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#include <xen/config.h>
#include <xen/percpu.h>
#include <xen/cpu.h>
#include <xen/init.h>
#include <xen/mm.h>
#include <xen/rcupdate.h>
unsigned long __per_cpu_offset[NR_CPUS];
/*
* Force uses of per_cpu() with an invalid area to attempt to access the
* middle of the non-canonical address space resulting in a #GP, rather than a
* possible #PF at (NULL + a little) which has security implications in the
* context of PV guests.
*/
#define INVALID_PERCPU_AREA (0x8000000000000000L - (long)__per_cpu_start)
#define PERCPU_ORDER (get_order_from_bytes(__per_cpu_data_end-__per_cpu_start))
void __init percpu_init_areas(void)
{
unsigned int cpu;
for ( cpu = 1; cpu < NR_CPUS; cpu++ )
__per_cpu_offset[cpu] = INVALID_PERCPU_AREA;
}
static int init_percpu_area(unsigned int cpu)
{
char *p;
if ( __per_cpu_offset[cpu] != INVALID_PERCPU_AREA )
return -EBUSY;
if ( (p = alloc_xenheap_pages(PERCPU_ORDER, 0)) == NULL )
return -ENOMEM;
memset(p, 0, __per_cpu_data_end - __per_cpu_start);
__per_cpu_offset[cpu] = p - __per_cpu_start;
return 0;
}
struct free_info {
unsigned int cpu;
struct rcu_head rcu;
};
static DEFINE_PER_CPU(struct free_info, free_info);
static void _free_percpu_area(struct rcu_head *head)
{
struct free_info *info = container_of(head, struct free_info, rcu);
unsigned int cpu = info->cpu;
char *p = __per_cpu_start + __per_cpu_offset[cpu];
free_xenheap_pages(p, PERCPU_ORDER);
__per_cpu_offset[cpu] = INVALID_PERCPU_AREA;
}
static void free_percpu_area(unsigned int cpu)
{
struct free_info *info = &per_cpu(free_info, cpu);
info->cpu = cpu;
call_rcu(&info->rcu, _free_percpu_area);
}
static int cpu_percpu_callback(
struct notifier_block *nfb, unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
int rc = 0;
switch ( action )
{
case CPU_UP_PREPARE:
rc = init_percpu_area(cpu);
break;
case CPU_UP_CANCELED:
case CPU_DEAD:
free_percpu_area(cpu);
break;
default:
break;
}
return !rc ? NOTIFY_DONE : notifier_from_errno(rc);
}
static struct notifier_block cpu_percpu_nfb = {
.notifier_call = cpu_percpu_callback,
.priority = 100 /* highest priority */
};
static int __init percpu_presmp_init(void)
{
register_cpu_notifier(&cpu_percpu_nfb);
return 0;
}
presmp_initcall(percpu_presmp_init);
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