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e76b027e64
LSL is faster than RDTSCP and works everywhere; there's no need to switch between them depending on CPU. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Cc: Andi Kleen <andi@firstfloor.org> Link: http://lkml.kernel.org/r/72f73d5ec4514e02bba345b9759177ef03742efb.1414706021.git.luto@amacapital.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
51 lines
1.4 KiB
C
51 lines
1.4 KiB
C
/*
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* vvar.h: Shared vDSO/kernel variable declarations
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* Copyright (c) 2011 Andy Lutomirski
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* Subject to the GNU General Public License, version 2
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*
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* A handful of variables are accessible (read-only) from userspace
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* code in the vsyscall page and the vdso. They are declared here.
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* Some other file must define them with DEFINE_VVAR.
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*
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* In normal kernel code, they are used like any other variable.
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* In user code, they are accessed through the VVAR macro.
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*
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* These variables live in a page of kernel data that has an extra RO
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* mapping for userspace. Each variable needs a unique offset within
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* that page; specify that offset with the DECLARE_VVAR macro. (If
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* you mess up, the linker will catch it.)
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*/
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#ifndef _ASM_X86_VVAR_H
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#define _ASM_X86_VVAR_H
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#if defined(__VVAR_KERNEL_LDS)
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/* The kernel linker script defines its own magic to put vvars in the
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* right place.
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*/
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#define DECLARE_VVAR(offset, type, name) \
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EMIT_VVAR(name, offset)
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#else
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extern char __vvar_page;
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#define DECLARE_VVAR(offset, type, name) \
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extern type vvar_ ## name __attribute__((visibility("hidden")));
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#define VVAR(name) (vvar_ ## name)
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#define DEFINE_VVAR(type, name) \
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type name \
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__attribute__((section(".vvar_" #name), aligned(16))) __visible
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#endif
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/* DECLARE_VVAR(offset, type, name) */
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DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
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#undef DECLARE_VVAR
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#endif
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