Date: Sat, 7 Jan 2017 15:12:59 -0800 From: Mark Millard <markmi@dsl-only.net> To: Roman Divacky <rdivacky@vlakno.cz>, Ed Maste <emaste@freebsd.org>, Justin Hibbits <chmeeedalf@gmail.com>, Nathan Whitehorn <nwhitehorn@freebsd.org> Cc: FreeBSD Toolchain <freebsd-toolchain@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: clang 3.9.0 buildkernel on old powerpc64's vs. trying to build hwpmc_e500.o and the like. . . [Actually .__start code failure vs. working and R_PPC64_ADDR16_DS vs. R_PPC64_TOC16_DS] Message-ID: <FB7F73D7-BF8F-4477-8057-1404D27622A8@dsl-only.net> In-Reply-To: <2B5FDD60-4D8B-4803-B59C-3C569BA36E68@dsl-only.net> References: <D3DE2D12-9885-4154-B680-6DA5A8B62A56@dsl-only.net> <D9C54972-8D21-4D55-A707-4FFC2BDCD9FE@dsl-only.net> <20161207190057.GA58950@vlakno.cz> <E1376C20-C1BD-418D-81C6-CDDE479342CA@dsl-only.net> <CE88C1F4-B9BD-4D45-8DF0-F1079C3257A5@dsl-only.net> <20161208185541.GA33364@vlakno.cz> <E49F7EE4-7A62-4601-98DC-4C4791B7158D@dsl-only.net> <20161208221452.GA42380@vlakno.cz> <20161212210922.GA27403@vlakno.cz> <613BB28B-46F1-4959-B576-C8AD42A21200@dsl-only.net> <20170107085126.GA82107@vlakno.cz> <2B5FDD60-4D8B-4803-B59C-3C569BA36E68@dsl-only.net>
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[I've supplied a list of places that adding @toc notation should
make clang 3.9.1 targeting powerpc64 do the right thing for
this issue.]
On 2017-Jan-7, at 2:07 PM, Mark Millard <markmi at dsl-only.net> wrote:
> On 2017-Jan-7, at 12:51 AM, Roman Divacky <rdivacky at vlakno.cz> =
wrote:
>=20
>> That's a great progress. Can you produce minimal self contained test =
case that
>> exhibits this bug? And submit it to llvm bugzilla?
>>=20
>> Also, clang3.9 defaults to using it's own internal asm, what happens =
if you
>> add -no-integrated-as to CFLAGS and recompile the kernel? That should =
remove
>> this llvm assembly problem. Does it boot?
>>=20
>> Thanks Mark, really great progress.
>>=20
>> Roman
>=20
> In attempting this I found how to control the behavior based on
> the assembler notation @toc being missing vs. being present.
>=20
> If llvm should change is strongly tied to llvm's criteria for
> gcc compatibility relative to filling-in/defaulting omitted
> @toc's in the assembler notation.
>=20
> FreeBSD has the option of always being explicit with @toc in order
> to avoid differences in handling of omitted notation.
>=20
> So I've no clue if FreebSD wants to claim that a llvm change
> is a requirement for using clang as the powerpc64 system compiler.
>=20
> [The issue of the distinction is submittable to llvm either way.]
>=20
> Details. . .
>=20
> For:
>=20
> .section ".toc","aw"
> tmpstk.L: .tc tmpstk[TC],tmpstk
> . . .
> /* Set up the stack pointer */
> ld %r1,tmpstk.L(%r2)
>=20
> using devel/powerpc64-gcc gets:
>=20
> # /usr/local/bin/powerpc64-unknown-freebsd12.0-gcc \ =
=
=
-c \ =
=
=
=
-x assembler-with-cpp \ =
=
=
=
-pipe \ =
=
=20
> =
locore64_simplified.S
> locore64_simplified.S: Assembler messages:
> locore64_simplified.S:80: Warning: assuming @toc on symbol
>=20
> and produces (with R_PPC64_TOC16_DS for .toc):
>=20
> # /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o
>=20
> locore64_simplified.o: file format elf64-powerpc-freebsd
>=20
> RELOCATION RECORDS FOR [.text]:
> OFFSET TYPE VALUE=20
> 0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
> 0000000000000046 R_PPC64_TOC16_DS .toc
>=20
>=20
> RELOCATION RECORDS FOR [.toc]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 tmpstk
>=20
>=20
> RELOCATION RECORDS FOR [.opd]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 .__start
> 0000000000000008 R_PPC64_TOC *ABS*
>=20
>=20
> By contrast clang is silent (cross compiler used):
>=20
> # =
/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bin/=
cc \ =
=
-target =
powerpc64-unknown-freebsd12.0 \ =
=
=
=
--sysroot=3D/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/=
tmp \ =
=
=
-B/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bi=
n \ =
=20
> =
-c \ =
=
=
=
-x assembler-with-cpp \ =
=
=
-pipe \ =
=
=
=
locore64_simplified.S
>=20
> and produces code with R_PPC64_ADDR16_DS for the .toc instead:
>=20
> # /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o | =
more =
=
=20
> locore64_simplified.o: file format elf64-powerpc-freebsd
>=20
> RELOCATION RECORDS FOR [.text]:
> OFFSET TYPE VALUE=20
> 0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
> 0000000000000046 R_PPC64_ADDR16_DS .toc
>=20
>=20
> RELOCATION RECORDS FOR [.toc]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 tmpstk
>=20
>=20
> RELOCATION RECORDS FOR [.opd]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 .__start
> 0000000000000008 R_PPC64_TOC *ABS*
>=20
>=20
>=20
> But for:
>=20
> .section ".toc","aw"
> tmpstk.L: .tc tmpstk[TC],tmpstk
> . . .
