netdev - [RFC PATCH bpf-next v1 09/14] MIPS: eBPF: drop src_reg restriction in BPF_LD|BPF_DW|BPF

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Message-Id: <e2c64e0121959db6216e1f6c23447c06ce2b14a3.1625970384.git.Tony.Ambardar@gmail.com>
Date:   Sun, 11 Jul 2021 17:34:55 -0700
From:   Tony Ambardar <tony.ambardar@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>
Cc:     Tony Ambardar <Tony.Ambardar@...il.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-mips@...r.kernel.org,
        Johan Almbladh <johan.almbladh@...finetworks.com>,
        Hassan Naveed <hnaveed@...ecomp.com>,
        David Daney <ddaney@...iumnetworks.com>,
        Luke Nelson <luke.r.nels@...il.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>
Subject: [RFC PATCH bpf-next v1 09/14] MIPS: eBPF: drop src_reg restriction in BPF_LD|BPF_DW|BPF_IMM

Stop enforcing (insn->src_reg == 0) and allow special verifier insns such
as "BPF_LD_MAP_FD(BPF_REG_2, 0)", used to refer to a process-local map fd
and introduced in 0246e64d9a5f ("bpf: handle pseudo BPF_LD_IMM64 insn").

This is consistent with other JITs such as riscv32 and also used by
test_verifier (e.g. "runtime/jit: tail_call within bounds, prog once").

Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.")
Signed-off-by: Tony Ambardar <Tony.Ambardar@...il.com>
---
 arch/mips/net/ebpf_jit.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
index f510c692975e..bba41f334d07 100644
--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c
@@ -1303,8 +1303,6 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 		emit_instr(ctx, nop);
 		break;
 	case BPF_LD | BPF_DW | BPF_IMM:
-		if (insn->src_reg != 0)
-			return -EINVAL;
 		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
 		if (dst < 0)
 			return dst;
-- 
2.25.1