[PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds

Kees Cook
2020-03-24T20:33:04Z

Right now, the state of CONFIG_INIT_ON_ALLOC_DEFAULT_ON (and
...ON_FREE...) did not change the assembly ordering of the static branch
tests. Use the new jump_label macro to check CONFIG settings to default
to the "expected" state, unpessimizes the resulting assembly code.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/mm.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 059658604dd6..64e911159ffa 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2665,7 +2665,8 @@ static inline void kernel_poison_pages(struct page *page, int numpages,
DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
static inline bool want_init_on_alloc(gfp_t flags)
{
- if (static_branch_unlikely(&init_on_alloc) &&
+ if (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,
+ &init_on_alloc) &&
!page_poisoning_enabled())
return true;
return flags & __GFP_ZERO;
@@ -2674,7 +2675,8 @@ static inline bool want_init_on_alloc(gfp_t flags)
DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
static inline bool want_init_on_free(void)
{
- return static_branch_unlikely(&init_on_free) &&
+ return static_branch_maybe(CONFIG_INIT_ON_FREE_DEFAULT_ON,
+ &init_on_free) &&
!page_poisoning_enabled();
}

--
2.20.1