89

Is it possible to dump the current memory allocated for a process (by PID) to a file? Or read it somehow?

Fragsworth
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9 Answers9

83

I've made a script that accomplishes this task.

The idea commes from James Lawrie's answer and this post: https://web.archive.org/web/20190921091546/http://www.linuxforums.org/forum/programming-scripting/52375-reading-memory-other-processes-post287195.html#post287195

#!/bin/bash

grep rw-p /proc/$1/maps 

| sed -n 's/^([0-9a-f])-([0-9a-f]) .*$/\1 \2/p' 

| while read start stop; do 

    gdb --batch --pid $1 -ex 

        "dump memory $1-$start-$stop.dump 0x$start 0x$stop"; 

done

put this in a file (eg. "dump-all-memory-of-pid.sh") and make it executable

usage: ./dump-all-memory-of-pid.sh [pid]

The output is printed to files with the names: pid-startaddress-stopaddress.dump

Dependencies: gdb

AsukaMinato
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A. Nilsson
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78

I'm not sure how you dump all the memory to a file without doing this repeatedly (if anyone knows an automated way to get gdb to do this please let me know), but the following works for any one batch of memory assuming you know the pid: 

$ cat /proc/[pid]/maps

This will be in the format (example): 

00400000-00421000 r-xp 00000000 08:01 592398                             /usr/libexec/dovecot/pop3-login
00621000-00622000 rw-p 00021000 08:01 592398                             /usr/libexec/dovecot/pop3-login
00622000-0066a000 rw-p 00622000 00:00 0                                  [heap]
3e73200000-3e7321c000 r-xp 00000000 08:01 229378                         /lib64/ld-2.5.so
3e7341b000-3e7341c000 r--p 0001b000 08:01 229378                         /lib64/ld-2.5.so

Pick one batch of memory (so for example 00621000-00622000) then use gdb as root to attach to the process and dump that memory: 

$ gdb --pid [pid]
(gdb) dump memory /root/output 0x00621000 0x00622000

Then analyse /root/output with the strings command, less you want the PuTTY all over your screen.

slm
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James L
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54

try 

    gcore $pid

where $pid is the actual number of the pid; for more info see: info gcore

may take some time for the dump to happen, and some memory may not be readable, but is good enough... be aware also that it can create big files, I just created a 2GB file that way..

Aquarius Power
  • 841
18

Pure bash solution:

procdump() 
( 
    cat /proc/$1/maps | grep "rw-p" | awk '{print $1}' | ( IFS="-"
    while read a b; do
        dd if=/proc/$1/mem bs=$( getconf PAGESIZE ) iflag=skip_bytes,count_bytes \
           skip=$(( 0x$a )) count=$(( 0x$b - 0x$a )) of="$1_mem_$a.bin"
    done )
)

Usage: procdump PID

for a cleaner dump filter out *.so memory mapped shared libraries and empty memory ranges:

procdump()
( 
    cat /proc/$1/maps | grep -Fv ".so" | grep " 0 " | awk '{print $1}' | ( IFS="-"
    while read a b; do
        dd if=/proc/$1/mem bs=$( getconf PAGESIZE ) iflag=skip_bytes,count_bytes \
           skip=$(( 0x$a )) count=$(( 0x$b - 0x$a )) of="$1_mem_$a.bin"
    done )
)
mxmlnkn
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Zibri
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5

I made my own program to dump the entire process memory as well, it's in C so it can be cross-compiled to Android, which is what I needed.

You can also specify IP address and tcp port. Source code here.

Community
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Tal Aloni
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3

man proc says :

/proc/[pid]/mem This file can be used to access the pages of a process's memory through open(2), read(2), and lseek(2).

Maybe it can help you

Dom
  • 6,873
2

Tool to dump process to standard output, pcat/memdump:

Michael Springer
  • 29
1

You can now use procdump from SysInternals suite on Linux:

https://github.com/Microsoft/ProcDump-for-Linux

makumo
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0

If you want to dump a separate memory segment of the running process without creating huge core file (say with gcore), you can use a small tool from here. There is also one-liner in README if you wish to dump all readable segments into separate files.

Nopius
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