lkml.org 
[lkml]   [2019]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.1 023/138] bpf, riscv: clear high 32 bits for ALU32 add/sub/neg/lsh/rsh/arsh
Date
[ Upstream commit 1e692f09e091bf5c8b38384f297d6dae5dbf0f12 ]

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>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 */
--
2.20.1


\
 
 \ /
  Last update: 2019-07-12 14:25    [W:0.420 / U:34.708 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site