@@ -325,12 +325,34 @@ struct bpf_func_state {
int allocated_stack;
};
-struct bpf_idx_pair {
- u32 prev_idx;
+#define MAX_CALL_FRAMES 8
+
+/* instruction history flags, used in bpf_jmp_history_entry.flags field */
+enum {
+ /* instruction references stack slot through PTR_TO_STACK register;
+ * we also store stack's frame number in lower 3 bits (MAX_CALL_FRAMES is 8)
+ * and accessed stack slot's index in next 6 bits (MAX_BPF_STACK is 512,
+ * 8 bytes per slot, so slot index (spi) is [0, 63])
+ */
+ INSN_F_FRAMENO_MASK = 0x7, /* 3 bits */
+
+ INSN_F_SPI_MASK = 0x3f, /* 6 bits */
+ INSN_F_SPI_SHIFT = 3, /* shifted 3 bits to the left */
+
+ INSN_F_STACK_ACCESS = BIT(9), /* we need 10 bits total */
+};
+
+static_assert(INSN_F_FRAMENO_MASK + 1 >= MAX_CALL_FRAMES);
+static_assert(INSN_F_SPI_MASK + 1 >= MAX_BPF_STACK / 8);
+
+struct bpf_jmp_history_entry {
u32 idx;
+ /* insn idx can't be bigger than 1 million */
+ u32 prev_idx : 22;
+ /* special flags, e.g., whether insn is doing register stack spill/load */
+ u32 flags : 10;
};
-#define MAX_CALL_FRAMES 8
/* Maximum number of register states that can exist at once */
#define BPF_ID_MAP_SIZE ((MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE) * MAX_CALL_FRAMES)
struct bpf_verifier_state {
@@ -413,7 +435,7 @@ struct bpf_verifier_state {
* For most states jmp_history_cnt is [0-3].
* For loops can go up to ~40.
*/
- struct bpf_idx_pair *jmp_history;
+ struct bpf_jmp_history_entry *jmp_history;
u32 jmp_history_cnt;
u32 dfs_depth;
u32 callback_unroll_depth;
@@ -656,6 +678,7 @@ struct bpf_verifier_env {
int cur_stack;
} cfg;
struct backtrack_state bt;
+ struct bpf_jmp_history_entry *cur_hist_ent;
u32 pass_cnt; /* number of times do_check() was called */
u32 subprog_cnt;
/* number of instructions analyzed by the verifier */
@@ -1355,8 +1355,8 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
int i, err;
dst_state->jmp_history = copy_array(dst_state->jmp_history, src->jmp_history,
- src->jmp_history_cnt, sizeof(struct bpf_idx_pair),
- GFP_USER);
+ src->jmp_history_cnt, sizeof(*dst_state->jmp_history),
+ GFP_USER);
if (!dst_state->jmp_history)
return -ENOMEM;
dst_state->jmp_history_cnt = src->jmp_history_cnt;
@@ -3221,6 +3221,21 @@ static int check_reg_arg(struct bpf_verifier_env *env, u32 regno,
return __check_reg_arg(env, state->regs, regno, t);
}
+static int insn_stack_access_flags(int frameno, int spi)
+{
+ return INSN_F_STACK_ACCESS | (spi << INSN_F_SPI_SHIFT) | frameno;
+}
+
+static int insn_stack_access_spi(int insn_flags)
+{
+ return (insn_flags >> INSN_F_SPI_SHIFT) & INSN_F_SPI_MASK;
+}
+
+static int insn_stack_access_frameno(int insn_flags)
+{
+ return insn_flags & INSN_F_FRAMENO_MASK;
+}
+
static void mark_jmp_point(struct bpf_verifier_env *env, int idx)
{
env->insn_aux_data[idx].jmp_point = true;
@@ -3232,28 +3247,51 @@ static bool is_jmp_point(struct bpf_verifier_env *env, int insn_idx)
}
/* for any branch, call, exit record the history of jmps in the given state */
-static int push_jmp_history(struct bpf_verifier_env *env,
- struct bpf_verifier_state *cur)
