On Wed, Aug 13, 2014 at 2:17 AM, Daniel Borkmann <dborkman@xxxxxxxxxx> wrote: > On 08/13/2014 09:57 AM, Alexei Starovoitov wrote: >> >> add BPF_LD_IMM64 instruction to load 64-bit immediate value into register. >> All previous instructions were 8-byte. This is first 16-byte instruction. >> Two consecutive 'struct bpf_insn' blocks are interpreted as single >> instruction: >> insn[0/1].code = BPF_LD | BPF_DW | BPF_IMM >> insn[0/1].dst_reg = destination register >> insn[0].imm = lower 32-bit >> insn[1].imm = upper 32-bit >> >> Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM >> which loads 32-bit immediate value into a register. >> >> x64 JITs it as single 'movabsq %rax, imm64' >> arm64 may JIT as sequence of four 'movk x0, #imm16, lsl #shift' insn >> >> Note that old eBPF programs are binary compatible with new interpreter. >> >> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxxxx> > > > For follow-ups on this series, can you put the actual motivation > for this change from the cover letter into this commit log as it > otherwise doesn't say anything clearly why it is needed. Code and > test case looks good to me. ok. As you saw the full explanation is long, so I opted for 'it_does_this' commit log. In the next rev will add more reasons to this log. Sure. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
