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Wed, 31 Jul 2019 10:33:23 -0700 (PDT) Date: Wed, 31 Jul 2019 10:33:22 -0700 From: Guenter Roeck To: Alex Ghiti Cc: Andrew Morton , Luis Chamberlain , Christoph Hellwig , Russell King , Catalin Marinas , Will Deacon , Ralf Baechle , Paul Burton , James Hogan , Palmer Dabbelt , Albert Ou , Alexander Viro , Kees Cook , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v5 14/14] riscv: Make mmap allocation top-down by default Message-ID: <20190731173322.GA30870@roeck-us.net> References: <20190730055113.23635-1-alex@ghiti.fr> <20190730055113.23635-15-alex@ghiti.fr> <88a9bbf8-872f-97cc-fc1a-83eb7694478f@ghiti.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <88a9bbf8-872f-97cc-fc1a-83eb7694478f@ghiti.fr> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 31, 2019 at 02:05:23AM -0400, Alex Ghiti wrote: > On 7/30/19 1:51 AM, 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 > >Reviewed-by: Christoph Hellwig > >Reviewed-by: Kees Cook > >Reviewed-by: Luis Chamberlain > >--- > > arch/riscv/Kconfig | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > > >diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > >index 8ef64fe2c2b3..8d0d8af1a744 100644 > >--- a/arch/riscv/Kconfig > >+++ b/arch/riscv/Kconfig > >@@ -54,6 +54,19 @@ 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 64BIT > >+ default 8 > >+ > >+# max bits determined by the following formula: > >+# VA_BITS - PAGE_SHIFT - 3 > >+config ARCH_MMAP_RND_BITS_MAX > >+ default 33 if RISCV_VM_SV48 > >+ default 24 if RISCV_VM_SV39 > >+ default 17 if RISCV_VM_SV32 > > config MMU > > def_bool y > > > Hi Andrew, > > I have just seen you took this series into mmotm but without Paul's patch > ("riscv: kbuild: add virtual memory system selection") on which this commit > relies, I'm not sure it could > compile without it as there is no default for ARCH_MMAP_RND_BITS_MAX. > Yes, this patch results in a bad configuration file. CONFIG_ARCH_MMAP_RND_BITS_MIN=18 CONFIG_HAVE_ARCH_MMAP_RND_BITS=y CONFIG_ARCH_MMAP_RND_BITS=0 CONFIG_ARCH_MMAP_RND_BITS=0 is outside the valid range, causing make to ask for a valid number. Since none exists, one is stuck with something like: Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 1 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 2 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 3 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 4 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 5 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 6 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 7 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 8 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 19 Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [0] (NEW) 18 when trying to compile riscv images. Plus, of course, all automatic builders bail out as result. Guenter