proc_pid_map_files(5) File Formats Manual proc_pid_map_files(5)
NAME
/proc/pid/map_files/ - memory-mapped files
DESCRIPTION
/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 exam-
ple, with the output wrapped and reformatted to fit on an 80-col-
umn display:
# ls -l /proc/self/map_files/
lr--------. 1 root root 64 Apr 16 21:31
3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
...
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 imple-
mented in Linux means that such regions also appear on this di-
rectory. 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 CON-
FIG_CHECKPOINT_RESTORE kernel configuration option was enabled.
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
proc(5)
Linux man-pages 6.9.1 2024-05-02 proc_pid_map_files(5)
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