From: Daniel Axtens <dja@axtens.net>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: kasan-dev <kasan-dev@googlegroups.com>,
Linux Memory Management List <linux-mm@kvack.org>,
the arch/x86 maintainers <x86@kernel.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Andy Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Dmitry Vyukov <dvyukov@google.com>,
Christophe Leroy <christophe.leroy@c-s.fr>,
PowerPC <linuxppc-dev@lists.ozlabs.org>,
gor@linux.ibm.com
Subject: Re: [PATCH v7 5/5] kasan debug: track pages allocated for vmalloc shadow
Date: Wed, 04 Sep 2019 09:41:51 +1000 [thread overview]
Message-ID: <87ef0xt0ao.fsf@dja-thinkpad.axtens.net> (raw)
In-Reply-To: <CAAeHK+w_HKVh___E0j3hctt_efSPR3PwKuO5XNpf=w5obfYSSA@mail.gmail.com>
Andrey Konovalov <andreyknvl@google.com> writes:
> On Tue, Sep 3, 2019 at 4:56 PM Daniel Axtens <dja@axtens.net> wrote:
>>
>> Provide the current number of vmalloc shadow pages in
>> /sys/kernel/debug/kasan_vmalloc/shadow_pages.
>
> Maybe it makes sense to put this into /sys/kernel/debug/kasan/
> (without _vmalloc) and name e.g. vmalloc_shadow_pages? In case we want
> to expose more generic KASAN debugging info later.
We certainly could. I just wonder if this patch is useful on an ongoing
basis. I wrote it to validate my work on lazy freeing of shadow pages -
which is why I included it - but I'm not sure it has much ongoing value
beyond demonstrating that the freeing code works.
If we think it's worth holding on to this patch, I can certainly adjust
the paths.
Regards,
Daniel
>
>>
>> Signed-off-by: Daniel Axtens <dja@axtens.net>
>>
>> ---
>>
>> Merging this is probably overkill, but I leave it to the discretion
>> of the broader community.
>>
>> 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..e40854512417 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_vmalloc_debugfs(void)
>> +{
>> + struct dentry *root, *count;
>> +
>> + root = debugfs_create_dir("kasan_vmalloc", NULL);
>> + if (IS_ERR(root)) {
>> + if (PTR_ERR(root) == -ENODEV)
>> + return 0;
>> + return PTR_ERR(root);
>> + }
>> +
>> + count = debugfs_create_u64("shadow_pages", 0444, root,
>> + &vmalloc_shadow_pages);
>> +
>> + if (IS_ERR(count))
>> + return PTR_ERR(root);
>> +
>> + return 0;
>> +}
>> +late_initcall(kasan_init_vmalloc_debugfs);
>> #endif
>> --
>> 2.20.1
>>
>> --
>> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
>> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
>> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20190903145536.3390-6-dja%40axtens.net.
next prev parent reply other threads:[~2019-09-03 23:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 14:55 [PATCH v7 0/5] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-09-03 14:55 ` [PATCH v7 1/5] " Daniel Axtens
2019-09-03 14:55 ` [PATCH v7 2/5] kasan: add test for vmalloc Daniel Axtens
2019-09-03 14:55 ` [PATCH v7 3/5] fork: support VMAP_STACK with KASAN_VMALLOC Daniel Axtens
2019-09-03 14:55 ` [PATCH v7 4/5] x86/kasan: support KASAN_VMALLOC Daniel Axtens
2019-09-03 14:55 ` [PATCH v7 5/5] kasan debug: track pages allocated for vmalloc shadow Daniel Axtens
2019-09-03 15:01 ` Andrey Konovalov
2019-09-03 23:41 ` Daniel Axtens [this message]
2019-09-11 6:27 ` [PATCH v7 0/5] kasan: support backing vmalloc space with real shadow memory Christophe Leroy
2019-09-11 11:20 ` Daniel Axtens
2019-09-11 12:38 ` Christophe Leroy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87ef0xt0ao.fsf@dja-thinkpad.axtens.net \
--to=dja@axtens.net \
--cc=andreyknvl@google.com \
--cc=aryabinin@virtuozzo.com \
--cc=christophe.leroy@c-s.fr \
--cc=dvyukov@google.com \
--cc=glider@google.com \
--cc=gor@linux.ibm.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=luto@kernel.org \
--cc=mark.rutland@arm.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).