The Linux VirtualMemory Map (as seen by a UserSpace program)
| Starts at| Contains
"BSS" means block started by symbol 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.
| 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
$ 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)
$ cat > x.c
- include <stdio.h>
int main(void) {printf("%p\n", main);return 0;}
$ gcc -o x x.c && ./x
0x8048344
$
(this is printing the address of the main function.)
$ cat > x2.c
<code>
int main(void) {char c;printf("%p\n", &c); return 0;}
</code> $ gcc -o x2 x2.c && ./x2
0xbffffab7
$ perl -e 'my $var; print \$var . "\n"'
SCALAR(0x814f38c)
(note that this is the address in the Perl interpreter)
$ cat > x3.c
- include <stdio.h>
- include <stdlib.h>
int main(void) {char *p=!malloc(3);printf("%p\n", p); return 0;}
$ gcc -o x3 x3.c && ./x3
0x8049628
Also,
cat /proc/pid/maps
gives you the memory map for a program :)
One page links to MemoryMap: