Differences between version 9 and predecessor to the previous major change of MemoryMap.
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| Newer page: | version 9 | Last edited on Tuesday, March 20, 2007 3:42:10 am | by DeanDavis | Revert |
| Older page: | version 8 | Last edited on Sunday, November 14, 2004 12:20:47 pm | by AristotlePagaltzis | Revert |
@@ -1,56 +1,60 @@
-The [Linux] VirtualMemory Map (as seen by a UserSpace program)
-
-| __Starts at__ | __Contains__
-| ffffffff |< End of the universe
-| ffffe000 |< vsyscall table (new in 2.5.x)
-| c0000000 |< Off limits, reserved for the kernel
-| bfffffff |< Process stack (grows down)
-| bffff000 |< Process heap (grows up)
-| 40000000 |< Libraries
-| zzzzzzzz |< Unused
-| yyyyyyyy |< __.bss__, uninitialised program data
-| xxxxxxxx |< __.data__ segment, initialised program data
-| 08048000 |< __.text__ segment, program code
-| 00000000 |< Unmapped to trap [NULL] pointers
-
+The [Linux] VirtualMemory Map (as seen by a UserSpace program)<br>
+<code>
+| __Starts at__| __Contains__<br>
+| ffffffff |< End of the universe<br>
+| ffffe000 |< vsyscall table (new in 2.5.x)<br>
+| c0000000 |< Off limits, reserved for the kernel<br>
+| bfffffff |< Process stack (grows down)<br>
+| bffff000 |< Process heap (grows up)<br>
+| 40000000 |< Libraries<br>
+| zzzzzzzz |< Unused<br>
+| yyyyyyyy |< __.bss__, uninitialised program data<br>
+| xxxxxxxx |< __.data__ segment, initialised program data<br>
+| 08048000 |< __.text__ segment, program code<br>
+| 00000000 |< Unmapped to trap [NULL] pointers<br><br>
+</code>
"BSS" means __b__lock __s__tarted by __s__ymbol and is a segment of uninitialised that is only stored in the BinaryExecutable image as a length and offset, since it would otherwise waste space. The "text" segment on the other hand contains ''initialized'' global variables and ''is'' stored in the BinaryExecutable.
!!Practical examples
!Library-mapped memory (using ldd(1))
- $ ldd /bin/ls
- librt.so.1 => /lib/librt.so.1 (0x40026000)
- libc.so.6 => /lib/libc.so.6 (0x40038000)
- libpthread.so.0 => /lib/libpthread.so.0 (0x4016a000)
- /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
+ $ ldd /bin/ls<br>
+ librt.so.1 => /lib/librt.so.1 (0x40026000)<br>
+ libc.so.6 => /lib/libc.so.6 (0x40038000)<br>
+ libpthread.so.0 => /lib/libpthread.so.0 (0x4016a000)<br>
+ /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)<br>
-!Program code
- $ cat > x.c
- #include <stdio.h>
- int main(void) {printf("%p\n", main);return ;}
- $ gcc -o x x.c && ./x
- 0x8048344
- $
-(this is printing the address of the main function.)
+!Program code<br>
+ $ cat > x.c<br>
+
+ #include <stdio.h><br
>
+ int main(void) {printf("%p\n", main);return ;}<br>
+ $ gcc -o x x.c && ./x<br>
+ 0x8048344<br>
+ $<br>
+(this is printing the address of the main function.)<br>
!Process Heap
- $ cat > x2.c
- #include <stdio.h>
- int main(void) {char c;printf("%p\n", &c); return ;}
- $ gcc -o x2 x2.c && ./x2
- 0xbffffab7
+ $ cat > x2.c<br>
+<code>
+ #include <stdio.h><br
>
+ int main(void) {char c;printf("%p\n", &c); return ;}<br></code>
+ $ gcc -o x2 x2.c && ./x2<br>
+ 0xbffffab7<br>
!Process Data and bss segment
-
$ perl -e 'my $var; print \$var . "\n"'
- SCALAR(0x814f38c)
-(note that this is the address in the [Perl] interpreter)
+
+
$ perl -e 'my $var; print \$var . "\n"'<br>
+ SCALAR(0x814f38c)<br>
+(note that this is the address in the [Perl] interpreter)<br>
$ cat > x3.c
-
#include <stdio.h>
- #include <stdlib.h>
- int main(void) {char *p=!malloc(3);printf("%p\n", p); return ;}
- $ gcc -o x3 x3.c && ./x3
- 0x8049628
+
+
#include <stdio.h><br
>
+ #include <stdlib.h><br
>
+ int main(void) {char *p=!malloc(3);printf("%p\n", p); return ;}<br>
+ $ gcc -o x3 x3.c && ./x3<br>
+ 0x8049628<br>
Also,
cat /proc/''pid''/maps
gives you the memory map for a program :)
