Re: [PATCH] i386 vsyscall DSO implementation

From: David Mosberger (davidm@napali.hpl.hp.com)
Date: Fri Apr 25 2003 - 16:50:54 EST


>>>>> On Fri, 25 Apr 2003 14:20:47 -0700, "H. Peter Anvin" <hpa@zytor.com> said:

  hpa> David Mosberger wrote:
>> >> To complete the picture, it would be nice if the kernel ELF
>> >> images were mappable files (either in /sysfs or /proc) and
>> would >> show up in /proc/PID/maps. That way, a distributed
>> application >> such as a remote debugger could gain access to the
>> kernel unwind >> tables on a remote machine (assuming you have a
>> remote >> filesystem).

  hpa> How about /boot?
>> You mean a regular file? I'm not sure whether this could be
>> made to work. The /proc/PID/maps entry (really: the vm_area for
>> the kernel ELF images) would have to be created by the kernel, at
>> a time when no real filesystem is available. Also, since the
>> kernel needs to store the data in kernel-memory anyhow, I don't
>> think there is much point in storing it on disk as well.

  hpa> Perhaps I misunderstood the statement. With "kernel ELF
  hpa> images" above, I am now gathering you're talking about only the
  hpa> segments exported to userspace (i.e. vsyscall code), not the
  hpa> kernel itself, which was my original reading of that statement.

Sort of. I used the term "kernel ELF images" to refer to kernel code
that is shared with the user. I thought that even on x86 this code is
pinned in memory, but perhaps I misunderstood.

Anyhow, it seems to me that using a special filesystem would be more
suitable, as otherwise you get into bootstrap problems etc.

        --david
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