RFH - fakeroot-ng and ptrace, not Debian specific
Hi all,
I'm sending this request for help in the hope that it randomly hit one
of the smart people on this list, but it is, as far as I can tell, not
Debian specific.
Fakeroot-ng is a clean re-implementation of the fakeroot principle,
based on ptrace rather than LD_PRELOAD. As a result it can go where
fakeroot cannot (no problem with statically compiled binaries, can do
almost full chroot with full chroot planned) on the one hand, but has
some drawbacks as well (no hope of being as quick as fakeroot, has some
highly platform specific code, fairly complex). You can read more about
it at http://fakeroot-ng.lingnu.com
The version currently in trunk has an attempt to remove some Linux
specific hacks when attaching to a newly created process. It does so by
changing a "fork" into "clone", and adding the "CLONE_PTRACE" whether
the original specified it or not. This is the exact same thing strace does.
Unlike strace, however, fakeroot-ng is failing to attach itself to newly
created threads. I'd say I was passing the wrong flags to the kernel,
but if I watch all system calls performed by the debugger (yes, using
strace), I seem to see that strace and fakeroot-ng do exactly the same
thing. The only difference is that for strace it works.
I need someone who is either a ptrace expert, or who has a fresh set of
eyes and some patience, to help me look at it and figure out what I'm
doing wrong.
Thanks,
Shachar
--
Shachar Shemesh
Lingnu Open Source Consulting Ltd.
http://www.lingnu.com
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