[bpf] add BPF disassembler

add BPF disassembler, so tools like llvm-objdump can be used:
$ llvm-objdump -d -no-show-raw-insn ./sockex1_kern.o

./sockex1_kern.o: file format ELF64-BPF

Disassembly of

[bpf] add BPF disassembler

add BPF disassembler, so tools like llvm-objdump can be used:
$ llvm-objdump -d -no-show-raw-insn ./sockex1_kern.o

./sockex1_kern.o: file format ELF64-BPF

Disassembly of section socket1:
bpf_prog1:
0: r6 = r1
8: r0 = *(u8 *)skb[23]
10: *(u32 *)(r10 - 4) = r0
18: r1 = *(u32 *)(r6 + 4)
20: if r1 != 4 goto 8
28: r2 = r10
30: r2 += -4

ld_imm64 (the only 16-byte insn) and special ld_abs/ld_ind instructions
had to be treated in a special way. The decoders for the rest of the insns
are automatically generated.

Add tests to cover new functionality.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 287477

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