On 4/28/17 1:33 PM, David Miller wrote:
New in this version: 1) All the relocation work I posted earlier today. 2) Teach readelf about a few bpf relocs as needed 3) Add a 'nop' instruction which facilitates the gas testsuite. I used "mov r0,r0" The whole gas testsuite passes now. :-) But that just means we have to add more tests I guess.... Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
it seems by default bpf target is not enabled, so I tried to build it with: ../configure --enable-targets=bpf,x86 make -j40 but it failed to build :( Then I did ../configure --target=bpf and it went better. At least I could compile objdump, but gas refused to be configured: checking whether byte ordering is bigendian... no This target is no longer supported in gas make[1]: *** [configure-gas] Error 1 Not sure what I'm doing wrong. At least i tested objdump: $ clang -O2 -target bpfeb -c test.c $ llvm-objdump -S test.o test.o: file format ELF64-BPF Disassembly of section .text: bpf_prog1:0: 18 10 00 00 83 98 47 39 00 00 00 00 00 00 00 89 r1 = 590618314553ll
2: 7b a1 ff f8 00 00 00 00 *(u64 *)(r10 - 8) = r1
3: 79 1a ff f8 00 00 00 00 r1 = *(u64 *)(r10 - 8)
4: 07 10 00 00 8f ff 00 02 r1 += -1879113726
5: 79 01 00 00 00 00 00 00 r0 = *(u64 *)(r1 + 0)
6: 95 00 00 00 00 00 00 00 exit
$ bld/binutils/objdump -S test.o
test.o: file format elf64-bpfbe
Disassembly of section .text:
0000000000000000 <bpf_prog1>:
0: 18 10 00 00 83 98 47 39 ldimm64 r1, 590618314553
8: 00 00 00 00 00 00 00 89
10: 7b a1 ff f8 00 00 00 00 stdw [r10+65528], r1
18: 79 1a ff f8 00 00 00 00 lddw r1, [r10+65528]
20: 07 10 00 00 8f ff 00 02 add r1, -1879113726
28: 79 01 00 00 00 00 00 00 lddw r0, [r1+0]
30: 95 00 00 00 00 00 00 00 exit
looks good except negative offsets are reported as large positive.
If compiled with clang -O2 -target bpfel and result is:
$ bld/binutils/objdump -S test.o
test.o: file format elf64-bpfle
Disassembly of section .text:
0000000000000000 <bpf_prog1>:
0: 18 01 00 00 39 47 98 83 ldimm64 r0, 590618314553
8: 00 00 00 00 89 00 00 00
10: 7b 1a f8 ff 00 00 00 00 stdw [r1+65528], r10
18: 79 a1 f8 ff 00 00 00 00 lddw r10, [r1+65528]
Now the src/dst registers are swapped :(
The bytes printed are correct though.
clang debug info is not recognized as well:
$ clang -O2 -g -target bpfel -c test.c
/w/binutils-gdb/bld/binutils/objdump -S test.o
test.o: file format elf64-bpfle
Disassembly of section .text:
0000000000000000 <bpf_prog1>:
/w/binutils-gdb/bld/binutils/objdump: invalid relocation type 10
/w/binutils-gdb/bld/binutils/objdump: BFD (GNU Binutils)
2.28.51.20170429 assertion fail ../../bfd/elf64-bpf.c:139
.../w/binutils-gdb/bld/binutils/objdump: BFD (GNU Binutils) 2.28.51.20170429 assertion fail ../../bfd/elf64-bpf.c:139
/w/binutils-gdb/bld/binutils/objdump: invalid relocation type 10/w/binutils-gdb/bld/binutils/objdump: BFD (GNU Binutils) 2.28.51.20170429 assertion fail ../../bfd/elf64-bpf.c:139
0: 18 01 00 00 39 47 98 83 ldimm64 r0, 590618314553 8: 00 00 00 00 89 00 00 00 10: 7b 1a f8 ff 00 00 00 00 stdw [r1+65528], r10 $ clang -O2 -g -target bpfeb -c test.c $ /w/binutils-gdb/bld/binutils/objdump -S test.o test.o: file format elf64-bpfbe Disassembly of section .text: 0000000000000000 <bpf_prog1>: /w/binutils-gdb/bld/binutils/objdump: invalid relocation type 10/w/binutils-gdb/bld/binutils/objdump: BFD (GNU Binutils) 2.28.51.20170429 assertion fail ../../bfd/elf64-bpf.c:139
... /w/binutils-gdb/bld/binutils/objdump: invalid relocation type 10/w/binutils-gdb/bld/binutils/objdump: Dwarf Error: found address size '0', this reader can only handle address sizes '2', '4' and '8'.
0: 18 10 00 00 83 98 47 39 ldimm64 r1, 590618314553
8: 00 00 00 00 00 00 00 89
10: 7b a1 ff f8 00 00 00 00 stdw [r10+65528], r1
18: 79 1a ff f8 00 00 00 00 lddw r1, [r10+65528]
With llvm it should be like this:
$ ./bin/clang -O2 -g -target bpfel -c test.c
$ ./bin/llvm-objdump -S test.o
test.o: file format ELF64-BPF
Disassembly of section .text:
bpf_prog1:
; {
0: 18 01 00 00 39 47 98 83 00 00 00 00 89 00 00 00 r1 =
590618314553ll
; volatile unsigned long t = 0x8983984739ull;
2: 7b 1a f8 ff 00 00 00 00 *(u64 *)(r10 - 8) = r1
; return *(unsigned long *)((0xffffffff8fff0002ull) + t);
3: 79 a1 f8 ff 00 00 00 00 r1 = *(u64 *)(r10 - 8)
4: 07 01 00 00 02 00 ff 8f r1 += -1879113726
5: 79 10 00 00 00 00 00 00 r0 = *(u64 *)(r1 + 0)
6: 95 00 00 00 00 00 00 00 exit
The output of llvm with '-g -target bpfeb' is probably partially broken,
since 'llvm-objdump -S test.o' doesn't see any debug in there.
So gnu objdump's error:
Dwarf Error: found address size '0'
is likely legit.
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