chatr - change program's internal attributes
chatr [+ed flag] file... [+bp flag] [value] [+l3 flag]
Change the program attribute that enables user code to
execute from data (stack or heap). The flag values are
enable and disable to change this attribute. Tune binary
files for properties different from the system-wide big
page memory allocation settings. This allows for more
flexible performance tuning. Enable big pages using any
big pages tuning parameters previously set with the chatr
utility. Disable big pages using any big pages tuning
parameters previously set with the chatr utility. Use
system-wide setting for big pages using any big pages tuning
parameters set with the chatr utility. Allow big
pages to distribute memory across RADs as a priority over
getting the largest page size possible.
Default value: 1 (Use smp)
Setting the value to 0 enables this feature. The
minimum amount of anonymous memory (in Kbytes) that
a user process must request before the kernel will
map a virtual page in the process address space to
more than one physical page. Anonymous memory is
requested by calls to mmap(), nmmap(), malloc(),
and amalloc().
Default value: 64 (Kbytes)
Minimum value: 0 (big pages allocation mode disabled
for anonymous memory)
Setting the value to 0 or -1 causes the value to be
set to system-wide value. The minimum amount of
memory (in Kbytes) that a user process must request
for a program text object before the kernel will
map a virtual page in the process address space to
more than one physical page. Allocations for program
text objects are generated when the process
executes a program or loads a shared library.
Default value: 64 (Kbytes)
Minimum value: 0 (big pages memory allocation disabled
for program text objects)
Setting the value to 0 or -1 causes the value to be
set to system-wide value. The minimum amount of
System V shared memory (in Kbytes) that a user process
must request before the kernel will map a virtual
page in the process address space to more than
one physical page.
Default value: 64 (Kbytes)
Minimum value: 0 (big pages memory allocation disabled
for program text objects)
Setting the value to 0 or -1 causes the value to be
set to system-wide value. The minimum amount (in
Kbytes) of segmented shared memory (System V shared
memory with shared page tables) that a user process
must request before the kernel will map a virtual
page in the process address space to more than one
physical page.
Default value: 64 (Kbytes)
Minimum value: 0 (big pages memory allocation disabled
for program text objects)
Setting the value to 0 or -1 causes the value to be
set to system-wide value. The minimum amount of
memory (in Kbytes) needed for the user process
stack before the kernel will map a virtual page in
the process address space to more than one physical
page.
Default value: 64 (Kbytes)
Minimum value: 0 (big pages memory allocation disabled
for program text objects)
Setting the value to 0 or -1 causes the value to be
set to system-wide value.
enable Enable big pages Tune binary files for properties
different from the system-wide level3 granularity
(l3gh). This allows for more flexible performance
tuning. Disable level 3 granualrity
hints. Enable level 3 granularity hints using
parameters previously set with the chatr utility.
Use system-wide setting for level 3 granularity
hints. Enable level 3 granularity hints in anonymous
memory. Anonymous memory is requested by
calls to mmap(), nmmap(), malloc(), and amalloc().
Setting the value to any non-zero value enables
this feature. Setting the value to zero disables
it. Enable level 3 granularity hints in System V
shared memory
Setting the value to any non-zero value enables
this feature. Setting the value to zero disables
it. Enable level 3 granularity hints in segmented
shared memory (System V shared memory with shared
page tables).
Setting the value to any non-zero value enables
this feature. Setting the value to zero disables
it.
The chatr command changes a program's internal attributes.
Upon completion, chatr prints the file's old and new values
to standard output.
The +ed option of chatr is used to specify that a particular
binary must be able to execute from its stack or heap,
regardless of the system default setting. This allows a
restrictive system default while not preventing legitimate
programs from executing code in data. Ideally this option
should be set (if needed) by the program's provider, to
minimize the need for manual intervention by system administrators.
The chatr command can only be used to modify the
attributes of executable object files, and shared
libraries. It does not support archived libraries, or
object files that have been relocated.
ENVIRONMENT VARIABLES [Toc] [Back] The following environment variables affect the execution
of the chatr command: Provides a default value for the
internationalization variables that are unset or null. If
LANG is unset or null, the corresponding value from the
default locale is used. If any of the internationalization
variables contain an invalid setting, the utility behaves
as if none of the variables had been defined. If set to a
non-empty string value, overrides the values of all the
other internationalization variables. Determines the
locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments). Determines
the locale for the format and contents of diagnostic
messages written to standard error. Determines the location
of message catalogues for the processing of LC_MESSAGES.
Functions: mmap(2)
chatr(1)
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