Date: Thu, 21 May 2020 12:54:50 -0400 From: Mark Johnston <markj@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, Antoine Brodin <antoine@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head@freebsd.org Subject: Re: svn commit: r361303 - in head: lib/libc/gen libexec/rtld-elf sys/sys Message-ID: <20200521165450.GC85681@raichu> In-Reply-To: <c7fce441-692e-e4d6-64cb-ae86ef13c6cb@FreeBSD.org> References: <202005202208.04KM8QPA020707@repo.freebsd.org> <CAALwa8mXfJZyRQ-Gx684mgoeTDZs14tEP26rJNqvh_rEiY18=Q@mail.gmail.com> <20200521134152.GE64045@kib.kiev.ua> <20200521151248.GA85681@raichu> <c7fce441-692e-e4d6-64cb-ae86ef13c6cb@FreeBSD.org>
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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@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@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 should be an absolute address, since dtrace appears to assume that an ELF header is mapped at l_addr. Here, "addr" is the value of l_addr for the RTLD_SELF linkmap: https://github.com/joyent/illumos-joyent/blob/master/usr/src/lib/libdtrace/common/dlink_common.c#L124
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