINSTR(oldinstr) \
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"661:\n\t" oldinstr "\n662:\n"
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#define ALTINSTR_ENTRY(facility, num) \
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"\t.long 661b - .\n" /* old instruction */ \
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"\t.long " b_altinstr(num)"b - .\n" /* alt instruction */ \
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"\t.word " __stringify(facility) "\n" /* facility bit */ \
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"\t.byte " oldinstr_len "\n" /* instruction len */ \
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"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n" \
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"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
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#define ALTINSTR_REPLACEMENT(altinstr, num) /* replacement */ \
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b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
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/* alternative assembly primitive: */
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#define ALTERNATIVE(oldinstr, altinstr, facility) \
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".pushsection .altinstr_replacement, \"ax\"\n" \
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ALTINSTR_REPLACEMENT(altinstr, 1) \
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".popsection\n" \
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OLDINSTR(oldinstr) \
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".pushsection .altinstructions,\"a\"\n" \
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ALTINSTR_ENTRY(facility, 1) \
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".popsection\n"
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#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
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".pushsection .altinstr_replacement, \"ax\"\n" \
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ALTINSTR_REPLACEMENT(altinstr1, 1) \
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ALTINSTR_REPLACEMENT(altinstr2, 2) \
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".popsection\n" \
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OLDINSTR(oldinstr) \
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".pushsection .altinstructions,\"a\"\n" \
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ALTINSTR_ENTRY(facility1, 1) \
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ALTINSTR_ENTRY(facility2, 2) \
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".popsection\n"
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/*
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* Alternative instructions for different CPU types or capabilities.
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*
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* This allows to use optimized instructions even on generic binary
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* kernels.
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*
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* oldinstr is padded with jump and nops at compile time if altinstr is
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* longer. altinstr is padded with jump and nops at run-time during patching.
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*
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* For non barrier like inlines please define new variants
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* without volatile and memory clobber.
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*/
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#define alternative(oldinstr, altinstr, facility) \
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asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
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#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
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asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1, \
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altinstr2, facility2) ::: "memory")
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/* Alternative inline assembly with input. */
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#define alternative_input(oldinstr, newinstr, feature, input...) \
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asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
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: : input)
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/* Like alternative_input, but with a single output argument */
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#define alternative_io(oldinstr, altinstr, facility, output, input...) \
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asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility) \
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: output : input)
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/* Use this macro if more than one output parameter is needed. */
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#define ASM_OUTPUT2(a...) a
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/* Use this macro if clobbers are needed without inputs. */
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#define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_S390_ALTERNATIVE_H */
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