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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4979CC433EF for ; Sun, 13 Mar 2022 23:44:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B206D6B0073; Sun, 13 Mar 2022 19:44:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AD05A6B0074; Sun, 13 Mar 2022 19:44:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 970716B0075; Sun, 13 Mar 2022 19:44:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0074.hostedemail.com [216.40.44.74]) by kanga.kvack.org (Postfix) with ESMTP id 8A6C76B0073 for ; Sun, 13 Mar 2022 19:44:19 -0400 (EDT) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 3C5F2181A5F8E for ; Sun, 13 Mar 2022 23:44:19 +0000 (UTC) X-FDA: 79240994238.31.FBA5DA1 Received: from mail-io1-f50.google.com (mail-io1-f50.google.com [209.85.166.50]) by imf24.hostedemail.com (Postfix) with ESMTP id C091318002C for ; Sun, 13 Mar 2022 23:44:18 +0000 (UTC) Received: by mail-io1-f50.google.com with SMTP id q11so16324217iod.6 for ; Sun, 13 Mar 2022 16:44:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8Y6GoVLUy81HdtypjoVfjZaaJkl3pvlY7l5U9nDab9U=; b=QwLaq6hTTwazfXOiSsmqZNItgMiNPPIF5v/VcRYcoPJN3WWYE7bdHvvdWAaqC3OlVz oPJGPf66ZBl4A0+VmVY3Tw0RLSKsYm5/HhaLtCl9Vqc71ZBAHlayUdu6s4TrxytdExxm KvPSFgLBMVsolLw2zCg8KYT6FfNMEYXCvLIlfKwWV+TeUaIn7n0xxqpF8E7EOu6yFnW3 ijMsimaSals9IiEfkXplc4KlOizcvlfOhBys83quskTgatcBXVFcmPsrpyFZXeBF2Ku/ OQwgaRd+ZRunYwVQjuhR0Uk4hJQtMmtlb82wSAnqmZBRG70umgZOVLxIBiPV01rJtvHf q2xw== 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=8Y6GoVLUy81HdtypjoVfjZaaJkl3pvlY7l5U9nDab9U=; b=lymSY0pqZ+HbHsHuTi1PA9uAM9YRIywn1OTK+eeG+UT426m4y0DX0O/AaesoKEq7Vr kt9Qdth6DNU1iSS0xgQenKustoPzoiAkD+cg6uz4U2eoS1btNGvoJkztnEZaLF6tzAi0 sxDS4gQOSF5EluG2s0ZMypzkQvdxS2xeb+VYl3PdJSpt3G+KeSWwfXjyEKU6S52o+7El GglDlaHoqtfGCuMSo6pM/HypnxM949tym6o8iYbErFP2Y005xt5VHsVYAFHuexc06N1J c3DOwsrFedj1CHRV+Y9QnYtL8N6r1LVlGDnoNkNSq1IXgePYFFlUmdRbsMwkFyPBHUkj +hDg== X-Gm-Message-State: AOAM532J7YNVbxZi1xIlXfVLGHxS4lZy61AOZaE7dNMf6WEuTlQNOJBU 9JFLHCOKjvbbmDFwvnM/xJljSAkYiFJ/xXXWO5M= X-Google-Smtp-Source: ABdhPJxeUMr9fsIxWbNq8YPG7hWDuaKrG8FpeP86LODHC0n6rpPIvhGNr5tMXeV/8gLdZ46qI7Is52Al8WDXVx7fWHg= X-Received: by 2002:a05:6602:2b8e:b0:5e9:74e7:6b01 with SMTP id r14-20020a0566022b8e00b005e974e76b01mr17690829iov.127.1647215058035; Sun, 13 Mar 2022 16:44:18 -0700 (PDT) MIME-Version: 1.0 References: <57133fafc4d74377a4a08d98e276d58fe4a127dc.1647115974.git.andreyknvl@google.com> In-Reply-To: <57133fafc4d74377a4a08d98e276d58fe4a127dc.1647115974.git.andreyknvl@google.com> From: Andrey Konovalov Date: Mon, 14 Mar 2022 00:44:07 +0100 Message-ID: Subject: Re: [PATCH] kasan, scs: collect stack traces from shadow stack To: andrey.konovalov@linux.dev Cc: Marco Elver , Alexander Potapenko , Andrew Morton , Dmitry Vyukov , Andrey Ryabinin , kasan-dev , Vincenzo Frascino , Catalin Marinas , Will Deacon , Mark Rutland , Sami Tolvanen , Peter Collingbourne , Evgenii Stepanov , Linux Memory Management List , LKML , Andrey Konovalov , Florian Mayer Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: C091318002C Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=QwLaq6hT; spf=pass (imf24.hostedemail.com: domain of andreyknvl@gmail.com designates 209.85.166.50 as permitted