Messages in this thread | | | Subject | Re: [PATCH v3 11/11] riscv: Make mmap allocation top-down by default | From | Alex Ghiti <> | Date | Thu, 18 Apr 2019 02:09:08 -0400 |
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On 4/18/19 1:31 AM, Kees Cook wrote: > On Wed, Apr 17, 2019 at 12:34 AM Alexandre Ghiti <alex@ghiti.fr> 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 >> 00018000-00039000 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 <alex@ghiti.fr> >> Reviewed-by: Christoph Hellwig <hch@lst.de> > Reviewed-by: Kees Cook <keescook@chromium.org>
Thank you very much for all your comments,
Alex
> > -Kees > >> --- >> arch/riscv/Kconfig | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig >> index eb56c82d8aa1..f5897e0dbc1c 100644 >> --- a/arch/riscv/Kconfig >> +++ b/arch/riscv/Kconfig >> @@ -49,6 +49,17 @@ config RISCV >> select GENERIC_IRQ_MULTI_HANDLER >> select ARCH_HAS_PTE_SPECIAL >> select HAVE_EBPF_JIT 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 >> + >> +# max bits determined by the following formula: >> +# VA_BITS - PAGE_SHIFT - 3 >> +config ARCH_MMAP_RND_BITS_MAX >> + default 33 if 64BIT # SV48 based >> + default 18 >> >> config MMU >> def_bool y >> -- >> 2.20.1 >> >
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