PR_SET_TAGGED_ADDR_CTRL(2const) — Linux manual page



NAME         top

       PR_SET_TAGGED_ADDR_CTRL - control support for passing tagged
       user-space addresses to the kernel

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <linux/prctl.h>  /* Definition of PR_* constants */
       #include <sys/prctl.h>

       int prctl(PR_SET_TAGGED_ADDR_CTRL, long mode, 0L, 0L, 0L);

DESCRIPTION         top

       Controls support for passing tagged user-space addresses to the
       kernel (i.e., addresses where bits 56—63 are not all zero).

       The level of support is selected by support, which can be one of
       the following:

       0L     Addresses that are passed for the purpose of being
              dereferenced by the kernel must be untagged.

              Addresses that are passed for the purpose of being
              dereferenced by the kernel may be tagged, with the
              exceptions summarized below.

       On success, the mode specified in mode is set for the calling

       If prctl(PR_SET_TAGGED_ADDR_CTRL, 0L, 0L, 0L, 0L) fails with
       EINVAL, then all addresses passed to the kernel must be untagged.

       Irrespective of which mode is set, addresses passed to certain
       interfaces must always be untagged:

       •  brk(2), mmap(2), shmat(2), shmdt(2), and the new_address
          argument of mremap(2).

          (Prior to Linux 5.6 these accepted tagged addresses, but the
          behaviour may not be what you expect.  Don't rely on it.)

       •  ‘polymorphic’ interfaces that accept pointers to arbitrary
          types cast to a void * or other generic type, specifically
          prctl(), ioctl(2), and in general setsockopt(2) (only certain
          specific setsockopt(2) options allow tagged addresses).

       This list of exclusions may shrink when moving from one kernel
       version to a later kernel version.  While the kernel may make
       some guarantees for backwards compatibility reasons, for the
       purposes of new software the effect of passing tagged addresses
       to these interfaces is unspecified.

       The mode set by this call is inherited across fork(2) and
       clone(2).  The mode is reset by execve(2) to 0 (i.e., tagged
       addresses not permitted in the user/kernel ABI).

RETURN VALUE         top

       On success, 0 is returned.  On error, -1 is returned, and errno
       is set to indicate the error.

ERRORS         top

       EINVAL mode is invalid or unsupported.

       EINVAL This feature is disabled via /proc/sys/abi/

FILES         top


STANDARDS         top

       Linux.  arm64 only.

HISTORY         top

       Linux 5.4 (arm64).

CAVEATS         top

       This call is primarily intended for use by the run-time
       environment.  A successful PR_SET_TAGGED_ADDR_CTRL call elsewhere
       may crash the calling process.  The conditions for using it
       safely are complex and system-dependent.  Don't use it unless you
       know what you are doing.

SEE ALSO         top

       prctl(2), PR_SET_TAGGED_ADDR_CTRL(2const)

       For more information, see the kernel source file

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
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Linux man-pages 6.9.1          2024-06-01PR_SET_TAGGED_ADDR_CTRL(2const)

Pages that refer to this page: prctl(2)PR_GET_TAGGED_ADDR_CTRL(2const)PR_SET_TAGGED_ADDR_CTRL(2const)