[PATCH bpf-next] bpf, arm64: Optimize BPF store/load using str/ldr with immediate offset
Xu Kuohai
xukuohai at huawei.com
Fri Mar 11 05:35:19 PST 2022
The current BPF store/load instruction is translated by the JIT into two
instructions. The first instruction moves the immediate offset into a
temporary register. The second instruction uses this temporary register
to do the real store/load.
In fact, arm64 supports addressing with immediate offsets. So This patch
introduces optimization that uses arm64 str/ldr instruction with immediate
offset when the offset fits.
Example of generated instuction for r2 = *(u64 *)(r1 + 0):
without optimization:
mov x10, 0
ldr x1, [x0, x10]
with optimization:
ldr x1, [x0, 0]
If the offset is negative, or is not aligned correctly, or exceeds max
value, rollback to the use of temporary register.
Signed-off-by: Xu Kuohai <xukuohai at huawei.com>
---
arch/arm64/include/asm/insn.h | 9 +++++
arch/arm64/lib/insn.c | 67 +++++++++++++++++++++++-------
arch/arm64/net/bpf_jit.h | 14 +++++++
arch/arm64/net/bpf_jit_comp.c | 76 +++++++++++++++++------------------
4 files changed, 113 insertions(+), 53 deletions(-)
diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index 0b6b31307e68..d507acfdf02d 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -200,6 +200,8 @@ enum aarch64_insn_size_type {
enum aarch64_insn_ldst_type {
AARCH64_INSN_LDST_LOAD_REG_OFFSET,
AARCH64_INSN_LDST_STORE_REG_OFFSET,
+ AARCH64_INSN_LDST_LOAD_IMM_OFFSET,
+ AARCH64_INSN_LDST_STORE_IMM_OFFSET,
AARCH64_INSN_LDST_LOAD_PAIR_PRE_INDEX,
AARCH64_INSN_LDST_STORE_PAIR_PRE_INDEX,
AARCH64_INSN_LDST_LOAD_PAIR_POST_INDEX,
@@ -334,6 +336,7 @@ __AARCH64_INSN_FUNCS(load_pre, 0x3FE00C00, 0x38400C00)
__AARCH64_INSN_FUNCS(store_post, 0x3FE00C00, 0x38000400)
__AARCH64_INSN_FUNCS(load_post, 0x3FE00C00, 0x38400400)
__AARCH64_INSN_FUNCS(str_reg, 0x3FE0EC00, 0x38206800)
+__AARCH64_INSN_FUNCS(str_imm, 0x3FC00000, 0x39000000)
__AARCH64_INSN_FUNCS(ldadd, 0x3F20FC00, 0x38200000)
__AARCH64_INSN_FUNCS(ldclr, 0x3F20FC00, 0x38201000)
__AARCH64_INSN_FUNCS(ldeor, 0x3F20FC00, 0x38202000)
@@ -341,6 +344,7 @@ __AARCH64_INSN_FUNCS(ldset, 0x3F20FC00, 0x38203000)
__AARCH64_INSN_FUNCS(swp, 0x3F20FC00, 0x38208000)
__AARCH64_INSN_FUNCS(cas, 0x3FA07C00, 0x08A07C00)
__AARCH64_INSN_FUNCS(ldr_reg, 0x3FE0EC00, 0x38606800)
+__AARCH64_INSN_FUNCS(ldr_imm, 0x3FC00000, 0x39400000)
__AARCH64_INSN_FUNCS(ldr_lit, 0xBF000000, 0x18000000)
__AARCH64_INSN_FUNCS(ldrsw_lit, 0xFF000000, 0x98000000)
__AARCH64_INSN_FUNCS(exclusive, 0x3F800000, 0x08000000)
@@ -500,6 +504,11 @@ u32 aarch64_insn_gen_load_store_reg(enum aarch64_insn_register reg,
enum aarch64_insn_register offset,
enum aarch64_insn_size_type size,
enum aarch64_insn_ldst_type type);
+u32 aarch64_insn_gen_load_store_imm(enum aarch64_insn_register reg,
+ enum aarch64_insn_register base,
+ unsigned int imm,
+ enum aarch64_insn_size_type size,
+ enum aarch64_insn_ldst_type type);
u32 aarch64_insn_gen_load_store_pair(enum aarch64_insn_register reg1,
enum aarch64_insn_register reg2,
enum aarch64_insn_register base,
diff --git a/arch/arm64/lib/insn.c b/arch/arm64/lib/insn.c
index 5e90887deec4..695d7368fadc 100644
