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Diffstat (limited to 'arch/arm64/include/asm/alternative.h')
| -rw-r--r-- | arch/arm64/include/asm/alternative.h | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h new file mode 100644 index 000000000..4fbbcdda7 --- /dev/null +++ b/arch/arm64/include/asm/alternative.h @@ -0,0 +1,298 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_ALTERNATIVE_H +#define __ASM_ALTERNATIVE_H + +#include <asm/cpucaps.h> +#include <asm/insn.h> + +#define ARM64_CB_PATCH ARM64_NCAPS + +#ifndef __ASSEMBLY__ + +#include <linux/init.h> +#include <linux/types.h> +#include <linux/stddef.h> +#include <linux/stringify.h> + +extern int alternatives_applied; + +struct alt_instr { + s32 orig_offset; /* offset to original instruction */ + s32 alt_offset; /* offset to replacement instruction */ + u16 cpufeature; /* cpufeature bit set for replacement */ + u8 orig_len; /* size of original instruction(s) */ + u8 alt_len; /* size of new instruction(s), <= orig_len */ +}; + +typedef void (*alternative_cb_t)(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, int nr_inst); + +void __init apply_alternatives_all(void); + +#ifdef CONFIG_MODULES +void apply_alternatives_module(void *start, size_t length); +#else +static inline void apply_alternatives_module(void *start, size_t length) { } +#endif + +#define ALTINSTR_ENTRY(feature) \ + " .word 661b - .\n" /* label */ \ + " .word 663f - .\n" /* new instruction */ \ + " .hword " __stringify(feature) "\n" /* feature bit */ \ + " .byte 662b-661b\n" /* source len */ \ + " .byte 664f-663f\n" /* replacement len */ + +#define ALTINSTR_ENTRY_CB(feature, cb) \ + " .word 661b - .\n" /* label */ \ + " .word " __stringify(cb) "- .\n" /* callback */ \ + " .hword " __stringify(feature) "\n" /* feature bit */ \ + " .byte 662b-661b\n" /* source len */ \ + " .byte 664f-663f\n" /* replacement len */ + +/* + * alternative assembly primitive: + * + * If any of these .org directive fail, it means that insn1 and insn2 + * don't have the same length. This used to be written as + * + * .if ((664b-663b) != (662b-661b)) + * .error "Alternatives instruction length mismatch" + * .endif + * + * but most assemblers die if insn1 or insn2 have a .inst. This should + * be fixed in a binutils release posterior to 2.25.51.0.2 (anything + * containing commit 4e4d08cf7399b606 or c1baaddf8861). + * + * Alternatives with callbacks do not generate replacement instructions. + */ +#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ + ".if "__stringify(cfg_enabled)" == 1\n" \ + "661:\n\t" \ + oldinstr "\n" \ + "662:\n" \ + ".pushsection .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(feature) \ + ".popsection\n" \ + ".subsection 1\n" \ + "663:\n\t" \ + newinstr "\n" \ + "664:\n\t" \ + ".org . - (664b-663b) + (662b-661b)\n\t" \ + ".org . - (662b-661b) + (664b-663b)\n\t" \ + ".previous\n" \ + ".endif\n" + +#define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb) \ + ".if "__stringify(cfg_enabled)" == 1\n" \ + "661:\n\t" \ + oldinstr "\n" \ + "662:\n" \ + ".pushsection .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY_CB(feature, cb) \ + ".popsection\n" \ + "663:\n\t" \ + "664:\n\t" \ + ".endif\n" + +#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ + __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) + +#define ALTERNATIVE_CB(oldinstr, cb) \ + __ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb) +#else + +#include <asm/assembler.h> + +.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len + .word \orig_offset - . + .word \alt_offset - . + .hword \feature + .byte \orig_len + .byte \alt_len +.endm + +.macro alternative_insn insn1, insn2, cap, enable = 1 + .if \enable +661: \insn1 +662: .pushsection .altinstructions, "a" + altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f + .popsection + .subsection 1 +663: \insn2 +664: .org . - (664b-663b) + (662b-661b) + .org . - (662b-661b) + (664b-663b) + .previous + .endif +.endm + +/* + * Alternative sequences + * + * The code for the case where the capability is not present will be + * assembled and linked as normal. There are