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MIPS: BPF: Free up some callee-saved registers
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Move the two scratch registers from s0 and s1 to t4 and t5 in order
to free up some callee-saved registers. We will use these callee-saved
registers to store some permanent data on them in a subsequent patch.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/10525/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Markos Chandras authored and Ralf Baechle committed Jun 21, 2015
1 parent de5792a commit ad152bd
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Showing 2 changed files with 17 additions and 20 deletions.
35 changes: 15 additions & 20 deletions arch/mips/net/bpf_jit.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,6 @@

/* ABI
*
* s0 1st scratch register
* s1 2nd scratch register
* s2 offset register
* s3 BPF register A
* s4 BPF register X
* s5 *skb
Expand Down Expand Up @@ -88,13 +85,13 @@
* any of the $s0-$s6 registers will only be preserved if
* they are going to actually be used.
*/
#define r_s0 MIPS_R_S0 /* scratch reg 1 */
#define r_s1 MIPS_R_S1 /* scratch reg 2 */
#define r_off MIPS_R_S2
#define r_A MIPS_R_S3
#define r_X MIPS_R_S4
#define r_skb MIPS_R_S5
#define r_M MIPS_R_S6
#define r_s0 MIPS_R_T4 /* scratch reg 1 */
#define r_s1 MIPS_R_T5 /* scratch reg 2 */
#define r_tmp_imm MIPS_R_T6 /* No need to preserve this */
#define r_tmp MIPS_R_T7 /* No need to preserve this */
#define r_zero MIPS_R_ZERO
Expand All @@ -108,8 +105,6 @@
#define SEEN_SREG_SFT (BPF_MEMWORDS + 1)
#define SEEN_SREG_BASE (1 << SEEN_SREG_SFT)
#define SEEN_SREG(x) (SEEN_SREG_BASE << (x))
#define SEEN_S0 SEEN_SREG(0)
#define SEEN_S1 SEEN_SREG(1)
#define SEEN_OFF SEEN_SREG(2)
#define SEEN_A SEEN_SREG(3)
#define SEEN_X SEEN_SREG(4)
Expand Down Expand Up @@ -813,7 +808,7 @@ static int build_body(struct jit_ctx *ctx)
b_imm(prog->len, ctx), ctx);
emit_reg_move(r_ret, r_zero, ctx);

ctx->flags |= SEEN_CALL | SEEN_OFF | SEEN_S0 |
ctx->flags |= SEEN_CALL | SEEN_OFF |
SEEN_SKB | SEEN_A;

emit_load_func(r_s0, (ptr)load_func[load_order],
Expand Down Expand Up @@ -879,7 +874,7 @@ static int build_body(struct jit_ctx *ctx)
return -ENOTSUPP;

