d167a51877
Changes are largely identical to the i386 version: * alternative #define are moved to the new alternative.h file. * one new elf section with pointers to the lock prefixes which can be nop'ed out for non-smp. * two new elf sections simliar to the "classic" alternatives to replace SMP code with simpler UP code. * fixup headers to use alternative.h instead of defining their own LOCK / LOCK_PREFIX macros. The patch reuses the i386 version of the alternatives code to avoid code duplication. The code in alternatives.c was shuffled around a bit to reduce the number of #ifdefs needed. It also got some tweaks needed for x86_64 (vsyscall page handling) and new features (noreplacement option which was x86_64 only up to now). Debug printk's are changed from compile-time to runtime. Loosely based on a early version from Bastian Blank <waldi@debian.org> Signed-off-by: Gerd Hoffmann <kraxel@suse.de> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
133 lines
4.7 KiB
C
133 lines
4.7 KiB
C
#ifndef _I386_ALTERNATIVE_H
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#define _I386_ALTERNATIVE_H
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#ifdef __KERNEL__
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#include <asm/types.h>
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#include <linux/types.h>
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struct alt_instr {
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u8 *instr; /* original instruction */
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u8 *replacement;
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u8 cpuid; /* cpuid bit set for replacement */
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u8 instrlen; /* length of original instruction */
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u8 replacementlen; /* length of new instruction, <= instrlen */
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u8 pad;
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};
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extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
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struct module;
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extern void alternatives_smp_module_add(struct module *mod, char *name,
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void *locks, void *locks_end,
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void *text, void *text_end);
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extern void alternatives_smp_module_del(struct module *mod);
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extern void alternatives_smp_switch(int smp);
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#endif
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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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* length of oldinstr must be longer or equal the length of newinstr
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* It can be padded with nops as needed.
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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, newinstr, feature) \
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asm volatile ("661:\n\t" oldinstr "\n662:\n" \
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".section .altinstructions,\"a\"\n" \
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" .align 4\n" \
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" .long 661b\n" /* label */ \
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" .long 663f\n" /* new instruction */ \
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" .byte %c0\n" /* feature bit */ \
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" .byte 662b-661b\n" /* sourcelen */ \
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" .byte 664f-663f\n" /* replacementlen */ \
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".previous\n" \
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".section .altinstr_replacement,\"ax\"\n" \
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"663:\n\t" newinstr "\n664:\n" /* replacement */\
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".previous" :: "i" (feature) : "memory")
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/*
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* Alternative inline assembly with input.
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*
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* Pecularities:
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* No memory clobber here.
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* Argument numbers start with 1.
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* Best is to use constraints that are fixed size (like (%1) ... "r")
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* If you use variable sized constraints like "m" or "g" in the
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* replacement maake sure to pad to the worst case length.
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*/
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#define alternative_input(oldinstr, newinstr, feature, input...) \
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asm volatile ("661:\n\t" oldinstr "\n662:\n" \
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".section .altinstructions,\"a\"\n" \
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" .align 4\n" \
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" .long 661b\n" /* label */ \
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" .long 663f\n" /* new instruction */ \
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" .byte %c0\n" /* feature bit */ \
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" .byte 662b-661b\n" /* sourcelen */ \
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" .byte 664f-663f\n" /* replacementlen */ \
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".previous\n" \
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".section .altinstr_replacement,\"ax\"\n" \
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"663:\n\t" newinstr "\n664:\n" /* replacement */\
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".previous" :: "i" (feature), ##input)
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/*
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* Alternative inline assembly for SMP.
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*
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* alternative_smp() takes two versions (SMP first, UP second) and is
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* for more complex stuff such as spinlocks.
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*
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* The LOCK_PREFIX macro defined here replaces the LOCK and
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* LOCK_PREFIX macros used everywhere in the source tree.
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*
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* SMP alternatives use the same data structures as the other
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* alternatives and the X86_FEATURE_UP flag to indicate the case of a
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* UP system running a SMP kernel. The existing apply_alternatives()
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* works fine for patching a SMP kernel for UP.
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*
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* The SMP alternative tables can be kept after boot and contain both
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* UP and SMP versions of the instructions to allow switching back to
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* SMP at runtime, when hotplugging in a new CPU, which is especially
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* useful in virtualized environments.
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*
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* The very common lock prefix is handled as special case in a
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* separate table which is a pure address list without replacement ptr
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* and size information. That keeps the table sizes small.
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*/
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#ifdef CONFIG_SMP
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#define alternative_smp(smpinstr, upinstr, args...) \
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asm volatile ("661:\n\t" smpinstr "\n662:\n" \
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".section .smp_altinstructions,\"a\"\n" \
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" .align 4\n" \
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" .long 661b\n" /* label */ \
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" .long 663f\n" /* new instruction */ \
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" .byte 0x68\n" /* X86_FEATURE_UP */ \
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" .byte 662b-661b\n" /* sourcelen */ \
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" .byte 664f-663f\n" /* replacementlen */ \
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".previous\n" \
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".section .smp_altinstr_replacement,\"awx\"\n" \
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"663:\n\t" upinstr "\n" /* replacement */ \
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"664:\n\t.fill 662b-661b,1,0x42\n" /* space for original */ \
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".previous" : args)
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#define LOCK_PREFIX \
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".section .smp_locks,\"a\"\n" \
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" .align 4\n" \
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" .long 661f\n" /* address */ \
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".previous\n" \
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"661:\n\tlock; "
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#else /* ! CONFIG_SMP */
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#define alternative_smp(smpinstr, upinstr, args...) \
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asm volatile (upinstr : args)
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#define LOCK_PREFIX ""
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#endif
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#endif /* _I386_ALTERNATIVE_H */
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