Hi Paul,
On Mon, Dec 09, 2019 at 07:52:52PM +0100, Paul Chaignon wrote:
> All BPF JIT compilers except RISC-V's and MIPS' enforce a 33-tail calls
> limit at runtime. In addition, a test was recently added, in tailcalls2,
> to check this limit.
>
> This patch updates the tail call limit in MIPS' JIT compiler to allow
> 33 tail calls.
>
> Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.")
> Reported-by: Mahshid Khezri <khezri.mahshid@xxxxxxxxx>
> Signed-off-by: Paul Chaignon <paul.chaignon@xxxxxxxxxx>
I'd be happy to take this through mips-fixes, but equally happy for it
to go through the BPF/net trees in which case:
Acked-by: Paul Burton <paulburton@xxxxxxxxxx>
Thanks,
Paul
> ---
> arch/mips/net/ebpf_jit.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
> index 46b76751f3a5..3ec69d9cbe88 100644
> --- a/arch/mips/net/ebpf_jit.c
> +++ b/arch/mips/net/ebpf_jit.c
> @@ -604,6 +604,7 @@ static void emit_const_to_reg(struct jit_ctx *ctx, int dst, u64 value)
> static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx)
> {
> int off, b_off;
> + int tcc_reg;
>
> ctx->flags |= EBPF_SEEN_TC;
> /*
> @@ -616,14 +617,14 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx)
> b_off = b_imm(this_idx + 1, ctx);
> emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off);
> /*
> - * if (--TCC < 0)
> + * if (TCC-- < 0)
> * goto out;
> */
> /* Delay slot */
> - emit_instr(ctx, daddiu, MIPS_R_T5,
> - (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4, -1);
> + tcc_reg = (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4;
> + emit_instr(ctx, daddiu, MIPS_R_T5, tcc_reg, -1);
> b_off = b_imm(this_idx + 1, ctx);
> - emit_instr(ctx, bltz, MIPS_R_T5, b_off);
> + emit_instr(ctx, bltz, tcc_reg, b_off);
> /*
> * prog = array->ptrs[index];
> * if (prog == NULL)
> --
> 2.17.1
>
