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authorRussell King <rmk+kernel@armlinux.org.uk>2018-07-11 10:32:12 +0100
committerDaniel Borkmann <daniel@iogearbox.net>2018-07-12 20:45:23 +0200
commit828e2b90e8e9b5bd844a25f22ceeb8df4dd18b07 (patch)
treec487a6b61c89ce646578cad5950403c945517a46 /arch/arm
parent1ca3b17b777c4136f9dba0195e13502c445f4ade (diff)
downloadlinux-828e2b90e8e9b5bd844a25f22ceeb8df4dd18b07.tar.bz2
ARM: net: bpf: use immediate forms of instructions where possible
Rather than moving constants to a register and then using them in a subsequent instruction, use them directly in the desired instruction cutting out the "middle" register. This removes two instructions from the tail call code path. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/net/bpf_jit_32.c21
-rw-r--r--arch/arm/net/bpf_jit_32.h1
2 files changed, 13 insertions, 9 deletions
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 2cc66aa44dfe..645653e1931e 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -304,7 +304,7 @@ static u32 arm_bpf_ldst_imm12(u32 op, u8 rt, u8 rn, s16 imm12)
op |= ARM_INST_LDST__U;
else
imm12 = -imm12;
- return op | (imm12 & 0xfff);
+ return op | (imm12 & ARM_INST_LDST__IMM12);
}
static u32 arm_bpf_ldst_imm8(u32 op, u8 rt, u8 rn, s16 imm8)
@@ -1054,17 +1054,19 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
const int idx0 = ctx->idx;
#define cur_offset (ctx->idx - idx0)
#define jmp_offset (out_offset - (cur_offset) - 2)
- u32 off, lo, hi;
+ u32 lo, hi;
s8 r_array, r_index;
+ int off;
/* if (index >= array->map.max_entries)
* goto out;
*/
+ BUILD_BUG_ON(offsetof(struct bpf_array, map.max_entries) >
+ ARM_INST_LDST__IMM12);
off = offsetof(struct bpf_array, map.max_entries);
/* array->map.max_entries */
- emit_a32_mov_i(tmp[1], off, ctx);
r_array = arm_bpf_get_reg32(r2[1], tmp2[1], ctx);
- emit(ARM_LDR_R(tmp[1], r_array, tmp[1]), ctx);
+ emit(ARM_LDR_I(tmp[1], r_array, off), ctx);
/* index is 32-bit for arrays */
r_index = arm_bpf_get_reg32(r3[1], tmp2[1], ctx);
/* index >= array->map.max_entries */
@@ -1089,10 +1091,10 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
* if (prog == NULL)
* goto out;
*/
- off = offsetof(struct bpf_array, ptrs);
- emit_a32_mov_i(tmp[1], off, ctx);
+ BUILD_BUG_ON(imm8m(offsetof(struct bpf_array, ptrs)) < 0);
+ off = imm8m(offsetof(struct bpf_array, ptrs));
r_array = arm_bpf_get_reg32(r2[1], tmp2[1], ctx);
- emit(ARM_ADD_R(tmp[1], r_array, tmp[1]), ctx);
+ emit(ARM_ADD_I(tmp[1], r_array, off), ctx);
r_index = arm_bpf_get_reg32(r3[1], tmp2[1], ctx);
emit(ARM_MOV_SI(tmp[0], r_index, SRTYPE_ASL, 2), ctx);
emit(ARM_LDR_R(tmp[1], tmp[1], tmp[0]), ctx);
@@ -1100,9 +1102,10 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
_emit(ARM_COND_EQ, ARM_B(jmp_offset), ctx);
/* goto *(prog->bpf_func + prologue_size); */
+ BUILD_BUG_ON(offsetof(struct bpf_prog, bpf_func) >
+ ARM_INST_LDST__IMM12);
off = offsetof(struct bpf_prog, bpf_func);
- emit_a32_mov_i(tmp2[1], off, ctx);
- emit(ARM_LDR_R(tmp[1], tmp[1], tmp2[1]), ctx);
+ emit(ARM_LDR_I(tmp[1], tmp[1], off), ctx);
emit(ARM_ADD_I(tmp[1], tmp[1], ctx->prologue_bytes), ctx);
emit_bx_r(tmp[1], ctx);
diff --git a/arch/arm/net/bpf_jit_32.h b/arch/arm/net/bpf_jit_32.h
index c55bc39d3e22..dee8a76fb0bc 100644
--- a/arch/arm/net/bpf_jit_32.h
+++ b/arch/arm/net/bpf_jit_32.h
@@ -78,6 +78,7 @@
#define ARM_INST_EOR_I 0x02200000
#define ARM_INST_LDST__U 0x00800000
+#define ARM_INST_LDST__IMM12 0x00000fff
#define ARM_INST_LDRB_I 0x05500000
#define ARM_INST_LDRB_R 0x07d00000
#define ARM_INST_LDRH_I 0x015000b0