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Re: rfc patch for buildid < shlib base address
- From: Roland McGrath <roland at redhat dot com>
- To: "Frank Ch. Eigler" <fche at elastic dot org>
- Cc: systemtap at sources dot redhat dot com
- Date: Tue, 24 Feb 2009 17:55:25 -0800 (PST)
- Subject: Re: rfc patch for buildid < shlib base address
- References: <20090225014622.GA17348@elastic.org>
> On my i686 F10 box, elfutils 0.140 probing /lib/libc-2.9.so, the
> buildid data logic results in an address that is smaller than the dwfl
> relocation base address for the module. readelf indicates the
> build-id .note section well before .text. This causes a negative
> offset, which in turn causes a pass-4 compile error.
It is normal that the build ID note appear earlier than the .text section.
What is not normal is that you should care about the .text section's
location at all. For any non-ET_REL module, the sole relocation base
should correspond to the beginning of its earliest PT_LOAD. (In fact,
libdwfl doesn't really care if no section info was retained at all in the
stripped file; canonical tools don't strip that way, but they could.)
This is by definition an address lower than where the note (or anything
else) appears.
Thanks,
Roland