diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 0abd082786e797d3ea4f86c90c15fef72dc39a5f..d7dd8e0db8daa557740ec2f7b5384c991b37cacc 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -891,6 +891,65 @@ static void emit_nops(u8 **pprog, int len) *pprog = prog; } +/* emit the 3-byte VEX prefix + * + * r: same as rex.r, extra bit for ModRM reg field + * x: same as rex.x, extra bit for SIB index field + * b: same as rex.b, extra bit for ModRM r/m, or SIB base + * m: opcode map select, encoding escape bytes e.g. 0x0f38 + * w: same as rex.w (32 bit or 64 bit) or opcode specific + * src_reg2: additional source reg (encoded as BPF reg) + * l: vector length (128 bit or 256 bit) or reserved + * pp: opcode prefix (none, 0x66, 0xf2 or 0xf3) + */ +static void emit_3vex(u8 **pprog, bool r, bool x, bool b, u8 m, + bool w, u8 src_reg2, bool l, u8 pp) +{ + u8 *prog = *pprog; + const u8 b0 = 0xc4; /* first byte of 3-byte VEX prefix */ + u8 b1, b2; + u8 vvvv = reg2hex[src_reg2]; + + /* reg2hex gives only the lower 3 bit of vvvv */ + if (is_ereg(src_reg2)) + vvvv |= 1 << 3; + + /* + * 2nd byte of 3-byte VEX prefix + * ~ means bit inverted encoding + * + * 7 0 + * +---+---+---+---+---+---+---+---+ + * |~R |~X |~B | m | + * +---+---+---+---+---+---+---+---+ + */ + b1 = (!r << 7) | (!x << 6) | (!b << 5) | (m & 0x1f); + /* + * 3rd byte of 3-byte VEX prefix + * + * 7 0 + * +---+---+---+---+---+---+---+---+ + * | W | ~vvvv | L | pp | + * +---+---+---+---+---+---+---+---+ + */ + b2 = (w << 7) | ((~vvvv & 0xf) << 3) | (l << 2) | (pp & 3); + + EMIT3(b0, b1, b2); + *pprog = prog; +} + +/* emit BMI2 shift instruction */ +static void emit_shiftx(u8 **pprog, u32 dst_reg, u8 src_reg, bool is64, u8 op) +{ + u8 *prog = *pprog; + bool r = is_ereg(dst_reg); + u8 m = 2; /* escape code 0f38 */ + + emit_3vex(&prog, r, false, r, m, is64, src_reg, false, op); + EMIT2(0xf7, add_2reg(0xC0, dst_reg, dst_reg)); + *pprog = prog; +} + #define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp))) static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image, @@ -1137,17 +1196,38 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image case BPF_ALU64 | BPF_LSH | BPF_X: case BPF_ALU64 | BPF_RSH | BPF_X: case BPF_ALU64 | BPF_ARSH | BPF_X: + /* BMI2 shifts aren't better when shift count is already in rcx */ + if (boot_cpu_has(X86_FEATURE_BMI2) && src_reg != BPF_REG_4) { + /* shrx/sarx/shlx dst_reg, dst_reg, src_reg */ + bool w = (BPF_CLASS(insn->code) == BPF_ALU64); + u8 op; + + switch (BPF_OP(insn->code)) { + case BPF_LSH: + op = 1; /* prefix 0x66 */ + break; + case BPF_RSH: + op = 3; /* prefix 0xf2 */ + break; + case BPF_ARSH: + op = 2; /* prefix 0xf3 */ + break; + } - /* Check for bad case when dst_reg == rcx */ - if (dst_reg == BPF_REG_4) { - /* mov r11, dst_reg */ - EMIT_mov(AUX_REG, dst_reg); - dst_reg = AUX_REG; + emit_shiftx(&prog, dst_reg, src_reg, w, op); + + break; } if (src_reg != BPF_REG_4) { /* common case */ - EMIT1(0x51); /* push rcx */ - + /* Check for bad case when dst_reg == rcx */ + if (dst_reg == BPF_REG_4) { + /* mov r11, dst_reg */ + EMIT_mov(AUX_REG, dst_reg); + dst_reg = AUX_REG; + } else { + EMIT1(0x51); /* push rcx */ + } /* mov rcx, src_reg */ EMIT_mov(BPF_REG_4, src_reg); } @@ -1159,12 +1239,14 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image b3 = simple_alu_opcodes[BPF_OP(insn->code)]; EMIT2(0xD3, add_1reg(b3, dst_reg)); - if (src_reg != BPF_REG_4) - EMIT1(0x59); /* pop rcx */ + if (src_reg != BPF_REG_4) { + if (insn->dst_reg == BPF_REG_4) + /* mov dst_reg, r11 */ + EMIT_mov(insn->dst_reg, AUX_REG); + else + EMIT1(0x59); /* pop rcx */ + } - if (insn->dst_reg == BPF_REG_4) - /* mov dst_reg, r11 */ - EMIT_mov(insn->dst_reg, AUX_REG); break; case BPF_ALU | BPF_END | BPF_FROM_BE: diff --git a/tools/testing/selftests/bpf/verifier/jit.c b/tools/testing/selftests/bpf/verifier/jit.c index 79021c30e51eb3d27cb06957c0b363ba31baa85a..8bf37e5207f106cc3cd8ffb8d62685f848c77bdd 100644 --- a/tools/testing/selftests/bpf/verifier/jit.c +++ b/tools/testing/selftests/bpf/verifier/jit.c @@ -20,6 +20,30 @@ .result = ACCEPT, .retval = 2, }, +{ + "jit: lsh, rsh, arsh by reg", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_MOV64_IMM(BPF_REG_4, 1), + BPF_MOV64_IMM(BPF_REG_1, 0xff), + BPF_ALU64_REG(BPF_LSH, BPF_REG_1, BPF_REG_0), + BPF_ALU32_REG(BPF_LSH, BPF_REG_1, BPF_REG_4), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0x3fc, 1), + BPF_EXIT_INSN(), + BPF_ALU64_REG(BPF_RSH, BPF_REG_1, BPF_REG_4), + BPF_MOV64_REG(BPF_REG_4, BPF_REG_1), + BPF_ALU32_REG(BPF_RSH, BPF_REG_4, BPF_REG_0), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_4, 0xff, 1), + BPF_EXIT_INSN(), + BPF_ALU64_REG(BPF_ARSH, BPF_REG_4, BPF_REG_4), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_4, 0, 1), + BPF_EXIT_INSN(), + BPF_MOV64_IMM(BPF_REG_0, 2), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .retval = 2, +}, { "jit: mov32 for ldimm64, 1", .insns = {