Strange Virtual Mem Mapping...

[Arijit Das <arijit_engg2001@xxxxxxxxx>]

I have RH3.0 installed in an AMD64 machine.

 

In this system, when I look at the virtual address space mappings of a process (say a sleep process), I see quite a few strange memory region mappings which are neither readable, nor writable/executable and all of them are Private (i.e. unshared). Check this:

 

      1024    ---p    /lib64/tls/libc-2.3.2.so

      1024    ---p    /lib64/tls/libm-2.3.2.so

      1024    ---p    /lib64/tls/librtkaio-2.3.2.so

      1024    ---p    /lib64/tls/libpthread-0.60.so

 

On the other hand, when I look at the same info in a Rh7.2 system, I don't see anything like that...

 

Question: How do I make sense of an unreadable/unwritable/unexecutable privately mapped memory region? What is its usage? It looks like a 100% wastage of the process's address space. How is the process using it? Any idea...anybody?

 

You can find the sample "sleep" commands below.

 

Thanks,
Arijit

 

RH3.0 on AMD64:

=============

vgamd126:arijit>sleep 400 &                                                                                    
[1] 19916

vgamd126:arijit>pmap 19916
 Size (KB)    Perm    Associated files (if any)                   
==========    ====    =============================================
        16    r-xp    /bin/sleep
         4    rw-p    /bin/sleep
       132    rwxp   
      1108    r-xp    /lib64/ld-2.3.2.so
         4    rw-p    /lib64/ld-2.3.2.so
         4    rw-p   
       540    r-xp    /lib64/tls/libm-2.3.2.so
      1024    ---p    /lib64/tls/libm-2.3.2.so
         4    rw-p    /lib64/tls/libm-2.3.2.so
         4    rw-p   
        36    r-xp    /lib64/tls/librtkaio-2.3.2.so
      1024    ---p    /lib64/tls/librtkaio-2.3.2.so
         4    rw-p    /lib64/tls/librtkaio-2.3.2.so
        64    rw-p   
      1260    r-xp    /lib64/tls/libc-2.3.2.so
      1024    ---p    /lib64/tls/libc-2.3.2.so
        20    rw-p    /lib64/tls/libc-2.3.2.so
        16    rw-p   
        60    r-xp    /lib64/tls/libpthread-0.60.so
      1024    ---p    /lib64/tls/libpthread-0.60.so
         4    rw-p    /lib64/tls/libpthread-0.60.so
        20    rw-p   
     31396    r--p    /usr/lib/locale/locale-archive
        24    rw-p   

Total Virtual Memory = 38816 KB
vgamd126:arijit>

 

 

RH7.2 in i686

==========

eurika120:arijit>sleep 400 &                                                                                           
[1] 11065

eurika120:arijit>pmap 11065
 Size (KB)    Perm    Associated files (if any)                   
==========    ====    =============================================
        12    r-xp    /bin/sleep
         4    rw-p    /bin/sleep
         8    rwxp   
        88    r-xp    /lib/ld-2.2.4.so
         4    rw-p    /lib/ld-2.2.4.so
         4    r--p    /usr/lib/locale/en_US/LC_IDENTIFICATION
         4    r--p    /usr/lib/locale/en_US/LC_MEASUREMENT
         4    r--p    /usr/lib/locale/en_US/LC_TELEPHONE
         4    r--p    /usr/lib/locale/en_US/LC_ADDRESS
         4    r--p    /usr/lib/locale/en_US/LC_NAME
         4    r--p    /usr/lib/locale/en_US/LC_PAPER
         4    r--p    /usr/lib/locale/en_US/LC_MESSAGES/SYS_LC_MESSAGES
         4    r--p    /usr/lib/locale/en_US/LC_MONETARY
        24    r--p    /usr/lib/locale/en_US/LC_COLLATE
         4    r--p    /usr/lib/locale/en_US/LC_TIME
         4    r--p    /usr/lib/locale/en_US/LC_NUMERIC
         4    rw-p   
       136    r-xp    /lib/i686/libm-2.2.4.so
         4    rw-p    /lib/i686/libm-2.2.4.so
        28    r-xp    /lib/librt-2.2.4.so
         4    rw-p    /lib/librt-2.2.4.so
        40    rw-p   
      1224    r-xp    /lib/i686/libc-2.2.4.so
        20    rw-p    /lib/i686/libc-2.2.4.so
        16    rw-p   
        52    r-xp    /lib/i686/libpthread-0.9.so
        32    rw-p    /lib/i686/libpthread-0.9.so
       172    r--p    /usr/lib/locale/en_US/LC_CTYPE
        24    rwxp   

Total Virtual Memory = 1936 KB
eurika120:arijit>

---

Yahoo! for Good
 
Click here to donate to the Hurricane Katrina relief effort. 
_______________________________________________
Redhat-devel-list mailing list
Redhat-devel-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/redhat-devel-list