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Tue, 8 Oct 2019 11:58:18 +0000 (UTC) Subject: Re: [PATCH v6 14/14] riscv: Make mmap allocation top-down by default To: Atish Patra Cc: "ralf@linux-mips.org" , "keescook@chromium.org" , "palmer@sifive.com" , "aou@eecs.berkeley.edu" , "linux-kernel@vger.kernel.org" , "will.deacon@arm.com" , "paul.walmsley@sifive.com" , "paul.burton@mips.com" , "linux@armlinux.org.uk" , "linux-mm@kvack.org" , "hch@lst.de" , "catalin.marinas@arm.com" , "viro@zeniv.linux.org.uk" , "akpm@linux-foundation.org" , "linux-fsdevel@vger.kernel.org" , "jhogan@kernel.org" , "mcgrof@kernel.org" , "linux-riscv@lists.infradead.org" , "linux-arm-kernel@lists.infradead.org" References: <20190808061756.19712-1-alex@ghiti.fr> <20190808061756.19712-15-alex@ghiti.fr> <208433f810b5b07b1e679d7eedb028697dff851b.camel@wdc.com> <60b52f20-a2c7-dee9-7cf3-a727f07400b9@ghiti.fr> From: Alex Ghiti Message-ID: <9e9a3fea-d8a3-ae62-317a-740773f0725c@ghiti.fr> Date: Tue, 8 Oct 2019 07:58:18 -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 Content-Language: sv-FI Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). 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 > [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_IDENTIFICAT > 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_MEASUREMENT > 155557e000-155557f000 r--p 00000000 103:01 > 50939 /usr/lib/locale/en_US.utf8/LC_TELEPHONE > 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_MESSAGES/SY > S_LC_MESSAGES > 1555583000-1555584000 r--p 00000000 103:01 > 50938 /usr/lib/locale/en_US.utf8/LC_MONETARY > 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. 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