Date: Tue, 17 Jan 2017 22:56:13 +0100 From: Roman Divacky <rdivacky@vlakno.cz> To: Mark Millard <markmi@dsl-only.net> Cc: Ed Maste <emaste@freebsd.org>, FreeBSD Toolchain <freebsd-toolchain@freebsd.org> Subject: Re: /usr/bin/ld.lld on powerpc64: produces a.out for which: ld-elf.so.1: assert failed: /usr/src/libexec/rtld-elf/powerpc64/reloc.c:374 Message-ID: <20170117215613.GA95258@vlakno.cz> In-Reply-To: <237EB920-0795-4B18-94D4-2EAC0FC76F01@dsl-only.net> References: <932E3C38-B226-4BF1-B587-5A2D5EA19300@dsl-only.net> <F3923971-6FDF-4269-A7CA-3428249A128F@dsl-only.net> <20170116194035.GA20175@vlakno.cz> <2B1414C5-C56D-42F2-A1CB-4B1FE074667B@dsl-only.net> <43DBF7C7-6632-4906-BB37-FD00621AF857@dsl-only.net> <82402941-D1B2-4938-A43D-E21A390DE041@dsl-only.net> <F38C9607-5AB9-4BF9-BEC1-88EA2518A9CE@dsl-only.net> <27422F1B-6906-4D37-860A-D1BC8DC83BBF@dsl-only.net> <20170117195424.GA89237@vlakno.cz> <237EB920-0795-4B18-94D4-2EAC0FC76F01@dsl-only.net>
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Go with Out.
On Tue, Jan 17, 2017 at 01:53:14PM -0800, Mark Millard wrote:
> On 2017-Jan-17, at 11:54 AM, Roman Divacky <rdivacky at vlakno.cz> wrote:
>
> . . .
> > I wonder if it doesnt work because of my first patch (the one to turn GOT
> > reloc into PLT one).
> >
> > LLD understands that we use GOT as TOC (which was true before my patch),
> > I wonder if something like this:
> >
> > ndex: tools/lld/ELF/Target.cpp
> > ===================================================================
> > --- tools/lld/ELF/Target.cpp (revision 292071)
> > +++ tools/lld/ELF/Target.cpp (working copy)
> > @@ -1070,7 +1070,8 @@
> > }
> >
> > PPC64TargetInfo::PPC64TargetInfo() {
> > - PltRel = GotRel = R_PPC64_GLOB_DAT;
> > + GotRel = R_PPC64_GLOB_DAT;
> > + PltRel = R_PPC64_JMP_SLOT;
> > RelativeRel = R_PPC64_RELATIVE;
> > GotEntrySize = 8;
> > GotPltEntrySize = 8;
> > @@ -1099,7 +1100,7 @@
> > // TOC starts where the first of these sections starts. We always create a
> > // .got when we see a relocation that uses it, so for us the start is always
> > // the .got.
> > - uint64_t TocVA = In<ELF64BE>::Got->getVA();
> > + uint64_t TocVA = In<ELF64BE>::Plt->getVA();
> >
> > // Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
> > // thus permitting a full 64 Kbytes segment. Note that the glibc startup
>
> The modern 3.9.1 source does not match for the last. Note the
> "Out" vs. "In" below ("svnlite status" does not show my source
> as different in this area):
>
> uint64_t getPPC64TocBase() {
> // The TOC consists of sections .got, .toc, .tocbss, .plt in that order. The
> // TOC starts where the first of these sections starts. We always create a
> // .got when we see a relocation that uses it, so for us the start is always
> // the .got.
> uint64_t TocVA = Out<ELF64BE>::Got->getVA();
>
> // Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
> // thus permitting a full 64 Kbytes segment. Note that the glibc startup
> // code (crt1.o) assumes that you can get from the TOC base to the
> // start of the .toc section with only a single (signed) 16-bit relocation.
> return TocVA + PPC64TocOffset;
> }
>
> [Also the "// TOC . . ." comment is at line 1005 (given the prior
> GotRel vs. PltRel split into separate lines).]
>
> Which should I use?: In vs. Out
>
> > would make any difference? It's not correct but might shed some light on what needs to be done
> > if I am right.
>
> Separately if I understand the change you are picking out which section
> is first of .got, .toc, .tocbss, .plt (.got.plt as well?). But for the
> order of things that would still make the .ctors, .dtors, .jcr, .dynamic,
> and .data sections as being inside the TOC and taking TOC address range
> space:
>
> 0x0000000010010560 - 0x00000000100105c0 is .plt <<<<<===== NOTE!!!!
> 0x0000000010020000 - 0x0000000010020010 is .ctors
> 0x0000000010020010 - 0x0000000010020020 is .dtors
> 0x0000000010020020 - 0x0000000010020028 is .jcr
> 0x0000000010020028 - 0x0000000010020138 is .dynamic
> 0x0000000010020138 - 0x0000000010020138 is .got <<<<<===== NOTE!!!!
> 0x0000000010030000 - 0x0000000010030019 is .data
> 0x0000000010030020 - 0x0000000010030050 is .got.plt <<<<<===== NOTE!!!!
> 0x0000000010030050 - 0x00000000100300a0 is .toc <<<<<===== NOTE!!!!
>
> Is that expected/desired/allowed?
>
> > Could you explore this please?
>
> After you report for sure for In vs. Out I'll take a stab
> at it.
>
> ===
> Mark Millard
> markmi at dsl-only.net
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