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 EB82AC001DE for ; Thu, 13 Jul 2023 07:28:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233880AbjGMH2P (ORCPT ); Thu, 13 Jul 2023 03:28:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234324AbjGMH2H (ORCPT ); Thu, 13 Jul 2023 03:28:07 -0400 Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EC34C2; Thu, 13 Jul 2023 00:28:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1689233250; x=1689838050; i=deller@gmx.de; bh=BzvXTHYc41zcqbAAV/+hJvg0vIxuqHt7OiQPT6yMRv4=; h=X-UI-Sender-Class:Date:From:To:Cc:Subject:References:In-Reply-To; b=mCj6Ir2NfRHrbtDot5VggBJSvAlw4rjHKa8bVZGC8CCe2ZWehPcE0fZnpwr6qiRQMFm9yBE dB7cjOcjdxuPCTKdYUayAlczB8UfuzCFFjirzG/HGrTaTTSuNnG8mMNRJS15pqRkRK3pP98RH ClvOT4zp9T+eqXR3lZdZuJ6QQaFGRdjJaVf8PYm0BLCpS7SdPxY5cfJ/wqTOCe4ahp9B/pSwY ibewls/yKTYKiNUAjJAbdXLbycN/trIJlhzHnDVEsNjrWzI1wNtSA9kuIn8Rj63nSonryZr0A W+5n2YksuQPSzc5ye5yvvSh1tI1dHevb76PEJYvTMVMuLMQBRZbg== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from ls3530 ([94.134.155.32]) by mail.gmx.net (mrgmx005 [212.227.17.190]) with ESMTPSA (Nemesis) id 1Mt75H-1pziO32gTh-00tTB1; Thu, 13 Jul 2023 09:27:30 +0200 Date: Thu, 13 Jul 2023 09:27:28 +0200 From: Helge Deller To: matoro Cc: Jens Axboe , io-uring@vger.kernel.org, Linux Ia64 , glaubitz@physik.fu-berlin.de, Sam James Subject: Re: [PATCH 1/5] io_uring: Adjust mapping wrt architecture aliasing requirements Message-ID: References: <20230314171641.10542-1-axboe@kernel.dk> <20230314171641.10542-2-axboe@kernel.dk> <1d5f8f99f39e2769b9c76fbc24e2cf50@matoro.tk> <802b84f7-94f4-638b-3742-26bca00b262d@gmx.de> <8bb091fb5fd00072842fe92b03abac9b@matoro.tk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <8bb091fb5fd00072842fe92b03abac9b@matoro.tk> X-Provags-ID: V03:K1:CRK/0yceaE+RM8qCVi8DTMn7X4b2jwsKLj1C+Pyw+i1t5+ZkfYk FC0hp3TkZ3zitbxkiON4ywV9wO5UlWu/9wGRtSmUkNcp5TOuPMZmdlftsA776ijqXLBu5Su Ftv6LijGXo17SSprFpmVY/Pc0fyQ4uWgreiuajs74dNc+Ak3OfGgBj+pclCTh+hW0FYGjOH v0RxA6DEt3FE7LAJ2zYmw== UI-OutboundReport: notjunk:1;M01:P0:W9jM8zDF1r0=;1QzWzZezLhiTJF6/DBgQKPm/ecT M3WjeFP1n0xURgoODlssgpMZxGal3n+6uVf3VD0bGdCnZyQW9a6EdfLDEPXfBWAJrNiF+n1sB HPMdVdtLHnGhxAg6h0Cbpi1/Xc4kDm3cv9twkydZImFSJuPKOoG46xQu6ne2z275NEh3sbDXz Rfcgnzi9jTWfG9qg4lnm+F6zzaBVFVhs9rDLNcAzrOwgJG93vQso2miKrwdP76eQZs+GBBcVb AwtTsfQQGztD7po9Cdkd4QbSurmHCrxJZDjO+aVA+/8BhDvktqYTkpU4UBcMMzGI8MqNmiwhW JywYja5FV2StZP0L/ZGbda//ADtShpADxQH3lxnUdHy0WoTyBwdog6rMagmyB2WV2clM8ZXm3 5jQnlS8U4lrdufT79Sl5G+A1/QIfiCfMF9WxljeKP8IkrN1OOv3uxSM65L/XT3IsEhAEaoQ7P E/O6GdwC+otslGe+eQj5ITALwKGLKn+hjL8NwFBx77BrvccJkWDzK/aIUb8/V8znD0hJ4x8VI tz29aZZiz1kxQ5F7AqfGxmIbyfBwrMyFapDy53IUJTDglIoHixkpovWA0pqFGzvxkSZgwUtXT j9IVqc0E127VDn/m83r9q/Oun5amfU/JAQ6dZLaPgKblfaiIxqoQDL7XUqjWgKH7tghCqiIPa gci5GK1qyUZoOlHwPZS5pm5m2wZ+3tXrzPemYfY21EwZj46QIGvv+dCheE7I0z75FnydEdbdg vb4kBn58fNuhCAJD3VwYDWPEfyj/xTDXilEr3OgaiGlVC0SGqHVY9mqLIszVxjj6sCBAkDYvD lAfJ2GknG4MbkTNp7DccposIiCTW0ep/0cDaZ+gGR3Sv2u63WA1a5rhbL9+Xj4fzTuGkvAZAF