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 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/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 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
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.