+static int push_jmp_history(struct bpf_verifier_env *env, struct bpf_verifier_state *cur,
+ int insn_flags)
{
u32 cnt = cur->jmp_history_cnt;
- struct bpf_idx_pair *p;
+ struct bpf_jmp_history_entry *p;
size_t alloc_size;
- if (!is_jmp_point(env, env->insn_idx))
+ /* combine instruction flags if we already recorded this instruction */
+ if (env->cur_hist_ent) {
+ /* atomic instructions push insn_flags twice, for READ and
+ * WRITE sides, but they should agree on stack slot
+ */
+ WARN_ONCE((env->cur_hist_ent->flags & insn_flags) &&
+ (env->cur_hist_ent->flags & insn_flags) != insn_flags,
+ "verifier insn history bug: insn_idx %d cur flags %x new flags %x\n",
+ env->insn_idx, env->cur_hist_ent->flags, insn_flags);
+ env->cur_hist_ent->flags |= insn_flags;
return 0;
+ }
cnt++;
alloc_size = kmalloc_size_roundup(size_mul(cnt, sizeof(*p)));
p = krealloc(cur->jmp_history, alloc_size, GFP_USER);
if (!p)
return -ENOMEM;
- p[cnt - 1].idx = env->insn_idx;
- p[cnt - 1].prev_idx = env->prev_insn_idx;
cur->jmp_history = p;
+
+ p = &cur->jmp_history[cnt - 1];
+ p->idx = env->insn_idx;
+ p->prev_idx = env->prev_insn_idx;
+ p->flags = insn_flags;
cur->jmp_history_cnt = cnt;
+ env->cur_hist_ent = p;
+
return 0;
}
+static struct bpf_jmp_history_entry *get_jmp_hist_entry(struct bpf_verifier_state *st,
+ u32 hist_end, int insn_idx)
+{
+ if (hist_end > 0 && st->jmp_history[hist_end - 1].idx == insn_idx)
+ return &st->jmp_history[hist_end - 1];
+ return NULL;
+}
+
/* Backtrack one insn at a time. If idx is not at the top of recorded
* history then previous instruction came from straight line execution.
* Return -ENOENT if we exhausted all instructions within given state.
@@ -3415,9 +3453,14 @@ static inline bool bt_is_reg_set(struct backtrack_state *bt, u32 reg)
return bt->reg_masks[bt->frame] & (1 << reg);
}
+static inline bool bt_is_frame_slot_set(struct backtrack_state *bt, u32 frame, u32 slot)
+{
+ return bt->stack_masks[frame] & (1ull << slot);
+}
+
static inline bool bt_is_slot_set(struct backtrack_state *bt, u32 slot)
{
- return bt->stack_masks[bt->frame] & (1ull << slot);
+ return bt_is_frame_slot_set(bt, bt->frame, slot);
}
/* format registers bitmask, e.g., "r0,r2,r4" for 0x15 mask */
@@ -3471,7 +3514,7 @@ static bool calls_callback(struct bpf_verifier_env *env, int insn_idx);
* - *was* processed previously during backtracking.
*/
static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
- struct backtrack_state *bt)
+ struct bpf_jmp_history_entry *hist, struct backtrack_state *bt)
{
const struct bpf_insn_cbs cbs = {
.cb_call = disasm_kfunc_name,
@@ -3484,7 +3527,7 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
u8 mode = BPF_MODE(insn->code);
u32 dreg = insn->dst_reg;
u32 sreg = insn->src_reg;
- u32 spi, i;
+ u32 spi, i, fr;
if (insn->code == 0)
return 0;
@@ -3545,20 +3588,15 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
* by 'precise' mark in corresponding register of this state.
* No further tracking necessary.
*/
- if (insn->src_reg != BPF_REG_FP)
+ if (!hist || !(hist->flags & INSN_F_STACK_ACCESS))
return 0;
-
/* dreg = *(u64 *)[fp - off] was a fill from the stack.
