summaryrefslogtreecommitdiff
path: root/kernel/scs.c
diff options
context:
space:
mode:
authorArd Biesheuvel <ardb@kernel.org>2022-10-27 17:59:07 +0200
committerWill Deacon <will@kernel.org>2022-11-09 18:06:35 +0000
commit9beccca0984022a844850e32f0d7dd80d4a225de (patch)
treef9a9128498d40dee1958e15b212707872f039e38 /kernel/scs.c
parent68c76ad4a9571a2b603665c85cf8229bcf04982a (diff)
scs: add support for dynamic shadow call stacks
In order to allow arches to use code patching to conditionally emit the shadow stack pushes and pops, rather than always taking the performance hit even on CPUs that implement alternatives such as stack pointer authentication on arm64, add a Kconfig symbol that can be set by the arch to omit the SCS codegen itself, without otherwise affecting how support code for SCS and compiler options (for register reservation, for instance) are emitted. Also, add a static key and some plumbing to omit the allocation of shadow call stack for dynamic SCS configurations if SCS is disabled at runtime. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sami Tolvanen <samitolvanen@google.com> Link: https://lore.kernel.org/r/20221027155908.1940624-3-ardb@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'kernel/scs.c')
-rw-r--r--kernel/scs.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/kernel/scs.c b/kernel/scs.c
index b7e1b096d906..d7809affe740 100644
--- a/kernel/scs.c
+++ b/kernel/scs.c
@@ -12,6 +12,10 @@
#include <linux/vmalloc.h>
#include <linux/vmstat.h>
+#ifdef CONFIG_DYNAMIC_SCS
+DEFINE_STATIC_KEY_FALSE(dynamic_scs_enabled);
+#endif
+
static void __scs_account(void *s, int account)
{
struct page *scs_page = vmalloc_to_page(s);
@@ -101,14 +105,20 @@ static int scs_cleanup(unsigned int cpu)
void __init scs_init(void)
{
+ if (!scs_is_enabled())
+ return;
cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "scs:scs_cache", NULL,
scs_cleanup);
}
int scs_prepare(struct task_struct *tsk, int node)
{
- void *s = scs_alloc(node);
+ void *s;
+ if (!scs_is_enabled())
+ return 0;
+
+ s = scs_alloc(node);
if (!s)
return -ENOMEM;
@@ -148,7 +158,7 @@ void scs_release(struct task_struct *tsk)
{
void *s = task_scs(tsk);
- if (!s)
+ if (!scs_is_enabled() || !s)
return;
WARN(task_scs_end_corrupted(tsk),