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Diffstat (limited to 'arch/x86/include/asm/alternative.h')
| -rw-r--r-- | arch/x86/include/asm/alternative.h | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h new file mode 100644 index 000000000..4cd6a3b71 --- /dev/null +++ b/arch/x86/include/asm/alternative.h @@ -0,0 +1,241 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_ALTERNATIVE_H +#define _ASM_X86_ALTERNATIVE_H + +#ifndef __ASSEMBLY__ + +#include <linux/types.h> +#include <linux/stddef.h> +#include <linux/stringify.h> +#include <asm/asm.h> + +/* + * Alternative inline assembly for SMP. + * + * The LOCK_PREFIX macro defined here replaces the LOCK and + * LOCK_PREFIX macros used everywhere in the source tree. + * + * SMP alternatives use the same data structures as the other + * alternatives and the X86_FEATURE_UP flag to indicate the case of a + * UP system running a SMP kernel. The existing apply_alternatives() + * works fine for patching a SMP kernel for UP. + * + * The SMP alternative tables can be kept after boot and contain both + * UP and SMP versions of the instructions to allow switching back to + * SMP at runtime, when hotplugging in a new CPU, which is especially + * useful in virtualized environments. + * + * The very common lock prefix is handled as special case in a + * separate table which is a pure address list without replacement ptr + * and size information. That keeps the table sizes small. + */ + +#ifdef CONFIG_SMP +#define LOCK_PREFIX_HERE \ + ".pushsection .smp_locks,\"a\"\n" \ + ".balign 4\n" \ + ".long 671f - .\n" /* offset */ \ + ".popsection\n" \ + "671:" + +#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " + +#else /* ! CONFIG_SMP */ +#define LOCK_PREFIX_HERE "" +#define LOCK_PREFIX "" +#endif + +struct alt_instr { + s32 instr_offset; /* original instruction */ + s32 repl_offset; /* offset to replacement instruction */ + u16 cpuid; /* cpuid bit set for replacement */ + u8 instrlen; /* length of original instruction */ + u8 replacementlen; /* length of new instruction */ + u8 padlen; /* length of build-time padding */ +} __packed; + +/* + * Debug flag that can be tested to see whether alternative + * instructions were patched in already: + */ +extern int alternatives_patched; + +extern void alternative_instructions(void); +extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); + +struct module; + +#ifdef CONFIG_SMP +extern void alternatives_smp_module_add(struct module *mod, char *name, + void *locks, void *locks_end, + void *text, void *text_end); +extern void alternatives_smp_module_del(struct module *mod); +extern void alternatives_enable_smp(void); +extern int alternatives_text_reserved(void *start, void *end); +extern bool skip_smp_alternatives; +#else +static inline void alternatives_smp_module_add(struct module *mod, char *name, + void *locks, void *locks_end, + void *text, void *text_end) {} +static inline void alternatives_smp_module_del(struct module *mod) {} +static inline void alternatives_enable_smp(void) {} +static inline int alternatives_text_reserved(void *start, void *end) +{ + return 0; +} +#endif /* CONFIG_SMP */ + +#define b_replacement(num) "664"#num +#define e_replacement(num) "665"#num + +#define alt_end_marker "663" +#define alt_slen "662b-661b" +#define alt_pad_len alt_end_marker"b-662b" +#define alt_total_slen alt_end_marker"b-661b" +#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" + +#define __OLDINSTR(oldinstr, num) \ + "661:\n\t" oldinstr "\n662:\n" \ + ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ + "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" + +#define OLDINSTR(oldinstr, num) \ + __OLDINSTR(oldinstr, num) \ + alt_end_marker ":\n" + +/* + * gas compatible max based on the idea from: + * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax + * + * The additional "-" is needed because gas uses a "true" value of -1. + */ +#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" + +/* + * Pad the second replacement alternative with additional NOPs if it is + * additionally longer than the first replacement alternative. + */ +#define OLDINSTR_2(oldinstr, num1, num2) \ + "661:\n\t" oldinstr "\n662:\n" \ + ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ + "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ + alt_end_marker ":\n" + +#define ALTINSTR_ENTRY(feature, num) \ + " .long 661b - .\n" /* label */ \ + " .long " b_replacement(num)"f - .\n" /* new instruction */ \ + " .word " __stringify(feature) "\n" /* feature bit */ \ + " .byte " alt_total_slen "\n" /* source len */ \ + " .byte " alt_rlen(num) "\n" /* replacement len */ \ + " .byte " alt_pad_len "\n" /* pad len */ + +#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ + b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t" + +/* alternative assembly primitive: */ +#define ALTERNATIVE(oldinstr, newinstr, feature) \ + OLDINSTR(oldinstr, 1) \ + ".pushsection .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(feature, 1) \ + ".popsection\n" \ + ".pushsection .altinstr_replacement, \"ax\"\n" \ + ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ + ".popsection\n" + +#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ + OLDINSTR_2(oldinstr, 1, 2) \ + ".pushsection .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(feature1, 1) \ + ALTINSTR_ENTRY(feature2, 2) \ + ".popsection\n" \ + ".pushsection .altinstr_replacement, \"ax\"\n" \ + ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ + ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ + ".popsection\n" + +/* + * Alternative instructions for different CPU types or capabilities. + * + * This allows to use optimized instructions even on generic binary + * kernels. + * + * length of oldinstr must be longer or equal the length of newinstr + * It can be padded with nops as needed. + * + * For non barrier like inlines please define new variants + * without volatile and memory clobber. + */ +#define alternative(oldinstr, newinstr, feature) \ + asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") + +#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ + asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") + +/* + * Alternative inline assembly with input. + * + * Pecularities: + * No memory clobber here. + * Argument numbers start with 1. + * Best is to use constraints that are fixed size (like (%1) ... "r") + * If you use variable sized constraints like "m" or "g" in the + * replacement make sure to pad to the worst case length. + * Leaving an unused argument 0 to keep API compatibility. + */ +#define alternative_input(oldinstr, newinstr, feature, input...) \ + asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ + : : "i" (0), ## input) + +/* + * This is similar to alternative_input. But it has two features and + * respective instructions. + * + * If CPU has feature2, newinstr2 is used. + * Otherwise, if CPU has feature1, newinstr1 is used. + * Otherwise, oldinstr is used. + */ +#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ + feature2, input...) \ + asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ + newinstr2, feature2) \ + : : "i" (0), ## input) + +/* Like alternative_input, but with a single output argument */ +#define alternative_io(oldinstr, newinstr, feature, output, input...) \ + asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ + : output : "i" (0), ## input) + +/* Like alternative_io, but for replacing a direct call with another one. */ +#define alternative_call(oldfunc, newfunc, feature, output, input...) \ + asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ + : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) + +/* + * Like alternative_call, but there are two features and respective functions. + * If CPU has feature2, function2 is used. + * Otherwise, if CPU has feature1, function1 is used. + * Otherwise, old function is used. + */ +#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ + output, input...) \ + asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ + "call %P[new2]", feature2) \ + : output, ASM_CALL_CONSTRAINT \ + : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ + [new2] "i" (newfunc2), ## input) + +/* + * use this macro(s) if you need more than one output parameter + * in alternative_io + */ +#define ASM_OUTPUT2(a...) a + +/* + * use this macro if you need clobbers but no inputs in + * alternative_{input,io,call}() + */ +#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_X86_ALTERNATIVE_H */ |