sender) smtp.mailfrom=andreyknvl@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Stat-Signature: qxjz5i53efye5h4gd7t88gcymnyzhzoe X-HE-Tag: 1647215058-155428 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 Sat, Mar 12, 2022 at 9:14 PM wrote: > > From: Andrey Konovalov > > Currently, KASAN always uses the normal stack trace collection routines, > which rely on the unwinder, when saving alloc and free stack traces. > > Instead of invoking the unwinder, collect the stack trace by copying > frames from the Shadow Call Stack whenever it is enabled. This reduces > boot time by 30% for all KASAN modes when Shadow Call Stack is enabled. > > To avoid potentially leaking PAC pointer tags, strip them when saving > the stack trace. > > Signed-off-by: Andrey Konovalov > > --- > > Things to consider: > > We could integrate shadow stack trace collection into kernel/stacktrace.c > as e.g. stack_trace_save_shadow(). However, using stack_trace_consume_fn > leads to invoking a callback on each saved from, which is undesirable. > The plain copy loop is faster. > > We could add a command line flag to switch between stack trace collection > modes. I noticed that Shadow Call Stack might be missing certain frames > in stacks originating from a fault that happens in the middle of a > function. I am not sure if this case is important to handle though. > > Looking forward to thoughts and comments. > > Thanks! > > --- > mm/kasan/common.c | 36 +++++++++++++++++++++++++++++++++++- > 1 file changed, 35 insertions(+), 1 deletion(-) > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index d9079ec11f31..65a0723370c7 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -9,6 +9,7 @@ > * Andrey Konovalov > */ > > +#include > #include > #include > #include > @@ -21,6 +22,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -30,12 +32,44 @@ > #include "kasan.h" > #include "../slab.h" > > +#ifdef CONFIG_SHADOW_CALL_STACK > + > +#ifdef CONFIG_ARM64_PTR_AUTH > +#define PAC_TAG_RESET(x) (x | GENMASK(63, CONFIG_ARM64_VA_BITS)) > +#else > +#define PAC_TAG_RESET(x) (x) > +#endif > + > +static unsigned int save_shadow_stack(unsigned long *entries, > + unsigned int nr_entries) > +{ > + unsigned long *scs_sp = task_scs_sp(current); > + unsigned long *scs_base = task_scs(current); > + unsigned long *frame; > + unsigned int i = 0; > + > + for (frame = scs_sp - 1; frame >= scs_base; frame--) { > + entries[i++] = PAC_TAG_RESET(*frame); > + if (i >= nr_entries) > + break; > + } > + > + return i; > +} > +#else /* CONFIG_SHADOW_CALL_STACK */ > +static inline unsigned int save_shadow_stack(unsigned long *entries, > + unsigned int nr_entries) { return 0; } > +#endif /* CONFIG_SHADOW_CALL_STACK */ > + > depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) > { > unsigned long entries[KASAN_STACK_DEPTH]; > unsigned int nr_entries; > > - nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); > + if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) > + nr_entries = save_shadow_stack(entries, ARRAY_SIZE(entries)); > + else > + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); > return __stack_depot_save(entries, nr_entries, flags, can_alloc); Another option here is to instruct stack depot to get the stack from the Shadow Call Stack. This would avoid copying the frames twice. > } > > -- > 2.25.1 >