diff options
| -rw-r--r-- | include/linux/bpf.h | 3 | ||||
| -rw-r--r-- | include/linux/bpf_verifier.h | 12 | ||||
| -rw-r--r-- | kernel/bpf/bpf_iter.c | 9 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 180 |
4 files changed, 195 insertions, 9 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 0edd7d2c0064..d05e1495a06e 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1286,6 +1286,9 @@ struct bpf_array { #define BPF_COMPLEXITY_LIMIT_INSNS 1000000 /* yes. 1M insns */ #define MAX_TAIL_CALL_CNT 33 +/* Maximum number of loops for bpf_loop */ +#define BPF_MAX_LOOPS BIT(23) + #define BPF_F_ACCESS_MASK (BPF_F_RDONLY | \ BPF_F_RDONLY_PROG | \ BPF_F_WRONLY | \ diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 3930c963fa67..81b19669efba 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -344,6 +344,14 @@ struct bpf_verifier_state_list { int miss_cnt, hit_cnt; }; +struct bpf_loop_inline_state { + int initialized:1; /* set to true upon first entry */ + int fit_for_inline:1; /* true if callback function is the same + * at each call and flags are always zero + */ + u32 callback_subprogno; /* valid when fit_for_inline is true */ +}; + /* Possible states for alu_state member. */ #define BPF_ALU_SANITIZE_SRC (1U << 0) #define BPF_ALU_SANITIZE_DST (1U << 1) @@ -373,6 +381,10 @@ struct bpf_insn_aux_data { u32 mem_size; /* mem_size for non-struct typed var */ }; } btf_var; + /* if instruction is a call to bpf_loop this field tracks + * the state of the relevant registers to make decision about inlining + */ + struct bpf_loop_inline_state loop_inline_state; }; u64 map_key_state; /* constant (32 bit) key tracking for maps */ int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c index d5d96ceca105..7e8fd49406f6 100644 --- a/kernel/bpf/bpf_iter.c +++ b/kernel/bpf/bpf_iter.c @@ -723,9 +723,6 @@ const struct bpf_func_proto bpf_for_each_map_elem_proto = { .arg4_type = ARG_ANYTHING, }; -/* maximum number of loops */ -#define MAX_LOOPS BIT(23) - BPF_CALL_4(bpf_loop, u32, nr_loops, void *, callback_fn, void *, callback_ctx, u64, flags) { @@ -733,9 +730,13 @@ BPF_CALL_4(bpf_loop, u32, nr_loops, void *, callback_fn, void *, callback_ctx, u64 ret; u32 i; + /* Note: these safety checks are also verified when bpf_loop + * is inlined, be careful to modify this code in sync. See + * function verifier.c:inline_bpf_loop. + */ if (flags) return -EINVAL; - if (nr_loops > MAX_LOOPS) + if (nr_loops > BPF_MAX_LOOPS) return -E2BIG; for (i = 0; i < nr_loops; i++) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2859901ffbe3..bf72dc511df6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7124,6 +7124,41 @@ static int check_get_func_ip(struct bpf_verifier_env *env) return -ENOTSUPP; } +static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env) +{ + return &env->insn_aux_data[env->insn_idx]; +} + +static bool loop_flag_is_zero(struct bpf_verifier_env *env) +{ + struct bpf_reg_state *regs = cur_regs(env); + struct bpf_reg_state *reg = ®s[BPF_REG_4]; + bool reg_is_null = register_is_null(reg); + + if (reg_is_null) + mark_chain_precision(env, BPF_REG_4); + + return reg_is_null; +} + +static void update_loop_inline_state(struct bpf_verifier_env *env, u32 subprogno) +{ + struct bpf_loop_inline_state *state = &cur_aux(env)->loop_inline_state; + + if (!state->initialized) { + state->initialized = 1; + state->fit_for_inline = loop_flag_is_zero(env); + state->callback_subprogno = subprogno; + return; + } + + if (!state->fit_for_inline) + return; + + state->fit_for_inline = (loop_flag_is_zero(env) && + state->callback_subprogno == subprogno); +} + static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn, int *insn_idx_p) { @@ -7276,6 +7311,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn err = check_bpf_snprintf_call(env, regs); break; case BPF_FUNC_loop: + update_loop_inline_state(env, meta.subprogno); err = __check_func_call(env, insn, insn_idx_p, meta.subprogno, set_loop_callback_state); break; @@ -7682,11 +7718,6 @@ static bool check_reg_sane_offset(struct bpf_verifier_env *env, return true; } -static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env) -{ - return &env->insn_aux_data[env->insn_idx]; -} - enum { REASON_BOUNDS = -1, REASON_TYPE = -2, @@ -14315,6 +14346,142 @@ patch_call_imm: return 0; } +static struct bpf_prog *inline_bpf_loop(struct bpf_verifier_env *env, + int position, + s32 stack_base, + u32 callback_subprogno, + u32 *cnt) +{ + s32 r6_offset = stack_base + 0 * BPF_REG_SIZE; + s32 r7_offset = stack_base + 1 * BPF_REG_SIZE; + s32 r8_offset = stack_base + 2 * BPF_REG_SIZE; + int reg_loop_max = BPF_REG_6; + int reg_loop_cnt = BPF_REG_7; + int reg_loop_ctx = BPF_REG_8; + + struct bpf_prog *new_prog; + u32 callback_start; + u32 call_insn_offset; + s32 callback_offset; + + /* This represents an inlined version of bpf_iter.c:bpf_loop, + * be careful to modify this code in sync. + */ + struct bpf_insn insn_buf[] = { + /* Return error and jump to the end of the patch if + * expected number of iterations is too big. + */ + BPF_JMP_IMM(BPF_JLE, BPF_REG_1, BPF_MAX_LOOPS, 2), + BPF_MOV32_IMM(BPF_REG_0, -E2BIG), + BPF_JMP_IMM(BPF_JA, 0, 0, 16), + /* spill R6, R7, R8 to use these as loop vars */ + BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_6, r6_offset), + BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_7, r7_offset), + BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_8, r8_offset), + /* initialize loop vars */ + BPF_MOV64_REG(reg_loop_max, BPF_REG_1), + BPF_MOV32_IMM(reg_loop_cnt, 0), + BPF_MOV64_REG(reg_loop_ctx, BPF_REG_3), + /* loop header, + * if reg_loop_cnt >= reg_loop_max skip the loop body + */ + BPF_JMP_REG(BPF_JGE, reg_loop_cnt, reg_loop_max, 5), + /* callback call, + * correct callback offset would be set after patching + */ + BPF_MOV64_REG(BPF_REG_1, reg_loop_cnt), + BPF_MOV64_REG(BPF_REG_2, reg_loop_ctx), + BPF_CALL_REL(0), + /* increment loop counter */ + BPF_ALU64_IMM(BPF_ADD, reg_loop_cnt, 1), + /* jump to loop header if callback returned 0 */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, -6), + /* return value of bpf_loop, + * set R0 to the number of iterations + */ + BPF_MOV64_REG(BPF_REG_0, reg_loop_cnt), + /* restore original values of R6, R7, R8 */ + BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_10, r6_offset), + BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_10, r7_offset), + BPF_LDX_MEM(BPF_DW, BPF_REG_8, BPF_REG_10, r8_offset), + }; + + *cnt = ARRAY_SIZE(insn_buf); + new_prog = bpf_patch_insn_data(env, position, insn_buf, *cnt); + if (!new_prog) + return new_prog; + + /* callback start is known only after patching */ + callback_start = env->subprog_info[callback_subprogno].start; + /* Note: insn_buf[12] is an offset of BPF_CALL_REL instruction */ + call_insn_offset = position + 12; + callback_offset = callback_start - call_insn_offset - 1; + env->prog->insnsi[call_insn_offset].imm = callback_offset; + + return new_prog; +} + +static bool is_bpf_loop_call(struct bpf_insn *insn) +{ + return insn->code == (BPF_JMP | BPF_CALL) && + insn->src_reg == 0 && + insn->imm == BPF_FUNC_loop; +} + +/* For all sub-programs in the program (including main) check + * insn_aux_data to see if there are bpf_loop calls that require + * inlining. If such calls are found the calls are replaced with a + * sequence of instructions produced by `inline_bpf_loop` function and + * subprog stack_depth is increased by the size of 3 registers. + * This stack space is used to spill values of the R6, R7, R8. These + * registers are used to store the loop bound, counter and context + * variables. + */ +static int optimize_bpf_loop(struct bpf_verifier_env *env) +{ + struct bpf_subprog_info *subprogs = env->subprog_info; + int i, cur_subprog = 0, cnt, delta = 0; + struct bpf_insn *insn = env->prog->insnsi; + int insn_cnt = env->prog->len; + u16 stack_depth = subprogs[cur_subprog].stack_depth; + u16 stack_depth_roundup = round_up(stack_depth, 8) - stack_depth; + u16 stack_depth_extra = 0; + + for (i = 0; i < insn_cnt; i++, insn++) { + struct bpf_loop_inline_state *inline_state = + &env->insn_aux_data[i + delta].loop_inline_state; + + if (is_bpf_loop_call(insn) && inline_state->fit_for_inline) { + struct bpf_prog *new_prog; + + stack_depth_extra = BPF_REG_SIZE * 3 + stack_depth_roundup; + new_prog = inline_bpf_loop(env, + i + delta, + -(stack_depth + stack_depth_extra), + inline_state->callback_subprogno, + &cnt); + if (!new_prog) + return -ENOMEM; + + delta += cnt - 1; + env->prog = new_prog; + insn = new_prog->insnsi + i + delta; + } + + if (subprogs[cur_subprog + 1].start == i + delta + 1) { + subprogs[cur_subprog].stack_depth += stack_depth_extra; + cur_subprog++; + stack_depth = subprogs[cur_subprog].stack_depth; + stack_depth_roundup = round_up(stack_depth, 8) - stack_depth; + stack_depth_extra = 0; + } + } + + env->prog->aux->stack_depth = env->subprog_info[0].stack_depth; + + return 0; +} + static void free_states(struct bpf_verifier_env *env) { struct bpf_verifier_state_list *sl, *sln; @@ -15052,6 +15219,9 @@ skip_full_check: ret = check_max_stack_depth(env); /* instruction rewrites happen after this point */ + if (ret == 0) + ret = optimize_bpf_loop(env); + if (is_priv) { if (ret == 0) opt_hard_wire_dead_code_branches(env); |