[PATCH net-next V2] ARM: net: support BPF_ALU | BPF_MOD instructions in the BPF JIT.
From: Nicolas Schichan
Date: Fri Oct 02 2015 - 11:07:07 EST
For ARMv7 with UDIV instruction support, generate an UDIV instruction
followed by an MLS instruction.
For other ARM variants, generate code calling a C wrapper similar to
the jit_udiv() function used for BPF_ALU | BPF_DIV instructions.
Some performance numbers reported by the test_bpf module (the duration
per filter run is reported in nanoseconds, between "jitted:<x>" and
"PASS":
ARMv7 QEMU nojit: test_bpf: #3 DIV_MOD_KX jited:0 2196 PASS
ARMv7 QEMU jit: test_bpf: #3 DIV_MOD_KX jited:1 104 PASS
ARMv5 QEMU nojit: test_bpf: #3 DIV_MOD_KX jited:0 2176 PASS
ARMv5 QEMU jit: test_bpf: #3 DIV_MOD_KX jited:1 1104 PASS
ARMv5 kirkwood nojit: test_bpf: #3 DIV_MOD_KX jited:0 1103 PASS
ARMv5 kirkwood jit: test_bpf: #3 DIV_MOD_KX jited:1 311 PASS
Signed-off-by: Nicolas Schichan <nschichan@xxxxxxxxxx>
---
Changes from V1:
- Address spelling in comment, following Russel's remarks.
arch/arm/net/bpf_jit_32.c | 38 ++++++++++++++++++++++++++++++++------
arch/arm/net/bpf_jit_32.h | 5 +++++
2 files changed, 37 insertions(+), 6 deletions(-)
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 876060b..36edd410 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -125,7 +125,7 @@ static u64 jit_get_skb_w(struct sk_buff *skb, int offset)
}
/*
- * Wrapper that handles both OABI and EABI and assures Thumb2 interworking
+ * Wrappers which handle both OABI and EABI and assures Thumb2 interworking
* (where the assembly routines like __aeabi_uidiv could cause problems).
*/
static u32 jit_udiv(u32 dividend, u32 divisor)
@@ -133,6 +133,11 @@ static u32 jit_udiv(u32 dividend, u32 divisor)
return dividend / divisor;
}
+static u32 jit_mod(u32 dividend, u32 divisor)
+{
+ return dividend % divisor;
+}
+
static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx)
{
inst |= (cond << 28);
@@ -471,11 +476,17 @@ static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx)
#endif
}
-static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx)
+static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx,
+ int bpf_op)
{
#if __LINUX_ARM_ARCH__ == 7
if (elf_hwcap & HWCAP_IDIVA) {
- emit(ARM_UDIV(rd, rm, rn), ctx);
+ if (bpf_op == BPF_DIV)
+ emit(ARM_UDIV(rd, rm, rn), ctx);
+ else {
+ emit(ARM_UDIV(ARM_R3, rm, rn), ctx);
+ emit(ARM_MLS(rd, rn, ARM_R3, rm), ctx);
+ }
return;
}
#endif
@@ -496,7 +507,8 @@ static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx)
emit(ARM_MOV_R(ARM_R0, rm), ctx);
ctx->seen |= SEEN_CALL;
- emit_mov_i(ARM_R3, (u32)jit_udiv, ctx);
+ emit_mov_i(ARM_R3, bpf_op == BPF_DIV ? (u32)jit_udiv : (u32)jit_mod,
+ ctx);
emit_blx_r(ARM_R3, ctx);
if (rd != ARM_R0)
@@ -697,13 +709,27 @@ load_ind:
if (k == 1)
break;
emit_mov_i(r_scratch, k, ctx);
- emit_udiv(r_A, r_A, r_scratch, ctx);
+ emit_udivmod(r_A, r_A, r_scratch, ctx, BPF_DIV);
break;
case BPF_ALU | BPF_DIV | BPF_X:
update_on_xread(ctx);
emit(ARM_CMP_I(r_X, 0), ctx);
emit_err_ret(ARM_COND_EQ, ctx);
- emit_udiv(r_A, r_A, r_X, ctx);
+ emit_udivmod(r_A, r_A, r_X, ctx, BPF_DIV);
+ break;
+ case BPF_ALU | BPF_MOD | BPF_K:
+ if (k == 1) {
+ emit_mov_i(r_A, 0, ctx);
+ break;
+ }
+ emit_mov_i(r_scratch, k, ctx);
+ emit_udivmod(r_A, r_A, r_scratch, ctx, BPF_MOD);
+ break;
+ case BPF_ALU | BPF_MOD | BPF_X:
+ update_on_xread(ctx);
+ emit(ARM_CMP_I(r_X, 0), ctx);
+ emit_err_ret(ARM_COND_EQ, ctx);
+ emit_udivmod(r_A, r_A, r_X, ctx, BPF_MOD);
break;
case BPF_ALU | BPF_OR | BPF_K:
/* A |= K */
diff --git a/arch/arm/net/bpf_jit_32.h b/arch/arm/net/bpf_jit_32.h
index 4b17d5ab..c46fca2 100644
--- a/arch/arm/net/bpf_jit_32.h
+++ b/arch/arm/net/bpf_jit_32.h
@@ -115,6 +115,8 @@
#define ARM_INST_UMULL 0x00800090
+#define ARM_INST_MLS 0x00600090
+
/*
* Use a suitable undefined instruction to use for ARM/Thumb2 faulting.
* We need to be careful not to conflict with those used by other modules
@@ -210,4 +212,7 @@
#define ARM_UMULL(rd_lo, rd_hi, rn, rm) (ARM_INST_UMULL | (rd_hi) << 16 \
| (rd_lo) << 12 | (rm) << 8 | rn)
+#define ARM_MLS(rd, rn, rm, ra) (ARM_INST_MLS | (rd) << 16 | (rn) | (rm) << 8 \
+ | (ra) << 12)
+
#endif /* PFILTER_OPCODES_ARM_H */
--
1.9.1
--
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