The cpuv4 added a new BPF_SDIV instruction that does signed division. The encoding is similar to BPF_DIV but BPF_SDIV sets offset=1.
ARM32 already supports 32-bit BPF_DIV which can be easily extended to support BPF_SDIV as ARM32 has the SDIV instruction. When the CPU is not ARM-v7, we implement that SDIV/SMOD with the function call similar to the implementation of DIV/MOD.
Signed-off-by: Puranjay Mohan puranjay12@gmail.com --- arch/arm/net/bpf_jit_32.c | 38 ++++++++++++++++++++++++++++++-------- arch/arm/net/bpf_jit_32.h | 2 ++ 2 files changed, 32 insertions(+), 8 deletions(-)
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index f837db5c71b1..91b3294963bc 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -228,6 +228,16 @@ static u32 jit_mod32(u32 dividend, u32 divisor) return dividend % divisor; }
+static s32 jit_sdiv32(s32 dividend, s32 divisor) +{ + return dividend / divisor; +} + +static s32 jit_smod32(s32 dividend, s32 divisor) +{ + return dividend % divisor; +} + static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx) { inst |= (cond << 28); @@ -477,17 +487,18 @@ static inline int epilogue_offset(const struct jit_ctx *ctx) return to - from - 2; }
-static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op) +static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op, u8 sign) { const int exclude_mask = BIT(ARM_R0) | BIT(ARM_R1); const s8 *tmp = bpf2a32[TMP_REG_1]; + u32 dst;
#if __LINUX_ARM_ARCH__ == 7 if (elf_hwcap & HWCAP_IDIVA) { - if (op == BPF_DIV) - emit(ARM_UDIV(rd, rm, rn), ctx); - else { - emit(ARM_UDIV(ARM_IP, rm, rn), ctx); + if (op == BPF_DIV) { + emit(sign ? ARM_SDIV(rd, rm, rn) : ARM_UDIV(rd, rm, rn), ctx); + } else { + emit(sign ? ARM_SDIV(ARM_IP, rm, rn) : ARM_UDIV(ARM_IP, rm, rn), ctx); emit(ARM_MLS(rd, rn, ARM_IP, rm), ctx); } return; @@ -515,8 +526,19 @@ static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op) emit(ARM_PUSH(CALLER_MASK & ~exclude_mask), ctx);
/* Call appropriate function */ - emit_mov_i(ARM_IP, op == BPF_DIV ? - (u32)jit_udiv32 : (u32)jit_mod32, ctx); + if (sign) { + if (op == BPF_DIV) + dst = (u32)jit_sdiv32; + else + dst = (u32)jit_smod32; + } else { + if (op == BPF_DIV) + dst = (u32)jit_udiv32; + else + dst = (u32)jit_mod32; + } + + emit_mov_i(ARM_IP, dst, ctx); emit_blx_r(ARM_IP, ctx);
/* Restore caller-saved registers from stack */ @@ -1547,7 +1569,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) rt = src_lo; break; } - emit_udivmod(rd_lo, rd_lo, rt, ctx, BPF_OP(code)); + emit_udivmod(rd_lo, rd_lo, rt, ctx, BPF_OP(code), off); arm_bpf_put_reg32(dst_lo, rd_lo, ctx); if (!ctx->prog->aux->verifier_zext) emit_a32_mov_i(dst_hi, 0, ctx); diff --git a/arch/arm/net/bpf_jit_32.h b/arch/arm/net/bpf_jit_32.h index 79c7373fadce..438f0e1f91a0 100644 --- a/arch/arm/net/bpf_jit_32.h +++ b/arch/arm/net/bpf_jit_32.h @@ -139,6 +139,7 @@ #define ARM_INST_TST_I 0x03100000
#define ARM_INST_UDIV 0x0730f010 +#define ARM_INST_SDIV 0x0710f010
#define ARM_INST_UMULL 0x00800090
@@ -267,6 +268,7 @@ #define ARM_TST_I(rn, imm) _AL3_I(ARM_INST_TST, 0, rn, imm)
#define ARM_UDIV(rd, rn, rm) (ARM_INST_UDIV | (rd) << 16 | (rn) | (rm) << 8) +#define ARM_SDIV(rd, rn, rm) (ARM_INST_SDIV | (rd) << 16 | (rn) | (rm) << 8)
#define ARM_UMULL(rd_lo, rd_hi, rn, rm) (ARM_INST_UMULL | (rd_hi) << 16 \ | (rd_lo) << 12 | (rm) << 8 | rn)