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bpf, arm64: support more atomic operations
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Atomics for eBPF patch series adds support for atomic[64]_fetch_add,
atomic[64]_[fetch_]{and,or,xor} and atomic[64]_{xchg|cmpxchg}, but
it only adds support for x86-64, so support these atomic operations
for arm64 as well.

Basically the implementation procedure is almost mechanical translation
of code snippets in atomic_ll_sc.h & atomic_lse.h & cmpxchg.h located
under arch/arm64/include/asm.

When LSE atomic is unavailable, an extra temporary register is needed for
(BPF_ADD | BPF_FETCH) to save the value of src register, instead of adding
TMP_REG_4 just use BPF_REG_AX instead. Also make emit_lse_atomic() as an
empty inline function when CONFIG_ARM64_LSE_ATOMICS is disabled.

For cpus_have_cap(ARM64_HAS_LSE_ATOMICS) case and no-LSE-ATOMICS case, the
following three tests: "./test_verifier", "./test_progs -t atomic" and
"insmod ./test_bpf.ko" are exercised and passed.

Signed-off-by: Hou Tao <houtao1@huawei.com>
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Hou Tao authored and Nobody committed Feb 20, 2022
1 parent 6fa408a commit 47063db
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Showing 2 changed files with 217 additions and 45 deletions.
39 changes: 35 additions & 4 deletions arch/arm64/net/bpf_jit.h
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Original file line number Diff line number Diff line change
Expand Up @@ -88,17 +88,42 @@
/* [Rn] = Rt; (atomic) Rs = [state] */
#define A64_STXR(sf, Rt, Rn, Rs) \
A64_LSX(sf, Rt, Rn, Rs, STORE_EX)
/* [Rn] = Rt (store release); (atomic) Rs = [state] */
#define A64_STLXR(sf, Rt, Rn, Rs) \
aarch64_insn_gen_load_store_ex(Rt, Rn, Rs, A64_SIZE(sf), \
AARCH64_INSN_LDST_STORE_REL_EX)

/*
* LSE atomics
*
* STADD is simply encoded as an alias for LDADD with XZR as
* the destination register.
* ST{ADD,CLR,SET,EOR} is simply encoded as an alias for
* LDD{ADD,CLR,SET,EOR} with XZR as the destination register.
*/
#define A64_STADD(sf, Rn, Rs) \
#define A64_ST_OP(sf, Rn, Rs, op) \
aarch64_insn_gen_atomic_ld_op(A64_ZR, Rn, Rs, \
A64_SIZE(sf), AARCH64_INSN_MEM_ATOMIC_ADD, \
A64_SIZE(sf), AARCH64_INSN_MEM_ATOMIC_##op, \
AARCH64_INSN_MEM_ORDER_NONE)
/* [Rn] <op>= Rs */
#define A64_STADD(sf, Rn, Rs) A64_ST_OP(sf, Rn, Rs, ADD)
#define A64_STCLR(sf, Rn, Rs) A64_ST_OP(sf, Rn, Rs, CLR)
#define A64_STEOR(sf, Rn, Rs) A64_ST_OP(sf, Rn, Rs, EOR)
#define A64_STSET(sf, Rn, Rs) A64_ST_OP(sf, Rn, Rs, SET)

#define A64_LD_OP_AL(sf, Rt, Rn, Rs, op) \
aarch64_insn_gen_atomic_ld_op(Rt, Rn, Rs, \
A64_SIZE(sf), AARCH64_INSN_MEM_ATOMIC_##op, \
AARCH64_INSN_MEM_ORDER_ACQREL)
/* Rt = [Rn] (load acquire); [Rn] <op>= Rs (store release) */
#define A64_LDADDAL(sf, Rt, Rn, Rs) A64_LD_OP_AL(sf, Rt, Rn, Rs, ADD)
#define A64_LDCLRAL(sf, Rt, Rn, Rs) A64_LD_OP_AL(sf, Rt, Rn, Rs, CLR)
#define A64_LDEORAL(sf, Rt, Rn, Rs) A64_LD_OP_AL(sf, Rt, Rn, Rs, EOR)
#define A64_LDSETAL(sf, Rt, Rn, Rs) A64_LD_OP_AL(sf, Rt, Rn, Rs, SET)
/* Rt = [Rn] (load acquire); [Rn] = Rs (store release) */
#define A64_SWPAL(sf, Rt, Rn, Rs) A64_LD_OP_AL(sf, Rt, Rn, Rs, SWP)
/* Rs = CAS(Rn, Rs, Rt) (load acquire & store release) */
#define A64_CASAL(sf, Rt, Rn, Rs) \
aarch64_insn_gen_cas(Rt, Rn, Rs, A64_SIZE(sf), \
AARCH64_INSN_MEM_ORDER_ACQREL)

