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https://github.com/torvalds/linux
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7c03156f34
This patch add the VDSO time support for the IA32 Emulation Layer. Due the nature of the kernel headers and the LP64 compiler where the size of a long and a pointer differs against a 32 bit compiler, there is some type hacking necessary for optimal performance. The vsyscall_gtod_data struture must be a rearranged to serve 32- and 64-bit code access at the same time: - The seqcount_t was replaced by an unsigned, this makes the vsyscall_gtod_data intedepend of kernel configuration and internal functions. - All kernel internal structures are replaced by fix size elements which works for 32- and 64-bit access - The inner struct clock was removed to pack the whole struct. The "unsigned seq" would be handled by functions derivated from seqcount_t. Signed-off-by: Stefani Seibold <stefani@seibold.net> Link: http://lkml.kernel.org/r/1395094933-14252-11-git-send-email-stefani@seibold.net Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
72 lines
1.8 KiB
C
72 lines
1.8 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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#ifdef BUILD_VDSO32
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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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#else
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extern char __vvar_page;
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/* Base address of vvars. This is not ABI. */
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#ifdef CONFIG_X86_64
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#define VVAR_ADDRESS (-10*1024*1024 - 4096)
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#else
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#define VVAR_ADDRESS (&__vvar_page)
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#endif
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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 *)(VVAR_ADDRESS + (offset));
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#define VVAR(name) (*vvaraddr_ ## name)
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#endif
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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(0, volatile unsigned long, jiffies)
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DECLARE_VVAR(16, 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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#endif
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