* that [fp - off] slot contains scalar that needs to be
* tracked with precision
*/
- spi = (-insn->off - 1) / BPF_REG_SIZE;
- if (spi >= 64) {
- verbose(env, "BUG spi %d\n", spi);
- WARN_ONCE(1, "verifier backtracking bug");
- return -EFAULT;
- }
- bt_set_slot(bt, spi);
+ spi = insn_stack_access_spi(hist->flags);
+ fr = insn_stack_access_frameno(hist->flags);
+ bt_set_frame_slot(bt, fr, spi);
} else if (class == BPF_STX || class == BPF_ST) {
if (bt_is_reg_set(bt, dreg))
/* stx & st shouldn't be using _scalar_ dst_reg
@@ -3567,17 +3605,13 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
*/
return -ENOTSUPP;
/* scalars can only be spilled into stack */
- if (insn->dst_reg != BPF_REG_FP)
+ if (!hist || !(hist->flags & INSN_F_STACK_ACCESS))
return 0;
- spi = (-insn->off - 1) / BPF_REG_SIZE;
- if (spi >= 64) {
- verbose(env, "BUG spi %d\n", spi);
- WARN_ONCE(1, "verifier backtracking bug");
- return -EFAULT;
- }
- if (!bt_is_slot_set(bt, spi))
+ spi = insn_stack_access_spi(hist->flags);
+ fr = insn_stack_access_frameno(hist->flags);
+ if (!bt_is_frame_slot_set(bt, fr, spi))
return 0;
- bt_clear_slot(bt, spi);
+ bt_clear_frame_slot(bt, fr, spi);
if (class == BPF_STX)
bt_set_reg(bt, sreg);
} else if (class == BPF_JMP || class == BPF_JMP32) {
@@ -3621,10 +3655,14 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
WARN_ONCE(1, "verifier backtracking bug");
return -EFAULT;
}
- /* we don't track register spills perfectly,
- * so fallback to force-precise instead of failing */
- if (bt_stack_mask(bt) != 0)
- return -ENOTSUPP;
+ /* we are now tracking register spills correctly,
+ * so any instance of leftover slots is a bug
+ */
+ if (bt_stack_mask(bt) != 0) {
+ verbose(env, "BUG stack slots %llx\n", bt_stack_mask(bt));
+ WARN_ONCE(1, "verifier backtracking bug (subprog leftover stack slots)");
+ return -EFAULT;
+ }
/* propagate r1-r5 to the caller */
for (i = BPF_REG_1; i <= BPF_REG_5; i++) {
if (bt_is_reg_set(bt, i)) {
@@ -3649,8 +3687,11 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
WARN_ONCE(1, "verifier backtracking bug");
return -EFAULT;
}
- if (bt_stack_mask(bt) != 0)
- return -ENOTSUPP;
+ if (bt_stack_mask(bt) != 0) {
+ verbose(env, "BUG stack slots %llx\n", bt_stack_mask(bt));
+ WARN_ONCE(1, "verifier backtracking bug (callback leftover stack slots)");
+ return -EFAULT;
+ }
/* clear r1-r5 in callback subprog's mask */
for (i = BPF_REG_1; i <= BPF_REG_5; i++)
bt_clear_reg(bt, i);
@@ -4087,6 +4128,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
for (;;) {
DECLARE_BITMAP(mask, 64);
u32 history = st->jmp_history_cnt;
+ struct bpf_jmp_history_entry *hist;
if (env->log.level & BPF_LOG_LEVEL2) {
verbose(env, "mark_precise: frame%d: last_idx %d first_idx %d subseq_idx %d \n",
@@ -4150,7 +4192,8 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
err = 0;
skip_first = false;
} else {
- err = backtrack_insn(env, i, subseq_idx, bt);
+ hist = get_jmp_hist_entry(st, history, i);
+ err = backtrack_insn(env, i, subseq_idx, hist, bt);
}
if (err == -ENOTSUPP) {
mark_all_scalars_precise(env, env->cur_state);
@@ -4203,22 +4246,10 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
bitmap_from_u64(mask, bt_frame_stack_mask(bt, fr));
for_each_set_bit(i, mask, 64) {
if (i >= func->allocated_stack / BPF_REG_SIZE) {
- /* the sequence of instructions:
- * 2: (bf) r3 = r10
- * 3: (7b) *(u64 *)(r3 -8) = r0
- * 4: (79) r4 = *(u64 *)(r10 -8)
- * doesn't contain jmps. It's backtracked
- * as a single block.
