[Bug 215819] head r311147's clang 3.9.1 for powerpc64: locore.o generation messed up: generates R_PPC64_ADDR16_DS instead of R_PPC64_TOC16_DS with .toc
bugzilla-noreply at freebsd.org
bugzilla-noreply at freebsd.org
Sat Jan 7 23:04:05 UTC 2017
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215819
--- Comment #3 from Mark Millard <markmi at dsl-only.net> ---
(In reply to Mark Millard from comment #0)
I found how to control the behavior based on
the assembler notation @toc being missing vs.
being present.
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.
FreeBSD has the option of always being explicit with @toc in order
to avoid differences in handling of omitted notation.
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.
[The issue of the distinction is submittable to llvm either way.]
Details. . .
For:
.section ".toc","aw"
tmpstk.L: .tc tmpstk[TC],tmpstk
. . .
/* Set up the stack pointer */
ld %r1,tmpstk.L(%r2)
using devel/powerpc64-gcc gets:
# /usr/local/bin/powerpc64-unknown-freebsd12.0-gcc \
-c \
-x assembler-with-cpp \
-pipe \
locore64_simplified.S
locore64_simplified.S: Assembler messages:
locore64_simplified.S:80: Warning: assuming @toc on symbol
and produces (with R_PPC64_TOC16_DS for .toc):
# /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o
locore64_simplified.o: file format elf64-powerpc-freebsd
RELOCATION RECORDS FOR [.text]:
OFFSET TYPE VALUE
0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
0000000000000046 R_PPC64_TOC16_DS .toc
RELOCATION RECORDS FOR [.toc]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 tmpstk
RELOCATION RECORDS FOR [.opd]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 .__start
0000000000000008 R_PPC64_TOC *ABS*
By contrast clang is silent (cross compiler used):
# /usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bin/cc
\ -target
powerpc64-unknown-freebsd12.0 \
--sysroot=/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp \
-B/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bin \
-c \ -x assembler-with-cpp \
-pipe \
locore64_simplified.S
and produces code with R_PPC64_ADDR16_DS for the .toc instead:
# /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o | more
locore64_simplified.o: file format elf64-powerpc-freebsd
RELOCATION RECORDS FOR [.text]:
OFFSET TYPE VALUE
0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
0000000000000046 R_PPC64_ADDR16_DS .toc
RELOCATION RECORDS FOR [.toc]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 tmpstk
RELOCATION RECORDS FOR [.opd]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 .__start
0000000000000008 R_PPC64_TOC *ABS*
But for:
.section ".toc","aw"
tmpstk.L: .tc tmpstk[TC],tmpstk
. . .
/* Set up the stack pointer */
ld %r1,tmpstk.L at toc(%r2)
(note the @toc notation) both compilers agree and use
R_PPC64_TOC16_DS for the .toc:
# /usr/local/bin/powerpc64-unknown-freebsd12.0-gcc \
-c \
-x assembler-with-cpp \
-pipe \
locore64_simplified.S
# /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o | more
locore64_simplified.o: file format elf64-powerpc-freebsd
RELOCATION RECORDS FOR [.text]:
OFFSET TYPE VALUE
0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
0000000000000046 R_PPC64_TOC16_DS .toc
RELOCATION RECORDS FOR [.toc]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 tmpstk
RELOCATION RECORDS FOR [.opd]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 .__start
0000000000000008 R_PPC64_TOC *ABS*
# /usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bin/cc
\ -target
powerpc64-unknown-freebsd12.0 \
--sysroot=/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp \
-B/usr/obj/powerpc64vtsc_clang_kernel/powerpc.powerpc64/usr/src/tmp/usr/bin \
-c \ -x assembler-with-cpp \
-pipe \
locore64_simplified.S
# /usr/local/powerpc64-freebsd/bin/objdump -r locore64_simplified.o | more
locore64_simplified.o: file format elf64-powerpc-freebsd
RELOCATION RECORDS FOR [.text]:
OFFSET TYPE VALUE
0000000000000028 R_PPC64_REL64 __tocbase+0x0000000000008000
0000000000000046 R_PPC64_TOC16_DS .toc
RELOCATION RECORDS FOR [.toc]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 tmpstk
RELOCATION RECORDS FOR [.opd]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_ADDR64 .__start
0000000000000008 R_PPC64_TOC *ABS*
I omitted "-f -gdwarf-2" to simplify things but with such
clang complains about:
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"
^
(buildkernel gets such messages.)
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 things:
# grep "@toc[^b]"
/root/sys_typescripts/typescript_make_powerpc64vtsc_nodebug_incl_clang_xtoolchain_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
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