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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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PR_MPX_ENABLE_MANAGEMENT(2const) PR_MPX_ENABLE_MANAGEMENT(2const)
PR_MPX_ENABLE_MANAGEMENT, PR_MPX_DISABLE_MANAGEMENT - enable or
disable kernel management of Memory Protection eXtensions (MPX)
Standard C library (libc, -lc)
#include <linux/prctl.h> /* Definition of PR_* constants */
#include <sys/prctl.h>
[[deprecated]] int prctl(PR_MPX_ENABLE_MANAGEMENT, 0L, 0L, 0L, 0L);
[[deprecated]] int prctl(PR_MPX_DISABLE_MANAGEMENT, 0L, 0L, 0L, 0L);
Enable or disable kernel management of Memory Protection
eXtensions (MPX) bounds tables.
MPX is a hardware-assisted mechanism for performing bounds
checking on pointers. It consists of a set of registers storing
bounds information and a set of special instruction prefixes that
tell the CPU on which instructions it should do bounds
enforcement. There is a limited number of these registers and
when there are more pointers than registers, their contents must
be "spilled" into a set of tables. These tables are called
"bounds tables" and the MPX prctl() operations control whether the
kernel manages their allocation and freeing.
When management is enabled, the kernel will take over allocation
and freeing of the bounds tables. It does this by trapping the
#BR exceptions that result at first use of missing bounds tables
and instead of delivering the exception to user space, it
allocates the table and populates the bounds directory with the
location of the new table. For freeing, the kernel checks to see
if bounds tables are present for memory which is not allocated,
and frees them if so.
Before enabling MPX management using PR_MPX_ENABLE_MANAGEMENT, the
application must first have allocated a user-space buffer for the
bounds directory and placed the location of that directory in the
bndcfgu register.
These calls fail if the CPU or kernel does not support MPX.
Kernel support for MPX is enabled via the CONFIG_X86_INTEL_MPX
configuration option. You can check whether the CPU supports MPX
by looking for the mpx CPUID bit, like with the following command:
cat /proc/cpuinfo | grep ' mpx '
A thread may not switch in or out of long (64-bit) mode while MPX
is enabled.
All threads in a process are affected by these calls.
The child of a fork(2) inherits the state of MPX management.
During execve(2), MPX management is reset to a state as if
PR_MPX_DISABLE_MANAGEMENT had been called.
On success, 0 is returned. On error, -1 is returned, and errno is
set to indicate the error.
ENXIO The kernel or the CPU does not support MPX management.
Check that the kernel and processor have MPX support.
None.
Linux 3.19. Removed in Linux 5.4. Only on x86.
Due to a lack of toolchain support, PR_MPX_ENABLE_MANAGEMENT and
PR_MPX_DISABLE_MANAGEMENT are not supported in Linux 5.4 and
later.
prctl(2)
For further information on Intel MPX, see the kernel source file
Documentation/x86/intel_mpx.txt.
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-06-02PR_MPX_ENABLE_MANAGEMENT(2const)
Pages that refer to this page: prctl(2)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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