Jan Engelhardt wrote:
Hi Edward,
that the environment buffer is assumed to immediately follow the
command line buffer.
The environment buffer is not assumed to be there, it is _known_ to come right
after the argument string, because that is how the kernel sets it up on execve
(for x86 at least).
Is that in a spec somewhere? Otherwise, I would argue that it isn't
_known_ to come right after the argument string, it just _happens_ to
come right after the argument string. This could change in future kernels.
I'm currently working on a patch that removes the one page limit on
the returned command line buffer but I'm not convinced I should
retain this behavior.
I think yes. proc_pid_cmdline() has these lines:
len = mm->arg_end - mm->arg_start
* if (len > PAGE_SIZE)
* len = PAGE_SIZE;
res = access_process_vm(task, mm->arg_start, buffer, len, 0);
and @buffer is allocated in the caller as only one page:
True, but that's an arbitrary limitation which I'm in the process of
removing. I have a new version of proc_pid_cmdline() which will return
the entire commandline buffer no matter what its length. If the
grab-more-data-from-environment-buffer behavior is actually broken, I'd
rather not propagate it to the new code.
-ed falk
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