Date: Thu, 19 Jan 2017 21:05:30 +0100 From: Roman Divacky <rdivacky@vlakno.cz> To: Mark Millard <markmi@dsl-only.net> Cc: 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: <20170119200530.GA58089@vlakno.cz> In-Reply-To: <278EB6CA-6A04-43D6-A9F2-84FF11A367C7@dsl-only.net> References: <27422F1B-6906-4D37-860A-D1BC8DC83BBF@dsl-only.net> <20170117195424.GA89237@vlakno.cz> <237EB920-0795-4B18-94D4-2EAC0FC76F01@dsl-only.net> <20170117215613.GA95258@vlakno.cz> <45D0BB1C-490A-4809-BAB1-F4E552FECEDD@dsl-only.net> <20170118215420.GA65399@vlakno.cz> <9023794B-0999-4F50-95DE-2D4156BC6E75@dsl-only.net> <DDC0F517-C606-402C-80D0-BE3C941D97CB@dsl-only.net> <545CE5A1-9E7F-46C0-8355-0C32B60D1C72@dsl-only.net> <278EB6CA-6A04-43D6-A9F2-84FF11A367C7@dsl-only.net>
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Type = 38 should be R_ABS so thats fine. If what I expected to be in .got
is in .got.plt, what happens if you modify the getPPC64TocBase() to
use ::GotPlt instead of ::Got ?
On Thu, Jan 19, 2017 at 01:46:02AM -0800, Mark Millard wrote:
> I should have noted that -pie gets the same sort of
> readonly segment errors as -shared did:
>
> # clang -fuse-ld=lld -g -pie empty_src.c
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 50
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 50
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 10
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 50
> Type = 48
> Type = 50
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> undefined symbol: main in /usr/lib/Scrt1.o
> clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> # more main.c
> int main ()
> {
> }
> # clang -fuse-ld=lld -g -pie main.c
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 50
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 50
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 10
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 50
> Type = 50
> Type = 48
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
>
> So making something with a relocatable global variable is problematical
> via lld.
>
> ===
> Mark Millard
> markmi at dsl-only.net
>
> On 2017-Jan-18, at 10:48 PM, Mark Millard <markmi at dsl-only.net> wrote:
>
> The log messages code does not work because of Assertion failures:
>
> # clang -fuse-ld=lld -g main.c
> Type = 50, name = Assertion failed: (!isLocal()), function getName, file /usr/src/contrib/llvm/tools/lld/ELF/Symbols.cpp, line 100.
> clang: error: unable to execute command: Abort trap (core dumped)
> clang: error: linker command failed due to signal (use -v to see invocation)
>
> So for now I've disabled the name part of the line. At least we will
> see the numeric type of each and the reports of any "unhandled" values.
>
> I decided to use the Got variation instead of the Plt variant first.
>
> Some examples:
>
> # more empty_src.c
>
> # clang -fuse-ld=lld -g -shared -o empty_src.so empty_src.c
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 50
> Type = 48
> Type = 50
> Type = 48
> Type = 10
> can't create dynamic relocation R_PPC64_REL24 against readonly segment
> Type = 38
> Unhandled type = 38
> Type = 51
> clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> # clang -fuse-ld=lld -g empty_src.c
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 50
> Type = 48
> Type = 50
> Type = 48
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> undefined symbol: main in /usr/lib/crt1.o
> clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> # more main.c
> volatile void* gblvar = 0;
>
> int main ()
> {
> gblvar = &gblvar;
> }
>
> # clang -fuse-ld=lld -g main.c
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 50
> Type = 48
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 48
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 1
> Unhandled type = 1
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
>
> # more main.c
> int main ()
> {
> }
>
> # clang -fuse-ld=lld -g main.c
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 50
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 10
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 50
> Type = 64
> Type = 64
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 64
> Type = 50
> Type = 48
> Type = 50
> Type = 64
> Type = 50
> Type = 64
> Type = 50
> Type = 48
> Type = 10
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 50
> Type = 48
> Type = 50
> Type = 48
> Type = 10
> Type = 38
> Unhandled type = 38
> Type = 51
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 1
> Unhandled type = 1
> Type = 38
> Unhandled type = 38
> Type = 38
> Unhandled type = 38
>
>
> ===
> Mark Millard
> markmi at dsl-only.net
>
> On 2017-Jan-18, at 3:41 PM, Mark Millard <markmi@dsl-only.net> wrote:
>
> On 2017-Jan-18, at 1:54 PM, Roman Divacky <rdivacky@vlakno.cz> wrote:
>
> > I think I got it all wrong. I think what lld is trying to achieve
> > is to have the PLT entry to jump to GOT which references the real symbol.