/* X <- 4 * (P[k:1] & 0xf) */
ctx->flags |= SEEN_X | SEEN_CALL | SEEN_S0 | SEEN_SKB;
ctx->flags |= SEEN_X | SEEN_CALL | SEEN_SKB;
/* Load offset to a1 */
emit_load_func(r_s0, (ptr)jit_get_skb_b, ctx);
/*
Expand Down Expand Up @@ -943,7 +938,7 @@ static int build_body(struct jit_ctx *ctx)
case BPF_ALU | BPF_MUL | BPF_K:
/* A *= K */
/* Load K to scratch register before MUL */
ctx->flags |= SEEN_A | SEEN_S0;
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
emit_mul(r_A, r_A, r_s0, ctx);
break;
Expand All @@ -961,7 +956,7 @@ static int build_body(struct jit_ctx *ctx)
emit_srl(r_A, r_A, k, ctx);
break;
}
ctx->flags |= SEEN_A | SEEN_S0;
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
emit_div(r_A, r_s0, ctx);
break;
Expand All @@ -971,7 +966,7 @@ static int build_body(struct jit_ctx *ctx)
ctx->flags |= SEEN_A;
emit_jit_reg_move(r_A, r_zero, ctx);
} else {
ctx->flags |= SEEN_A | SEEN_S0;
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
emit_mod(r_A, r_s0, ctx);
}
Expand Down Expand Up @@ -1085,10 +1080,10 @@ static int build_body(struct jit_ctx *ctx)
if ((condt & MIPS_COND_GE) ||
(condt & MIPS_COND_GT)) {
if (condt & MIPS_COND_K) { /* K */
ctx->flags |= SEEN_S0 | SEEN_A;
ctx->flags |= SEEN_A;
emit_sltiu(r_s0, r_A, k, ctx);
} else { /* X */
ctx->flags |= SEEN_S0 | SEEN_A |
ctx->flags |= SEEN_A |
SEEN_X;
emit_sltu(r_s0, r_A, r_X, ctx);
}
Expand All @@ -1100,7 +1095,7 @@ static int build_body(struct jit_ctx *ctx)
/* A > (K|X) ? scratch = 0 */
if (condt & MIPS_COND_GT) {
/* Checking for equality */
ctx->flags |= SEEN_S0 | SEEN_A | SEEN_X;
ctx->flags |= SEEN_A | SEEN_X;
if (condt & MIPS_COND_K)
emit_load_imm(r_s0, k, ctx);
else
Expand All @@ -1123,7 +1118,7 @@ static int build_body(struct jit_ctx *ctx)
} else {
/* A == K|X */
if (condt & MIPS_COND_K) { /* K */
ctx->flags |= SEEN_S0 | SEEN_A;
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
/* jump true */
b_off = b_imm(i + inst->jt + 1, ctx);
Expand Down Expand Up @@ -1153,7 +1148,7 @@ static int build_body(struct jit_ctx *ctx)
}
break;
case BPF_JMP | BPF_JSET | BPF_K:
ctx->flags |= SEEN_S0 | SEEN_S1 | SEEN_A;
ctx->flags |= SEEN_A;
/* pc += (A & K) ? pc -> jt : pc -> jf */
emit_load_imm(r_s1, k, ctx);
emit_and(r_s0, r_A, r_s1, ctx);
Expand All @@ -1167,7 +1162,7 @@ static int build_body(struct jit_ctx *ctx)
emit_nop(ctx);
break;
case BPF_JMP | BPF_JSET | BPF_X:
ctx->flags |= SEEN_S0 | SEEN_X | SEEN_A;
ctx->flags |= SEEN_X | SEEN_A;
/* pc += (A & X) ? pc -> jt : pc -> jf */
emit_and(r_s0, r_A, r_X, ctx);
/* jump true */
Expand Down Expand Up @@ -1251,7 +1246,7 @@ static int build_body(struct jit_ctx *ctx)
break;
case BPF_ANC | SKF_AD_IFINDEX:
/* A = skb->dev->ifindex */
ctx->flags |= SEEN_SKB | SEEN_A | SEEN_S0;
ctx->flags |= SEEN_SKB | SEEN_A;
off = offsetof(struct sk_buff, dev);
/* Load *dev pointer */
emit_load_ptr(r_s0, r_skb, off, ctx);
Expand All @@ -1278,7 +1273,7 @@ static int build_body(struct jit_ctx *ctx)
break;
case BPF_ANC | SKF_AD_VLAN_TAG:
case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
ctx->flags |= SEEN_SKB | SEEN_S0 | SEEN_A;
ctx->flags |= SEEN_SKB | SEEN_A;
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
vlan_tci) != 2);
off = offsetof(struct sk_buff, vlan_tci);
Expand Down
2 changes: 2 additions & 0 deletions arch/mips/net/bpf_jit.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@
#define MIPS_R_V1 3
#define MIPS_R_A0 4
#define MIPS_R_A1 5
#define MIPS_R_T4 12
#define MIPS_R_T5 13
#define MIPS_R_T6 14
#define MIPS_R_T7 15
#define MIPS_R_S0 16
Expand Down

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