From fd49591cb49b72abd1b665222a635ccb17df7923 Mon Sep 17 00:00:00 2001 From: Luke Nelson Date: Fri, 8 May 2020 11:15:45 -0700 Subject: [PATCH] bpf, arm64: Optimize AND,OR,XOR,JSET BPF_K using arm64 logical immediates The current code for BPF_{AND,OR,XOR,JSET} BPF_K loads the immediate to a temporary register before use. This patch changes the code to avoid using a temporary register when the BPF immediate is encodable using an arm64 logical immediate instruction. If the encoding fails (due to the immediate not being encodable), it falls back to using a temporary register. Example of generated code for BPF_ALU32_IMM(BPF_AND, R0, 0x80000001): without optimization: 24: mov w10, #0x8000ffff 28: movk w10, #0x1 2c: and w7, w7, w10 with optimization: 24: and w7, w7, #0x80000001 Since the encoding process is quite complex, the JIT reuses existing functionality in arch/arm64/kernel/insn.c for encoding logical immediates rather than duplicate it in the JIT. Co-developed-by: Xi Wang Signed-off-by: Xi Wang Signed-off-by: Luke Nelson Acked-by: Daniel Borkmann Link: https://lore.kernel.org/r/20200508181547.24783-3-luke.r.nels@gmail.com Signed-off-by: Will Deacon --- arch/arm64/net/bpf_jit.h | 14 +++++++++++++ arch/arm64/net/bpf_jit_comp.c | 37 +++++++++++++++++++++++++++-------- 2 files changed, 43 insertions(+), 8 deletions(-) diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h index eb73f9f72c46..f36a779949e6 100644 --- a/arch/arm64/net/bpf_jit.h +++ b/arch/arm64/net/bpf_jit.h @@ -189,4 +189,18 @@ /* Rn & Rm; set condition flags */ #define A64_TST(sf, Rn, Rm) A64_ANDS(sf, A64_ZR, Rn, Rm) +/* Logical (immediate) */ +#define A64_LOGIC_IMM(sf, Rd, Rn, imm, type) ({ \ + u64 imm64 = (sf) ? (u64)imm : (u64)(u32)imm; \ + aarch64_insn_gen_logical_immediate(AARCH64_INSN_LOGIC_##type, \ + A64_VARIANT(sf), Rn, Rd, imm64); \ +}) +/* Rd = Rn OP imm */ +#define A64_AND_I(sf, Rd, Rn, imm) A64_LOGIC_IMM(sf, Rd, Rn, imm, AND) +#define A64_ORR_I(sf, Rd, Rn, imm) A64_LOGIC_IMM(sf, Rd, Rn, imm, ORR) +#define A64_EOR_I(sf, Rd, Rn, imm) A64_LOGIC_IMM(sf, Rd, Rn, imm, EOR) +#define A64_ANDS_I(sf, Rd, Rn, imm) A64_LOGIC_IMM(sf, Rd, Rn, imm, AND_SETFLAGS) +/* Rn & imm; set condition flags */ +#define A64_TST_I(sf, Rn, imm) A64_ANDS_I(sf, A64_ZR, Rn, imm) + #endif /* _BPF_JIT_H */ diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index cdc79de0c794..083e5d8a5e2c 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -356,6 +356,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, const bool isdw = BPF_SIZE(code) == BPF_DW; u8 jmp_cond, reg; s32 jmp_offset; + u32 a64_insn; #define check_imm(bits, imm) do { \ if ((((imm) > 0) && ((imm) >> (bits))) || \ @@ -488,18 +489,33 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, break; case BPF_ALU | BPF_AND | BPF_K: case BPF_ALU64 | BPF_AND | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_AND(is64, dst, dst, tmp), ctx); + a64_insn = A64_AND_I(is64, dst, dst, imm); + if (a64_insn != AARCH64_BREAK_FAULT) { + emit(a64_insn, ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_AND(is64, dst, dst, tmp), ctx); + } break; case BPF_ALU | BPF_OR | BPF_K: case BPF_ALU64 | BPF_OR | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_ORR(is64, dst, dst, tmp), ctx); + a64_insn = A64_ORR_I(is64, dst, dst, imm); + if (a64_insn != AARCH64_BREAK_FAULT) { + emit(a64_insn, ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_ORR(is64, dst, dst, tmp), ctx); + } break; case BPF_ALU | BPF_XOR | BPF_K: case BPF_ALU64 | BPF_XOR | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_EOR(is64, dst, dst, tmp), ctx); + a64_insn = A64_EOR_I(is64, dst, dst, imm); + if (a64_insn != AARCH64_BREAK_FAULT) { + emit(a64_insn, ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_EOR(is64, dst, dst, tmp), ctx); + } break; case BPF_ALU | BPF_MUL | BPF_K: case BPF_ALU64 | BPF_MUL | BPF_K: @@ -628,8 +644,13 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, goto emit_cond_jmp; case BPF_JMP | BPF_JSET | BPF_K: case BPF_JMP32 | BPF_JSET | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_TST(is64, dst, tmp), ctx); + a64_insn = A64_TST_I(is64, dst, imm); + if (a64_insn != AARCH64_BREAK_FAULT) { + emit(a64_insn, ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_TST(is64, dst, tmp), ctx); + } goto emit_cond_jmp; /* function call */ case BPF_JMP | BPF_CALL: