From: Palmer Dabbelt <palmer@sifive.com>
To: luke.r.nels@gmail.com
Cc: songliubraving@fb.com, aou@eecs.berkeley.edu,
bpf@vger.kernel.org, daniel@iogearbox.net, bjorn.topel@gmail.com,
ast@kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, yhs@fb.com,
linux-riscv@lists.infradead.org, kafai@fb.com, xi.wang@gmail.com
Subject: Re: [PATCH bpf v2] bpf, riscv: clear high 32 bits for ALU32 add/sub/neg/lsh/rsh/arsh
Date: Fri, 31 May 2019 13:40:35 -0700 (PDT) [thread overview]
Message-ID: <mhng-b4ce883e-9ec7-4098-9acc-18eb140f93e0@palmer-si-x1c4> (raw)
In-Reply-To: <20190530222922.4269-1-luke.r.nels@gmail.com>
On Thu, 30 May 2019 15:29:22 PDT (-0700), luke.r.nels@gmail.com wrote:
> In BPF, 32-bit ALU operations should zero-extend their results into
> the 64-bit registers.
>
> The current BPF JIT on RISC-V emits incorrect instructions that perform
> sign extension only (e.g., addw, subw) on 32-bit add, sub, lsh, rsh,
> arsh, and neg. This behavior diverges from the interpreter and JITs
> for other architectures.
>
> This patch fixes the bugs by performing zero extension on the destination
> register of 32-bit ALU operations.
>
> Fixes: 2353ecc6f91f ("bpf, riscv: add BPF JIT for RV64G")
> Cc: Xi Wang <xi.wang@gmail.com>
> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Thanks! I'm assuming this is going in through a BPF tree and not the RISC-V
tree, but LMK if that's not the case.
> ---
> The original patch is
> https://lkml.org/lkml/2019/5/30/1370
>
> This version is rebased against the bpf tree.
> ---
> arch/riscv/net/bpf_jit_comp.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
> index e5c8d675bd6e..426d5c33ea90 100644
> --- a/arch/riscv/net/bpf_jit_comp.c
> +++ b/arch/riscv/net/bpf_jit_comp.c
> @@ -751,10 +751,14 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
> case BPF_ALU | BPF_ADD | BPF_X:
> case BPF_ALU64 | BPF_ADD | BPF_X:
> emit(is64 ? rv_add(rd, rd, rs) : rv_addw(rd, rd, rs), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
> case BPF_ALU | BPF_SUB | BPF_X:
> case BPF_ALU64 | BPF_SUB | BPF_X:
> emit(is64 ? rv_sub(rd, rd, rs) : rv_subw(rd, rd, rs), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
> case BPF_ALU | BPF_AND | BPF_X:
> case BPF_ALU64 | BPF_AND | BPF_X:
> @@ -795,14 +799,20 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
> case BPF_ALU | BPF_LSH | BPF_X:
> case BPF_ALU64 | BPF_LSH | BPF_X:
> emit(is64 ? rv_sll(rd, rd, rs) : rv_sllw(rd, rd, rs), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
> case BPF_ALU | BPF_RSH | BPF_X:
> case BPF_ALU64 | BPF_RSH | BPF_X:
> emit(is64 ? rv_srl(rd, rd, rs) : rv_srlw(rd, rd, rs), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
> case BPF_ALU | BPF_ARSH | BPF_X:
> case BPF_ALU64 | BPF_ARSH | BPF_X:
> emit(is64 ? rv_sra(rd, rd, rs) : rv_sraw(rd, rd, rs), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
>
> /* dst = -dst */
> @@ -810,6 +820,8 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
> case BPF_ALU64 | BPF_NEG:
> emit(is64 ? rv_sub(rd, RV_REG_ZERO, rd) :
> rv_subw(rd, RV_REG_ZERO, rd), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
>
> /* dst = BSWAP##imm(dst) */
> @@ -964,14 +976,20 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
> case BPF_ALU | BPF_LSH | BPF_K:
> case BPF_ALU64 | BPF_LSH | BPF_K:
> emit(is64 ? rv_slli(rd, rd, imm) : rv_slliw(rd, rd, imm), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
> case BPF_ALU | BPF_RSH | BPF_K:
> case BPF_ALU64 | BPF_RSH | BPF_K:
> emit(is64 ? rv_srli(rd, rd, imm) : rv_srliw(rd, rd, imm), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
> case BPF_ALU | BPF_ARSH | BPF_K:
> case BPF_ALU64 | BPF_ARSH | BPF_K:
> emit(is64 ? rv_srai(rd, rd, imm) : rv_sraiw(rd, rd, imm), ctx);
> + if (!is64)
> + emit_zext_32(rd, ctx);
> break;
>
> /* JUMP off */
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next prev parent reply other threads:[~2019-05-31 20:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-30 22:29 [PATCH bpf v2] bpf, riscv: clear high 32 bits for ALU32 add/sub/neg/lsh/rsh/arsh Luke Nelson
2019-05-30 23:08 ` Song Liu
2019-05-31 8:16 ` Björn Töpel
2019-05-31 20:40 ` Palmer Dabbelt [this message]
2019-06-01 0:09 ` Alexei Starovoitov
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