[PATCH v8 5/5] kasan debug: track pages allocated for vmalloc shadow
From: Daniel Axtens <hidden>
Date: 2019-10-01 06:59:11
Also in:
linux-mm, lkml
Subsystem:
kasan, memory management, the rest · Maintainers:
Andrey Ryabinin, Andrew Morton, Linus Torvalds
Provide the current number of vmalloc shadow pages in
/sys/kernel/debug/kasan/vmalloc_shadow_pages.
Signed-off-by: Daniel Axtens <redacted>
---
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 a/mm/kasan/common.c b/mm/kasan/common.c
index e33cbab83309..5b924f860a32 100644
--- a/mm/kasan/common.c
+++ b/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) {
@@ -776,6 +779,7 @@ 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)
@@ -829,6 +833,7 @@ static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, if (likely(!pte_none(*ptep))) { pte_clear(&init_mm, addr, ptep); free_page(page); + vmalloc_shadow_pages--; } spin_unlock(&init_mm.page_table_lock);
@@ -947,4 +952,25 @@ 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