105 строки
1.9 KiB
C
105 строки
1.9 KiB
C
// 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>
|
|
|
|
static struct kmem_cache *scs_cache;
|
|
|
|
static void __scs_account(void *s, int account)
|
|
{
|
|
struct page *scs_page = virt_to_page(s);
|
|
|
|
mod_zone_page_state(page_zone(scs_page), NR_KERNEL_SCS_KB,
|
|
account * (SCS_SIZE / SZ_1K));
|
|
}
|
|
|
|
static void *scs_alloc(int node)
|
|
{
|
|
void *s = kmem_cache_alloc_node(scs_cache, GFP_SCS, node);
|
|
|
|
if (!s)
|
|
return NULL;
|
|
|
|
*__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);
|
|
__scs_account(s, 1);
|
|
return s;
|
|
}
|
|
|
|
static void scs_free(void *s)
|
|
{
|
|
__scs_account(s, -1);
|
|
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);
|
|
}
|
|
|
|
int scs_prepare(struct task_struct *tsk, int node)
|
|
{
|
|
void *s = scs_alloc(node);
|
|
|
|
if (!s)
|
|
return -ENOMEM;
|
|
|
|
task_scs(tsk) = task_scs_sp(tsk) = s;
|
|
return 0;
|
|
}
|
|
|
|
static void scs_check_usage(struct task_struct *tsk)
|
|
{
|
|
static unsigned long highest;
|
|
|
|
unsigned long *p, prev, curr = highest, used = 0;
|
|
|
|
if (!IS_ENABLED(CONFIG_DEBUG_STACK_USAGE))
|
|
return;
|
|
|
|
for (p = task_scs(tsk); p < __scs_magic(tsk); ++p) {
|
|
if (!READ_ONCE_NOCHECK(*p))
|
|
break;
|
|
used++;
|
|
}
|
|
|
|
while (used > curr) {
|
|
prev = cmpxchg_relaxed(&highest, curr, used);
|
|
|
|
if (prev == curr) {
|
|
pr_info("%s (%d): highest shadow stack usage: %lu bytes\n",
|
|
tsk->comm, task_pid_nr(tsk), used);
|
|
break;
|
|
}
|
|
|
|
curr = prev;
|
|
}
|
|
}
|
|
|
|
void scs_release(struct task_struct *tsk)
|
|
{
|
|
void *s = task_scs(tsk);
|
|
|
|
if (!s)
|
|
return;
|
|
|
|
WARN(task_scs_end_corrupted(tsk),
|
|
"corrupted shadow stack detected when freeing task\n");
|
|
scs_check_usage(tsk);
|
|
scs_free(s);
|
|
}
|