>
> From what I've read: for code references the .got.plt section would
> be involved when it exists, not the .got section.
>
> > For some reason, GOT is empty, in our case.
>
> I think that I've already explained this: lld produces two different
> sections instead of just one .got section: .got and .got.plt .
>
> .got is now for only global variables. (These can be in the
> RELRO region: read-only after upfront relocation.) My program
> had no global variables. If you want I can change it to have one
> and use it so that the .got will not be empty.
>
> .got.plt is for code references that allow lazy relocation.
> (These can not being the the RELRO region.) Having the global
> variable would not change this from what I can tell.
>
> In the older toolchain these were both in the .got section and
> the global variable relocations could not be in the RELRO region
> because of the mixing in one section.
>
> > I believe this might be caused
> > by a relocation thats wrongly mapped to R_ABS in PPC64TargetInfo::getRelExpr().
>
> That is not it from what I can tell reading about what the .got.plt
> section is for and why it was split from the .got section.
>
> I think I'll add a global variable and use it so that their is no
> question what goes in the .got section instead of having no examples.
>
> I think you are not going in the right direction now for what the
> .got section is for as lld is producing things for powerpc64 (not
> that I'm an expert in the older or newer techniques).
>
> > Mark, can you apply this patch and rerun the linking and send me back what
> > relocations are applied to what symbols? Or even, if there's an unhandled
> > relocation, try to adjust the switch and rerun your test?
>
> I think that I will first add the global variable and its use
> and show what the last change with Plt instead of Got ends
> up looking like --but with your log notices added.
>
> Then I'll retry with the Plt use reverted.
>
> > Thanks
> >
> > Index: ../tools/lld/ELF/Target.cpp
> > ===================================================================
> > --- ../tools/lld/ELF/Target.cpp (revision 292428)
> > +++ ../tools/lld/ELF/Target.cpp (working copy)
> > @@ -1075,7 +1075,8 @@
> > }
> >
> > 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;
> > @@ -1114,8 +1115,10 @@
> > }
> >
> > RelExpr PPC64TargetInfo::getRelExpr(uint32_t Type, const SymbolBody &S) const {
> > + llvm::outs() << "Type = " << Type << ", name = " << S.getName() << "\n";
> > switch (Type) {
> > default:
> > + llvm::outs() << "Unhandled type = " << Type << "\n";
> > return R_ABS;
> > case R_PPC64_TOC16:
> > case R_PPC64_TOC16_DS:
>
> It may be a bit before I get the Plt and/or Got examples done.
> I might report the Plt case first and separately, later report
> the Got case.
>
> ===
> Mark Millard
> markmi at dsl-only.net
>
> On Tue, Jan 17, 2017 at 09:38:07PM -0800, Mark Millard wrote:
> > Using the new changed line (Plt use now):
> >
> > uint64_t TocVA = Out<ELF64BE>::Plt->getVA();
> >
> > changed the behavior and it gets farther for
> > -fuse-ld=lld based linking. But it is r2 leading
> > to r3 content that is dereferenced and 8(r3) fails
> > this time. This was in the process of finding
> > the new r2 value for the following bctrl.
> > r2==0x10018560 initially in __do_global_ctors_aux
> > seems wrong. If so then objlist_call_init produced
> > a wrong r2 value.
> >
> > [I've no clue if this is what you expected from
> > the Plt experiment or not.]
> >
> > Details. . .
> >
> > # /usr/local/bin/gdb a.out
> > GNU gdb (GDB) 7.11.1 [GDB v7.11.1 for FreeBSD]
> > . . .
> > Reading symbols from a.out...done.
> > (gdb) run
> > Starting program: /root/c_tests/a.out
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x00000000100104a8 in .__do_global_ctors_aux ()
> > (gdb) bt
> > #0 0x00000000100104a8 in .__do_global_ctors_aux ()
> > #1 0x0000000010010518 in ._init ()
> > #2 0x000000005002ac78 in objlist_call_init (list=<optimized out>, lockstate=<optimized out>) at /usr/src/libexec/rtld-elf/rtld.c:2541
> > #3 0x0000000050029fa8 in _rtld (sp=<optimized out>, exit_proc=<optimized out>, objp=<optimized out>) at /usr/src/libexec/rtld-elf/rtld.c:668
> > #4 0x00000000500279b0 in ._rtld_start () at /usr/src/libexec/rtld-elf/powerpc64/rtld_start.S:83
> > Backtrace stopped: frame did not save the PC
> > (gdb) disass
> > Dump of assembler code for function .__do_global_ctors_aux:
> > 0x0000000010010470 <+0>: mflr r0
> > 0x0000000010010474 <+4>: std r31,-8(r1)
> > 0x0000000010010478 <+8>: std r0,16(r1)
> > 0x000000001001047c <+12>: stdu r1,-128(r1)
> > 0x0000000010010480 <+16>: addis r3,r2,-1 <<<<<==== Note: r3 derives from r2
> > 0x0000000010010484 <+20>: mr r31,r1
> > 0x0000000010010488 <+24>: addi r3,r3,32464
> > 0x000000001001048c <+28>: std r30,112(r31)
> > 0x0000000010010490 <+32>: ld r3,-8(r3)
> > 0x0000000010010494 <+36>: cmpdi r3,-1
> > 0x0000000010010498 <+40>: beq 0x100104d4 <.__do_global_ctors_aux+100>
> > 0x000000001001049c <+44>: addis r4,r2,-1
> > 0x00000000100104a0 <+48>: addi r4,r4,32464
> > 0x00000000100104a4 <+52>: addi r30,r4,-8
> > => 0x00000000100104a8 <+56>: ld r4,8(r3) <<<<<==== Note: 8(r3) fails.
> > 0x00000000100104ac <+60>: ld r11,16(r3)
> > 0x00000000100104b0 <+64>: ld r3,0(r3)
> > 0x00000000100104b4 <+68>: std r2,40(r1)
> > 0x00000000100104b8 <+72>: mr r2,r4 <<<<<==== Note: 8(r3) result should have been the new r2 value
> > 0x00000000100104bc <+76>: mtctr r3
> > 0x00000000100104c0 <+80>: bctrl
> > 0x00000000100104c4 <+84>: ld r2,40(r1)
> > 0x00000000100104c8 <+88>: ldu r3,-8(r30)
> > 0x00000000100104cc <+92>: cmpdi r3,-1
> > 0x00000000100104d0 <+96>: bne 0x100104a8 <.__do_global_ctors_aux+56>
> > 0x00000000100104d4 <+100>: ld r30,112(r31)
> > 0x00000000100104d8 <+104>: addi r1,r1,128
> > 0x00000000100104dc <+108>: ld r0,16(r1)
> > 0x00000000100104e0 <+112>: ld r31,-8(r1)
> > 0x00000000100104e4 <+116>: mtlr r0
> > 0x00000000100104e8 <+120>: blr
> > 0x00000000100104ec <+124>: .long 0x0
> > 0x00000000100104f0 <+128>: .long 0x0
> > 0x00000000100104f4 <+132>: .long 0x0
> > End of assembler dump.
