PMAP(1) BSD General Commands Manual PMAP(1)NAMEpmap — display process memory map
SYNOPSISpmap [-adlmPRsv] [-A address] [-D number] [-E address] [-M core]
[-N system] [-p pid] [-S address] [-V address] [pid ...]
DESCRIPTION
The pmap utility lists the virtual memory mappings underlying the given
process. The start address of each entry is always given, and, depending
on the options given, other information such as the end address, the
underlying file's device and inode numbers, and various protection infor‐
mation will be displayed, along with the path to the file, if such data
is available.
By default, pmap displays information for its parent process, so that
when run from a shell prompt, the shell's memory information is dis‐
played. If other PIDs are given as arguments on the command line, infor‐
mation for those processes will be printed also. If the special PID of 0
is given, then information for the kernel's memory map is printed.
The options are as follows:
-A address Dumps the vm_amap structure found at address.
-a Display “all” information from the process's memory map.
This output mode is an amalgam of the contents of the
Solaris, Linux, and NetBSD style output modes.
-D number Enable various debug facilities. The number is a bit mask
of the values:
0x01 dump the process's vmspace structure
0x02 dump the process's vm_map structure
0x04 dump the vm_map.header structure
0x08 dump each vm_map_entry in its entirety
0x10 dump the vm_amap structure attached to the
vm_map_entry, if applicable
0x20 dump the vm_amap slot data, if present (requires
0x10)
0x40 dump the vm_anon data from the am_anon array, if
present (requires 0x20)
0x1000 dump the namei cache as it is traversed
-d Dumps the vm_map and vm_map_entry structures in a style sim‐
ilar to that of ddb(4). When combined with the -v option,
the device number, inode number, name, vnode addresses, or
other identifying information from the vm_map_entries will
be printed.
-E address Dumps the vm_map_entry structure found at address.
-l Dumps information in a format like the contents of the maps
pseudo-file under the /proc file system which was, in turn,
modeled after the similarly named entry in the Linux /proc
file system. When combined with the -v option, identifiers
for all entries are printed.
-M core Extract values associated with the name list from the speci‐
fied core instead of the default /dev/kmem.
-m Dumps information in the same format as the map pseudo-file
of the /proc file system. When the -v option is also given,
device number, inode number, and filename or other identify‐
ing information is printed.
-N system Extract the name list from the specified system instead of
the default /netbsd.
-P Causes pmap to print information about itself.
-p pid Tells pmap to print information about the given process. If
-p pid occurs last on the command line, the -p is optional.
-R Recurse into submaps. In some cases, a vm_map_entry in the
kernel will point to a submap. Using this flag tells pmap
to print the entries of the submap as well. The submap out‐
put is indented, and does not affect any total printed at
the bottom of the output.
-S address Dumps the vmspace structure found at address.
-s The Solaris style output format, modeled after the Solaris
command of the same name. This is the default output style.
-V address Dumps the vm_map structure found at address. Note that if
you print the vm_map of a process, there may not be a way to
properly determine which map entries are related to the
stack.
-v Verbose output. When used with -d, -l, or -m, more informa‐
tion is printed, possibly including device and inode num‐
bers, file path names, or other identifying information. If
specified more than once, a small note will be printed in
between two entries that are not adjacent, making the visual
identification of spaces in the process's map easier to see,
that indicates the number of pages and the amount of memory
space that is skipped.
The -P and -p options override each other, so the last one to appear on
the command line takes effect. If you do wish to see information about
pmap and another process as the same time, simply omit the -p and place
the extra PID at the end of the command line.
EXIT STATUSpmap exits 0 on success, and >0 if an error occurred.
EXAMPLES
While the meaning of most of the output is self-evident, some pieces of
it may appear to be a little inscrutable.
Here is a portion of the default output from pmap being run at an sh(1)
prompt showing the starting address of the map entry, the size of the map
entry, the current protection level of the map entry, and either the name
of the file backing the entry or some other descriptive text.
$ pmap
08048000 420K read/exec /bin/sh
080B1000 8K read/write /bin/sh
080B3000 28K read/write [ anon ]
080BA000 16K read/write/exec [ heap ]
...
When the ddb(4) output style is selected, the first thing printed is the
contents of the vm_map structure, followed by the individual map entries.
$ pmap-d
MAP 0xcf7cac84: [0x0->0xbfbfe000]
#ent=8, sz=34041856, ref=1, version=20, flags=0x41
pmap=0xcf44cee0(resident=<unknown>)
- 0xcfa3a358: 0x8048000->0x80b1000: obj=0xcf45a8e8/0x0, amap=0x0/0
submap=F, cow=T, nc=T, prot(max)=5/7, inh=1, wc=0, adv=0
...