iskzdJuHMnZU3CWzDmzB0dr7LQZvHIPNVaNJcbApMEee3IbTY+VWL6Kxk08ISo8OsJHeanRgO KCNff1EvXBAnUVToBOTpQr49H3s= Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org * matoro : > On 2023-07-12 16:30, Helge Deller wrote: > > On 7/12/23 21:05, Helge Deller wrote: > > > On 7/12/23 19:28, matoro wrote: > > > > On 2023-07-12 12:24, Helge Deller wrote: > > > > > Hi Matoro, > > > > > > > > > > * matoro : > > > > > > On 2023-03-14 13:16, Jens Axboe wrote: > > > > > > > From: Helge Deller > > > > > > > > > > > > > > Some architectures have memory cache aliasing requirements (= e.g. parisc) > > > > > > > if memory is shared between userspace and kernel. This patch= fixes the > > > > > > > kernel to return an aliased address when asked by userspace = via mmap(). > > > > > > > > > > > > > > Signed-off-by: Helge Deller > > > > > > > Signed-off-by: Jens Axboe > > > > > > > --- > > > > > > >=A0 io_uring/io_uring.c | 51 ++++++++++++++++++++++++++++++++= +++++++++++++ > > > > > > >=A0 1 file changed, 51 insertions(+) > > > > > > > > > > > > > > diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c > > > > > > > index 722624b6d0dc..3adecebbac71 100644 > > > > > > > --- a/io_uring/io_uring.c > > > > > > > +++ b/io_uring/io_uring.c > > > > > > > @@ -72,6 +72,7 @@ > > > > > > >=A0 #include > > > > > > >=A0 #include > > > > > > >=A0 #include > > > > > > > +#include > > > > > > > > > > > > > >=A0 #define CREATE_TRACE_POINTS > > > > > > >=A0 #include > > > > > > > @@ -3317,6 +3318,54 @@ static __cold int io_uring_mmap(struc= t file > > > > > > > *file, struct vm_area_struct *vma) > > > > > > >=A0=A0=A0=A0=A0 return remap_pfn_range(vma, vma->vm_start, pf= n, sz, > > > > > > > vma->vm_page_prot); > > > > > > >=A0 } > > > > > > > > > > > > > > +static unsigned long io_uring_mmu_get_unmapped_area(struct = file *filp, > > > > > > > +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 unsigned long addr, unsig= ned long len, > > > > > > > +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 unsigned long pgoff, unsi= gned long flags) > > > > > > > +{ > > > > > > > +=A0=A0=A0 const unsigned long mmap_end =3D arch_get_mmap_en= d(addr, len, flags); > > > > > > > +=A0=A0=A0 struct vm_unmapped_area_info info; > > > > > > > +=A0=A0=A0 void *ptr; > > > > > > > + > > > > > > > +=A0=A0=A0 /* > > > > > > > +=A0=A0=A0=A0 * Do not allow to map to user-provided address= to avoid breaking the > > > > > > > +=A0=A0=A0=A0 * aliasing rules. Userspace is not able to gue= ss the offset address > > > > > > > of > > > > > > > +=A0=A0=A0=A0 * kernel kmalloc()ed memory area. > > > > > > > +=A0=A0=A0=A0 */ > > > > > > > +=A0=A0=A0 if (addr) > > > > > > > +=A0=A0=A0=A0=A0=A0=A0 return -EINVAL; > > > > > > > + > > > > > > > +=A0=A0=A0 ptr =3D io_uring_validate_mmap_request(filp, pgof= f, len); > > > > > > > +=A0=A0=A0 if (IS_ERR(ptr)) > > > > > > > +=A0=A0=A0=A0=A0=A0=A0 return -ENOMEM; > > > > > > > + > > > > > > > +=A0=A0=A0 info.flags =3D VM_UNMAPPED_AREA_TOPDOWN; > > > > > > > +=A0=A0=A0 info.length =3D len; > > > > > > > +=A0=A0=A0 info.low_limit =3D max(PAGE_SIZE, mmap_min_addr); > > > > > > > +=A0=A0=A0 info.high_limit =3D arch_get_mmap_base(addr, curr= ent->mm->mmap_base); > > > > > > > +#ifdef SHM_COLOUR > > > > > > > +=A0=A0=A0 info.align_mask =3D PAGE_MASK & (SHM_COLOUR - 1UL= ); > > > > > > > +#else > > > > > > > +=A0=A0=A0 info.align_mask =3D PAGE_MASK & (SHMLBA - 1UL); > > > > > > > +#endif > > > > > > > +=A0=A0=A0 info.align_offset =3D (unsigned long) ptr; > > > > > > > + > > > > > > > +=A0=A0=A0 /* > > > > > > > +=A0=A0=A0=A0 * A failed mmap() very likely causes applicati= on failure, > > > > > > > +=A0=A0=A0=A0 * so fall back to the bottom-up function here.= This scenario > > > > > > > +=A0=A0=A0=A0 * can happen with large stack limits and large= mmap() > > > > > > > +=A0=A0=A0=A0 * allocations. > > > > > > > +=A0=A0=A0=A0 */ > > > > > > > +=A0=A0=A0 addr =3D vm_unmapped_area(&info); > > > > > > > +=A0=A0=A0 if (offset_in_page(addr)) { > > > > > > > +=A0=A0=A0=A0=A0=A0=A0 info.flags =3D 0; > > > > > > > +=A0=A0=A0=A0=A0=A0=A0 info.low_limit =3D TASK_UNMAPPED_BASE= ; > > > > > > > +=A0=A0=A0=A0=A0=A0=A0 info.high_limit =3D mmap_end; > > > > > > > +=A0=A0=A0=A0=A0=A0=A0 addr =3D vm_unmapped_area(&info); > > > > > > > +=A0=A0=A0 } > > > > > > > + > > > > > > > +=A0=A0=A0 return addr; > > > > > > > +} > > > > > > > + > > > > > > >=A0 #else /* !CONFIG_MMU */ > > > > > > > > > > > > > >=A0 static int io_uring_mmap(struct file *file, struct vm_are= a_struct *vma) > > > > > > > @@ -3529,6 +3578,8 @@ static const struct file_operations io= _uring_fops > > > > > > > =3D { > > > > > > >=A0 #ifndef CONFIG_MMU > > > > > > >=A0=A0=A0=A0=A0 .get_unmapped_area =3D io_uring_nommu_get_unm= apped_area, > > > > > > >=A0=A0=A0=A0=A0 .mmap_capabilities =3D io_uring_nommu_mmap_ca= pabilities, > > > > > > > +#else > > > > > > > +=A0=A0=A0 .get_unmapped_area =3D io_uring_mmu_get_unmapped_= area, > > > > > > >=A0 #endif > > > > > > >=A0=A0=A0=A0=A0 .poll=A0=A0=A0=A0=A0=A0=A0 =3D io_uring_poll, > > > > > > >=A0 #ifdef CONFIG_PROC_FS > > > > > > > > > > > > Hi Jens, Helge - I've bisected a regression with > > > > > > io_uring on ia64 to this > > > > > > patch in 6.4.=A0 Unfortunately this breaks userspace > > > > > > programs using io_uring, > > > > > > the easiest one to test is cmake with an io_uring > > > > > > enabled libuv (i.e., libuv > > > > > > >=3D 1.45.0) which will hang. > > > > > > > > > > > > I am aware that ia64 is in a vulnerable place right now > > > > > > which I why I am > > > > > > keeping this spread limited.=A0 Since this clearly involves > > > > > > architecture-specific changes for parisc, > > > > > > > > > > it isn't so much architecture-specific... (just one ifdef) > > > > > > > > > > > is there any chance of looking at > > > > > > what is required to do the same for ia64?