8c49d9a74b
Variables that are shared between the vdso and the kernel are currently a bit of a mess. They are each defined with their own magic, they are accessed differently in the kernel, the vsyscall page, and the vdso, and one of them (vsyscall_clock) doesn't even really exist. This changes them all to use a common mechanism. All of them are delcared in vvar.h with a fixed address (validated by the linker script). In the kernel (as before), they look like ordinary read-write variables. In the vsyscall page and the vdso, they are accessed through a new macro VVAR, which gives read-only access. The vdso is now loaded verbatim into memory without any fixups. As a side bonus, access from the vdso is faster because a level of indirection is removed. While we're at it, pack jiffies and vgetcpu_mode into the same cacheline. Signed-off-by: Andy Lutomirski <luto@mit.edu> Cc: Andi Kleen <andi@firstfloor.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Borislav Petkov <bp@amd64.org> Link: http://lkml.kernel.org/r/%3C7357882fbb51fa30491636a7b6528747301b7ee9.1306156808.git.luto%40mit.edu%3E Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
52 lines
1.6 KiB
C
52 lines
1.6 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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* 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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