From 877301fa8215856e527085a7b1c8f39b4bc1e6a2 Mon Sep 17 00:00:00 2001 From: Luke Nelson Date: Fri, 8 May 2020 11:15:46 -0700 Subject: [PATCH] UPSTREAM: bpf, arm64: Optimize ADD,SUB,JMP BPF_K using arm64 add/sub immediates The current code for BPF_{ADD,SUB} BPF_K loads the BPF immediate to a temporary register before performing the addition/subtraction. Similarly, BPF_JMP BPF_K cases load the immediate to a temporary register before comparison. This patch introduces optimizations that use arm64 immediate add, sub, cmn, or cmp instructions when the BPF immediate fits. If the immediate does not fit, it falls back to using a temporary register. Example of generated code for BPF_ALU64_IMM(BPF_ADD, R0, 2): without optimization: 24: mov x10, #0x2 28: add x7, x7, x10 with optimization: 24: add x7, x7, #0x2 The code could use A64_{ADD,SUB}_I directly and check if it returns AARCH64_BREAK_FAULT, similar to how logical immediates are handled. However, aarch64_insn_gen_add_sub_imm from insn.c prints error messages when the immediate does not fit, and it's simpler to check if the immediate fits ahead of time. Co-developed-by: Xi Wang Change-Id: Ifef487e1ad1e701bcffafe78c8f7c7a4015126fa Signed-off-by: Xi Wang Signed-off-by: Luke Nelson Acked-by: Daniel Borkmann Link: https://lore.kernel.org/r/20200508181547.24783-4-luke.r.nels@gmail.com Signed-off-by: Will Deacon --- arch/arm64/net/bpf_jit.h | 8 ++++++++ arch/arm64/net/bpf_jit_comp.c | 36 +++++++++++++++++++++++++++++------ 2 files changed, 38 insertions(+), 6 deletions(-) diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h index be0a15e46fb9..b028e6d7e9d3 100644 --- a/arch/arm64/net/bpf_jit.h +++ b/arch/arm64/net/bpf_jit.h @@ -111,6 +111,14 @@ /* Rd = Rn OP imm12 */ #define A64_ADD_I(sf, Rd, Rn, imm12) A64_ADDSUB_IMM(sf, Rd, Rn, imm12, ADD) #define A64_SUB_I(sf, Rd, Rn, imm12) A64_ADDSUB_IMM(sf, Rd, Rn, imm12, SUB) +#define A64_ADDS_I(sf, Rd, Rn, imm12) \ + A64_ADDSUB_IMM(sf, Rd, Rn, imm12, ADD_SETFLAGS) +#define A64_SUBS_I(sf, Rd, Rn, imm12) \ + A64_ADDSUB_IMM(sf, Rd, Rn, imm12, SUB_SETFLAGS) +/* Rn + imm12; set condition flags */ +#define A64_CMN_I(sf, Rn, imm12) A64_ADDS_I(sf, A64_ZR, Rn, imm12) +/* Rn - imm12; set condition flags */ +#define A64_CMP_I(sf, Rn, imm12) A64_SUBS_I(sf, A64_ZR, Rn, imm12) /* Rd = Rn */ #define A64_MOV(sf, Rd, Rn) A64_ADD_I(sf, Rd, Rn, 0) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index fee2a6196f3a..233140cf1c49 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -179,6 +179,12 @@ static inline int epilogue_offset(const struct jit_ctx *ctx) return to - from; } +static bool is_addsub_imm(u32 imm) +{ + /* Either imm12 or shifted imm12. */ + return !(imm & ~0xfff) || !(imm & ~0xfff000); +} + /* Stack must be multiples of 16B */ #define STACK_ALIGN(sz) (((sz) + 15) & ~15) @@ -503,13 +509,25 @@ emit_bswap_uxt: /* dst = dst OP imm */ case BPF_ALU | BPF_ADD | BPF_K: case BPF_ALU64 | BPF_ADD | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_ADD(is64, dst, dst, tmp), ctx); + if (is_addsub_imm(imm)) { + emit(A64_ADD_I(is64, dst, dst, imm), ctx); + } else if (is_addsub_imm(-imm)) { + emit(A64_SUB_I(is64, dst, dst, -imm), ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_ADD(is64, dst, dst, tmp), ctx); + } break; case BPF_ALU | BPF_SUB | BPF_K: case BPF_ALU64 | BPF_SUB | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_SUB(is64, dst, dst, tmp), ctx); + if (is_addsub_imm(imm)) { + emit(A64_SUB_I(is64, dst, dst, imm), ctx); + } else if (is_addsub_imm(-imm)) { + emit(A64_ADD_I(is64, dst, dst, -imm), ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_SUB(is64, dst, dst, tmp), ctx); + } break; case BPF_ALU | BPF_AND | BPF_K: case BPF_ALU64 | BPF_AND | BPF_K: @@ -663,8 +681,14 @@ emit_cond_jmp: case BPF_JMP32 | BPF_JSLT | BPF_K: case BPF_JMP32 | BPF_JSGE | BPF_K: case BPF_JMP32 | BPF_JSLE | BPF_K: - emit_a64_mov_i(is64, tmp, imm, ctx); - emit(A64_CMP(is64, dst, tmp), ctx); + if (is_addsub_imm(imm)) { + emit(A64_CMP_I(is64, dst, imm), ctx); + } else if (is_addsub_imm(-imm)) { + emit(A64_CMN_I(is64, dst, -imm), ctx); + } else { + emit_a64_mov_i(is64, tmp, imm, ctx); + emit(A64_CMP(is64, dst, tmp), ctx); + } goto emit_cond_jmp; case BPF_JMP | BPF_JSET | BPF_K: case BPF_JMP32 | BPF_JSET | BPF_K: