[pso] NULLed fork()

[Stefan Bucur]

Salutare!

Experimentand un pic cu tabela apelurilor de sistem, am dat peste o situatie
ciudata: orice functie de interceptare as seta pe pozitia __NR_fork (cu
valoarea 2), aceasta nu are nici un efect. Mai mult, chiar daca pun NULL in
acel loc, in continuare sistemul functioneaza fara probleme:

blackwing:~# gdb /usr/src/linux/vmlinux /proc/kcore
GNU gdb 6.4.90-debian
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
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Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...Using host libthread_db
library "/lib/tls/i686/cmov/libthread_db.so.1".


warning: shared library handler failed to enable breakpoint
Core was generated by `root=/dev/hda2 ro'.
*(gdb) print /x ((long*)&sys_call_table)[0]
$1 = 0xc8826050*
(gdb) print /x ((long*)&sys_call_table)[1]
$2 = 0xc011a7d0
*(gdb) print /x ((long*)&sys_call_table)[2]
$3 = 0x0*
(gdb) print /x ((long*)&sys_call_table)[3]
$4 = 0xc016a8e0
(gdb) print /x ((long*)&sys_call_table)[4]
$5 = 0xc016a950

In acelasi timp, pe pozitia 0 se regaseste "my_syscall", care functioneaza
fara probleme (in log-uri imi arata ca este apelata de catre tester).

Care poate fi explicatia? :-/

Stefan Bucur
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