proc_pid_map_files(5) — Linux manual page


proc_pid_map_files(5)      File Formats Manual     proc_pid_map_files(5)

NAME         top

       /proc/pid/map_files/ - memory-mapped files

DESCRIPTION         top

       /proc/pid/map_files/ (since Linux 3.3)
              This subdirectory contains entries corresponding to
              memory-mapped files (see mmap(2)).  Entries are named by
              memory region start and end address pair (expressed as
              hexadecimal numbers), and are symbolic links to the mapped
              files themselves.  Here is an example, with the output
              wrapped and reformatted to fit on an 80-column display:

                  # ls -l /proc/self/map_files/
                  lr--------. 1 root root 64 Apr 16 21:31
                              3252e00000-3252e20000 -> /usr/lib64/

              Although these entries are present for memory regions that
              were mapped with the MAP_FILE flag, the way anonymous
              shared memory (regions created with the MAP_ANON |
              MAP_SHARED flags) is implemented in Linux means that such
              regions also appear on this directory.  Here is an example
              where the target file is the deleted /dev/zero one:

                  lrw-------. 1 root root 64 Apr 16 21:33
                              7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)

              Permission to access this file is governed by a ptrace
              access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

              Until Linux 4.3, this directory appeared only if the
              CONFIG_CHECKPOINT_RESTORE kernel configuration option was

              Capabilities are required to read the contents of the
              symbolic links in this directory: before Linux 5.9, the
              reading process requires CAP_SYS_ADMIN in the initial user
              namespace; since Linux 5.9, the reading process must have
              either CAP_SYS_ADMIN or CAP_CHECKPOINT_RESTORE in the
              initial (i.e. root) user namespace.

SEE ALSO         top


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Linux man-pages 6.9.1          2024-05-02          proc_pid_map_files(5)