> > (gdb) info registers
> > r0 0x10010518 268502296
> > r1 0xffffffffffffcbf0 18446744073709538288
> > r2 0x10018560 268535136
> > r3 0x7ca903a64e800421 8982714944583631905
> > r4 0x10010430 268502064
> > r5 0x100300d0 268632272
> > r6 0x50043ab0 1342454448
> > r7 0x50067f00 1342603008
> > r8 0xffffffffffffdfcc 18446744073709543372
> > r9 0x0 0
> > r10 0x0 0
> > r11 0x0 0
> > r12 0xffffffffffffdfd0 18446744073709543376
> > r13 0x50057010 1342533648
> > r14 0x0 0
> > r15 0x0 0
> > r16 0x50047f00 1342471936
> > r17 0x500613e0 1342575584
> > r18 0x50253388 1344615304
> > r19 0x2 2
> > r20 0x0 0
> > r21 0x9 9
> > r22 0x0 0
> > r23 0x40000000000000 18014398509481984
> > r24 0x5004a100 1342480640
> > r25 0x5004c400 1342489600
> > r26 0xffffffffffffcd18 18446744073709538584
> > r27 0xffffffffffffcd3c 18446744073709538620
> > r28 0xffffffffffffcd3c 18446744073709538620
> > r29 0x0 0
> > r30 0x10010428 268502056
> > r31 0xffffffffffffcbf0 18446744073709538288
> > pc 0x100104a8 0x100104a8 <.__do_global_ctors_aux+56>
> > msr <unavailable>
> > cr 0x48200c00 1210059776
> > lr 0x10010518 0x10010518 <._init+24>
> > ctr 0x10010500 268502272
> > xer 0x20000000 536870912
> > (gdb) info file
> > Symbols from "/root/c_tests/a.out".
> > Native process:
> > Using the running image of child LWP 100093 of process 1091.
> > While running this, GDB does not access memory from...
> > Local exec file:
> > `/root/c_tests/a.out', file type elf64-powerpc-freebsd.
> > Entry point: 0x100300a0
> > 0x0000000010000270 - 0x0000000010000285 is .interp
> > 0x0000000010000288 - 0x00000000100002b8 is .note.tag
> > 0x00000000100002b8 - 0x00000000100002b9 is .rodata
> > 0x00000000100002bc - 0x00000000100002bc is .eh_frame
> > 0x00000000100002c0 - 0x0000000010000368 is .dynsym
> > 0x0000000010000368 - 0x0000000010000376 is .gnu.version
> > 0x0000000010000378 - 0x0000000010000398 is .gnu.version_r
> > 0x0000000010000398 - 0x00000000100003d8 is .hash
> > 0x00000000100003d8 - 0x000000001000041a is .dynstr
> > 0x0000000010000420 - 0x0000000010000468 is .rela.plt
> > 0x0000000010000468 - 0x0000000010000474 is .eh_frame_hdr
> > 0x0000000010010000 - 0x00000000100104f8 is .text
> > 0x0000000010010500 - 0x000000001001052c is .init
> > 0x0000000010010530 - 0x0000000010010554 is .fini
> > 0x0000000010010560 - 0x00000000100105c0 is .plt
> > 0x0000000010020000 - 0x0000000010020010 is .ctors
> > 0x0000000010020010 - 0x0000000010020020 is .dtors
> > 0x0000000010020020 - 0x0000000010020028 is .jcr
> > 0x0000000010020028 - 0x0000000010020138 is .dynamic
> > 0x0000000010020138 - 0x0000000010020138 is .got
> > 0x0000000010030000 - 0x0000000010030019 is .data
> > 0x0000000010030020 - 0x0000000010030050 is .got.plt
> > 0x0000000010030050 - 0x00000000100300a0 is .toc
> > 0x00000000100300a0 - 0x0000000010030160 is .opd
> > 0x0000000010030160 - 0x0000000010030170 is .bss
> > 0x0000000050020158 - 0x0000000050020228 is .hash in /libexec/ld-elf.so.1
> > 0x0000000050020228 - 0x0000000050020540 is .dynsym in /libexec/ld-elf.so.1
> > 0x0000000050020540 - 0x00000000500206b6 is .dynstr in /libexec/ld-elf.so.1
> > 0x00000000500206b6 - 0x00000000500206f8 is .gnu.version in /libexec/ld-elf.so.1