- * During backtracking insn 3 is not recognized as
- * stack access, so at the end of backtracking
- * stack slot fp-8 is still marked in stack_mask.
- * However the parent state may not have accessed
- * fp-8 and it's "unallocated" stack space.
- * In such case fallback to conservative.
- */
- mark_all_scalars_precise(env, env->cur_state);
- bt_reset(bt);
- return 0;
+ verbose(env, "BUG backtracking (stack slot %d, total slots %d)\n",
+ i, func->allocated_stack / BPF_REG_SIZE);
+ WARN_ONCE(1, "verifier backtracking bug (stack slot out of bounds)");
+ return -EFAULT;
}
if (!is_spilled_scalar_reg(&func->stack[i])) {
@@ -4391,7 +4422,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
int i, slot = -off - 1, spi = slot / BPF_REG_SIZE, err;
struct bpf_insn *insn = &env->prog->insnsi[insn_idx];
struct bpf_reg_state *reg = NULL;
- u32 dst_reg = insn->dst_reg;
+ int insn_flags = insn_stack_access_flags(state->frameno, spi);
err = grow_stack_state(state, round_up(slot + 1, BPF_REG_SIZE));
if (err)
@@ -4432,17 +4463,6 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
mark_stack_slot_scratched(env, spi);
if (reg && !(off % BPF_REG_SIZE) && register_is_bounded(reg) &&
!register_is_null(reg) && env->bpf_capable) {
- if (dst_reg != BPF_REG_FP) {
- /* The backtracking logic can only recognize explicit
- * stack slot address like [fp - 8]. Other spill of
- * scalar via different register has to be conservative.
- * Backtrack from here and mark all registers as precise
- * that contributed into 'reg' being a constant.
- */
- err = mark_chain_precision(env, value_regno);
- if (err)
- return err;
- }
save_register_state(state, spi, reg, size);
/* Break the relation on a narrowing spill. */
if (fls64(reg->umax_value) > BITS_PER_BYTE * size)
@@ -4454,6 +4474,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
__mark_reg_known(&fake_reg, insn->imm);
fake_reg.type = SCALAR_VALUE;
save_register_state(state, spi, &fake_reg, size);
+ insn_flags = 0; /* not a register spill */
} else if (reg && is_spillable_regtype(reg->type)) {
/* register containing pointer is being spilled into stack */
if (size != BPF_REG_SIZE) {
@@ -4499,9 +4520,12 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
/* Mark slots affected by this stack write. */
for (i = 0; i < size; i++)
- state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] =
- type;
+ state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] = type;
+ insn_flags = 0; /* not a register spill */
}
+
+ if (insn_flags)
+ return push_jmp_history(env, env->cur_state, insn_flags);
return 0;
}
@@ -4694,6 +4718,7 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
int i, slot = -off - 1, spi = slot / BPF_REG_SIZE;
struct bpf_reg_state *reg;
u8 *stype, type;
+ int insn_flags = insn_stack_access_flags(reg_state->frameno, spi);
stype = reg_state->stack[spi].slot_type;
reg = ®_state->stack[spi].spilled_ptr;
@@ -4739,12 +4764,10 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
return -EACCES;
}
mark_reg_unknown(env, state->regs, dst_regno);
+ insn_flags = 0; /* not restoring original register state */
}
state->regs[dst_regno].live |= REG_LIVE_WRITTEN;
- return 0;
- }
-
- if (dst_regno >= 0) {
+ } else if (dst_regno >= 0) {
/* restore register state from stack */
copy_register_state(&state->regs[dst_regno], reg);
/* mark reg as written since spilled pointer state likely
@@ -4780,7 +4803,10 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
mark_reg_read(env, reg, reg->parent, REG_LIVE_READ64);
if (dst_regno >= 0)
mark_reg_stack_read(env, reg_state, off, off + size, dst_regno);
+ insn_flags = 0; /* we are not restoring spilled register */
}
+ if (insn_flags)
+ return push_jmp_history(env, env->cur_state, insn_flags);
return 0;
}
@@ -6940,7 +6966,6 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
BPF_SIZE(insn->code), BPF_WRITE, -1, true, false);
if (err)
return err;
-
return 0;
}
@@ -16910,7 +16935,8 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
* the precision needs to be propagated back in
* the current state.
