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From: Daniel Axtens <dja@axtens.net>
To: kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org,
	aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org,
	linux-kernel@vger.kernel.org, mark.rutland@arm.com,
	dvyukov@google.com, christophe.leroy@c-s.fr
Cc: linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com,
	Daniel Axtens <dja@axtens.net>
Subject: [PATCH v9 5/5] kasan debug: track pages allocated for vmalloc shadow
Date: Thu, 17 Oct 2019 12:25:06 +1100	[thread overview]
Message-ID: <20191017012506.28503-6-dja@axtens.net> (raw)
In-Reply-To: <20191017012506.28503-1-dja@axtens.net>

Provide the current number of vmalloc shadow pages in
/sys/kernel/debug/kasan/vmalloc_shadow_pages.

Signed-off-by: Daniel Axtens <dja@axtens.net>

---

v8: rename kasan_vmalloc/shadow_pages -> kasan/vmalloc_shadow_pages

On v4 (no dynamic freeing), I saw the following approximate figures
on my test VM:

 - fresh boot: 720
 - after test_vmalloc: ~14000

With v5 (lazy dynamic freeing):

 - boot: ~490-500
 - running modprobe test_vmalloc pushes the figures up to sometimes
    as high as ~14000, but they drop down to ~560 after the test ends.
    I'm not sure where the extra sixty pages are from, but running the
    test repeately doesn't cause the number to keep growing, so I don't
    think we're leaking.
 - with vmap_stack, spawning tasks pushes the figure up to ~4200, then
    some clearing kicks in and drops it down to previous levels again.
---
 mm/kasan/common.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git mm/kasan/common.c mm/kasan/common.c
index 81521d180bec..ac05038afa5a 100644
--- mm/kasan/common.c
+++ mm/kasan/common.c
@@ -35,6 +35,7 @@
 #include <linux/vmalloc.h>
 #include <linux/bug.h>
 #include <linux/uaccess.h>
+#include <linux/debugfs.h>
 
 #include <asm/tlbflush.h>
 
@@ -750,6 +751,8 @@ core_initcall(kasan_memhotplug_init);
 #endif
 
 #ifdef CONFIG_KASAN_VMALLOC
+static u64 vmalloc_shadow_pages;
+
 static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 				      void *unused)
 {
@@ -782,6 +785,7 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 	if (likely(pte_none(*ptep))) {
 		set_pte_at(&init_mm, addr, ptep, pte);
 		page = 0;
+		vmalloc_shadow_pages++;
 	}
 	spin_unlock(&init_mm.page_table_lock);
 	if (page)
@@ -836,6 +840,7 @@ static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 		pte_clear(&init_mm, addr, ptep);
 		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 		free_page(page);
+		vmalloc_shadow_pages--;
 	}
 	spin_unlock(&init_mm.page_table_lock);
 
@@ -954,4 +959,25 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
 				       (unsigned long)shadow_end);
 	}
 }
+
+static __init int kasan_init_debugfs(void)
+{
+	struct dentry *root, *count;
+
+	root = debugfs_create_dir("kasan", NULL);
+	if (IS_ERR(root)) {
+		if (PTR_ERR(root) == -ENODEV)
+			return 0;
+		return PTR_ERR(root);
+	}
+
+	count = debugfs_create_u64("vmalloc_shadow_pages", 0444, root,
+				   &vmalloc_shadow_pages);
+
+	if (IS_ERR(count))
+		return PTR_ERR(root);
+
+	return 0;
+}
+late_initcall(kasan_init_debugfs);
 #endif
-- 
2.20.1



      parent reply	other threads:[~2019-10-17  1:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17  1:25 [PATCH v9 0/5] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-10-17  1:25 ` [PATCH v9 1/5] " Daniel Axtens
2019-10-17  1:25 ` [PATCH v9 2/5] kasan: add test for vmalloc Daniel Axtens
2019-10-17  1:25 ` [PATCH v9 3/5] fork: support VMAP_STACK with KASAN_VMALLOC Daniel Axtens
2019-10-17  1:25 ` [PATCH v9 4/5] x86/kasan: support KASAN_VMALLOC Daniel Axtens
2019-10-17  1:25 ` Daniel Axtens [this message]

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