Justus Winter <4win...@informatik.uni-hamburg.de> skribis:
> Quoting Samuel Thibault (2013-09-09 19:40:23)
>> Ludovic Courtès, le Mon 09 Sep 2013 18:48:03 +0200, a écrit :
>> > Samuel Thibault <samuel.thiba...@gnu.org> skribis:
>> > > Ludovic Courtès, le Sat 07 Sep 2013 22:04:06 +0200, a écrit :
>> > >> However, wouldn’t it be preferable to fix it by interposing on
>> > >> ‘task_create’ calls, à la clans & chiefs? (IIUC, this can be done with
>> > >> by setting the TASK_KERNEL_PORT of a task.)
>> > >
>> > > Apparently task_create is a kernel trap.
>> >
>> > Isn’t rpctrace able to interpose on it?
>>
>> I don't think there is any way to interpose a trap.
>>
>> It probably happens that libc nicely uses the RPC, but nothing prevents
>> a process from raising a trap.
>
> As I understand [0] one can interpose all Mach system calls
Yes, and ‘task_create’ is no exception to the rule:
--8<---------------cut here---------------start------------->8---
ludo@darnassus:~$ rpctrace -o ,,s sh -c 'sleep 2 & true'
rpctrace: get an unknown send right from process 19817
rpctrace: get an unknown send right from process 19816
rpctrace: get an unknown send right from process 19816
rpctrace: get an unknown send right from process 19816
ludo@darnassus:~$ grep task_ ,,s
task110(pid19816)->task_get_special_port (4) = 0 117<--115(pid19816)
task110(pid19816)->task_set_special_port (4 (null)) = 0
task110(pid19816)->vm_allocate (0 4096
1)task110(pid19816)->task_set_special_port (3 117<--130(pid-1)) = 0 19226624
task110(pid19816)->task_create (1) = 0 140<--139(pid19816)
task110(pid19816)->task_threads () = 0 {thread112(pid19816) thread128(pid19816)}
task140(pid19816)->task_set_special_port (3 115) = 0
task140(pid19817)->mach_port_set_qlimit (pn{ 20}
1)task110(pid19816)->task_terminate () = 0
task140(pid19817)->task_get_special_port (4) = 0 141<--136(pid19817)
task140(pid19817)->task_set_special_port (4 (null)) = 0
task140(pid19817)->vm_allocate (0 4096
1)task140(pid19817)->task_set_special_port (3 141<--159(pid-1)) = 0 19226624
--8<---------------cut here---------------end--------------->8---
So what about using that technique to achieve what you want? :-)
Ludo’.