*/
- err = err ? : push_jmp_history(env, cur);
+ if (is_jmp_point(env, env->insn_idx))
+ err = err ? : push_jmp_history(env, cur, 0);
err = err ? : propagate_precision(env, &sl->state);
if (err)
return err;
@@ -17135,6 +17161,9 @@ static int do_check(struct bpf_verifier_env *env)
u8 class;
int err;
+ /* reset current history entry on each new instruction */
+ env->cur_hist_ent = NULL;
+
env->prev_insn_idx = prev_insn_idx;
if (env->insn_idx >= insn_cnt) {
verbose(env, "invalid insn idx %d insn_cnt %d\n",
@@ -17174,7 +17203,7 @@ static int do_check(struct bpf_verifier_env *env)
}
if (is_jmp_point(env, env->insn_idx)) {
- err = push_jmp_history(env, state);
+ err = push_jmp_history(env, state, 0);
if (err)
return err;
}
@@ -589,11 +589,24 @@ static __u64 subprog_spill_reg_precise(void)
SEC("?raw_tp")
__success __log_level(2)
-/* precision backtracking can't currently handle stack access not through r10,
- * so we won't be able to mark stack slot fp-8 as precise, and so will
- * fallback to forcing all as precise
- */
-__msg("mark_precise: frame0: falling back to forcing all scalars precise")
+__msg("10: (0f) r1 += r7")
+__msg("mark_precise: frame0: last_idx 10 first_idx 7 subseq_idx -1")
+__msg("mark_precise: frame0: regs=r7 stack= before 9: (bf) r1 = r8")
+__msg("mark_precise: frame0: regs=r7 stack= before 8: (27) r7 *= 4")
+__msg("mark_precise: frame0: regs=r7 stack= before 7: (79) r7 = *(u64 *)(r10 -8)")
+__msg("mark_precise: frame0: parent state regs= stack=-8: R0_w=2 R6_w=1 R8_rw=map_value(map=.data.vals,ks=4,vs=16) R10=fp0 fp-8_rw=P1")
+__msg("mark_precise: frame0: last_idx 18 first_idx 0 subseq_idx 7")
+__msg("mark_precise: frame0: regs= stack=-8 before 18: (95) exit")
+__msg("mark_precise: frame1: regs= stack= before 17: (0f) r0 += r2")
+__msg("mark_precise: frame1: regs= stack= before 16: (79) r2 = *(u64 *)(r1 +0)")
+__msg("mark_precise: frame1: regs= stack= before 15: (79) r0 = *(u64 *)(r10 -16)")
+__msg("mark_precise: frame1: regs= stack= before 14: (7b) *(u64 *)(r10 -16) = r2")
+__msg("mark_precise: frame1: regs= stack= before 13: (7b) *(u64 *)(r1 +0) = r2")
+__msg("mark_precise: frame1: regs=r2 stack= before 6: (85) call pc+6")
+__msg("mark_precise: frame0: regs=r2 stack= before 5: (bf) r2 = r6")
+__msg("mark_precise: frame0: regs=r6 stack= before 4: (07) r1 += -8")
+__msg("mark_precise: frame0: regs=r6 stack= before 3: (bf) r1 = r10")
+__msg("mark_precise: frame0: regs=r6 stack= before 2: (b7) r6 = 1")
__naked int subprog_spill_into_parent_stack_slot_precise(void)
{
asm volatile (
@@ -140,10 +140,11 @@
.result = REJECT,
},
{
- "precise: ST insn causing spi > allocated_stack",
+ "precise: ST zero to stack insn is supported",
.insns = {
BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
BPF_JMP_IMM(BPF_JNE, BPF_REG_3, 123, 0),
+ /* not a register spill, so we stop precision propagation for R4 here */
