Hi Tiezhu,
On Mon, Feb 13, 2023 at 11:02 AM Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> wrote:
>
> Hi Hengqi,
>
> On 02/12/2023 11:52 AM, Hengqi Chen wrote:
> > Let's always use 4 instructions for function address in JIT.
> > So that the instruction sequences don't change between the first
> > pass and the extra pass for function calls.
> >
> > Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
> > Signed-off-by: Hengqi Chen <hengqi.chen@xxxxxxxxx>
> > ---
> > arch/loongarch/net/bpf_jit.c | 23 ++++++++++++++++++++++-
> > 1 file changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> > index c4b1947ebf76..2d952110be72 100644
> > --- a/arch/loongarch/net/bpf_jit.c
> > +++ b/arch/loongarch/net/bpf_jit.c
> > @@ -446,6 +446,27 @@ static int add_exception_handler(const struct bpf_insn *insn,
> > return 0;
> > }
> >
> > +static inline void emit_addr_move(struct jit_ctx *ctx, enum loongarch_gpr rd, u64 addr)
> > +{
> > + u64 imm_11_0, imm_31_12, imm_51_32, imm_63_52;
> > +
> > + /* lu12iw rd, imm_31_12 */
> > + imm_31_12 = (addr >> 12) & 0xfffff;
> > + emit_insn(ctx, lu12iw, rd, imm_31_12);
> > +
> > + /* ori rd, rd, imm_11_0 */
> > + imm_11_0 = addr & 0xfff;
> > + emit_insn(ctx, ori, rd, rd, imm_11_0);
> > +
> > + /* lu32id rd, imm_51_32 */
> > + imm_51_32 = (addr >> 32) & 0xfffff;
> > + emit_insn(ctx, lu32id, rd, imm_51_32);
> > +
> > + /* lu52id rd, rd, imm_63_52 */
> > + imm_63_52 = (addr >> 52) & 0xfff;
> > + emit_insn(ctx, lu52id, rd, rd, imm_63_52);
> > +}
> > +
> > static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool extra_pass)
> > {
> > u8 tm = -1;
> > @@ -841,7 +862,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
> > if (ret < 0)
> > return ret;
> >
> > - move_imm(ctx, t1, func_addr, is32);
> > + emit_addr_move(ctx, t1, func_addr);
> > emit_insn(ctx, jirl, t1, LOONGARCH_GPR_RA, 0);
> > move_reg(ctx, regmap[BPF_REG_0], LOONGARCH_GPR_A0);
> > break;
> >
>
> The code itself looks good to me.
>
> Could you please give more detailed info in the commit message?
> For example, description of problem, steps to reproduce, ...
> I think the descriptions in the cover letter are useful, it is
> better to record them in the commit message.
>
> Additionally, emit_addr_move() is similar with move_imm(), it is
> better to define emit_addr_move() before move_imm() in bpf_jit.h.
>
> Thanks,
> Tiezhu
>
I've addressed your comments and send a v2 for review.
The second patch is dropped, as it is incomplete.
Cheers,
---
Hengqi
