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RE: [PATCH, MIPS] Support shared library debug with MIPS PIE (glibc)
- From: Matthew Fortune <Matthew dot Fortune at imgtec dot com>
- To: Joseph Myers <joseph at codesourcery dot com>
- Cc: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Tue, 23 Jun 2015 15:20:58 +0000
- Subject: RE: [PATCH, MIPS] Support shared library debug with MIPS PIE (glibc)
- Authentication-results: sourceware.org; auth=none
- References: <6D39441BF12EF246A7ABCE6654B0235321175F69 at LEMAIL01 dot le dot imgtec dot org> <alpine dot DEB dot 2 dot 10 dot 1506231512570 dot 4489 at digraph dot polyomino dot org dot uk>
Joseph Myers <joseph@codesourcery.com> writes:
> On Tue, 23 Jun 2015, Matthew Fortune wrote:
>
> > -/* If there is a DT_MIPS_RLD_MAP entry in the dynamic section, fill
> it in
> > - with the run-time address of the r_debug structure */
> > +/* If there is a DT_MIPS_RLD_MAP2 or DT_MIPS_RLD_MAP entry in the
> dynamic
> > + section, fill in the debug map pointer with the run-time address
> of the
> > + r_debug structure. */
> > #define ELF_MACHINE_DEBUG_SETUP(l,r) \ -do { if ((l)->l_info[DT_MIPS
> > (RLD_MAP)]) \
> > +do { if ((l)->l_info[DT_MIPS (RLD_MAP2)]) \
> > + { \
> > + char *ptr = (char *)(l)->l_info[DT_MIPS (RLD_MAP2)]; \
> > + ptr += (l)->l_info[DT_MIPS (RLD_MAP2)]->d_un.d_val; \
> > + *(ElfW(Addr) *)ptr = (ElfW(Addr)) (r); \
> > + } \
> > + else if ((l)->l_info[DT_MIPS (RLD_MAP)]) \
>
> What if there are both DT_MIPS_RLD_MAP2 and DT_MIPS_RLD_MAP? Will that
> never happen?
That will happen for executables much like MIPS has an unused DT_DEBUG
entry. I figured it would be better to add DT_MIPS_RLD_MAP2 to all
executables allowing this to be the only tag supported by dynamic linkers
that may not care about compatibility with pre-existing executables.
Are you thinking there should be a consistency check that the two tags
lead to the same address? I guess there would be no harm in that but
equally it may not be of much value. What do you think?
Matthew