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ARM: net: support BPF_ALU | BPF_MOD instructions in the BPF JIT.

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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@freebox.fr>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Schichan 2015-10-02 17:06:47 +02:00 committed by David S. Miller
parent df7b601542
commit 4560cdff03
2 changed files with 37 additions and 6 deletions
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38
arch/arm/net/bpf_jit_32.c
View file

@ -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 @@ static int build_body(struct jit_ctx *ctx)
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 */

5
arch/arm/net/bpf_jit_32.h
View file

@ -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 */