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LoongArch: BPF: Zero-extend signed ALU32 div/mod results

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ALU32 operations write a 32-bit result and leave the upper 32 bits of
the BPF register zero. The LoongArch JIT sign-extends the result of
signed ALU32 BPF_DIV and BPF_MOD (off=1), so a negative 32-bit quotient
or remainder leaves bits 63:32 set in JITted code while the verifier
and interpreter model those bits as zero.

Keep sign-extension on the operands, which signed divide needs, and
zero-extend the ALU32 result after the divide or modulo instruction,
matching the unsigned ALU32 div/mod paths and every other ALU32
operation in this JIT.

Fixes: 2425c9e002 ("LoongArch: BPF: Support signed div instructions")
Fixes: 7b6b13d329 ("LoongArch: BPF: Support signed mod instructions")
Assisted-by: Claude:claude-opus-4-8
Acked-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Nicholas Dudar 2026-07-23 22:27:35 +08:00 committed by Huacai Chen
parent 73555fdab5
commit dacd348b8a
1 changed files with 4 additions and 4 deletions
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8
arch/loongarch/net/bpf_jit.c
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@ -835,7 +835,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
move_reg(ctx, t1, src);
emit_sext_32(ctx, t1, is32);
emit_insn(ctx, divd, dst, dst, t1);
emit_sext_32(ctx, dst, is32);
emit_zext_32(ctx, dst, is32);
}
break;
@ -852,7 +852,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
emit_sext_32(ctx, t1, is32);
emit_sext_32(ctx, dst, is32);
emit_insn(ctx, divd, dst, dst, t1);
emit_sext_32(ctx, dst, is32);
emit_zext_32(ctx, dst, is32);
}
break;
@ -870,7 +870,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
move_reg(ctx, t1, src);
emit_sext_32(ctx, t1, is32);
emit_insn(ctx, modd, dst, dst, t1);
emit_sext_32(ctx, dst, is32);
emit_zext_32(ctx, dst, is32);
}
break;
@ -887,7 +887,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
emit_sext_32(ctx, t1, is32);
emit_sext_32(ctx, dst, is32);
emit_insn(ctx, modd, dst, dst, t1);
emit_sext_32(ctx, dst, is32);
emit_zext_32(ctx, dst, is32);
}
break;