svn commit: r361303 - in head: lib/libc/gen libexec/rtld-elf sys/sys

[Konstantin Belousov]

On Thu, May 21, 2020 at 12:30:47PM -0700, John Baldwin wrote:
> On 5/21/20 9:56 AM, Konstantin Belousov wrote:
> > On Thu, May 21, 2020 at 09:03:44AM -0700, John Baldwin wrote:
> >> On 5/21/20 8:12 AM, Mark Johnston wrote:
> >>> On Thu, May 21, 2020 at 04:41:52PM +0300, Konstantin Belousov wrote:
> >>>> On Thu, May 21, 2020 at 03:02:07PM +0200, Antoine Brodin wrote:
> >>>>> On Thu, May 21, 2020 at 12:08 AM Konstantin Belousov <kib at freebsd.org> wrote:
> >>>>>>
> >>>>>> Author: kib
> >>>>>> Date: Wed May 20 22:08:26 2020
> >>>>>> New Revision: 361303
> >>>>>> URL: https://svnweb.freebsd.org/changeset/base/361303
> >>>>>>
> >>>>>> Log:
> >>>>>>   Change the samantic of struct link_map l_addr member.
> >>>>>>
> >>>>>>   It previously returned the object map base address, while all other
> >>>>>>   ELF operating systems return load offset, i.e. the difference between
> >>>>>>   map base and the link base.
> >>>>>>
> >>>>>>   Explain the meaning of the field in the man page.
> >>>>>>
> >>>>>>   Stop filling the mips-only l_offs member, which is apparently unused.
> >>>>>>
> >>>>>>   PR:   246561
> >>>>>>   Requested by: Damjan Jovanovic <damjan.jov at gmail.com>
> >>>>>>   Reviewed by:  emaste, jhb, cem (previous version)
> >>>>>>   Sponsored by: The FreeBSD Foundation
> >>>>>>   MFC after:    1 week
> >>>>>>   Differential revision:        https://reviews.freebsd.org/D24918
> >>>>>>
> >>>>>> Modified:
> >>>>>>   head/lib/libc/gen/dlinfo.3
> >>>>>>   head/libexec/rtld-elf/rtld.c
> >>>>>>   head/sys/sys/link_elf.h
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> After this commit,  some ports fail to build with signal 11.
> >>>>> For instance lang/perl5.30 fails to build with default options (DTRACE on)
> >>>>> Disabling the DTRACE option makes it able to build again.
> >>>>>
> >>>> I see, thank you for reporting.
> >>>>
> >>>> So drti.c:dtrace_dof_init() does read l_addr, and the dtrace code assumes
> >>>> that l_addr is the base, not relocbase.
> >>>>
> >>>> Mark, was dofhp_addr initialization changed comparing to Solaris ?
> >>>
> >>> It appears it has been the same since DTrace was imported.  illumos
> >>> still has similar code.
> >>>
> >>> Note that drti.o is linked into any executable and shlib that defines
> >>> static probes, so the ABI change affects more than just dtrace(1).
> >>> Would it be possible to define a new value for RTLD_DI_LINKMAP, and
> >>> preserve the old behaviour for the old value?
> >>
> >> I think a bigger question is if Solaris/illumos treat l_addr as mapbase
> >> (absolute address) or relocbase (relative address).  In the discussion
> >> in the phabricator I had assumed that all other OS's treated l_addr as
> >> the relative offset (relocbase).  Does the code for illumos assume an
> >> absolute address or does it assume a relative address in l_addr?
> > 
> > It is rather clear, since the dtrace code was pristine, that Solaris
> > provides the mapbase.  I do not have Solaris/Illumos box anymore
> > (for quite some time), so I cannot check directly.
> > 
> > My current PoV is that l_addr semantic must be restored, and relocbase
> > provided by newly added member.
> 
> I am fine with reverting the l_addr semantic.  I'm still not sure how to
> resolve the original PR, though perhaps Wine just has to carry a local
> patch forever?  GDB will work via the current accident so long as we
> never pre-link libraries.  As long as PIE binaries have a starting VA of
> 0 like our shared libraries then I think GDB will be ok with our PIE
> binaries as well.

Wine should work without patch now, and after the D24918 is applied, too.
I do not intend to revert l_addr to the 'load address' semantic.

I am actually trying to find a solaris box to compile the test program.