[OpenWrt-Devel] [PATCH] kernel: MIPS: math-emu Write-protect delay slot emulation pages

Kevin 'ldir' Darbyshire-Bryant ldir at darbyshire-bryant.me.uk
Mon Dec 24 17:16:22 EST 2018

> On 24 Dec 2018, at 03:53, Yousong Zhou <yszhou4tech at gmail.com> wrote:
> Hi, Kevin
> I just took another look at the build system.  On OpenWrt, we have a
> pending patch 304-mips_disable_fpu.patch that makes fpu emulation for
> mips an optional feature.  We have most mips targets have that feature
> disabled.   The absence should be fine as we tell toolchain to use
> soft-float explicitly for the whole build.
> So another approach would be enhancing the disable-fpu patch to also
> not mapping the dsemu page at all.

ha - you can’t exploit a page that doesn’t exist :-)

Just pushed the backport to openwrt and I have your ‘don’t allocate the page’ patch as an additional commit in my staging tree here https://git.openwrt.org/?p=openwrt/staging/ldir.git;a=summary

It’s all running on my box ok so far

cat /proc/self/maps
00400000-0047a000 r-xp 00000000 1f:03 1825       /bin/busybox
00489000-0048a000 r-xp 00079000 1f:03 1825       /bin/busybox
0048a000-0048b000 rwxp 0007a000 1f:03 1825       /bin/busybox
77e9e000-77ec3000 r-xp 00000000 1f:03 2298       /lib/libgcc_s.so.1
77ec3000-77ec4000 rwxp 00015000 1f:03 2298       /lib/libgcc_s.so.1
77ec4000-77f57000 r-xp 00000000 1f:03 2474       /lib/libc.so
77f66000-77f68000 rwxp 00092000 1f:03 2474       /lib/libc.so
77f68000-77f6a000 rwxp 00000000 00:00 0 
7f744000-7f765000 rw-p 00000000 00:00 0          [stack]
7ff88000-7ff89000 r--p 00000000 00:00 0          [vvar]
7ff89000-7ff8a000 r-xp 00000000 00:00 0          [vdso]

Nothing 7xxxxxxx related has a static address :-)


Kevin D-B

012C ACB2 28C6 C53E 9775  9123 B3A2 389B 9DE2 334A

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