> /* Set up the stack pointer */
> ld %r1,tmpstk.L@toc(%r2)
>=20
> (note the @toc notation) both compilers agree and use
> R_PPC64_TOC16_DS for the .toc:
>=20
> # /usr/local/bin/powerpc64-unknown-freebsd12.0-gcc \ =
=
=
-c \ =
=
=
=
-x assembler-with-cpp \ =
=
=
=
-pipe \ =
=
=20
> =
locore64_simplified.S
>=20
> # /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o | =
more =
=
=20
> locore64_simplified.o: file format elf64-powerpc-freebsd
>=20
> RELOCATION RECORDS FOR [.text]:
> OFFSET TYPE VALUE=20
> 0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
> 0000000000000046 R_PPC64_TOC16_DS .toc
>=20
>=20
> RELOCATION RECORDS FOR [.toc]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 tmpstk
>=20
>=20
> RELOCATION RECORDS FOR [.opd]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 .__start
> 0000000000000008 R_PPC64_TOC *ABS*
>=20
>=20
> # =
/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bin/=
cc \ =
=
-target =
powerpc64-unknown-freebsd12.0 \ =
=
=
=
--sysroot=3D/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/=
tmp \ =
=
=
-B/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bi=
n \ =
=20
> =
-c \ =
=
=
=
-x assembler-with-cpp \ =
=
=
-pipe \ =
=
=
=
locore64_simplified.S
>=20
> # /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o | =
more =
=
=20
> locore64_simplified.o: file format elf64-powerpc-freebsd
>=20
> RELOCATION RECORDS FOR [.text]:
> OFFSET TYPE VALUE=20
> 0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
> 0000000000000046 R_PPC64_TOC16_DS .toc
>=20
>=20
> RELOCATION RECORDS FOR [.toc]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 tmpstk
>=20
>=20
> RELOCATION RECORDS FOR [.opd]:
> OFFSET TYPE VALUE=20
> 0000000000000000 R_PPC64_ADDR64 .__start
> 0000000000000008 R_PPC64_TOC *ABS*
>=20
>=20
>=20
> I omitted "-f -gdwarf-2" to simplify things but with such
> clang complains about:
>=20
> locore64_simplified.S:36:2: warning: DWARF2 only supports one section =
per compilation unit
> .section ".toc","aw"
> ^
> locore64_simplified.S:47:2: warning: DWARF2 only supports one section =
per compilation unit
> .section ".opd","aw"
> ^
>=20
> (buildkernel gets such messages.)
>=20
>=20
> I expect I can simplify the .S code more than I have so far but
> I figured I'd report the discovery of the choice FreeBSD needs
> to make for powerpc64 for if llvm changes are to be required
> vs. not.
The following should be a list of the places that adding @toc usage
would fix some things for using clang 3.9.1 to target powerpc64:
# grep "@toc[^b]" =
/root/sys_typescripts/typescript_make_powerpc64vtsc_nodebug_incl_clang_xto=
olchain_kernel-amd64-host-2017-01-03:23:48:41 | more
/usr/src/sys/powerpc/aim/locore64.S:102: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/aim/trap_subr64.S:320: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/aim/trap_subr64.S:797: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/ofw/ofwcall64.S:104: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/ofw/ofwcall64.S:108: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/ofw/ofwcall64.S:116: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/ofw/ofwcall64.S:226: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/ofw/ofwcall64.S:228: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/ofw/ofwcall64.S:235: Warning: assuming @toc on =
symbol
/usr/src/sys/powerpc/powerpc/swtch64.S:153: Warning: assuming @toc on =
symbol
devel/powerpc64-gcc and devel/powerpc64-binutils together happens to =
report
on missing @toc 's.
But, of course, if some sections of code are conditionally compiled and
excluded above they would not be listed.
=3D=3D=3D
Mark Millard
markmi at dsl-only.net
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