proc.5: Add info about /proc/[pid]/map_files directory

It was added into Linux v3.3 and provides info about files being mmap-ed in a way _very_ similar to how /proc/[pid]/fd works. Thus I thought that the best place for the map_files' doc is where where the fd's doc is.

Signed-off-by Pavel Emelyanov <[email protected]>

---

man5/proc.5 +17 -0

index 30ca3a9..1226747 100644
@@ -285,6 +285,23 @@ Thus the example command above could be written as:
 .RB "$" " foobar \-i /dev/stdin \-o /dev/stdout ..."
 .fi
 .in
+.TP
+.IR /proc/[pid]/map_files/ " (since kernel 3.3)
+This subdirectory contains entries corresponding to memory mapped
+files (see
+.BR mmap (2)).
+Entries are named by memory region start and end pair,
+and are symbolic links to the corresponding files.
+
+Although these entries are present for memory regions that were
+mapped with
+.BR MAP_FILE
+flag, the way anonymous shared memory (regions created with
+.B MAP_ANON | MAP_SHARED
+flags)
+is implemented in Linux
+makes such regions also appear on this directory. In that case
+the target file would be the /dev/zero one.
 .\" FIXME Describe /proc/[pid]/loginuid
 .\"       Added in 2.6.11; updating requires CAP_AUDIT_CONTROL
 .\"       CONFIG_AUDITSYSCALL

Hi Pavel,

Quoted 5 lines · Pavel Emelyanov

It was added into Linux v3.3 and provides info about files being mmap-ed in a way _very_ similar to how /proc/[pid]/fd works. Thus I thought that the best place for the map_files' doc is where where the fd's doc is.

Signed-off-by Pavel Emelyanov <[email protected]>

Could you please resubmit with some added text that shows an example of what you see in this file (including a /dev/zero case)? Also, the patch should mention that CONFIG_CHECKPOINT_RESTORE is required.

Thanks,

Michael

Quoted 29 lines

---

man5/proc.5 +17 -0

index 30ca3a9..1226747 100644
@@ -285,6 +285,23 @@ Thus the example command above could be written as:
 .RB "$" " foobar \-i /dev/stdin \-o /dev/stdout ..."
 .fi
 .in
+.TP
+.IR /proc/[pid]/map_files/ " (since kernel 3.3)
+This subdirectory contains entries corresponding to memory mapped
+files (see
+.BR mmap (2)).
+Entries are named by memory region start and end pair,
+and are symbolic links to the corresponding files.
+
+Although these entries are present for memory regions that were
+mapped with
+.BR MAP_FILE
+flag, the way anonymous shared memory (regions created with
+.B MAP_ANON | MAP_SHARED
+flags)
+is implemented in Linux
+makes such regions also appear on this directory. In that case
+the target file would be the /dev/zero one.
 .\" FIXME Describe /proc/[pid]/loginuid
 .\"       Added in 2.6.11; updating requires CAP_AUDIT_CONTROL

man5/proc.5 Thus the example command above could be written as: · line 307

Quoted 1 line

man5/proc.5 +0 -0

 .\"       CONFIG_AUDITSYSCALL

--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/

Hi Pavel... Ping!

Cheers,

Michael

Quoted 46 lines · Michael Kerrisk (man-pages)

Hi Pavel,

Quoted 5 lines · Pavel Emelyanov

It was added into Linux v3.3 and provides info about files being mmap-ed in a way _very_ similar to how /proc/[pid]/fd works. Thus I thought that the best place for the map_files' doc is where where the fd's doc is.

Signed-off-by Pavel Emelyanov <[email protected]>

Could you please resubmit with some added text that shows an example of what you see in this file (including a /dev/zero case)? Also, the patch should mention that CONFIG_CHECKPOINT_RESTORE is required.

Thanks,

Michael

Quoted 29 lines

---

man5/proc.5 +17 -0

index 30ca3a9..1226747 100644
@@ -285,6 +285,23 @@ Thus the example command above could be written as:
 .RB "$" " foobar \-i /dev/stdin \-o /dev/stdout ..."
 .fi
 .in
+.TP
+.IR /proc/[pid]/map_files/ " (since kernel 3.3)
+This subdirectory contains entries corresponding to memory mapped
+files (see
+.BR mmap (2)).
+Entries are named by memory region start and end pair,
+and are symbolic links to the corresponding files.
+
+Although these entries are present for memory regions that were
+mapped with
+.BR MAP_FILE
+flag, the way anonymous shared memory (regions created with
+.B MAP_ANON | MAP_SHARED
+flags)
+is implemented in Linux
+makes such regions also appear on this directory. In that case
+the target file would be the /dev/zero one.
 .\" FIXME Describe /proc/[pid]/loginuid
 .\"       Added in 2.6.11; updating requires CAP_AUDIT_CONTROL

Quoted 8 lines

man5/proc.5 Thus the example command above could be written as: · line 307

Quoted 1 line

man5/proc.5 +0 -0

 .\"       CONFIG_AUDITSYSCALL

--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/

--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
.