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 2B011C433EF for ; Sun, 29 May 2022 17:04:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231338AbiE2RE2 (ORCPT ); Sun, 29 May 2022 13:04:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbiE2REY (ORCPT ); Sun, 29 May 2022 13:04:24 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 68BCC84A14 for ; Sun, 29 May 2022 10:04:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=MIME-Version:Content-Transfer-Encoding: Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=BLA4aQRvfntqLMm99a+1xZPVRcOluvd10rffKGFrc10=; t=1653843862; x=1655053462; b=nEM4ayaSXa19ifF6VUJVLPIsXrOLCakZlQEfnPxHYRwUNWQ sX6843SuagJYeQkiR6oJNqPHep5/uFNAkqvu0y3Mm+6jrNYuxnqmu8vIFP9Gt1Xg71+CMNigVRl/6 lYUiE0D9+lFJ9MPAyXKKCLR+rQSTT3LIIVm5iGXwoI/gSchcJ3kT1dIpBLg/EcP5DbIXdtl/jgkBK LpO6UQHZ+nG1lI3hI9VlhUM7wDOi6lVhAaxWRGPo5ftlEYZHXk6nY/sAESrtcyvAQwgPA+5CARBbH j386URRSDpJn1Aj3NwsyXwCby7/sJ4QShWKrVHLvWozMGi54dtyhgZKNaQXvjbCQ==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.95) (envelope-from ) id 1nvMKn-007myT-UG; Sun, 29 May 2022 19:04:10 +0200 Message-ID: <1a4e51a4d2ed51e7ae1ff55bd4da6a47fad7c0bf.camel@sipsolutions.net> Subject: Re: [PATCH v2 2/2] UML: add support for KASAN under x86_64 From: Johannes Berg To: David Gow , Vincent Whitchurch , Patricia Alfonso , Jeff Dike , Richard Weinberger , anton.ivanov@cambridgegreys.com, Dmitry Vyukov , Brendan Higgins , Andrew Morton , Andrey Konovalov , Andrey Ryabinin Cc: kasan-dev , linux-um@lists.infradead.org, LKML , Daniel Latypov , linux-mm@kvack.org Date: Sun, 29 May 2022 19:04:08 +0200 In-Reply-To: <20220527185600.1236769-2-davidgow@google.com> References: <20220527185600.1236769-1-davidgow@google.com> <20220527185600.1236769-2-davidgow@google.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.1 (3.44.1-1.fc36) MIME-Version: 1.0 X-malware-bazaar: not-scanned Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2022-05-27 at 11:56 -0700, David Gow wrote: >=20 > The UML-specific KASAN initializer uses mmap to map the roughly 2.25TB You say 2.25TB here, and =20 > +config KASAN_SHADOW_OFFSET > + hex > + depends on KASAN > + default 0x100000000000 > + help > + This is the offset at which the ~2.25TB of shadow memory is here too, of course. But I notice that I get ~16TB address space use when running, > +/* used in kasan_mem_to_shadow to divide by 8 */ > +#define KASAN_SHADOW_SCALE_SHIFT 3 > + > +#ifdef CONFIG_X86_64 > +#define KASAN_HOST_USER_SPACE_END_ADDR 0x00007fffffffffffUL > +/* KASAN_SHADOW_SIZE is the size of total address space divided by 8 */ > +#define KASAN_SHADOW_SIZE ((KASAN_HOST_USER_SPACE_END_ADDR + 1) >> \ > + KASAN_SHADOW_SCALE_SHIFT) because this ends up being 0x100000000000, i.e. 16 TiB. Is that intentional? Was something missed? Maybe KASAN_HOST_USER_SPACE_END_ADDR was too big? It doesn't really matter, but I guess then the documentation should be updated. johannes