BPF_ST_MEM(BPF_DW, BPF_REG_3, -8, 0),
BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8),
BPF_MOV64_IMM(BPF_REG_0, -1),
@@ -157,11 +158,11 @@
mark_precise: frame0: last_idx 4 first_idx 2\
mark_precise: frame0: regs=r4 stack= before 4\
mark_precise: frame0: regs=r4 stack= before 3\
- mark_precise: frame0: regs= stack=-8 before 2\
- mark_precise: frame0: falling back to forcing all scalars precise\
- force_precise: frame0: forcing r0 to be precise\
mark_precise: frame0: last_idx 5 first_idx 5\
- mark_precise: frame0: parent state regs= stack=:",
+ mark_precise: frame0: parent state regs=r0 stack=:\
+ mark_precise: frame0: last_idx 4 first_idx 2\
+ mark_precise: frame0: regs=r0 stack= before 4\
+ 5: R0=-1 R4=0",
.result = VERBOSE_ACCEPT,
.retval = -1,
},
@@ -169,6 +170,8 @@
"precise: STX insn causing spi > allocated_stack",
.insns = {
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_prandom_u32),
+ /* make later reg spill more interesting by having somewhat known scalar */
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xff),
BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
BPF_JMP_IMM(BPF_JNE, BPF_REG_3, 123, 0),
BPF_STX_MEM(BPF_DW, BPF_REG_3, BPF_REG_0, -8),
@@ -179,18 +182,21 @@
},
.prog_type = BPF_PROG_TYPE_XDP,
.flags = BPF_F_TEST_STATE_FREQ,
- .errstr = "mark_precise: frame0: last_idx 6 first_idx 6\
+ .errstr = "mark_precise: frame0: last_idx 7 first_idx 7\
mark_precise: frame0: parent state regs=r4 stack=:\
- mark_precise: frame0: last_idx 5 first_idx 3\
- mark_precise: frame0: regs=r4 stack= before 5\
- mark_precise: frame0: regs=r4 stack= before 4\
- mark_precise: frame0: regs= stack=-8 before 3\
- mark_precise: frame0: falling back to forcing all scalars precise\
- force_precise: frame0: forcing r0 to be precise\
- force_precise: frame0: forcing r0 to be precise\
- force_precise: frame0: forcing r0 to be precise\
- force_precise: frame0: forcing r0 to be precise\
- mark_precise: frame0: last_idx 6 first_idx 6\
+ mark_precise: frame0: last_idx 6 first_idx 4\
+ mark_precise: frame0: regs=r4 stack= before 6: (b7) r0 = -1\
+ mark_precise: frame0: regs=r4 stack= before 5: (79) r4 = *(u64 *)(r10 -8)\
+ mark_precise: frame0: regs= stack=-8 before 4: (7b) *(u64 *)(r3 -8) = r0\
+ mark_precise: frame0: parent state regs=r0 stack=:\
+ mark_precise: frame0: last_idx 3 first_idx 3\
+ mark_precise: frame0: regs=r0 stack= before 3: (55) if r3 != 0x7b goto pc+0\
+ mark_precise: frame0: regs=r0 stack= before 2: (bf) r3 = r10\
+ mark_precise: frame0: regs=r0 stack= before 1: (57) r0 &= 255\
+ mark_precise: frame0: parent state regs=r0 stack=:\
+ mark_precise: frame0: last_idx 0 first_idx 0\
+ mark_precise: frame0: regs=r0 stack= before 0: (85) call bpf_get_prandom_u32#7\
+ mark_precise: frame0: last_idx 7 first_idx 7\
mark_precise: frame0: parent state regs= stack=:",
.result = VERBOSE_ACCEPT,
.retval = -1,