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Commit 25880156 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/vdso: Change the PER_CPU segment to use struct desc_struct 



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

Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/d492f7b55136cbc60f016adae79160707b2e03b7.1411494540.git.luto@amacapital.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d4f829dd

arch/x86/vdso/vma.c

+12 −7
Original line number Diff line number Diff line
@@ -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);

}