anolis: kfence: add PG_kfence to recognize kfence address in fast path

ANBZ: #28

To improve performance, we add PG_kfence flag to recognize whether an
address is in kfence pool first. If true, other works may be done by
calling no-inline functions.

Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Reviewed-by: Xunlei Pang <xlpang@linux.alibaba.com>

include/linux/kfence.h

@@ -70,10 +70,7 @@ static __always_inline bool is_kfence_address_node(const void *addr, const int n
  */
 static __always_inline bool is_kfence_address(const void *addr)
 {
-	if (!static_branch_unlikely(&kfence_once_inited) || unlikely(!virt_addr_valid(addr)))
+	return static_branch_unlikely(&kfence_once_inited) && PageKfence(virt_to_page(addr));
-		return false;
-
-	return unlikely(is_kfence_address_node(addr, page_to_nid(virt_to_page(addr))));
 }
 
 /**
@@ -273,12 +270,10 @@ static __always_inline __must_check bool kfence_free_page(struct page *page)
 {
 	void *addr;
 
-	if (!static_branch_unlikely(&kfence_once_inited))
+	if (!static_branch_unlikely(&kfence_once_inited) || !PageKfence(page))
 		return false;
 
 	addr = page_to_virt(page);
-	if (!is_kfence_address_node(addr, page_to_nid(page)))
-		return false;
 	__kfence_free_page(page, addr);
 	return true;
 }

include/linux/page-flags.h

@@ -141,6 +141,9 @@ enum pageflags {
 #endif
 #ifdef CONFIG_DUPTEXT
 	PG_dup,			/* Page has NUMA replicas */
+#endif
+#ifdef CONFIG_KFENCE
+	PG_kfence,		/* Page in kfence pool */
 #endif
 	__NR_PAGEFLAGS,
 
@@ -460,6 +463,10 @@ __PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
 PAGEFLAG(Dup, dup, PF_HEAD)
 #endif
 
+#ifdef CONFIG_KFENCE
+__PAGEFLAG(Kfence, kfence, PF_ANY)
+#endif
+
 /*
  * On an anonymous page mapped into a user virtual memory area,
  * page->mapping points to its anon_vma, not to a struct address_space;
@@ -858,6 +865,12 @@ static inline void ClearPageSlabPfmemalloc(struct page *page)
 #define __PG_DUP		0
 #endif
 
+#ifdef CONFIG_KFENCE
+#define __PG_KFENCE		(1UL << PG_kfence)
+#else
+#define __PG_KFENCE		0
+#endif
+
 /*
  * Flags checked when a page is freed.  Pages being freed should not have
  * these flags set.  It they are, there is a problem.

include/trace/events/mmflags.h

@@ -91,6 +91,12 @@
 #define IF_HAVE_PG_DUP(flag,string)
 #endif
 
+#ifdef CONFIG_KFENCE
+#define IF_HAVE_PG_KFENCE(flag,string) ,{1UL << flag, string}
+#else
+#define IF_HAVE_PG_KFENCE(flag,string)
+#endif
+
 #define __def_pageflag_names						\
 	{1UL << PG_locked,		"locked"	},		\
 	{1UL << PG_waiters,		"waiters"	},		\
@@ -119,7 +125,8 @@ IF_HAVE_PG_HWPOISON(PG_hwpoison,	"hwpoison"	)		\
 IF_HAVE_PG_IDLE(PG_young,		"young"		)		\
 IF_HAVE_PG_IDLE(PG_idle,		"idle"		)		\
 IF_HAVE_PG_ARCH_2(PG_arch_2,		"arch_2"	)		\
-IF_HAVE_PG_DUP(PG_dup,			"dup"		)
+IF_HAVE_PG_DUP(PG_dup,			"dup"		)		\
+IF_HAVE_PG_KFENCE(PG_kfence,		"kfence"	)
 
 #define show_page_flags(flags)						\
 	(flags) ? __print_flags(flags, "|",				\

mm/kfence/core.c

@@ -748,6 +748,21 @@ static void rcu_guarded_free(struct rcu_head *h)
 	kfence_guarded_free((void *)meta->addr, meta, false);
 }
 
+static inline void kfence_clear_page_info(unsigned long addr, unsigned long size)
+{
+	unsigned long i;
+
+	for (i = addr; i < addr + size; i += PAGE_SIZE) {
+		struct page *page = virt_to_page(i);
+
+		__ClearPageKfence(page);
+		__ClearPageSlab(page);
+		page->mapping = NULL;
+		atomic_set(&page->_refcount, 1);
+		kfence_unprotect(i);
+	}
+}
+
 static bool __init kfence_init_pool_node(int node)
 {
 	char *__kfence_pool = __kfence_pool_node[node];
@@ -775,6 +790,8 @@ static bool __init kfence_init_pool_node(int node)
 	 * enters __slab_free() slow-path.
 	 */
 	for (i = 0; i < kfence_pool_size / PAGE_SIZE; i++) {
+		__SetPageKfence(&pages[i]);
+
 		if (!i || (i % 2))
 			continue;
 
@@ -826,13 +843,11 @@ static bool __init kfence_init_pool_node(int node)
 
 err:
 	/*
-	 * Only release unprotected pages, and do not try to go back and change
+	 * We will support freeing unused kfence pools in the following patches,
-	 * page attributes due to risk of failing to do so as well. If changing
+	 * so here we can also free all pages in the pool.
-	 * page attributes for some pages fails, it is very likely that it also
-	 * fails for the first page, and therefore expect addr==__kfence_pool in
-	 * most failure cases.
 	 */
-	memblock_free_late(__pa(addr), kfence_pool_size - (addr - (unsigned long)__kfence_pool));
+	kfence_clear_page_info((unsigned long)__kfence_pool, kfence_pool_size);
+	memblock_free_late(__pa(__kfence_pool), kfence_pool_size);
 	memblock_free_late(__pa(kfence_metadata), metadata_size);
 	__kfence_pool_node[node] = NULL;
 	kfence_metadata_node[node] = NULL;

mm/page_alloc.c

@@ -1281,7 +1281,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
 
 	page_cpupid_reset_last(page);
 	kidled_set_page_age(page_pgdat(page), page_to_pfn(page), 0);
-	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_KFENCE;
 	reset_page_owner(page, order);
 
 	if (!PageHighMem(page)) {