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