Lev Olshvang wrote:
Hi Sha*C*har,
About disadvantages of ptrace (IMHO):
1. controlling process should take care of signal processing (signals
are delivered to the caller ??)
No. Signals halt the debugged process, and the controlling process gets
notified. It just needs to call "ptrace( PTRACE_CONT" with the right
signal - no big deal if you know what you are doing. Of course, you do
need to block the SIGSTOP the process receives when it gets attached to.
or just resent them to the tracee. I am not sure signal delivery
is reliable
Pretty reliable.
2. You introduce new daemon wasting the tiny RAM you have.
No, it is an already existing daemon. Besides, 32MB is not tiny. 32MB is
yamba.
I'll just note that I can understand why people don't like ptrace. It is
a complicated interface with a lot of platform specific cases,
especially as you dive deeper and deeper into the application. Truth be
told, after writing fakeroot-ng, I have lost a lot of my fear of it.
And one thing I did learn from working on fakeroot-ng: it is neither
unreliable nor inconsistent. It can be a bit unpredictable at times,
true, as you move between platforms, but not when what you are trying to
do is as basic as what I offered here.
Still, given a better solution (such as Oron's), I will prefer a
non-ptrace solution (not to mention that it required even less lines of
code than the ptrace one, which was already fairly small).
Shachar
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