> On Sat, Jan 27, 2024 at 10:59 PM <dthaler1968@xxxxxxxxxxxxxx> wrote:
>>
>> I asked:
>> > >> What about DW and LDX variants of BPF_IND and BPF_ABS?
>>
>> Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> wrote:
>> > These we support:
>> >
>> > /* Absolute load instructions, designed to be used in socket filters.
>> */
>> > {BPF_INSN_LDABSB, "ldabsb%W%i32", "r0 = * ( u8 * ) skb [ %i32 ]",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LD|BPF_SIZE_B|BPF_MODE_ABS},
>> > {BPF_INSN_LDABSH, "ldabsh%W%i32", "r0 = * ( u16 * ) skb [ %i32 ]",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LD|BPF_SIZE_H|BPF_MODE_ABS},
>> > {BPF_INSN_LDABSW, "ldabsw%W%i32", "r0 = * ( u32 * ) skb [ %i32 ]",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LD|BPF_SIZE_W|BPF_MODE_ABS},
>> > {BPF_INSN_LDABSDW, "ldabsdw%W%i32", "r0 = * ( u64 * ) skb [ %i32 ]",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LD|BPF_SIZE_DW|BPF_MODE_ABS},
>> >
>> > /* Generic load instructions (to register.) */
>> > {BPF_INSN_LDXB, "ldxb%W%dr , [ %sr %o16 ]", "%dr = * ( u8 * ) ( %sr %o16
>> )",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LDX|BPF_SIZE_B|BPF_MODE_MEM},
>> > {BPF_INSN_LDXH, "ldxh%W%dr , [ %sr %o16 ]", "%dr = * ( u16 * ) ( %sr
>> %o16
>> > )",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LDX|BPF_SIZE_H|BPF_MODE_MEM},
>> > {BPF_INSN_LDXW, "ldxw%W%dr , [ %sr %o16 ]", "%dr = * ( u32 * ) ( %sr
>> %o16
>> > )",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LDX|BPF_SIZE_W|BPF_MODE_MEM},
>> > {BPF_INSN_LDXDW, "ldxdw%W%dr , [ %sr %o16 ]","%dr = * ( u64 * ) ( %sr
>> > %o16 )",
>> > BPF_V1, BPF_CODE, BPF_CLASS_LDX|BPF_SIZE_DW|BPF_MODE_MEM},
>>
>> Yonghong Song <yonghong.song@xxxxxxxxx> wrote:
>> > I don't know how to do proper wording in the standard. But DW and LDX
>> > variants of BPF_IND/BPF_ABS are not supported by verifier for now and they
>> > are considered illegal insns.
>>
>> Although the Linux verifier doesn't support them, the fact that gcc does
>> support
>> them tells me that it's probably safest to list the DW and LDX variants as
>> deprecated as well, which is what the draft already did in the appendix so
>> that's good (nothing to change there, I think).
>
> DW never existed in classic bpf, so abs/ind never had DW flavor.
> If some assembler/compiler decided to "support" them it's on them.
> The standard must not list such things as deprecated. They never
> existed. So nothing is deprecated.
We have no reason to support these instructions in the assembler, and
GCC certainly never generates these. So I will remove the ABS/IND DW
instructions from the assembler today.
> Same with MSH. BPF_LDX | BPF_MSH | BPF_B is the only insn ever existed.
> It's a legacy insn. Just like abs/ind.