--- a/arch/arm64/lib/insn.c
+++ b/arch/arm64/lib/insn.c
@@ -299,29 +299,24 @@ static u32 aarch64_insn_encode_register(enum aarch64_insn_register_type type,
return insn;
}
+static const u32 aarch64_insn_ldst_size[] = {
+ [AARCH64_INSN_SIZE_8] = 0,
+ [AARCH64_INSN_SIZE_16] = 1,
+ [AARCH64_INSN_SIZE_32] = 2,
+ [AARCH64_INSN_SIZE_64] = 3,
+};
+
static u32 aarch64_insn_encode_ldst_size(enum aarch64_insn_size_type type,
u32 insn)
{
u32 size;
- switch (type) {
- case AARCH64_INSN_SIZE_8:
- size = 0;
- break;
- case AARCH64_INSN_SIZE_16:
- size = 1;
- break;
- case AARCH64_INSN_SIZE_32:
- size = 2;
- break;
- case AARCH64_INSN_SIZE_64:
- size = 3;
- break;
- default:
+ if (type < AARCH64_INSN_SIZE_8 || type > AARCH64_INSN_SIZE_64) {
pr_err("%s: unknown size encoding %d\n", __func__, type);
return AARCH64_BREAK_FAULT;
}
+ size = aarch64_insn_ldst_size[type];
insn &= ~GENMASK(31, 30);
insn |= size << 30;
@@ -504,6 +499,50 @@ u32 aarch64_insn_gen_load_store_reg(enum aarch64_insn_register reg,
offset);
}
+u32 aarch64_insn_gen_load_store_imm(enum aarch64_insn_register reg,
+ enum aarch64_insn_register base,
+ unsigned int imm,
+ enum aarch64_insn_size_type size,
+ enum aarch64_insn_ldst_type type)
+{
+ u32 insn;
+ u32 shift;
+
+ if (size < AARCH64_INSN_SIZE_8 || size > AARCH64_INSN_SIZE_64) {
+ pr_err("%s: unknown size encoding %d\n", __func__, type);
+ return AARCH64_BREAK_FAULT;
+ }
+
+ shift = aarch64_insn_ldst_size[size];
+ if (imm & ~(BIT(12 + shift) - BIT(shift))) {
+ pr_err("%s: invalid imm: %d\n", __func__, imm);
+ return AARCH64_BREAK_FAULT;
+ }
+
+ imm >>= shift;
+
+ switch (type) {
+ case AARCH64_INSN_LDST_LOAD_IMM_OFFSET:
+ insn = aarch64_insn_get_ldr_imm_value();
+ break;
+ case AARCH64_INSN_LDST_STORE_IMM_OFFSET:
+ insn = aarch64_insn_get_str_imm_value();
+ break;
+ default:
+ pr_err("%s: unknown load/store encoding %d\n", __func__, type);
+ return AARCH64_BREAK_FAULT;
+ }
+
+ insn = aarch64_insn_encode_ldst_size(size, insn);
+
+ insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RT, insn, reg);
+
+ insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RN, insn,
+ base);
+
+ return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_12, insn, imm);
+}
+
u32 aarch64_insn_gen_load_store_pair(enum aarch64_insn_register reg1,
enum aarch64_insn_register reg2,
enum aarch64_insn_register base,
diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h
index dd59b5ad8fe4..3920213244f0 100644
--- a/arch/arm64/net/bpf_jit.h
+++ b/arch/arm64/net/bpf_jit.h
@@ -66,6 +66,20 @@
#define A64_STR64(Xt, Xn, Xm) A64_LS_REG(Xt, Xn, Xm, 64, STORE)
#define A64_LDR64(Xt, Xn, Xm) A64_LS_REG(Xt, Xn, Xm, 64, LOAD)
+/* Load/store register (immediate offset) */
+#define A64_LS_IMM(Rt, Rn, imm, size, type) \
+ aarch64_insn_gen_load_store_imm(Rt, Rn, imm, \
+ AARCH64_INSN_SIZE_##size, \
+ AARCH64_INSN_LDST_##type##_IMM_OFFSET)
+#define A64_STRBI(Wt, Xn, imm) A64_LS_IMM(Wt, Xn, imm, 8, STORE)
+#define A64_LDRBI(Wt, Xn, imm) A64_LS_IMM(Wt, Xn, imm, 8, LOAD)
+#define A64_STRHI(Wt, Xn, imm) A64_LS_IMM(Wt, Xn, imm, 16, STORE)
+#define A64_LDRHI(Wt, Xn, imm) A64_LS_IMM(Wt, Xn, imm, 16, LOAD)
+#define A64_STR32I(Wt, Xn, imm) A64_LS_IMM(Wt, Xn, imm, 32, STORE)
