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Re: [PATCH] libdwfl: Special case linux-gate/ in core_file_read_eagerly.

The XXX comment right above there says what we really want.  It should have
the read-from-core option in its back pocket and do that only when locating
a disk file by build-id failed.  I've lost track now of how much
refactoring would be required to do that.

At least in Fedora/RH-flavored distros the file generally is available on
disk (/lib/modules/V-R.A/vdso/*.so).  But I guess you still don't have a
pointer to that keyed on build-id unless you've installed the debuginfo
package.  (I said years ago that someone should integrate some build-id
knowledge magic into rpm or something, so that you can readily look up by
build-id every binary installed via your package system.)

But I can't think of a real downside to using the in-core image when it is
the whole file.  That logic applies at least as well when the data is
mmap'd, so the core->map_address check should move before the build-id
check, shouldn't it?

And I think you should rewrite the comment:

	if (whole > MAX_EAGER_COST && mod->build_id_len > 0)
	  /* We can't cheaply read the whole file here, so we'd
	     be using a partial file.  But there is a build ID that could
	     help us find the whole file, which might be more useful than
	     what we have.  We'll just rely on that.  */
	  return false;


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