> > 0x00000000500206f8 - 0x0000000050020808 is .gnu.version_d in /libexec/ld-elf.so.1
> > 0x0000000050020808 - 0x0000000050027960 is .rela.dyn in /libexec/ld-elf.so.1
> > 0x0000000050027960 - 0x0000000050045a04 is .text in /libexec/ld-elf.so.1
> > 0x0000000050045a04 - 0x00000000500484a3 is .rodata in /libexec/ld-elf.so.1
> > 0x00000000500484a4 - 0x00000000500484a4 is .eh_frame in /libexec/ld-elf.so.1
> > 0x000000005005cf50 - 0x000000005005cf58 is .fini_array in /libexec/ld-elf.so.1
> > 0x000000005005cf58 - 0x000000005005d260 is .data.rel.ro in /libexec/ld-elf.so.1
> > 0x000000005005d260 - 0x000000005005d3b0 is .dynamic in /libexec/ld-elf.so.1
> > 0x000000005005d3b0 - 0x000000005005ff00 is .opd in /libexec/ld-elf.so.1
> > 0x000000005005ff00 - 0x000000005005ff08 is .got in /libexec/ld-elf.so.1
> > 0x0000000050060000 - 0x0000000050060628 is .data in /libexec/ld-elf.so.1
> > 0x0000000050060628 - 0x0000000050061478 is .bss in /libexec/ld-elf.so.1
> > 0x00000000500621c8 - 0x00000000500672b0 is .hash in /lib/libc.so.7
> > 0x00000000500672b0 - 0x0000000050079778 is .dynsym in /lib/libc.so.7
> > 0x0000000050079778 - 0x0000000050080846 is .dynstr in /lib/libc.so.7
> > 0x0000000050080846 - 0x00000000500820ac is .gnu.version in /lib/libc.so.7
> > 0x00000000500820b0 - 0x00000000500821c0 is .gnu.version_d in /lib/libc.so.7
> > 0x00000000500821c0 - 0x00000000500c2678 is .rela.dyn in /lib/libc.so.7
> > 0x00000000500c2678 - 0x00000000500c7868 is .rela.plt in /lib/libc.so.7
> > 0x00000000500c7870 - 0x00000000500c789c is .init in /lib/libc.so.7
> > 0x00000000500c78a0 - 0x0000000050227ca0 is .text in /lib/libc.so.7
> > 0x0000000050227ca0 - 0x0000000050227cc4 is .fini in /lib/libc.so.7
> > 0x0000000050227d00 - 0x000000005023b606 is .rodata in /lib/libc.so.7
> > 0x000000005023b608 - 0x000000005023b6ec is .eh_frame_hdr in /lib/libc.so.7
> > 0x000000005023b6f0 - 0x000000005023bad4 is .eh_frame in /lib/libc.so.7
> > 0x0000000050253318 - 0x0000000050253380 is .tdata in /lib/libc.so.7
> > 0x0000000050253380 - 0x0000000050253390 is .tbss in /lib/libc.so.7
> > 0x0000000050253380 - 0x0000000050253390 is .init_array in /lib/libc.so.7
> > 0x0000000050253390 - 0x0000000050253398 is .fini_array in /lib/libc.so.7
> > 0x0000000050253398 - 0x00000000502533a8 is .ctors in /lib/libc.so.7
> > 0x00000000502533a8 - 0x00000000502533b8 is .dtors in /lib/libc.so.7
> > 0x00000000502533b8 - 0x00000000502533c0 is .jcr in /lib/libc.so.7
> > 0x00000000502533c0 - 0x0000000050258a90 is .data.rel.ro in /lib/libc.so.7
> > 0x0000000050258a90 - 0x0000000050258c60 is .dynamic in /lib/libc.so.7
> > 0x0000000050258c60 - 0x000000005026f8f8 is .opd in /lib/libc.so.7
> > 0x000000005026f900 - 0x0000000050271f98 is .got in /lib/libc.so.7
> > 0x0000000050272000 - 0x0000000050277208 is .plt in /lib/libc.so.7
> > 0x0000000050277208 - 0x000000005027b0b0 is .data in /lib/libc.so.7
> > 0x000000005027b0b0 - 0x0000000050294738 is .bss in /lib/libc.so.7
> >
> >
> > ===
> > Mark Millard
> > markmi at dsl-only.net
> >
> > On 2017-Jan-17, at 1:56 PM, Roman Divacky <rdivacky at vlakno.cz> wrote:
> >
> >> 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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