+#define A64_LDR32I(Wt, Xn, imm) A64_LS_IMM(Wt, Xn, imm, 32, LOAD)
+#define A64_STR64I(Xt, Xn, imm) A64_LS_IMM(Xt, Xn, imm, 64, STORE)
+#define A64_LDR64I(Xt, Xn, imm) A64_LS_IMM(Xt, Xn, imm, 64, LOAD)
+
/* Load/store register pair */
#define A64_LS_PAIR(Rt, Rt2, Rn, offset, ls, type) \
aarch64_insn_gen_load_store_pair(Rt, Rt2, Rn, offset, \
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index e850c69e128c..027666ff00e8 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -971,20 +971,22 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
case BPF_LDX | BPF_PROBE_MEM | BPF_W:
case BPF_LDX | BPF_PROBE_MEM | BPF_H:
case BPF_LDX | BPF_PROBE_MEM | BPF_B:
- emit_a64_mov_i(1, tmp, off, ctx);
+
+#define BUILD_LDX_INSN(a, b, c) \
+case BPF_##a: \
+ if ((off & ((1 << c) - 1)) == 0 && off >= 0 && off <= (0xFFF << c)) { \
+ emit(A64_LDR##b##I(dst, src, off), ctx); \
+ } else { \
+ emit_a64_mov_i(1, tmp, off, ctx); \
+ emit(A64_LDR##b(dst, src, tmp), ctx); \
+ } \
+ break;
+
switch (BPF_SIZE(code)) {
- case BPF_W:
- emit(A64_LDR32(dst, src, tmp), ctx);
- break;
- case BPF_H:
- emit(A64_LDRH(dst, src, tmp), ctx);
- break;
- case BPF_B:
- emit(A64_LDRB(dst, src, tmp), ctx);
- break;
- case BPF_DW:
- emit(A64_LDR64(dst, src, tmp), ctx);
- break;
+ BUILD_LDX_INSN(W, 32, 2)
+ BUILD_LDX_INSN(H, H, 1)
+ BUILD_LDX_INSN(B, B, 0)
+ BUILD_LDX_INSN(DW, 64, 3)
}
ret = add_exception_handler(insn, ctx, dst);
@@ -1010,22 +1012,25 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
case BPF_ST | BPF_MEM | BPF_H:
case BPF_ST | BPF_MEM | BPF_B:
case BPF_ST | BPF_MEM | BPF_DW:
+
+#define __BUILD_STX_INSN(a, b, c, d, e) \
+ case BPF_##a: \
+ if ((off & ((1 << c) - 1)) == 0 && off >= 0 && off <= (0xFFF << c)) { \
+ emit(A64_STR##b##I(d, dst, off), ctx); \
+ } else { \
+ emit_a64_mov_i(1, e, off, ctx); \
+ emit(A64_STR##b(d, dst, e), ctx); \
+ } \
+ break;
+
+#define BUILD_ST_INSN(a, b, c) __BUILD_STX_INSN(a, b, c, tmp, tmp2)
/* Load imm to a register then store it */
- emit_a64_mov_i(1, tmp2, off, ctx);
emit_a64_mov_i(1, tmp, imm, ctx);
switch (BPF_SIZE(code)) {
- case BPF_W:
- emit(A64_STR32(tmp, dst, tmp2), ctx);
- break;
- case BPF_H:
- emit(A64_STRH(tmp, dst, tmp2), ctx);
- break;
- case BPF_B:
- emit(A64_STRB(tmp, dst, tmp2), ctx);
- break;
- case BPF_DW:
- emit(A64_STR64(tmp, dst, tmp2), ctx);
- break;
+ BUILD_ST_INSN(W, 32, 2)
+ BUILD_ST_INSN(H, H, 1)
+ BUILD_ST_INSN(B, B, 0)
+ BUILD_ST_INSN(DW, 64, 3)
}
break;
@@ -1034,20 +1039,13 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
case BPF_STX | BPF_MEM | BPF_H:
case BPF_STX | BPF_MEM | BPF_B:
case BPF_STX | BPF_MEM | BPF_DW:
- emit_a64_mov_i(1, tmp, off, ctx);
+
+#define BUILD_STX_INSN(a, b, c) __BUILD_STX_INSN(a, b, c, src, tmp)
switch (BPF_SIZE(code)) {
- case BPF_W:
- emit(A64_STR32(src, dst, tmp), ctx);
- break;
- case BPF_H:
- emit(A64_STRH(src, dst, tmp), ctx);
- break;
- case BPF_B:
- emit(A64_STRB(src, dst, tmp), ctx);
- break;
- case BPF_DW:
- emit(A64_STR64(src, dst, tmp), ctx);
- break;
+ BUILD_STX_INSN(W, 32, 2)
+ BUILD_STX_INSN(H, H, 1)
+ BUILD_STX_INSN(B, B, 0)
+ BUILD_STX_INSN(DW, 64, 3)
}
break;
--
2.30.2
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