no restrictions on this + * code. + * + * The code for the case where the capability is present will be + * assembled into a special section to be used for dynamic patching. + * Code for that case must: + * + * 1. Be exactly the same length (in bytes) as the default code + * sequence. + * + * 2. Not contain a branch target that is used outside of the + * alternative sequence it is defined in (branches into an + * alternative sequence are not fixed up). + */ + +/* + * Begin an alternative code sequence. + */ +.macro alternative_if_not cap + .set .Lasm_alt_mode, 0 + .pushsection .altinstructions, "a" + altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f + .popsection +661: +.endm + +.macro alternative_if cap + .set .Lasm_alt_mode, 1 + .pushsection .altinstructions, "a" + altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f + .popsection + .subsection 1 + .align 2 /* So GAS knows label 661 is suitably aligned */ +661: +.endm + +.macro alternative_cb cb + .set .Lasm_alt_mode, 0 + .pushsection .altinstructions, "a" + altinstruction_entry 661f, \cb, ARM64_CB_PATCH, 662f-661f, 0 + .popsection +661: +.endm + +/* + * Provide the other half of the alternative code sequence. + */ +.macro alternative_else +662: + .if .Lasm_alt_mode==0 + .subsection 1 + .else + .previous + .endif +663: +.endm + +/* + * Complete an alternative code sequence. + */ +.macro alternative_endif +664: + .org . - (664b-663b) + (662b-661b) + .org . - (662b-661b) + (664b-663b) + .if .Lasm_alt_mode==0 + .previous + .endif +.endm + +/* + * Callback-based alternative epilogue + */ +.macro alternative_cb_end +662: +.endm + +/* + * Provides a trivial alternative or default sequence consisting solely + * of NOPs. The number of NOPs is chosen automatically to match the + * previous case. + */ +.macro alternative_else_nop_endif +alternative_else + nops (662b-661b) / AARCH64_INSN_SIZE +alternative_endif +.endm + +#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ + alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) + +.macro user_alt, label, oldinstr, newinstr, cond +9999: alternative_insn "\oldinstr", "\newinstr", \cond + _asm_extable 9999b, \label +.endm + +/* + * Generate the assembly for UAO alternatives with exception table entries. + * This is complicated as there is no post-increment or pair versions of the + * unprivileged instructions, and USER() only works for single instructions. + */ +#ifdef CONFIG_ARM64_UAO + .macro uao_ldp l, reg1, reg2, addr, post_inc + alternative_if_not ARM64_HAS_UAO +8888: ldp \reg1, \reg2, [\addr], \post_inc; +8889: nop; + nop; + alternative_else + ldtr \reg1, [\addr]; + ldtr \reg2, [\addr, #8]; + add \addr, \addr, \post_inc; + alternative_endif + + _asm_extable 8888b,\l; + _asm_extable 8889b,\l; + .endm + + .macro uao_stp l, reg1, reg2, addr, post_inc + alternative_if_not ARM64_HAS_UAO +8888: stp \reg1, \reg2, [\addr], \post_inc; +8889: nop; + nop; + alternative_else + sttr \reg1, [\addr]; + sttr \reg2, [\addr, #8]; + add \addr, \addr, \post_inc; + alternative_endif + + _asm_extable 8888b,\l; + _asm_extable 8889b,\l; + .endm + + .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc + alternative_if_not ARM64_HAS_UAO +8888: \inst \reg, [\addr], \post_inc; + nop; + alternative_else + \alt_inst \reg, [\addr]; + add \addr, \addr, \post_inc; + alternative_endif + + _asm_extable 8888b,\l; + .endm +#else + .macro uao_ldp l, reg1, reg2, addr, post_inc + USER(\l, ldp \reg1, \reg2, [\addr], \post_inc) + .endm + .macro uao_stp l, reg1, reg2, addr, post_inc + USER(\l, stp \reg1, \reg2, [\addr], \post_inc) + .endm + .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc + USER(\l, \inst \reg, [\addr], \post_inc) + .endm +#endif + +#endif /* __ASSEMBLY__ */ + +/* + * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); + * + * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); + * N.B. If CONFIG_FOO is specified, but not selected, the whole block + * will be omitted, including oldinstr. + */ +#define ALTERNATIVE(oldinstr, newinstr, ...) \ + _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) + +#endif /* __ASM_ALTERNATIVE_H */ |