/* Add/subtract (immediate) */
#define A64_ADDSUB_IMM(sf, Rd, Rn, imm12, type) \
Expand Down Expand Up @@ -203,6 +228,9 @@
#define A64_ANDS(sf, Rd, Rn, Rm) A64_LOGIC_SREG(sf, Rd, Rn, Rm, AND_SETFLAGS)
/* Rn & Rm; set condition flags */
#define A64_TST(sf, Rn, Rm) A64_ANDS(sf, A64_ZR, Rn, Rm)
/* Rd = ~Rm (alias of ORN with A64_ZR as Rn) */
#define A64_MVN(sf, Rd, Rm) \
A64_LOGIC_SREG(sf, Rd, A64_ZR, Rm, ORN)

/* Logical (immediate) */
#define A64_LOGIC_IMM(sf, Rd, Rn, imm, type) ({ \
Expand All @@ -226,4 +254,7 @@
#define A64_BTI_J A64_HINT(AARCH64_INSN_HINT_BTIJ)
#define A64_BTI_JC A64_HINT(AARCH64_INSN_HINT_BTIJC)

/* DMB */
#define A64_DMB_ISH aarch64_insn_gen_dmb(AARCH64_INSN_MB_ISH)

#endif /* _BPF_JIT_H */
223 changes: 182 additions & 41 deletions arch/arm64/net/bpf_jit_comp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,17 @@
#define TCALL_CNT (MAX_BPF_JIT_REG + 2)
#define TMP_REG_3 (MAX_BPF_JIT_REG + 3)

#define check_imm(bits, imm) do { \
if ((((imm) > 0) && ((imm) >> (bits))) || \
(((imm) < 0) && (~(imm) >> (bits)))) { \
pr_info("[%2d] imm=%d(0x%x) out of range\n", \
i, imm, imm); \
return -EINVAL; \
} \
} while (0)
#define check_imm19(imm) check_imm(19, imm)
#define check_imm26(imm) check_imm(26, imm)

/* Map BPF registers to A64 registers */
static const int bpf2a64[] = {
/* return value from in-kernel function, and exit value from eBPF */
Expand Down Expand Up @@ -329,6 +340,170 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
#undef jmp_offset
}

#ifdef CONFIG_ARM64_LSE_ATOMICS
static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
const u8 code = insn->code;
const u8 dst = bpf2a64[insn->dst_reg];
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const bool isdw = BPF_SIZE(code) == BPF_DW;
const s16 off = insn->off;
u8 reg;

if (!off) {
reg = dst;
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
}

switch (insn->imm) {
/* lock *(u32/u64 *)(dst_reg + off) <op>= src_reg */
case BPF_ADD:
emit(A64_STADD(isdw, reg, src), ctx);
break;
case BPF_AND:
emit(A64_MVN(isdw, tmp2, src), ctx);
emit(A64_STCLR(isdw, reg, tmp2), ctx);
break;
case BPF_OR:
emit(A64_STSET(isdw, reg, src), ctx);
break;
case BPF_XOR:
emit(A64_STEOR(isdw, reg, src), ctx);
break;
/* src_reg = atomic_fetch_<op>(dst_reg + off, src_reg) */
case BPF_ADD | BPF_FETCH:
emit(A64_LDADDAL(isdw, src, reg, src), ctx);
break;
case BPF_AND | BPF_FETCH:
emit(A64_MVN(isdw, tmp2, src), ctx);
emit(A64_LDCLRAL(isdw, src, reg, tmp2), ctx);
break;
case BPF_OR | BPF_FETCH:
emit(A64_LDSETAL(isdw, src, reg, src), ctx);
break;
case BPF_XOR | BPF_FETCH:
emit(A64_LDEORAL(isdw, src, reg, src), ctx);
break;
/* src_reg = atomic_xchg(dst_reg + off, src_reg); */
case BPF_XCHG:
emit(A64_SWPAL(isdw, src, reg, src), ctx);
break;
/* r0 = atomic_cmpxchg(dst_reg + off, r0, src_reg); */
case BPF_CMPXCHG:
emit(A64_CASAL(isdw, src, reg, bpf2a64[BPF_REG_0]), ctx);
break;
default:
pr_err_once("unknown atomic op code %02x\n", insn->imm);
return -EINVAL;
}

return 0;
}
#else
static inline int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
return -EINVAL;
}
#endif

static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
const u8 code = insn->code;
const u8 dst = bpf2a64[insn->dst_reg];
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const u8 tmp3 = bpf2a64[TMP_REG_3];
const int i = insn - ctx->prog->insnsi;
const s32 imm = insn->imm;
const s16 off = insn->off;
const bool isdw = BPF_SIZE(code) == BPF_DW;
u8 reg;
s32 jmp_offset;

