From: Daniel Borkmann <daniel@iogearbox.net>
To: ast@kernel.org
Cc: netdev@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>,
David Daney <david.daney@cavium.com>
Subject: [PATCH bpf-next 11/13] bpf, mips64: remove unneeded zero check from div/mod with k
Date: Fri, 26 Jan 2018 23:33:46 +0100 [thread overview]
Message-ID: <20180126223348.11250-12-daniel@iogearbox.net> (raw)
In-Reply-To: <20180126223348.11250-1-daniel@iogearbox.net>
The verifier in both cBPF and eBPF reject div/mod by 0 imm,
so this can never load. Remove emitting such test and reject
it from being JITed instead (the latter is actually also not
needed, but given practice in sparc64, ppc64 today, so
doesn't hurt to add it here either).
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Daney <david.daney@cavium.com>
---
arch/mips/net/ebpf_jit.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)
diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
index 296f1410..3e2798b 100644
--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c
@@ -741,16 +741,11 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
break;
case BPF_ALU | BPF_DIV | BPF_K: /* ALU_IMM */
case BPF_ALU | BPF_MOD | BPF_K: /* ALU_IMM */
+ if (insn->imm == 0)
+ return -EINVAL;
dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
if (dst < 0)
return dst;
- if (insn->imm == 0) { /* Div by zero */
- b_off = b_imm(exit_idx, ctx);
- if (is_bad_offset(b_off))
- return -E2BIG;
- emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
- emit_instr(ctx, addu, MIPS_R_V0, MIPS_R_ZERO, MIPS_R_ZERO);
- }
td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
if (td == REG_64BIT || td == REG_32BIT_ZERO_EX)
/* sign extend */
@@ -770,19 +765,13 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
break;
case BPF_ALU64 | BPF_DIV | BPF_K: /* ALU_IMM */
case BPF_ALU64 | BPF_MOD | BPF_K: /* ALU_IMM */
+ if (insn->imm == 0)
+ return -EINVAL;
dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
if (dst < 0)
return dst;
- if (insn->imm == 0) { /* Div by zero */
- b_off = b_imm(exit_idx, ctx);
- if (is_bad_offset(b_off))
- return -E2BIG;
- emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
- emit_instr(ctx, addu, MIPS_R_V0, MIPS_R_ZERO, MIPS_R_ZERO);
- }
if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
-
if (insn->imm == 1) {
/* div by 1 is a nop, mod by 1 is zero */
if (bpf_op == BPF_MOD)
--
2.9.5
next prev parent reply other threads:[~2018-01-26 22:34 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-26 22:33 [PATCH bpf-next 00/13] BPF improvements and fixes Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 01/13] bpf: xor of a/x in cbpf can be done in 32 bit alu Daniel Borkmann
2018-01-28 18:58 ` [PATCH bpf-next 01/13] bpf: xor of a/x in cbpf can be done Naveen N. Rao
2018-01-28 20:51 ` Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 02/13] bpf: improve dead code sanitizing Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 03/13] bpf: make unknown opcode handling more robust Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 04/13] bpf: fix subprog verifier bypass by div/mod by 0 exception Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 05/13] bpf, x86_64: remove obsolete exception handling from div/mod Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 06/13] bpf, arm64: " Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 07/13] bpf, s390x: " Daniel Borkmann
2018-01-29 14:33 ` Michael Holzheu
2018-01-29 15:52 ` Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 08/13] bpf, ppc64: " Daniel Borkmann
2018-01-28 18:52 ` Naveen N. Rao
2018-01-26 22:33 ` [PATCH bpf-next 09/13] bpf, sparc64: " Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 10/13] bpf, mips64: " Daniel Borkmann
2018-01-26 22:39 ` David Daney
2018-01-26 22:33 ` Daniel Borkmann [this message]
2018-01-26 22:36 ` [PATCH bpf-next 11/13] bpf, mips64: remove unneeded zero check from div/mod with k David Daney
2018-01-26 22:33 ` [PATCH bpf-next 12/13] bpf, arm: remove obsolete exception handling from div/mod Daniel Borkmann
2018-01-26 22:33 ` [PATCH bpf-next 13/13] bpf: add further test cases around div/mod and others Daniel Borkmann
2018-01-27 0:48 ` [PATCH bpf-next 00/13] BPF improvements and fixes Alexei Starovoitov
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