=A0 I looked at > > > > > > 0ef36bd2b37815719e31a72d2beecc28ca8ecd26 ("parisc: > > > > > > change value of SHMLBA > > > > > > from 0x00400000 to PAGE_SIZE") and tried to replicate the SHML= BA -> > > > > > > SHM_COLOUR change, but it made no difference. > > > > > > > > > > > > If hardware is necessary for testing, I can provide it, > > > > > > including remote BMC > > > > > > access for restarts/kernel debugging.=A0 Any takers? > > > > > > > > > > I won't have time to test myself, but maybe you could test? > > > > > > > > > > Basically we should try to find out why > > > > > io_uring_mmu_get_unmapped_area() > > > > > doesn't return valid addresses, while arch_get_unmapped_area() > > > > > [in arch/ia64/kernel/sys_ia64.c] does. > > > > > > > > > > You could apply this patch first: > > > > > It introduces a memory leak (as it requests memory twice), > > > > > but maybe we > > > > > get an idea? > > > > > The ia64 arch_get_unmapped_area() searches for memory from botto= m > > > > > (flags=3D0), while io_uring function tries top-down first. > > > > > Maybe that's > > > > > the problem. And I don't understand the offset_in_page() check r= ight > > > > > now. > > > > > > > > > > diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c > > > > > index 3bca7a79efda..93b1964d2bbb 100644 > > > > > --- a/io_uring/io_uring.c > > > > > +++ b/io_uring/io_uring.c > > > > > @@ -3431,13 +3431,17 @@ static unsigned long > > > > > io_uring_mmu_get_unmapped_area(struct file *filp, > > > > > =A0=A0=A0=A0=A0 * can happen with large stack limits and large m= map() > > > > > =A0=A0=A0=A0=A0 * allocations. > > > > > =A0=A0=A0=A0=A0 */ > > > > > +/* compare to arch_get_unmapped_area() in > > > > > arch/ia64/kernel/sys_ia64.c */ > > > > > =A0=A0=A0=A0 addr =3D vm_unmapped_area(&info); > > > > > -=A0=A0=A0 if (offset_in_page(addr)) { > > > > > +printk("io_uring_mmu_get_unmapped_area() address 1 is: > > > > > %px\n", addr); > > > > > +=A0=A0=A0 addr =3D NULL; > > > > > +=A0=A0=A0 if (!addr) { > > > > > =A0=A0=A0=A0=A0=A0=A0=A0 info.flags =3D 0; > > > > > =A0=A0=A0=A0=A0=A0=A0=A0 info.low_limit =3D TASK_UNMAPPED_BASE; > > > > > =A0=A0=A0=A0=A0=A0=A0=A0 info.high_limit =3D mmap_end; > > > > > =A0=A0=A0=A0=A0=A0=A0=A0 addr =3D vm_unmapped_area(&info); > > > > > =A0=A0=A0=A0 } > > > > > +printk("io_uring_mmu_get_unmapped_area() returns address > > > > > %px\n", addr); > > > > > > > > > > =A0=A0=A0=A0 return addr; > > > > > =A0} > > > > > > > > > > > > > > > Another option is to disable the call to > > > > > io_uring_nommu_get_unmapped_area()) > > > > > with the next patch. Maybe you could add printks() to ia64's > > > > > arch_get_unmapped_area() > > > > > and check what it returns there? > > > > > > > > > > @@ -3654,6 +3658,8 @@ static const struct file_operations > > > > > io_uring_fops =3D { > > > > > =A0#ifndef CONFIG_MMU > > > > > =A0=A0=A0=A0 .get_unmapped_area =3D io_uring_nommu_get_unmapped_= area, > > > > > =A0=A0=A0=A0 .mmap_capabilities =3D io_uring_nommu_mmap_capabili= ties, > > > > > +#elif 0=A0=A0=A0 /* IS_ENABLED(CONFIG_IA64) */ > > > > > +=A0=A0=A0 .get_unmapped_area =3D NULL, > > > > > =A0#else > > > > > =A0=A0=A0=A0 .get_unmapped_area =3D io_uring_mmu_get_unmapped_ar= ea, > > > > > =A0#endif > > > > > > > > > > Helge > > > > > > > > Thanks Helge.=A0 Sample output from that first patch: > > > > > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > address 1 is: 1ffffffffff40000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > returns address 2000000001e40000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > address 1 is: 1ffffffffff20000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > returns address 2000000001f20000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > address 1 is: 1ffffffffff30000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > returns address 2000000001f30000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > address 1 is: 1ffffffffff90000 > > > > [Wed Jul 12 13:09:50 2023] io_uring_mmu_get_unmapped_area() > > > > returns address 2000000001f90000 > > > > > > > > This pattern seems to be pretty stable, I tried instead just > > > > directly returning the result of a call to > > > > arch_get_unmapped_area() at the end of the function and it seems > > > > similar: > > > > > > > > [Wed Jul 12 13:27:07 2023] io_uring_mmu_get_unmapped_area() > > > > would return address 1ffffffffffd0000 > > > > [Wed Jul 12 13:27:07 2023] but arch_get_unmapped_area() would > > > > return address 2000000001f00000 > > > > [Wed Jul 12 13:27:07 2023] io_uring_mmu_get_unmapped_area() > > > > would return address 1ffffffffff00000 > > > > [Wed Jul 12 13:27:07 2023] but arch_get_unmapped_area() would > > > > return address 1ffffffffff00000 > > > > [Wed Jul 12 13:27:07 2023] io_uring_mmu_get_unmapped_area() > > > > would return address 1fffffffffe20000 > > > > [Wed Jul 12 13:27:07 2023] but arch_get_unmapped_area() would > > > > return address 2000000002000000 > > > > [Wed Jul 12 13:27:07 2023] io_uring_mmu_get_unmapped_area() > > > > would return address 1fffffffffe30000 > > > > [Wed Jul 12 13:27:07 2023] but arch_get_unmapped_area() would > > > > return address 2000000002100000 > > > > > > > > Is that enough of a clue to go on? > > > > > > SHMLBA on ia64 is 0x100000: > > > arch/ia64/include/asm/shmparam.h:#define=A0=A0=A0=A0=A0=A0=A0 SHMLBA= =A0 (1024*1024) > > > but the values returned by io_uring_mmu_get_unmapped_area() does not > > > fullfill this. > > > > > > So, probably ia64's SHMLBA isn't pulled in correctly in > > > io_uring/io_uring.c. > > > Check value of this line: > > > =A0=A0=A0=A0info.align_mask =3D PAGE_MASK & (SHMLBA - 1UL); > > > > > > You could also add > > > #define SHM_COLOUR=A0 0x100000 > > > in front of the > > > =A0=A0=A0=A0#ifdef SHM_COLOUR > > > (define SHM_COLOUR in io_uring/kbuf.c too). > > > > What is the value of PAGE_SIZE and "ptr" on your machine? > > For 4k page size I get: > > SHMLBA -1 -> FFFFF > > PAGE_MASK -> FFFFFFFFF000 > > so, > > info.align_mask =3D PAGE_MASK & (SHMLBA - 1UL) =3D 0xFF000; > > You could try to set nfo.align_mask =3D 0xfffff; > > > > Helge > > Using 64KiB (65536) PAGE_SIZE here. 64-bit pointers. > > Tried both #define SHM_COLOUR 0x100000, as well and info.align_mask =3D > 0xFFFFF, but both of them made the problem change from 100% reproducible= , to > intermittent. > > After inspecting the ouput I observed that it hangs only when the first > allocation returns an address below 0x2000000000000000, and the second > returns an address above it. When both addresses are above it, it does = not > hang. Examples: > > When it works: > $ cmake --version > cmake version 3.26.4 > > CMake suite maintained and supported by Kitware (kitware.com/cmake). > $ dmesg --color=3Dalways -T | tail -n 4 > [Wed Jul 12 20:32:37 2023] io_uring_mmu_get_unmapped_area() would return > address 1fffffffffe20000 > [Wed Jul 12 20:32:37 2023] but arch_get_unmapped_area() would return add= ress > 2000000002000000 > [Wed Jul 12 20:32:37 2023] io_uring_mmu_get_unmapped_area() would return > address 1fffffffffe50000 > [Wed Jul 12 20:32:37 2023] but arch_get_unmapped_area() would return add= ress > 2000000002100000 > > > When it hangs: > $ cmake --version > cmake version 3.26.4 > > CMake suite maintained and supported by Kitware (kitware.com/cmake). > ^C > $ dmesg --color=3Dalways -T | tail -n 4 > [Wed Jul 12 20:33:12 2023] io_uring_mmu_get_unmapped_area() would return > address 1ffffffffff00000 > [Wed Jul 12 20:33:12 2023] but arch_get_unmapped_area() would return add= ress > 1ffffffffff00000 > [Wed Jul 12 20:33:12 2023] io_uring_mmu_get_unmapped_area() would return > address 1fffffffffe60000 > [Wed Jul 12 20:33:12 2023] but arch_get_unmapped_area() would return add= ress > 2000000001f00000 > > Is io_uring_mmu_get_unmapped_area supported to always return addresses a= bove > 0x2000000000000000? Yes, with the patch below. > Any reason why it is not doing so sometimes? It depends on the parameters for vm_unmapped_area(). Specifically info.flags=3D0. Try this patch: diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 3bca7a79efda..b259794ab53b 100644 =2D-- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3429,10 +3429,13 @@ static unsigned long io_uring_mmu_get_unmapped_are= a(struct file *filp, * A failed mmap() very likely causes application failure, * so fall back to the bottom-up function here. This scenario * can happen with large stack limits and large mmap() - * allocations. + * allocations. Use bottom-up on IA64 for correct aliasing. */ - addr =3D vm_unmapped_area(&info); - if (offset_in_page(addr)) { + if (IS_ENABLED(CONFIG_IA64)) + addr =3D NULL; + else + addr =3D vm_unmapped_area(&info); + if (!addr) { info.flags =3D 0; info.low_limit =3D TASK_UNMAPPED_BASE; info.high_limit =3D mmap_end; Helge