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mpas_readonly_text.5 (2010 09)

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mpas_readonly_text(5) mpas_readonly_text(5)
(Tunable Kernel Parameters)
NAME
mpas_readonly_text - dynamically enable or disable read-only text segment for 32-bit MPAS executables
VALUES
Fail Safe
0 (off)
Default
0 (off) mpas_readonly_text
semantics are disabled
Allowed values
0 (off) or 1 (on)
DESCRIPTION
This tunable allows 32-bit MPAS executables to have readonly text segment. By default, text segment is
writable for 32-bit MPAS executables.
In addition to setting this tunable to 1, the data segment should also start on a page aligned boundary (as
set by the tunable base_pagesize
). If not, the text segment will continue to be writable even when
this tunable is set.
When text and data are part of the same page, the text segment cannot be made read-only as data seg-
ment needs to be writable.
When the tunable
base_pagesize
is set to the default of 4K, data segment starts on its own page. So,
setting
mpas_readonly_text
to 1 will always result in a read-only text segment in this case.
When the tunable
base_pagesize
is set to one of the supported page sizes other than 4K, chances are
that text and data segment are part of the same page. In that case, setting
mpas_readonly_text
to 1
may or may not give a read-only text segment.
See the Adaptive Address Space Whitepaper for more information on MPAS.
Who Is Expected to Change This Tunable?
System administrators who wish to have read-only text segment for 32-bit MPAS executables.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Tunable Be Turned Off?
If there is any legacy 32-bit MPAS application that depended on the writable attribute of the text seg-
ment, the tunable should be turned off.
When Should the Tunable Be Turned On?
If a 32-bit MPAS application wishes to have its text segment read-only, this tunable must be turned on.
What Other Tunables Should Be Changed at the Same Time?
None.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its
meaning changed in future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-
ter values. After installation, some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable values, consult the documentation for
the kernel software being installed. For information about optional kernel software that was factory
installed on your system, see HP-UX Release Notes at
http://www.hp.com/go/hpux-core-docs.
AUTHOR
mpas_readonly_text was developed by HP.
SEE ALSO
ld(1), kctune(1M), base_pagesize(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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