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

John Baldwin jhb at FreeBSD.org
Thu May 21 16:03:46 UTC 2020


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?

-- 
John Baldwin


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