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Date: Mon, 26 Oct 2020 18:33:56 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Alexander Potapenko <glider@...gle.com>,
Kees Cook <keescook@...omium.org>,
Michal Hocko <mhocko@...nel.org>,
David Hildenbrand <david@...hat.com>,
Mateusz Nosek <mateusznosek0@...il.com>,
Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 1/3] mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters
Enabling page_poison=1 together with init_on_alloc=1 or init_on_free=1 produces
a warning in dmesg that page_poison takes precendence. 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() function for that,
and move the related debug_pagealloc processing there as well.
As a result init_mem_debugging() 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_* tracepoint at all, if page poisoning is
enabled. This results in a simpler and more effective code.
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
include/linux/mm.h | 20 ++--------
init/main.c | 2 +-
mm/page_alloc.c | 94 +++++++++++++++++++++++-----------------------
3 files changed, 50 insertions(+), 66 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ef360fe70aaf..c6a0adccf2fe 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2865,6 +2865,7 @@ extern int apply_to_existing_page_range(struct mm_struct *mm,
unsigned long address, unsigned long size,
pte_fn_t fn, void *data);
+extern void init_mem_debugging(void);
#ifdef CONFIG_PAGE_POISONING
extern bool page_poisoning_enabled(void);
extern void kernel_poison_pages(struct page *page, int numpages, int enable);
@@ -2874,35 +2875,20 @@ static inline void kernel_poison_pages(struct page *page, int numpages,
int enable) { }
#endif
-#ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON
-DECLARE_STATIC_KEY_TRUE(init_on_alloc);
-#else
DECLARE_STATIC_KEY_FALSE(init_on_alloc);
-#endif
static inline bool want_init_on_alloc(gfp_t flags)
{
- if (static_branch_unlikely(&init_on_alloc) &&
- !page_poisoning_enabled())
+ if (static_branch_unlikely(&init_on_alloc))
return true;
return flags & __GFP_ZERO;
}
-#ifdef CONFIG_INIT_ON_FREE_DEFAULT_ON
-DECLARE_STATIC_KEY_TRUE(init_on_free);
-#else
DECLARE_STATIC_KEY_FALSE(init_on_free);
-#endif
static inline bool want_init_on_free(void)
{
- return static_branch_unlikely(&init_on_free) &&
- !page_poisoning_enabled();
+ return static_branch_unlikely(&init_on_free);
}
-#ifdef CONFIG_DEBUG_PAGEALLOC
-extern void init_debug_pagealloc(void);
-#else
-static inline void init_debug_pagealloc(void) {}
-#endif
extern bool _debug_pagealloc_enabled_early;
DECLARE_STATIC_KEY_FALSE(_debug_pagealloc_enabled);
diff --git a/init/main.c b/init/main.c
index 130376ec10ba..dca5b9093742 100644
--- a/init/main.c
+++ b/init/main.c
@@ -815,7 +815,7 @@ static void __init mm_init(void)
* bigger than MAX_ORDER unless SPARSEMEM.
*/
page_ext_init_flatmem();
- init_debug_pagealloc();
+ init_mem_debugging();
report_meminit();
mem_init();
kmem_cache_init();
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 23f5066bd4a5..b168c58ef337 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -165,53 +165,26 @@ 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
+DEFINE_STATIC_KEY_FALSE_RO(init_on_alloc);
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
+DEFINE_STATIC_KEY_FALSE_RO(init_on_free);
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);
@@ -728,19 +701,6 @@ 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;
@@ -792,6 +752,44 @@ 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()
+{
+ 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);
--
2.29.0
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