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From: Palmer Dabbelt <palmerdabbelt@google.com>
To: Bjorn Topel <bjorn.topel@gmail.com>
Cc: daniel@iogearbox.net, netdev@vger.kernel.org, ast@kernel.org,
	Bjorn Topel <bjorn.topel@gmail.com>,
	linux-riscv@lists.infradead.org, bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next v2 3/9] riscv, bpf: add support for far branching when emitting tail call
Date: Mon, 23 Dec 2019 10:18:31 -0800 (PST)
Message-ID: <mhng-09e718bb-9ed9-4bc7-a4e6-e39eb0888acc@palmerdabbelt-glaptop> (raw)
In-Reply-To: <20191216091343.23260-4-bjorn.topel@gmail.com>

On Mon, 16 Dec 2019 01:13:37 PST (-0800), Bjorn Topel wrote:
> Start use the emit_branch() function in the tail call emitter in order
> to support far branching.
>
> Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
> ---
>  arch/riscv/net/bpf_jit_comp.c | 22 +++-------------------
>  1 file changed, 3 insertions(+), 19 deletions(-)
>
> diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
> index e599458a9bcd..c38c95df3440 100644
> --- a/arch/riscv/net/bpf_jit_comp.c
> +++ b/arch/riscv/net/bpf_jit_comp.c
> @@ -496,16 +496,6 @@ static int is_12b_check(int off, int insn)
>  	return 0;
>  }
>
> -static int is_13b_check(int off, int insn)
> -{
> -	if (!is_13b_int(off)) {
> -		pr_err("bpf-jit: insn=%d 13b < offset=%d not supported yet!\n",
> -		       insn, (int)off);
> -		return -1;
> -	}
> -	return 0;
> -}
> -
>  static int is_21b_check(int off, int insn)
>  {
>  	if (!is_21b_int(off)) {
> @@ -744,18 +734,14 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
>  		return -1;
>  	emit(rv_lwu(RV_REG_T1, off, RV_REG_A1), ctx);
>  	off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
> -	if (is_13b_check(off, insn))
> -		return -1;
> -	emit(rv_bgeu(RV_REG_A2, RV_REG_T1, off >> 1), ctx);
> +	emit_branch(BPF_JGE, RV_REG_A2, RV_REG_T1, off, ctx);
>
>  	/* if (--TCC < 0)
>  	 *     goto out;
>  	 */
>  	emit(rv_addi(RV_REG_T1, tcc, -1), ctx);
>  	off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
> -	if (is_13b_check(off, insn))
> -		return -1;
> -	emit(rv_blt(RV_REG_T1, RV_REG_ZERO, off >> 1), ctx);
> +	emit_branch(BPF_JSLT, RV_REG_T1, RV_REG_ZERO, off, ctx);
>
>  	/* prog = array->ptrs[index];
>  	 * if (!prog)
> @@ -768,9 +754,7 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
>  		return -1;
>  	emit(rv_ld(RV_REG_T2, off, RV_REG_T2), ctx);
>  	off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
> -	if (is_13b_check(off, insn))
> -		return -1;
> -	emit(rv_beq(RV_REG_T2, RV_REG_ZERO, off >> 1), ctx);
> +	emit_branch(BPF_JEQ, RV_REG_T2, RV_REG_ZERO, off, ctx);
>
>  	/* goto *(prog->bpf_func + 4); */
>  	off = offsetof(struct bpf_prog, bpf_func);

Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>


  parent reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-16  9:13 [PATCH bpf-next v2 0/9] riscv: BPF JIT fix, optimizations and far jumps support Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 1/9] riscv, bpf: fix broken BPF tail calls Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 3/9] riscv, bpf: add support for far branching when emitting tail call Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 4/9] riscv, bpf: add support for far jumps and exits Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free Björn Töpel
2019-12-16 15:09   ` Daniel Borkmann
2019-12-18  6:23     ` Björn Töpel
2020-01-04  1:32       ` Paul Walmsley
2020-01-07 10:24         ` Björn Töpel
2020-01-07 10:47           ` Paul Walmsley
2020-02-02 13:37   ` Alex Ghiti
2020-02-03 12:28     ` Björn Töpel
2020-02-03 20:57       ` Alex Ghiti
2019-12-16  9:13 ` [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 8/9] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 9/9] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs Björn Töpel
2019-12-19 15:07 ` [PATCH bpf-next v2 0/9] riscv: BPF JIT fix, optimizations and far jumps support Daniel Borkmann
2019-12-19 22:02 ` [PATCH bpf-next v2 1/9] riscv, bpf: fix broken BPF tail calls Palmer Dabbelt
2019-12-23 18:03 ` [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching Palmer Dabbelt
2020-01-07  8:13   ` Björn Töpel
2020-01-23  2:08   ` Palmer Dabbelt
2019-12-23 18:18 ` Palmer Dabbelt [this message]
2019-12-23 18:18 ` [PATCH bpf-next v2 4/9] riscv, bpf: add support for far jumps and exits Palmer Dabbelt
2019-12-23 18:29 ` [PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls Palmer Dabbelt
2019-12-23 18:30 ` [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free Palmer Dabbelt
2019-12-23 18:58 ` [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls Palmer Dabbelt
2020-01-07 10:14   ` Björn Töpel
2020-01-28  2:15   ` Palmer Dabbelt
2020-02-03 12:11     ` Björn Töpel
2019-12-23 18:58 ` [PATCH bpf-next v2 8/9] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs Palmer Dabbelt
2019-12-23 18:58 ` [PATCH bpf-next v2 9/9] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs Palmer Dabbelt

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