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// SPDX-License-Identifier: GPL-2.0
/*
* Shadow Call Stack support.
*
* Copyright (C) 2019 Google LLC
*/
#include <linux/kasan.h>
#include <linux/mm.h>
#include <linux/scs.h>
#include <linux/slab.h>
#include <linux/vmstat.h>
#include <asm/scs.h>
static struct kmem_cache *scs_cache;
static void *scs_alloc(int node)
{
void *s;
s = kmem_cache_alloc_node(scs_cache, GFP_SCS, node);
if (s) {
*__scs_magic(s) = SCS_END_MAGIC;
/*
* Poison the allocation to catch unintentional accesses to
* the shadow stack when KASAN is enabled.
*/
kasan_poison_object_data(scs_cache, s);
}
return s;
}
static void scs_free(void *s)
{
kasan_unpoison_object_data(scs_cache, s);
kmem_cache_free(scs_cache, s);
}
void __init scs_init(void)
{
scs_cache = kmem_cache_create("scs_cache", SCS_SIZE, 0, 0, NULL);
}
static struct page *__scs_page(struct task_struct *tsk)
{
return virt_to_page(task_scs(tsk));
}
static void scs_account(struct task_struct *tsk, int account)
{
mod_zone_page_state(page_zone(__scs_page(tsk)), NR_KERNEL_SCS_KB,
account * (SCS_SIZE / 1024));
}
int scs_prepare(struct task_struct *tsk, int node)
{
void *s = scs_alloc(node);
if (!s)
return -ENOMEM;
task_scs(tsk) = s;
task_scs_offset(tsk) = 0;
scs_account(tsk, 1);
return 0;
}
void scs_release(struct task_struct *tsk)
{
void *s = task_scs(tsk);
if (!s)
return;
WARN(scs_corrupted(tsk), "corrupted shadow stack detected when freeing task\n");
scs_account(tsk, -1);
scs_free(s);
}
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