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53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
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/*
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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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* Each of these variables lives in the vsyscall page, and each
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* one needs a unique offset within the little piece of the page
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* reserved for vvars. Specify that offset in DECLARE_VVAR.
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* (There are 896 bytes available. If you mess up, the linker will
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* catch it.)
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*/
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/* Offset of vars within vsyscall page */
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#define VSYSCALL_VARS_OFFSET (3072 + 128)
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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, VSYSCALL_VARS_OFFSET + offset)
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#else
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#define DECLARE_VVAR(offset, type, name) \
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static type const * const vvaraddr_ ## name = \
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(void *)(VSYSCALL_START + VSYSCALL_VARS_OFFSET + (offset));
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#define DEFINE_VVAR(type, name) \
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type __vvar_ ## name \
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__attribute__((section(".vsyscall_var_" #name), aligned(16)))
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#define VVAR(name) (*vvaraddr_ ## name)
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#endif
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/* DECLARE_VVAR(offset, type, name) */
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DECLARE_VVAR(0, volatile unsigned long, jiffies)
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DECLARE_VVAR(8, int, vgetcpu_mode)
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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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#undef VSYSCALL_VARS_OFFSET
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