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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>
36 lines
804 B
C
36 lines
804 B
C
/*
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* Copyright 2006 Andi Kleen, SUSE Labs.
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* Subject to the GNU Public License, v.2
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*
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* Fast user context implementation of getcpu()
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*/
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#include <linux/kernel.h>
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#include <linux/getcpu.h>
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#include <linux/jiffies.h>
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#include <linux/time.h>
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#include <asm/vsyscall.h>
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#include <asm/vgtod.h>
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notrace long
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__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
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{
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unsigned int p;
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if (VVAR(vgetcpu_mode) == VGETCPU_RDTSCP) {
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/* Load per CPU data from RDTSCP */
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native_read_tscp(&p);
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} else {
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/* Load per CPU data from GDT */
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asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
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}
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if (cpu)
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*cpu = p & 0xfff;
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if (node)
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*node = p >> 12;
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return 0;
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}
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long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
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__attribute__((weak, alias("__vdso_getcpu")));
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