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x86/vdso: Change the PER_CPU segment to use struct desc_struct

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This makes it easier to see what's going on.  It produces
exactly the same segment descriptor as the old code.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/d492f7b55136cbc60f016adae79160707b2e03b7.1411494540.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2014-09-23 10:50:53 -07:00 committed by Ingo Molnar
parent d4f829dd90
commit 258801563b
1 changed files with 12 additions and 7 deletions
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19
arch/x86/vdso/vma.c
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@ -248,7 +248,7 @@ __setup("vdso=", vdso_setup);
*/
static void vsyscall_set_cpu(int cpu)
{
unsigned long d;
struct desc_struct d;
unsigned long node = 0;
#ifdef CONFIG_NUMA
node = cpu_to_node(cpu);
@ -257,13 +257,18 @@ static void vsyscall_set_cpu(int cpu)
write_rdtscp_aux((node << 12) | cpu);
/*
* Store cpu number in limit so that it can be loaded quickly
* in user space in vgetcpu. (12 bits for the CPU and 8 bits for the node)
* Store cpu number in limit so that it can be loaded
* quickly in user space in vgetcpu. (12 bits for the CPU
* and 8 bits for the node)
*/
d = 0x0f40000000000ULL;
d |= cpu;
d |= (node & 0xf) << 12;
d |= (node >> 4) << 48;
d = (struct desc_struct) {
.limit0 = cpu | ((node & 0xf) << 12),
.limit = node >> 4,
.type = 4, /* RO data, expand down */
.dpl = 3, /* Visible to user code */
.s = 1, /* Not a system segment */
.p = 1, /* Present */
};
write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
}