if (!off) {
reg = dst;
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
}

if (imm == BPF_ADD || imm == BPF_AND ||
imm == BPF_OR || imm == BPF_XOR) {
/* lock *(u32/u64 *)(dst_reg + off) <op>= src_reg */
emit(A64_LDXR(isdw, tmp2, reg), ctx);
if (imm == BPF_ADD)
emit(A64_ADD(isdw, tmp2, tmp2, src), ctx);
else if (imm == BPF_AND)
emit(A64_AND(isdw, tmp2, tmp2, src), ctx);
else if (imm == BPF_OR)
emit(A64_ORR(isdw, tmp2, tmp2, src), ctx);
else
emit(A64_EOR(isdw, tmp2, tmp2, src), ctx);
emit(A64_STXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -3;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
} else if (imm == (BPF_ADD | BPF_FETCH) ||
imm == (BPF_AND | BPF_FETCH) ||
imm == (BPF_OR | BPF_FETCH) ||
imm == (BPF_XOR | BPF_FETCH)) {
/* src_reg = atomic_fetch_<op>(dst_reg + off, src_reg) */
const u8 ax = bpf2a64[BPF_REG_AX];

emit(A64_MOV(isdw, ax, src), ctx);
emit(A64_LDXR(isdw, src, reg), ctx);
if (imm == (BPF_ADD | BPF_FETCH))
emit(A64_ADD(isdw, tmp2, src, ax), ctx);
else if (imm == (BPF_AND | BPF_FETCH))
emit(A64_AND(isdw, tmp2, src, ax), ctx);
else if (imm == (BPF_OR | BPF_FETCH))
emit(A64_ORR(isdw, tmp2, src, ax), ctx);
else
emit(A64_EOR(isdw, tmp2, src, ax), ctx);
emit(A64_STLXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -3;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
emit(A64_DMB_ISH, ctx);
} else if (imm == BPF_XCHG) {
/* src_reg = atomic_xchg(dst_reg + off, src_reg); */
emit(A64_MOV(isdw, tmp2, src), ctx);
emit(A64_LDXR(isdw, src, reg), ctx);
emit(A64_STLXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -2;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
emit(A64_DMB_ISH, ctx);
} else if (imm == BPF_CMPXCHG) {
/* r0 = atomic_cmpxchg(dst_reg + off, r0, src_reg); */
const u8 r0 = bpf2a64[BPF_REG_0];

emit(A64_MOV(isdw, tmp2, r0), ctx);
emit(A64_LDXR(isdw, r0, reg), ctx);
emit(A64_EOR(isdw, tmp3, r0, tmp2), ctx);
jmp_offset = 4;
check_imm19(jmp_offset);
emit(A64_CBNZ(isdw, tmp3, jmp_offset), ctx);
emit(A64_STLXR(isdw, src, reg, tmp3), ctx);
jmp_offset = -4;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
emit(A64_DMB_ISH, ctx);
} else {
pr_err_once("unknown atomic op code %02x\n", imm);
return -EINVAL;
}

return 0;
}

static void build_epilogue(struct jit_ctx *ctx)
{
const u8 r0 = bpf2a64[BPF_REG_0];
Expand Down Expand Up @@ -434,29 +609,16 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const u8 tmp3 = bpf2a64[TMP_REG_3];
const s16 off = insn->off;
const s32 imm = insn->imm;
const int i = insn - ctx->prog->insnsi;
const bool is64 = BPF_CLASS(code) == BPF_ALU64 ||
BPF_CLASS(code) == BPF_JMP;
const bool isdw = BPF_SIZE(code) == BPF_DW;
u8 jmp_cond, reg;
u8 jmp_cond;
s32 jmp_offset;
u32 a64_insn;
int ret;

#define check_imm(bits, imm) do { \
if ((((imm) > 0) && ((imm) >> (bits))) || \
(((imm) < 0) && (~(imm) >> (bits)))) { \
pr_info("[%2d] imm=%d(0x%x) out of range\n", \
i, imm, imm); \
return -EINVAL; \
} \
} while (0)
#define check_imm19(imm) check_imm(19, imm)
#define check_imm26(imm) check_imm(26, imm)

switch (code) {
/* dst = src */
case BPF_ALU | BPF_MOV | BPF_X:
Expand Down Expand Up @@ -891,33 +1053,12 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,

case BPF_STX | BPF_ATOMIC | BPF_W:
case BPF_STX | BPF_ATOMIC | BPF_DW:
if (insn->imm != BPF_ADD) {
pr_err_once("unknown atomic op code %02x\n", insn->imm);
return -EINVAL;
}

/* STX XADD: lock *(u32 *)(dst + off) += src
* and
* STX XADD: lock *(u64 *)(dst + off) += src
*/

if (!off) {
reg = dst;
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
}
if (cpus_have_cap(ARM64_HAS_LSE_ATOMICS)) {
emit(A64_STADD(isdw, reg, src), ctx);
} else {
emit(A64_LDXR(isdw, tmp2, reg), ctx);
emit(A64_ADD(isdw, tmp2, tmp2, src), ctx);
emit(A64_STXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -3;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
}
if (cpus_have_cap(ARM64_HAS_LSE_ATOMICS))
ret = emit_lse_atomic(insn, ctx);
else
ret = emit_ll_sc_atomic(insn, ctx);
if (ret)
return ret;
break;

default:
Expand Down

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