The value of the flags field (in hexadecimal) is taken from the include
file <uvm/uvm_map.h>:
VM_MAP_PAGEABLE 0x01 entries are pageable
VM_MAP_INTRSAFE 0x02 interrupt safe map
VM_MAP_WIREFUTURE 0x04 future mappings are wired
VM_MAP_BUSY 0x08 map is busy
VM_MAP_WANTLOCK 0x10 want to write-lock
VM_MAP_DYING 0x20 map is being destroyed
VM_MAP_TOPDOWN 0x40 arrange map top-down
The “submap”, “cow”, and “nc” fields are true or false, and indicate
whether the map is a submap, whether it is marked for copy on write, and
whether it needs a copy. The “prot” (or protection) field, along with
“max” (maximum protection allowed) are made up of the following flags
from <uvm/uvm_extern.h>:
UVM_PROT_READ 0x01 read allowed
UVM_PROT_WRITE 0x02 write allowed
UVM_PROT_EXEC 0x04 execute allowed
The “obj” and “amap” fields are pointers to, and offsets into, the under‐
lying uvm_object or amap. The value for resident is always unknown
because digging such information out of the kernel is beyond the scope of
this application.
The two output styles that mirror the contents of the /proc file system
appear as follows:
$ pmap-m
0x8048000 0x80b1000 r-x rwx COW NC 1 0 0
0x80b1000 0x80b3000 rw- rwx COW NC 1 0 0
0x80b3000 0x80ba000 rw- rwx COW NNC 1 0 0
0x80ba000 0x80be000 rwx rwx COW NNC 1 0 0
...
$ pmap-l
08048000-080b1000 r-xp 00000000 00:00 70173 /bin/sh
080b1000-080b3000 rw-p 00068000 00:00 70173 /bin/sh
080b3000-080ba000 rw-p 00000000 00:00 0
080ba000-080be000 rwxp 00000000 00:00 0
...
Here the protection and maximum protection values are indicated with ‘r’,
‘w’, and ‘x’ characters, indicating read permission, write permission,
and execute permission, respectively. The “COW”, “NC”, and “NNC” values
that follow indicate, again, that the map is marked for copy on write and
either needs or does not need a copy. It is also possible to see the
value “NCOW” here, which indicates that an entry will not be copied. The
three following numbers indicate the inheritance type of the map, the
wired count of the map, and any advice value assigned via madvise(2).
In the second form, the permissions indicated are followed by a ‘p’ or
‘s’ character indicating whether the map entry is private or shared (copy
on write or not), and the numbers are the offset into the underlying
object, the device and numbers of the object if it is a file, and the
path to the file (if available).
As noted above (see section DESCRIPTION), the “all” output format is an
amalgam of the previous output formats.
$ pmap-a
Start End Size Offset rwxpc RWX I/W/A ...
08048000-080b0fff 420k 00000000 r-xp+ (rwx) 1/0/0 ...
...
In this format, the column labeled “rwxpc” contains the permissions for
the mapping along with the shared/private flag, and a character indicat‐
ing whether the mapping needs to be copied on write (‘+’) or has already
been copied (‘-’) and is followed by a column that indicates the maximum
permissions for the map entry. The column labeled “I/W/A” indicates the
inheritance, wired, and advice values for the map entry, as previously
described. The pointer value at the end of the output line for entries
backed by vnodes is the address of the vnode in question.
SEE ALSOls(1), stat(1), madvise(2), mmap(2), kvm(3), ddb(4), mount_procfs(8),
pmap(9)HISTORY
The pmap utility appeared in NetBSD 2.0.
AUTHORS
The pmap utility and documentation was written by Andrew Brown
⟨atatat@NetBSD.org⟩.
BUGS
Very little will work unless pmap is reading from the correct kernel in
order to retrieve the proper symbol information.
Since processes can change state while pmap is running, some of the
information printed may be inaccurate. This is especially important to
consider when examining the kernel's map, since merely executing pmap
will cause some of the information to change.
The pathnames to files backing certain vnodes (such as the text and data
sections of programs and shared libraries) are extracted from the ker‐
nel's namei cache which is considerably volatile. If a path is not found
there in its entirety, as much information as was available will be
printed. In most cases, simply running ls(1) or stat(1) with the
expected path to the file will cause the information to be reentered into
the cache.
The Solaris command by the same name has some interesting command line
flags that would be nice to emulate here. In particular, the -r option
that lists a process's reserved addresses, and the -x option that prints
resident/shared/private mapping details for each entry.
Some of the output modes can be or are wider than the standard 80 columns
of a terminal. Some sort of formatting might be nice.
SECURITY CONSIDERATIONS
The Solaris command controls access to processes the user does not own
via the permissions of its /proc file system. Since pmap uses kvm(3) to
read the requested data directly from kernel memory, no such limitation
exists.
If any of the -A, -E, -M, -N, -S, or -V options are used, any extra priv‐
ileges that pmap has will be dropped.
BSD February 6, 2009 BSD
