From: Uladzislau Rezki <urezki@gmail.com>
To: Daniel Axtens <dja@axtens.net>
Cc: 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,
linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com
Subject: Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory
Date: Mon, 7 Oct 2019 10:02:09 +0200 [thread overview]
Message-ID: <20191007080209.GA22997@pc636> (raw)
In-Reply-To: <20191001065834.8880-2-dja@axtens.net>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a3c70e275f4e..9fb7a16f42ae 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -690,8 +690,19 @@ merge_or_add_vmap_area(struct vmap_area *va,
> struct list_head *next;
> struct rb_node **link;
> struct rb_node *parent;
> + unsigned long orig_start, orig_end;
> bool merged = false;
>
> + /*
> + * To manage KASAN vmalloc memory usage, we use this opportunity to
> + * clean up the shadow memory allocated to back this allocation.
> + * Because a vmalloc shadow page covers several pages, the start or end
> + * of an allocation might not align with a shadow page. Use the merging
> + * opportunities to try to extend the region we can release.
> + */
> + orig_start = va->va_start;
> + orig_end = va->va_end;
> +
> /*
> * Find a place in the tree where VA potentially will be
> * inserted, unless it is merged with its sibling/siblings.
> @@ -741,6 +752,10 @@ merge_or_add_vmap_area(struct vmap_area *va,
> if (sibling->va_end == va->va_start) {
> sibling->va_end = va->va_end;
>
> + kasan_release_vmalloc(orig_start, orig_end,
> + sibling->va_start,
> + sibling->va_end);
> +
> /* Check and update the tree if needed. */
> augment_tree_propagate_from(sibling);
>
> @@ -754,6 +769,8 @@ merge_or_add_vmap_area(struct vmap_area *va,
> }
>
> insert:
> + kasan_release_vmalloc(orig_start, orig_end, va->va_start, va->va_end);
> +
> if (!merged) {
> link_va(va, root, parent, link, head);
> augment_tree_propagate_from(va);
Hello, Daniel.
Looking at it one more, i think above part of code is a bit wrong
and should be separated from merge_or_add_vmap_area() logic. The
reason is to keep it simple and do only what it is supposed to do:
merging or adding.
Also the kasan_release_vmalloc() gets called twice there and looks like
a duplication. Apart of that, merge_or_add_vmap_area() can be called via
recovery path when vmap/vmaps is/are not even setup. See percpu
allocator.
I guess your part could be moved directly to the __purge_vmap_area_lazy()
where all vmaps are lazily freed. To do so, we also need to modify
merge_or_add_vmap_area() to return merged area:
<snip>
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index e92ff5f7dd8b..fecde4312d68 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -683,7 +683,7 @@ insert_vmap_area_augment(struct vmap_area *va,
* free area is inserted. If VA has been merged, it is
* freed.
*/
-static __always_inline void
+static __always_inline struct vmap_area *
merge_or_add_vmap_area(struct vmap_area *va,
struct rb_root *root, struct list_head *head)
{
@@ -750,7 +750,10 @@ merge_or_add_vmap_area(struct vmap_area *va,
/* Free vmap_area object. */
kmem_cache_free(vmap_area_cachep, va);
- return;
+
+ /* Point to the new merged area. */
+ va = sibling;
+ merged = true;
}
}
@@ -759,6 +762,8 @@ merge_or_add_vmap_area(struct vmap_area *va,
link_va(va, root, parent, link, head);
augment_tree_propagate_from(va);
}
+
+ return va;
}
static __always_inline bool
@@ -1172,7 +1177,7 @@ static void __free_vmap_area(struct vmap_area *va)
/*
* Merge VA with its neighbors, otherwise just add it.
*/
- merge_or_add_vmap_area(va,
+ (void) merge_or_add_vmap_area(va,
&free_vmap_area_root, &free_vmap_area_list);
}
@@ -1279,15 +1284,20 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
spin_lock(&vmap_area_lock);
llist_for_each_entry_safe(va, n_va, valist, purge_list) {
unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT;
+ unsigned long orig_start = va->va_start;
+ unsigned long orig_end = va->va_end;
/*
* Finally insert or merge lazily-freed area. It is
* detached and there is no need to "unlink" it from
* anything.
*/
- merge_or_add_vmap_area(va,
+ va = merge_or_add_vmap_area(va,
&free_vmap_area_root, &free_vmap_area_list);
+ kasan_release_vmalloc(orig_start,
+ orig_end, va->va_start, va->va_end);
+
atomic_long_sub(nr, &vmap_lazy_nr);
if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)
<snip>
--
Vlad Rezki
next prev parent reply other threads:[~2019-10-07 8:02 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-01 6:58 [PATCH v8 0/5] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 1/5] " Daniel Axtens
2019-10-01 10:17 ` Uladzislau Rezki
2019-10-02 1:23 ` Daniel Axtens
2019-10-02 7:13 ` Christophe Leroy
2019-10-02 11:49 ` Uladzislau Rezki
2019-10-07 8:02 ` Uladzislau Rezki [this message]
2019-10-11 5:15 ` Daniel Axtens
2019-10-11 19:57 ` Andrey Ryabinin
2019-10-14 13:57 ` Daniel Axtens
2019-10-14 15:27 ` Mark Rutland
2019-10-15 6:32 ` Daniel Axtens
2019-10-15 6:29 ` Daniel Axtens
2019-10-16 12:19 ` Andrey Ryabinin
2019-10-16 13:22 ` Mark Rutland
2019-10-18 10:43 ` Andrey Ryabinin
2019-10-28 7:39 ` Daniel Axtens
2019-10-28 1:26 ` Daniel Axtens
2019-10-14 15:43 ` Mark Rutland
2019-10-15 6:27 ` Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 2/5] kasan: add test for vmalloc Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 3/5] fork: support VMAP_STACK with KASAN_VMALLOC Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 4/5] x86/kasan: support KASAN_VMALLOC Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 5/5] kasan debug: track pages allocated for vmalloc shadow Daniel Axtens
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=20191007080209.GA22997@pc636 \
--to=urezki@gmail.com \
--cc=aryabinin@virtuozzo.com \
--cc=christophe.leroy@c-s.fr \
--cc=dja@axtens.net \
--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).