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Wed, 03 Aug 2022 13:09:36 -0700 (PDT) Date: Wed, 3 Aug 2022 22:09:29 +0200 From: Marco Elver To: andrey.konovalov@linux.dev Cc: Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, Peter Collingbourne , Evgenii Stepanov , Florian Mayer , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov Subject: Re: [PATCH mm v2 32/33] kasan: dynamically allocate stack ring entries Message-ID: References: <4db564768f1cb900b9687849a062156b470eb902.1658189199.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4db564768f1cb900b9687849a062156b470eb902.1658189199.git.andreyknvl@google.com> User-Agent: Mutt/2.2.4 (2022-04-30) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659557378; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf06.hostedemail.com: domain of elver@google.com designates 209.85.221.41 as permitted sender) smtp.mailfrom=elver@google.com X-Rspam-User: X-HE-Tag: 1659557378-695514 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 19, 2022 at 02:10AM +0200, andrey.konovalov@linux.dev wrote: > From: Andrey Konovalov > > Instead of using a large static array, allocate the stack ring dynamically > via memblock_alloc(). > > The size of the stack ring is controlled by a new kasan.stack_ring_size > command-line parameter. When kasan.stack_ring_size is not provided, the > default value of 32 << 10 is used. > > When the stack trace collection is disabled via kasan.stacktrace=off, > the stack ring is not allocated. > > Signed-off-by: Andrey Konovalov > > --- > > Changes v1->v2: > - This is a new patch. > --- > mm/kasan/kasan.h | 5 +++-- > mm/kasan/report_tags.c | 4 ++-- > mm/kasan/tags.c | 22 +++++++++++++++++++++- > 3 files changed, 26 insertions(+), 5 deletions(-) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 447baf1a7a2e..4afe4db751da 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -252,12 +252,13 @@ struct kasan_stack_ring_entry { > bool is_free; > }; > > -#define KASAN_STACK_RING_SIZE (32 << 10) > +#define KASAN_STACK_RING_SIZE_DEFAULT (32 << 10) > This could be moved to tags.c, as there are no other users elsewhere. > struct kasan_stack_ring { > rwlock_t lock; > + size_t size; > atomic64_t pos; > - struct kasan_stack_ring_entry entries[KASAN_STACK_RING_SIZE]; > + struct kasan_stack_ring_entry *entries; > }; > > #endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */ > diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c > index a996489e6dac..7e267e69ce19 100644 > --- a/mm/kasan/report_tags.c > +++ b/mm/kasan/report_tags.c > @@ -56,11 +56,11 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info) > * entries relevant to the buggy object can be overwritten. > */ > > - for (u64 i = pos - 1; i != pos - 1 - KASAN_STACK_RING_SIZE; i--) { > + for (u64 i = pos - 1; i != pos - 1 - stack_ring.size; i--) { > if (alloc_found && free_found) > break; > > - entry = &stack_ring.entries[i % KASAN_STACK_RING_SIZE]; > + entry = &stack_ring.entries[i % stack_ring.size]; > > /* Paired with smp_store_release() in save_stack_info(). */ > ptr = (void *)smp_load_acquire(&entry->ptr); > diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c > index 0eb6cf6717db..fd8c5f919156 100644 > --- a/mm/kasan/tags.c > +++ b/mm/kasan/tags.c > @@ -10,6 +10,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -52,6 +53,16 @@ static int __init early_kasan_flag_stacktrace(char *arg) > } > early_param("kasan.stacktrace", early_kasan_flag_stacktrace); > > +/* kasan.stack_ring_size=32768 */ What does that comment say? Is it "kasan.stack_ring_size="? Is it already in the documentation? > +static int __init early_kasan_flag_stack_ring_size(char *arg) > +{ > + if (!arg) > + return -EINVAL; > + > + return kstrtoul(arg, 0, &stack_ring.size); > +} > +early_param("kasan.stack_ring_size", early_kasan_flag_stack_ring_size); > + > void __init kasan_init_tags(void) > { > switch (kasan_arg_stacktrace) { > @@ -65,6 +76,15 @@ void __init kasan_init_tags(void) > static_branch_enable(&kasan_flag_stacktrace); > break; > } > + > + if (kasan_stack_collection_enabled()) { > + if (!stack_ring.size) > + stack_ring.size = KASAN_STACK_RING_SIZE_DEFAULT; > + stack_ring.entries = memblock_alloc( > + sizeof(stack_ring.entries[0]) * > + stack_ring.size, > + SMP_CACHE_BYTES); memblock_alloc() can fail. Because unlikely, stack collection should probably just be disabled. (minor: excessive line breaks makes the above unreadable.) > + } > } > > static void save_stack_info(struct kmem_cache *cache, void *object, > @@ -86,7 +106,7 @@ static void save_stack_info(struct kmem_cache *cache, void *object, > > next: > pos = atomic64_fetch_add(1, &stack_ring.pos); > - entry = &stack_ring.entries[pos % KASAN_STACK_RING_SIZE]; > + entry = &stack_ring.entries[pos % stack_ring.size]; > > /* Detect stack ring entry slots that are being written to. */ > old_ptr = READ_ONCE(entry->ptr); > -- > 2.25.1