From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86156C433EF for ; Tue, 12 Jul 2022 14:18:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233418AbiGLOR6 (ORCPT ); Tue, 12 Jul 2022 10:17:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233426AbiGLORj (ORCPT ); Tue, 12 Jul 2022 10:17:39 -0400 Received: from mail-yw1-x1136.google.com (mail-yw1-x1136.google.com [IPv6:2607:f8b0:4864:20::1136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7554CB3D4B for ; Tue, 12 Jul 2022 07:17:37 -0700 (PDT) Received: by mail-yw1-x1136.google.com with SMTP id 00721157ae682-31d7db3e6e5so51808327b3.11 for ; Tue, 12 Jul 2022 07:17:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fEuio4lP8DLja3+6yBSWoacIG45qoddRrq8lnL8+qJY=; b=A0yawrSyuBD1BrwqS6XcHwx7HkNd0M32tyf3plN3UdAYm30JPg6qQngknmH04thTbJ 01pYsA15md6pUA3C11uIz2irvTBZSdPs7zdizz+Aum6XH6V5I5bu+UiwYKvovCdHMDhY cCTn72UsXaPzlUEh+LalWHMPc1hi/zDNwfeGbIoJFuD5rYP10OnBSTa8QkIWy/kcIxOP jX+u42g5fYdEGJExuQBn2AMnycuF9sCpZ3v3/kakGZuz6NiSs0qxmuVIanloI5ObVSFR cBsdFV9KC60+VkN+0U2LN1JxoveviS8QUXyZW8fQdZv5Ga1AI9NHYySSL5skT1gUxkTG hf8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=fEuio4lP8DLja3+6yBSWoacIG45qoddRrq8lnL8+qJY=; b=sEmDuwJGJflakFJbVfTPtKZUlrBjh/u9ryPhC+hCUxosmoeg/Gz3+7NIwmQDz+YXc6 BHG1vFT1KNGbtQvYWQ8aK47wRfsNOih4aFz60neYcyUoqwybXl2C86uW+gS27h6BtAXL jZJYuIusmd4Tp4SMQCvBZ/7lP284bDptAB5675L17dFRVW++2QxuwGA/OOo+DPGDzFcY owoO24e9Wdlnk8iGDY5xybKjK+6SbkgCHZSF8X3kX1gRv4B2N243Y510gOPWFc9+53Ax fVf0pRAZqHpPOdOk1RNF+zhShiA9G9SgMAj5tT0+E7bF4BViZqR4ggEoHm1dL6VEBPJp G+pA== X-Gm-Message-State: AJIora/tBp3I7Y9XNLbbBW/jQz8BbiN0C9ml0GynOQpRy5wO+rpX1DRV 52ADVTxZJlcChvhCXle3Pf10bdE8cHeOkvPy+LNghw== X-Google-Smtp-Source: AGRyM1uQtghvNUKgdsR3kXQMmbgVawdVDZj57u52IyZ42Le1Qp7LffGVDk5K2rPGxqdKdxST/O5XSgOcyPO8vCvxbr8= X-Received: by 2002:a0d:cf07:0:b0:31d:17cb:ec11 with SMTP id r7-20020a0dcf07000000b0031d17cbec11mr26264367ywd.264.1657635456390; Tue, 12 Jul 2022 07:17:36 -0700 (PDT) MIME-Version: 1.0 References: <20220701142310.2188015-1-glider@google.com> <20220701142310.2188015-3-glider@google.com> In-Reply-To: <20220701142310.2188015-3-glider@google.com> From: Marco Elver Date: Tue, 12 Jul 2022 16:17:00 +0200 Message-ID: Subject: Re: [PATCH v4 02/45] stackdepot: reserve 5 extra bits in depot_stack_handle_t To: Alexander Potapenko Cc: Alexander Viro , Alexei Starovoitov , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 1 Jul 2022 at 16:23, Alexander Potapenko wrote: > > Some users (currently only KMSAN) may want to use spare bits in > depot_stack_handle_t. Let them do so by adding @extra_bits to > __stack_depot_save() to store arbitrary flags, and providing > stack_depot_get_extra_bits() to retrieve those flags. > > Also adapt KASAN to the new prototype by passing extra_bits=0, as KASAN > does not intend to store additional information in the stack handle. > > Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver > --- > v4: > -- per Marco Elver's request, fold "kasan: common: adapt to the new > prototype of __stack_depot_save()" into this patch to prevent > bisection breakages. > > Link: https://linux-review.googlesource.com/id/I0587f6c777667864768daf07821d594bce6d8ff9 > --- > include/linux/stackdepot.h | 8 ++++++++ > lib/stackdepot.c | 29 ++++++++++++++++++++++++----- > mm/kasan/common.c | 2 +- > 3 files changed, 33 insertions(+), 6 deletions(-) > > diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h > index bc2797955de90..9ca7798d7a318 100644 > --- a/include/linux/stackdepot.h > +++ b/include/linux/stackdepot.h > @@ -14,9 +14,15 @@ > #include > > typedef u32 depot_stack_handle_t; > +/* > + * Number of bits in the handle that stack depot doesn't use. Users may store > + * information in them. > + */ > +#define STACK_DEPOT_EXTRA_BITS 5 > > depot_stack_handle_t __stack_depot_save(unsigned long *entries, > unsigned int nr_entries, > + unsigned int extra_bits, > gfp_t gfp_flags, bool can_alloc); > > /* > @@ -59,6 +65,8 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, > unsigned int stack_depot_fetch(depot_stack_handle_t handle, > unsigned long **entries); > > +unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle); > + > int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, > int spaces); > > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > index 5ca0d086ef4a3..3d1dbdd5a87f6 100644 > --- a/lib/stackdepot.c > +++ b/lib/stackdepot.c > @@ -42,7 +42,8 @@ > #define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \ > STACK_ALLOC_ALIGN) > #define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \ > - STACK_ALLOC_NULL_PROTECTION_BITS - STACK_ALLOC_OFFSET_BITS) > + STACK_ALLOC_NULL_PROTECTION_BITS - \ > + STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS) > #define STACK_ALLOC_SLABS_CAP 8192 > #define STACK_ALLOC_MAX_SLABS \ > (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \ > @@ -55,6 +56,7 @@ union handle_parts { > u32 slabindex : STACK_ALLOC_INDEX_BITS; > u32 offset : STACK_ALLOC_OFFSET_BITS; > u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS; > + u32 extra : STACK_DEPOT_EXTRA_BITS; > }; > }; > > @@ -76,6 +78,14 @@ static int next_slab_inited; > static size_t depot_offset; > static DEFINE_RAW_SPINLOCK(depot_lock); > > +unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle) > +{ > + union handle_parts parts = { .handle = handle }; > + > + return parts.extra; > +} > +EXPORT_SYMBOL(stack_depot_get_extra_bits); > + > static bool init_stack_slab(void **prealloc) > { > if (!*prealloc) > @@ -139,6 +149,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) > stack->handle.slabindex = depot_index; > stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN; > stack->handle.valid = 1; > + stack->handle.extra = 0; > memcpy(stack->entries, entries, flex_array_size(stack, entries, size)); > depot_offset += required_size; > > @@ -343,6 +354,7 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); > * > * @entries: Pointer to storage array > * @nr_entries: Size of the storage array > + * @extra_bits: Flags to store in unused bits of depot_stack_handle_t > * @alloc_flags: Allocation gfp flags > * @can_alloc: Allocate stack slabs (increased chance of failure if false) > * > @@ -354,6 +366,10 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); > * If the stack trace in @entries is from an interrupt, only the portion up to > * interrupt entry is saved. > * > + * Additional opaque flags can be passed in @extra_bits, stored in the unused > + * bits of the stack handle, and retrieved using stack_depot_get_extra_bits() > + * without calling stack_depot_fetch(). > + * > * Context: Any context, but setting @can_alloc to %false is required if > * alloc_pages() cannot be used from the current context. Currently > * this is the case from contexts where neither %GFP_ATOMIC nor > @@ -363,10 +379,11 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); > */ > depot_stack_handle_t __stack_depot_save(unsigned long *entries, > unsigned int nr_entries, > + unsigned int extra_bits, > gfp_t alloc_flags, bool can_alloc) > { > struct stack_record *found = NULL, **bucket; > - depot_stack_handle_t retval = 0; > + union handle_parts retval = { .handle = 0 }; > struct page *page = NULL; > void *prealloc = NULL; > unsigned long flags; > @@ -450,9 +467,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, > free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER); > } > if (found) > - retval = found->handle.handle; > + retval.handle = found->handle.handle; > fast_exit: > - return retval; > + retval.extra = extra_bits; > + > + return retval.handle; > } > EXPORT_SYMBOL_GPL(__stack_depot_save); > > @@ -472,6 +491,6 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, > unsigned int nr_entries, > gfp_t alloc_flags) > { > - return __stack_depot_save(entries, nr_entries, alloc_flags, true); > + return __stack_depot_save(entries, nr_entries, 0, alloc_flags, true); > } > EXPORT_SYMBOL_GPL(stack_depot_save); > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index c40c0e7b3b5f1..ba4fceeec173c 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -36,7 +36,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) > unsigned int nr_entries; > > nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); > - return __stack_depot_save(entries, nr_entries, flags, can_alloc); > + return __stack_depot_save(entries, nr_entries, 0, flags, can_alloc); > } > > void kasan_set_track(struct kasan_track *track, gfp_t flags) > -- > 2.37.0.rc0.161.g10f37bed90-goog >