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x86-64: Clean up vdso/kernel shared variables

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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>
This commit is contained in:
Andy Lutomirski
2011-05-23 09:31:24 -04:00
committed by Thomas Gleixner
parent d762f43831
commit 8c49d9a74b
15 changed files with 91 additions and 145 deletions
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27
arch/x86/vdso/vma.c
View File

@@ -15,9 +15,6 @@
#include <asm/proto.h>
#include <asm/vdso.h>
#include "vextern.h" /* Just for VMAGIC. */
#undef VEXTERN
unsigned int __read_mostly vdso_enabled = 1;
extern char vdso_start[], vdso_end[];
@@ -26,20 +23,10 @@ extern unsigned short vdso_sync_cpuid;
static struct page **vdso_pages;
static unsigned vdso_size;
static inline void *var_ref(void *p, char *name)
{
if (*(void **)p != (void *)VMAGIC) {
printk("VDSO: variable %s broken\n", name);
vdso_enabled = 0;
}
return p;
}
static int __init init_vdso_vars(void)
{
int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
int i;
char *vbase;
vdso_size = npages << PAGE_SHIFT;
vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
@@ -54,20 +41,6 @@ static int __init init_vdso_vars(void)
copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
}
vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL);
if (!vbase)
goto oom;
if (memcmp(vbase, "\177ELF", 4)) {
printk("VDSO: I'm broken; not ELF\n");
vdso_enabled = 0;
}
#define VEXTERN(x) \
*(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x;
#include "vextern.h"
#undef VEXTERN
vunmap(vbase);
return 0;
oom: