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Message #52797
[Bug 1415481] Re: default mmap_min_addr for arm64 prevents running arm32 applications
I've done multiple armhf builds on both trusty and utopic arm64 with the
-proposed package, and everything seems happy.
** Tags removed: verification-done-trusty verification-needed-utopic
** Tags added: verification-done
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https://bugs.launchpad.net/bugs/1415481
Title:
default mmap_min_addr for arm64 prevents running arm32 applications
Status in procps package in Ubuntu:
Fix Released
Status in procps source package in Trusty:
Fix Committed
Status in procps source package in Utopic:
Fix Committed
Bug description:
[ SRU Justification ]
Executing 32-bit arm binaries as user fails on arm64. Turns out, this is bad.
[ Test Case ]
Grab a 32-bit binary (either multiarch via armhf, or compile a quick static hello) and try to run it. Also, check /proc/sys/vm/mmap_min_addr is set to 32k instead of 64k after boot.
[ Regression Potential ]
Shouldn't be any issue with 4k pagesize kernels, and this was already the default on 32-bit ARM for the same reasons. It could, potentially, mean that the zero page is no longer entirely protected from mmap when running a 64k pagesize kernel, however we don't currently ship such a kernel, preferring instead to have 32-bit compatibility.
[ Original Bug Report ]
Executing 32-bit arm binaries as user fails on arm64:
# file hello
hello: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV),
statically linked, for GNU/Linux 2.6.32,
BuildID[sha1]=c37a3b366d645eee600963a535370fa0bad9b2c0, not stripped
# ./hello
hello world
# su - linaro
$ /root/hello
Segmentation fault
Root cause was identified to /etc/sysctl.d/10-zeropage.conf, which is
set on arm64 to 65536. To run legacy binaries, this should be set to
32768 like on armhf anr armel.
Reference discussion:
http://lists.infradead.org/pipermail/linux-arm-
kernel/2015-January/320454.html
Affects trusty, utopic and vivid
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References