percpu.c

	int left = 0, right = pcpul_nr_lpages - 1;
	int pos;

	/* pcpul in use at all? */
	if (!pcpul_map)
		return NULL;

	/* okay, perform binary search */
	while (left <= right) {
		pos = (left + right) / 2;

		if (pcpul_map[pos].ptr < lpage_addr)
			left = pos + 1;
		else if (pcpul_map[pos].ptr > lpage_addr)
			right = pos - 1;
		else
			return pcpul_map[pos].map_addr + offset;
	}

	return NULL;
}
#endif /* CONFIG_NEED_PER_CPU_LPAGE_FIRST_CHUNK */

/*
 * Generic percpu area setup.
 *
 * The embedding helper is used because its behavior closely resembles
 * the original non-dynamic generic percpu area setup.  This is
 * important because many archs have addressing restrictions and might
 * fail if the percpu area is located far away from the previous
 * location.  As an added bonus, in non-NUMA cases, embedding is
 * generally a good idea TLB-wise because percpu area can piggy back
 * on the physical linear memory mapping which uses large page
 * mappings on applicable archs.
 */
#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(__per_cpu_offset);

void __init setup_per_cpu_areas(void)
{
	ssize_t unit_size;
	unsigned long delta;
	unsigned int cpu;

	/*
	 * Always reserve area for module percpu variables.  That's
	 * what the legacy allocator did.
	 */
	unit_size = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
					   PERCPU_DYNAMIC_RESERVE);
	if (unit_size < 0)
		panic("Failed to initialized percpu areas.");

	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
	for_each_possible_cpu(cpu)
		__per_cpu_offset[cpu] = delta + cpu * unit_size;
}
#endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */