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Wed, 9 Oct 2019 18:39:44 +0000 (UTC) From: Alex Ghiti To: Atish Patra Cc: "aou@eecs.berkeley.edu" , "keescook@chromium.org" , "jhogan@kernel.org" , "catalin.marinas@arm.com" , "palmer@sifive.com" , "will.deacon@arm.com" , "linux-kernel@vger.kernel.org" , "ralf@linux-mips.org" , "linux@armlinux.org.uk" , "linux-mm@kvack.org" , "paul.burton@mips.com" , "linux-riscv@lists.infradead.org" , "viro@zeniv.linux.org.uk" , "paul.walmsley@sifive.com" , "linux-fsdevel@vger.kernel.org" , "akpm@linux-foundation.org" , "hch@lst.de" , "linux-arm-kernel@lists.infradead.org" , "mcgrof@kernel.org" Subject: Re: [PATCH v6 14/14] riscv: Make mmap allocation top-down by default References: <20190808061756.19712-1-alex@ghiti.fr> <20190808061756.19712-15-alex@ghiti.fr> <208433f810b5b07b1e679d7eedb028697dff851b.camel@wdc.com> <60b52f20-a2c7-dee9-7cf3-a727f07400b9@ghiti.fr> <9e9a3fea-d8a3-ae62-317a-740773f0725c@ghiti.fr> Message-ID: <4192e5ef-2e9c-950c-1899-ee8ce9a05ec3@ghiti.fr> Date: Wed, 9 Oct 2019 14:39:43 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/8/19 10:07 PM, Atish Patra wrote: > On Tue, 2019-10-08 at 07:58 -0400, Alex Ghiti wrote: >> On 10/7/19 8:46 PM, Atish Patra wrote: >>> On Mon, 2019-10-07 at 05:11 -0400, Alex Ghiti wrote: >>>> On 10/4/19 10:12 PM, Atish Patra wrote: >>>>> On Thu, 2019-08-08 at 02:17 -0400, Alexandre Ghiti wrote: >>>>>> In order to avoid wasting user address space by using bottom- >>>>>> up >>>>>> mmap >>>>>> allocation scheme, prefer top-down scheme when possible. >>>>>> >>>>>> Before: >>>>>> root@qemuriscv64:~# cat /proc/self/maps >>>>>> 00010000-00016000 r-xp 00000000 fe:00 >>>>>> 6389 /bin/cat.coreutils >>>>>> 00016000-00017000 r--p 00005000 fe:00 >>>>>> 6389 /bin/cat.coreutils >>>>>> 00017000-00018000 rw-p 00006000 fe:00 >>>>>> 6389 /bin/cat.coreutils >>>>>> 00018000-00039000 rw-p 00000000 00:00 0 [heap] >>>>>> 1555556000-155556d000 r-xp 00000000 fe:00 7193 /lib/ld- >>>>>> 2.28.so >>>>>> 155556d000-155556e000 r--p 00016000 fe:00 7193 /lib/ld- >>>>>> 2.28.so >>>>>> 155556e000-155556f000 rw-p 00017000 fe:00 7193 /lib/ld- >>>>>> 2.28.so >>>>>> 155556f000-1555570000 rw-p 00000000 00:00 0 >>>>>> 1555570000-1555572000 r-xp 00000000 00:00 0 [vdso] >>>>>> 1555574000-1555576000 rw-p 00000000 00:00 0 >>>>>> 1555576000-1555674000 r-xp 00000000 fe:00 7187 /lib/libc- >>>>>> 2.28.so >>>>>> 1555674000-1555678000 r--p 000fd000 fe:00 7187 /lib/libc- >>>>>> 2.28.so >>>>>> 1555678000-155567a000 rw-p 00101000 fe:00 7187 /lib/libc- >>>>>> 2.28.so >>>>>> 155567a000-15556a0000 rw-p 00000000 00:00 0 >>>>>> 3fffb90000-3fffbb1000 rw-p 00000000 00:00 0 [stack] >>>>>> >>>>>> After: >>>>>> root@qemuriscv64:~# cat /proc/self/maps >>>>>> 00010000-00016000 r-xp 00000000 fe:00 >>>>>> 6389 /bin/cat.coreutils >>>>>> 00016000-00017000 r--p 00005000 fe:00 >>>>>> 6389 /bin/cat.coreutils >>>>>> 00017000-00018000 rw-p 00006000 fe:00 >>>>>> 6389 /bin/cat.coreutils >>>>>> 2de81000-2dea2000 rw-p 00000000 00:00 0 [heap] >>>>>> 3ff7eb6000-3ff7ed8000 rw-p 00000000 00:00 0 >>>>>> 3ff7ed8000-3ff7fd6000 r-xp 00000000 fe:00 7187 /lib/libc- >>>>>> 2.28.so >>>>>> 3ff7fd6000-3ff7fda000 r--p 000fd000 fe:00 7187 /lib/libc- >>>>>> 2.28.so >>>>>> 3ff7fda000-3ff7fdc000 rw-p 00101000 fe:00 7187 /lib/libc- >>>>>> 2.28.so >>>>>> 3ff7fdc000-3ff7fe2000 rw-p 00000000 00:00 0 >>>>>> 3ff7fe4000-3ff7fe6000 r-xp 00000000 00:00 0 [vdso] >>>>>> 3ff7fe6000-3ff7ffd000 r-xp 00000000 fe:00 7193 /lib/ld- >>>>>> 2.28.so >>>>>> 3ff7ffd000-3ff7ffe000 r--p 00016000 fe:00 7193 /lib/ld- >>>>>> 2.28.so >>>>>> 3ff7ffe000-3ff7fff000 rw-p 00017000 fe:00 7193 /lib/ld- >>>>>> 2.28.so >>>>>> 3ff7fff000-3ff8000000 rw-p 00000000 00:00 0 >>>>>> 3fff888000-3fff8a9000 rw-p 00000000 00:00 0 [stack] >>>>>> >>>>>> Signed-off-by: Alexandre Ghiti >>>>>> Acked-by: Paul Walmsley >>>>>> Reviewed-by: Christoph Hellwig >>>>>> Reviewed-by: Kees Cook >>>>>> Reviewed-by: Luis Chamberlain >>>>>> --- >>>>>> arch/riscv/Kconfig | 12 ++++++++++++ >>>>>> 1 file changed, 12 insertions(+) >>>>>> >>>>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig >>>>>> index 59a4727ecd6c..87dc5370becb 100644 >>>>>> --- a/arch/riscv/Kconfig >>>>>> +++ b/arch/riscv/Kconfig >>>>>> @@ -54,6 +54,18 @@ config RISCV >>>>>> select EDAC_SUPPORT >>>>>> select ARCH_HAS_GIGANTIC_PAGE >>>>>> select ARCH_WANT_HUGE_PMD_SHARE if 64BIT >>>>>> + select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU >>>>>> + select HAVE_ARCH_MMAP_RND_BITS >>>>>> + >>>>>> +config ARCH_MMAP_RND_BITS_MIN >>>>>> + default 18 if 6legacy_va_layout4BIT >>>>>> + default 8 >>>>>> + >>>>>> +# max bits determined by the following formula: >>>>>> +# VA_BITS - PAGE_SHIFT - 3 >>>>>> +config ARCH_MMAP_RND_BITS_MAX >>>>>> + default 24 if 64BIT # SV39 based >>>>>> + default 17 >>>>>> >>>>>> config MMU >>>>>> def_bool y >>>>> With this patch, I am not able to boot a Fedora Linux(a Gnome >>>>> desktop >>>>> image) on RISC-V hardware (Unleashed + Microsemi Expansion >>>>> board). >>>>> The >>>>> booting gets stuck right after systemd starts. >>>>> >>>>> https://paste.fedoraproject.org/paste/TOrUMqqKH-pGFX7CnfajDg >>>>> >>>>> Reverting just this patch allow to boot Fedora successfully on >>>>> specific >>>>> RISC-V hardware. I have not root caused the issue but it looks >>>>> like >>>>> it >>>>> might have messed userpsace mapping. >>>> It might have messed userspace mapping but not enough to make >>>> userspace >>>> completely broken >>>> as systemd does some things. I would try to boot in legacy >>>> layout: >>>> if >>>> you can try to set sysctl legacy_va_layout >>>> at boottime, it will map userspace as it was before (bottom-up). >>>> If >>>> that >>>> does not work, the problem could >>>> be the randomization that is activated by default now. >>> Randomization may not be the issue. I just removed >>> ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT from the config and that >>> seems to >>> work. Here is the bottom-up layout with randomization on. >> Oups, sorry for my previous answer, I missed yours that landed in >> another folder. >> >> Removing ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT also removes >> randomization >> as this config selects ARCH_HAS_ELF_RANDOMIZE. >> You could remove ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT and selects by >> hand >> ARCH_HAS_ELF_RANDOMIZE but you would have to implement arch_mmap_rnd >> and >> arch_randomize_brk (elf-randomize.h). >> > Ahh okay. > >> The simplest would be to boot in legacy layout: I did not find a way >> to >> set this in kernel >> command line, but you can by modifying it directly in the code: >> >> https://elixir.bootlin.com/linux/v5.4-rc2/source/kernel/sysctl.c#L269 >> > Setting this to 1 works. > >>> [root@fedora-riscv ~]# cat /proc/self/maps >>> 1555556000-1555570000 r-xp 00000000 103:01 >>> 280098 /usr/lib64/ld-2.28.so >>> 1555570000-1555571000 r--p 00019000 103:01 >>> 280098 /usr/lib64/ld-2.28.so >>> 1555571000-1555572000 rw-p 0001a000 103:01 >>> 280098 /usr/lib64/ld-2.28.so >>> 1555572000-1555573000 rw-p 00000000 00:00 0 >>> 1555573000-1555575000 r-xp 00000000 00:00 >>> 0 [vdso] >>> 1555575000-1555576000 r--p 00000000 103:01 >>> 50936 /usr/lib/locale/en_US.utf8/LC_IDENTIF >>> ICAT >>> ION >>> 1555576000-155557d000 r--s 00000000 103:01 >>> 280826 /usr/lib64/gconv/gconv-modules.cache >>> 155557d000-155557e000 r--p 00000000 103:01 >>> 50937 /usr/lib/locale/en_US.utf8/LC_MEASURE >>> MENT >>> 155557e000-155557f000 r--p 00000000 103:01 >>> 50939 /usr/lib/locale/en_US.utf8/LC_TELEPHO >>> NE >>> 155557f000-1555580000 r--p 00000000 103:01 >>> 3706 /usr/lib/locale/en_US.utf8/LC_ADDRESS >>> 1555580000-1555581000 r--p 00000000 103:01 >>> 50944 /usr/lib/locale/en_US.utf8/LC_NAME >>> 1555581000-1555582000 r--p 00000000 103:01 >>> 3775 /usr/lib/locale/en_US.utf8/LC_PAPER >>> 1555582000-1555583000 r--p 00000000 103:01 >>> 3758 /usr/lib/locale/en_US.utf8/LC_MESSAGE >>> S/SY >>> S_LC_MESSAGES >>> 1555583000-1555584000 r--p 00000000 103:01 >>> 50938 /usr/lib/locale/en_US.utf8/LC_MONETAR >>> Y >>> 1555584000-1555585000 r--p 00000000 103:01 >>> 50940 /usr/lib/locale/en_US.utf8/LC_TIME >>> 1555585000-1555586000 r--p 00000000 103:01 >>> 50945 /usr/lib/locale/en_US.utf8/LC_NUMERIC >>> 1555590000-1555592000 rw-p 00000000 00:00 0 >>> 1555592000-15556b1000 r-xp 00000000 103:01 >>> 280105 /usr/lib64/libc-2.28.so >>> 15556b1000-15556b5000 r--p 0011e000 103:01 >>> 280105 /usr/lib64/libc-2.28.so >>> 15556b5000-15556b7000 rw-p 00122000 103:01 >>> 280105 /usr/lib64/libc-2.28.so >>> 15556b7000-15556bb000 rw-p 00000000 00:00 0 >>> 15556bb000-1555933000 r--p 00000000 103:01 >>> 3755 /usr/lib/locale/en_US.utf8/LC_COLLATE >>> 1555933000-1555986000 r--p 00000000 103:01 >>> 50942 /usr/lib/locale/en_US.utf8/LC_CTYPE >>> 1555986000-15559a8000 rw-p 00000000 00:00 0 >>> 2aaaaaa000-2aaaab1000 r-xp 00000000 103:01 >>> 283975 /usr/bin/cat >>> 2aaaab1000-2aaaab2000 r--p 00006000 103:01 >>> 283975 /usr/bin/cat >>> 2aaaab2000-2aaaab3000 rw-p 00007000 103:01 >>> 283975 /usr/bin/cat >>> 2aaaab3000-2aaaad4000 rw-p 00000000 00:00 >>> 0 [heap] >>> 3fffc97000-3fffcb8000 rw-p 00000000 00:00 >>> 0 [stack] >>> >>> >>>> Anyway, it's weird since userspace should not depend on how the >>>> mapping is. >>>> >>>> If you can identify the program that stalls, that would be >>>> fantastic >>>> :) >>>> >>> It stucks while booting. So I am not sure how to figure out which >>> program stalls. It is difficult to figure out from boot log as it >>> stucks at different places but soon after systemd starts. >> If you can attach the running kernel, I would use vmlinux-gdb.py >> commands >> to figure out which processes are running (lx-ps command in >> particular could >> give us a hint). You can also add traces directly in the kernel and >> either use >> lx-dmesg command to print them from gdb or use your standard serial >> output: >> I would then print task_struct->comm at context switch to see which >> process >> is stuck. >> To use the python script, you need to recompile with DEBUG_INFO and >> GDB_SCRIPTS enabled. >> >> FYI, I have just booted a custom buildroot image based on kernel 5.4- >> rc2. >> > vmlinux-gdb.py works only if you are running in Qemu or have a JTAG. > Right ? Yes. Does the problem appear on qemu too ? > I am seeing this issue only on HiFive Unleashed + Microsemi Expansion > board with Fedora Gnome desktop image. I can even boot a Fedora > developer image on same hardware and a busybox image in Unleashed > without any issues. But the issue is not specific to fedora as we see > the same issue in OpenEmbedded disk image as well (HiFive Unleashed + > Microsemi Expansion board). > > May be it gets triggerd only if bigger userspace ? The purpose of this patch is, on the contrary, to not lose address space by setting an arbitrary starting point (TASK_UNMAPPED_BASE) for mmap. Do you a link to an image that fails to boot and reproduce the problem on Qemu ? I don't have much idea here, the only thing I can think of is finding the application that makes the boot stall and understand what is wrong. > >> Let me know if I can do anything. >> >> Alex >> >>>> As the code is common to mips and arm now and I did not hear from >>>> them, >>>> I imagine the problem comes >>>> from us. >>>> >>>> Alex