Commit bee348fa authored by Will Deacon's avatar Will Deacon
Browse files

scs: Move accounting into alloc/free functions 



There's no need to perform the shadow stack page accounting independently
of the lifetime of the underlying allocation, so call the accounting code
from the {alloc,free}() functions and simplify the code in the process.

Tested-by: default avatarSami Tolvanen <samitolvanen@google.com>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 51189c7a

kernel/scs.c

+21 −24
Original line number Diff line number Diff line
@@ -14,25 +14,35 @@ 


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;

	void *s = kmem_cache_alloc_node(scs_cache, GFP_SCS, node);



	if (!s)

		return NULL;



	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);

	}



	__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);

}
@@ -42,17 +52,6 @@ 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);
@@ -61,7 +60,6 @@ int scs_prepare(struct task_struct *tsk, int node) 
		return -ENOMEM;



	task_scs(tsk) = task_scs_sp(tsk) = s;

	scs_account(tsk, 1);

	return 0;

}
@@ -102,6 +100,5 @@ void scs_release(struct task_struct *tsk) 


	WARN(scs_corrupted(tsk), "corrupted shadow stack detected when freeing task\n");

	scs_check_usage(tsk);

	scs_account(tsk, -1);

	scs_free(s);

}