diff mbox series

[v5,14/14] riscv: Make mmap allocation top-down by default

Message ID 20190730055113.23635-15-alex@ghiti.fr (mailing list archive)
State New, archived
Headers show
Series Provide generic top-down mmap layout functions | expand

Commit Message

Alexandre Ghiti July 30, 2019, 5:51 a.m. UTC 
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 <alex@ghiti.fr>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/riscv/Kconfig | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

Alexandre Ghiti July 31, 2019, 6:05 a.m. UTC | #1 
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 <alex@ghiti.fr>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>   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.

Thanks,

Alex
Guenter Roeck July 31, 2019, 5:33 p.m. UTC | #2 
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 <alex@ghiti.fr>
> >Reviewed-by: Christoph Hellwig <hch@lst.de>
> >Reviewed-by: Kees Cook <keescook@chromium.org>
> >Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> >---
> >  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
Paul Walmsley July 31, 2019, 10:40 p.m. UTC | #3 
On Tue, 30 Jul 2019, 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 <alex@ghiti.fr>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

Acked-by: Paul Walmsley <paul.walmsley@sifive.com> # for arch/riscv

As Alex notes, this patch depends on "[PATCH] riscv: kbuild: add virtual 
memory system selection":

https://lore.kernel.org/linux-riscv/alpine.DEB.2.21.9999.1907301218560.3486@viisi.sifive.com/T/#t

which will likely go up during v5.3-rc.


- Paul
diff mbox series

Patch

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