Date: Thu, 10 Aug 2017 22:24:56 -0700 From: Mark Millard <markmi@dsl-only.net> To: Dimitry Andric <dim@freebsd.org>, Ed Maste <emaste@freebsd.org>, FreeBSD Toolchain <freebsd-toolchain@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: I have submitted bugzilla 221107 for a (e.g.) -r321706 system clang 5 vintage TARGET_ARCH=powerpc buildkernel failure for aha.kld: R_PPC_PLTREL24 reloc against local symbol Message-ID: <F9F0D662-0C1D-48E8-8BCA-8E79E17FE0DB@dsl-only.net> In-Reply-To: <46806707-4FB6-4265-A5B3-F3D4EF3C861C@dsl-only.net> References: <186BF66E-04E5-4663-AD0B-E07A9C631925@dsl-only.net> <636276E6-BA4C-4C28-84FF-A34BDF1F1702@dsl-only.net> <51700A90-8DB5-4D81-AC83-D3FB0FDEFED7@dsl-only.net> <46806707-4FB6-4265-A5B3-F3D4EF3C861C@dsl-only.net>
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[clang 5 generates R_PPC_PLTREL24 in the .o files
for global symbols in places gcc 4.2.1 generates
R_PPC_ADDR16_HA / R_PPC_ADDR16_LO pairs.]
On 2017-Aug-10, at 7:22 PM, Mark Millard <markmi at dsl-only.net> wrote:
> [A top post about the failing R_PPC_PLTREL24 since
> the material does not flow well as a sequential
> read from prior material. I found that the .kld
> does not match the contributing .o for GLOBAL
> status for routines and the LOCAL in the .kld is
> rejected by ld in ppc_elf_check_relocs.]
>=20
> There is something consistent between the two example
> failures. (The examples here are from a more recent
> head version for a buildkernel attempt.)
>=20
> (I inserted some lines not matched by the shown grep.)
>=20
> # readelf -a =
/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/sys/GENERICvtsc-NODBG/m=
odules/usr/src/sys/modules/aha/aha.kld | grep aha_alloc
> 00002b8c 00003e12 R_PPC_PLTREL24 00000000 aha_alloc + 0
> 000031a8 00003e12 R_PPC_PLTREL24 00000000 aha_alloc + 0
> Symbol table (.symtab) contains 180 entries:
> Num: Value Size Type Bind Vis Ndx Name
> 62: 0000000000000000 96 FUNC LOCAL DEFAULT 1 aha_alloc
>=20
> but in aha.o :
>=20
> 44: 0000000000000000 96 FUNC GLOBAL DEFAULT 2 aha_alloc
>=20
> # readelf -a =
/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/sys/GENERICvtsc-NODBG/m=
odules/usr/src/sys/modules/agp/agp.kld | grep agp_find_caps
> 00002e08 00004912 R_PPC_PLTREL24 00000000 agp_find_caps + 0
> Symbol table (.symtab) contains 180 entries:
> Num: Value Size Type Bind Vis Ndx Name
> 73: 0000000000000000 172 FUNC LOCAL DEFAULT 1 =
agp_find_caps
>=20
> but in agp.o :
>=20
> 58: 0000000000000000 172 FUNC GLOBAL DEFAULT 2 =
agp_find_caps
>=20
> building the .kld's is turning GLOBAL into LOCAL -- and the LOCAL
> is being rejected by:
>=20
> /usr/src/contrib/binutils/bfd/elf32-ppc.c
>=20
> in its routine:
>=20
> /* Look through the relocs for a section during the first phase, and
> allocate space in the global offset table or procedure linkage
> table. */
>=20
> static bfd_boolean
> ppc_elf_check_relocs (bfd *abfd,
> struct bfd_link_info *info,
> asection *sec,
> const Elf_Internal_Rela *relocs)
>=20
> via:
>=20
>=20
> r_symndx =3D ELF32_R_SYM (rel->r_info);
> if (r_symndx < symtab_hdr->sh_info)
> h =3D NULL;
> else =20
>=20
> . . .
> tls_type =3D 0;
> r_type =3D ELF32_R_TYPE (rel->r_info);
> . . . =20
> switch (r_type)
> {
> . . .
