Question

How can I find the address bounds of the call stack at runtime (via some symbol or register)? I’m using nm and readelf to pick through my symbols and I’m not finding one. In the case of registers, it seems I’m limited to the current frame’s base and stack pointers and not the starting address.

I’d like to shy away from answers that involve parsing /proc/pid/maps – I always feel awkward parsing text for a systems-related problem. I’m using g++ on Linux x86/x86_64.

EDIT: Can I use the x86 segment register SS to calculate it?

Answer 1

The /proc/pid/maps file on Linux provides some information on a process’s memory mappings:

$ cat /proc/self/maps 
00400000-0040b000 r-xp 00000000 08:03 709349                             /bin/cat
0060a000-0060b000 r--p 0000a000 08:03 709349                             /bin/cat
0060b000-0060c000 rw-p 0000b000 08:03 709349                             /bin/cat
00a2d000-00a4e000 rw-p 00000000 00:00 0                                  [heap]
7f6fdf418000-7f6fdf6bd000 r--p 00000000 08:03 489885                     /usr/lib/locale/locale-archive
...
7fff4669e000-7fff466bf000 rw-p 00000000 00:00 0                          [stack]
7fff467ff000-7fff46800000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

The pmap(1) command formats this information into a display that I find more pleasing:

$ pmap $$
11680:   bash
0000000000400000    896K r-x--  /bin/bash
...
00007ff31ae2d000      8K rw---  /lib/x86_64-linux-gnu/ld-2.13.so
00007fff66dd2000    132K rw---    [ stack ]
00007fff66dff000      4K r-x--    [ anon ]
ffffffffff600000      4K r-x--    [ anon ]
 total            29336K

Incidentally, in the eglibc source file dl-execstack.c, I found the following comment: There is no portable way to know the bounds of the initial thread’s stack so as to mprotect it. This probably means the best mechanism is to parse the /proc/pid/maps files, even though I think we’re all agreed it is tacky.