From 04013513cc84c401c7de9023ff3eda7863fc4add Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Mon, 14 Dec 2020 19:13:30 -0800 Subject: mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters Patch series "cleanup page poisoning", v3. I have identified a number of issues and opportunities for cleanup with CONFIG_PAGE_POISON and friends: - interaction with init_on_alloc and init_on_free parameters depends on the order of parameters (Patch 1) - the boot time enabling uses static key, but inefficienty (Patch 2) - sanity checking is incompatible with hibernation (Patch 3) - CONFIG_PAGE_POISONING_NO_SANITY can be removed now that we have init_on_free (Patch 4) - CONFIG_PAGE_POISONING_ZERO can be most likely removed now that we have init_on_free (Patch 5) This patch (of 5): Enabling page_poison=1 together with init_on_alloc=1 or init_on_free=1 produces a warning in dmesg that page_poison takes precedence. However, as these warnings are printed in early_param handlers for init_on_alloc/free, they are not printed if page_poison is enabled later on the command line (handlers are called in the order of their parameters), or when init_on_alloc/free is always enabled by the respective config option - before the page_poison early param handler is called, it is not considered to be enabled. This is inconsistent. We can remove the dependency on order by making the init_on_* parameters only set a boolean variable, and postponing the evaluation after all early params have been processed. Introduce a new init_mem_debugging_and_hardening() function for that, and move the related debug_pagealloc processing there as well. As a result init_mem_debugging_and_hardening() knows always accurately if init_on_* and/or page_poison options were enabled. Thus we can also optimize want_init_on_alloc() and want_init_on_free(). We don't need to check page_poisoning_enabled() there, we can instead not enable the init_on_* static keys at all, if page poisoning is enabled. This results in a simpler and more effective code. Link: https://lkml.kernel.org/r/20201113104033.22907-1-vbabka@suse.cz Link: https://lkml.kernel.org/r/20201113104033.22907-2-vbabka@suse.cz Signed-off-by: Vlastimil Babka Reviewed-by: David Hildenbrand Reviewed-by: Mike Rapoport Cc: Rafael J. Wysocki Cc: Alexander Potapenko Cc: Kees Cook Cc: Michal Hocko Cc: Mateusz Nosek Cc: Laura Abbott Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 88 +++++++++++++++++++++++++++------------------------------ 1 file changed, 42 insertions(+), 46 deletions(-) (limited to 'mm') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 521d29718c9e..3fd0c8d5745f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -167,53 +167,26 @@ unsigned long totalcma_pages __read_mostly; int percpu_pagelist_fraction; gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; -#ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON -DEFINE_STATIC_KEY_TRUE(init_on_alloc); -#else DEFINE_STATIC_KEY_FALSE(init_on_alloc); -#endif EXPORT_SYMBOL(init_on_alloc); -#ifdef CONFIG_INIT_ON_FREE_DEFAULT_ON -DEFINE_STATIC_KEY_TRUE(init_on_free); -#else DEFINE_STATIC_KEY_FALSE(init_on_free); -#endif EXPORT_SYMBOL(init_on_free); +static bool _init_on_alloc_enabled_early __read_mostly + = IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON); static int __init early_init_on_alloc(char *buf) { - int ret; - bool bool_result; - ret = kstrtobool(buf, &bool_result); - if (ret) - return ret; - if (bool_result && page_poisoning_enabled()) - pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, will take precedence over init_on_alloc\n"); - if (bool_result) - static_branch_enable(&init_on_alloc); - else - static_branch_disable(&init_on_alloc); - return 0; + return kstrtobool(buf, &_init_on_alloc_enabled_early); } early_param("init_on_alloc", early_init_on_alloc); +static bool _init_on_free_enabled_early __read_mostly + = IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON); static int __init early_init_on_free(char *buf) { - int ret; - bool bool_result; - - ret = kstrtobool(buf, &bool_result); - if (ret) - return ret; - if (bool_result && page_poisoning_enabled()) - pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, will take precedence over init_on_free\n"); - if (bool_result) - static_branch_enable(&init_on_free); - else - static_branch_disable(&init_on_free); - return 0; + return kstrtobool(buf, &_init_on_free_enabled_early); } early_param("init_on_free", early_init_on_free); @@ -730,19 +703,6 @@ static int __init early_debug_pagealloc(char *buf) } early_param("debug_pagealloc", early_debug_pagealloc); -void init_debug_pagealloc(void) -{ - if (!debug_pagealloc_enabled()) - return; - - static_branch_enable(&_debug_pagealloc_enabled); - - if (!debug_guardpage_minorder()) - return; - - static_branch_enable(&_debug_guardpage_enabled); -} - static int __init debug_guardpage_minorder_setup(char *buf) { unsigned long res; @@ -794,6 +754,42 @@ static inline void clear_page_guard(struct zone *zone, struct page *page, unsigned int order, int migratetype) {} #endif +/* + * Enable static keys related to various memory debugging and hardening options. + * Some override others, and depend on early params that are evaluated in the + * order of appearance. So we need to first gather the full picture of what was + * enabled, and then make decisions. + */ +void init_mem_debugging_and_hardening(void) +{ + if (_init_on_alloc_enabled_early) { + if (page_poisoning_enabled()) + pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, " + "will take precedence over init_on_alloc\n"); + else + static_branch_enable(&init_on_alloc); + } + if (_init_on_free_enabled_early) { + if (page_poisoning_enabled()) + pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, " + "will take precedence over init_on_free\n"); + else + static_branch_enable(&init_on_free); + } + +#ifdef CONFIG_DEBUG_PAGEALLOC + if (!debug_pagealloc_enabled()) + return; + + static_branch_enable(&_debug_pagealloc_enabled); + + if (!debug_guardpage_minorder()) + return; + + static_branch_enable(&_debug_guardpage_enabled); +#endif +} + static inline void set_buddy_order(struct page *page, unsigned int order) { set_page_private(page, order); -- cgit v1.2.3-58-ga151