> case R_PPC_PLT32:
> case R_PPC_PLTREL24:
> case R_PPC_PLTREL32:
> case R_PPC_PLT16_LO:
> case R_PPC_PLT16_HI:
> case R_PPC_PLT16_HA:
> #ifdef DEBUG
> fprintf (stderr, "Reloc requires a PLT entry\n");
> #endif
> /* This symbol requires a procedure linkage table entry. We
> actually build the entry in finish_dynamic_symbol,
> because this might be a case of linking PIC code without
> linking in any dynamic objects, in which case we don't
> need to generate a procedure linkage table after all. */
>=20
> if (h =3D=3D NULL)
> {
> /* It does not make sense to have a procedure linkage
> table entry for a local symbol. */
> (*_bfd_error_handler) (_("%B(%A+0x%lx): %s reloc against =
"
> "local symbol"),
> abfd,
> sec,
> (long) rel->r_offset,
> =
ppc_elf_howto_table[r_type]->name);
> bfd_set_error (bfd_error_bad_value);
> return FALSE;
> }
> else
> . . .
clang 5 and gcc 4.2.1 do not match for what
goes in aha*.o and agp*.o files for the
problem symbols in clang 5's output:
gcc 4.2.1 ( R_PPC_ADDR16_HA / R_PPC_ADDR16_LO ):
# readelf -at =
/usr/obj/powerpcvtsc_gcc421/powerpc.powerpc/usr/src/sys/GENERICvtsc-NODBG/=
modules/usr/src/sys/modules/aha/aha*.o | grep aha_alloc
50: 0000000000000514 112 FUNC GLOBAL DEFAULT 1 aha_alloc
00000032 00003206 R_PPC_ADDR16_HA 00000000 aha_alloc + 0
0000003e 00003204 R_PPC_ADDR16_LO 00000000 aha_alloc + 0
0000052a 00003206 R_PPC_ADDR16_HA 00000000 aha_alloc + 0
0000052e 00003204 R_PPC_ADDR16_LO 00000000 aha_alloc + 0
50: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND aha_alloc
# readelf -at =
/usr/obj/powerpcvtsc_gcc421/powerpc.powerpc/usr/src/sys/GENERICvtsc-NODBG/=
modules/usr/src/sys/modules/agp/agp*.o | grep caps
0000204a 00003a06 R_PPC_ADDR16_HA 00000434 agp_find_caps + 0
0000204e 00003a04 R_PPC_ADDR16_LO 00000434 agp_find_caps + 0
00002312 00003a06 R_PPC_ADDR16_HA 00000434 agp_find_caps + 0
0000231a 00003a04 R_PPC_ADDR16_LO 00000434 agp_find_caps + 0
00000000 00003a01 R_PPC_ADDR32 00000434 agp_find_caps + 0
58: 0000000000000434 192 FUNC GLOBAL DEFAULT 1 agp_find_caps
000002be 00003906 R_PPC_ADDR16_HA 00000000 agp_find_caps + 0
000002c6 00003904 R_PPC_ADDR16_LO 00000000 agp_find_caps + 0
57: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND agp_find_caps
clang 5 ( R_PPC_PLTREL24 ):
# readelf -at =
/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/sys/GENERICvtsc-NODBG/m=
odules/usr/src/sys/modules/aha/aha*.o | grep aha_alloc
44: 0000000000000000 96 FUNC GLOBAL DEFAULT 2 aha_alloc
000000f0 00002e12 R_PPC_PLTREL24 00000000 aha_alloc + 0
0000070c 00002e12 R_PPC_PLTREL24 00000000 aha_alloc + 0
46: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND aha_alloc
# readelf -at =
/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/sys/GENERICvtsc-NODBG/m=
odules/usr/src/sys/modules/agp/agp*.o | grep caps
58: 0000000000000000 172 FUNC GLOBAL DEFAULT 2 agp_find_caps
00000138 00003512 R_PPC_PLTREL24 00000000 agp_find_caps + 0
53: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND agp_find_caps
(Turning some R_PPC_PLTREL24 into LOCAL for *.kld files
is a no-no as far as powerpc (32-bit) ld is concerned.)
=3D=3D=3D
Mark Millard
markmi at dsl-only.net
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