From: Andrii Nakryiko andrii@kernel.org
[ Upstream commit d9439c21a9e4769bfd83a03ab39056164d44ac31 ]
Add helper to format register and stack masks in more human-readable format. Adjust logging a bit during backtrack propagation and especially during forcing precision fallback logic to make it clearer what's going on (with log_level=2, of course), and also start reporting affected frame depth. This is in preparation for having more than one active frame later when precision propagation between subprog calls is added.
Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20230505043317.3629845-5-andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Stable-dep-of: f655badf2a8f ("bpf: fix propagate_precision() logic for inner frames") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/bpf_verifier.h | 13 ++- kernel/bpf/verifier.c | 72 ++++++++++-- .../testing/selftests/bpf/verifier/precise.c | 106 +++++++++--------- 3 files changed, 128 insertions(+), 63 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 33f541366f4e7..5b11a3b0fec0b 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -18,8 +18,11 @@ * that converting umax_value to int cannot overflow. */ #define BPF_MAX_VAR_SIZ (1 << 29) -/* size of type_str_buf in bpf_verifier. */ -#define TYPE_STR_BUF_LEN 128 +/* size of tmp_str_buf in bpf_verifier. + * we need at least 306 bytes to fit full stack mask representation + * (in the "-8,-16,...,-512" form) + */ +#define TMP_STR_BUF_LEN 320
/* Liveness marks, used for registers and spilled-regs (in stack slots). * Read marks propagate upwards until they find a write mark; they record that @@ -620,8 +623,10 @@ struct bpf_verifier_env { /* Same as scratched_regs but for stack slots */ u64 scratched_stack_slots; u64 prev_log_pos, prev_insn_print_pos; - /* buffer used in reg_type_str() to generate reg_type string */ - char type_str_buf[TYPE_STR_BUF_LEN]; + /* buffer used to generate temporary string representations, + * e.g., in reg_type_str() to generate reg_type string + */ + char tmp_str_buf[TMP_STR_BUF_LEN]; };
__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log, diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index acd0780f9b907..9260006c13823 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -604,9 +604,9 @@ static const char *reg_type_str(struct bpf_verifier_env *env, type & PTR_TRUSTED ? "trusted_" : "" );
- snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s%s", + snprintf(env->tmp_str_buf, TMP_STR_BUF_LEN, "%s%s%s", prefix, str[base_type(type)], postfix); - return env->type_str_buf; + return env->tmp_str_buf; }
static char slot_type_char[] = { @@ -3266,6 +3266,45 @@ static inline bool bt_is_slot_set(struct backtrack_state *bt, u32 slot) return bt->stack_masks[bt->frame] & (1ull << slot); }
+/* format registers bitmask, e.g., "r0,r2,r4" for 0x15 mask */ +static void fmt_reg_mask(char *buf, ssize_t buf_sz, u32 reg_mask) +{ + DECLARE_BITMAP(mask, 64); + bool first = true; + int i, n; + + buf[0] = '\0'; + + bitmap_from_u64(mask, reg_mask); + for_each_set_bit(i, mask, 32) { + n = snprintf(buf, buf_sz, "%sr%d", first ? "" : ",", i); + first = false; + buf += n; + buf_sz -= n; + if (buf_sz < 0) + break; + } +} +/* format stack slots bitmask, e.g., "-8,-24,-40" for 0x15 mask */ +static void fmt_stack_mask(char *buf, ssize_t buf_sz, u64 stack_mask) +{ + DECLARE_BITMAP(mask, 64); + bool first = true; + int i, n; + + buf[0] = '\0'; + + bitmap_from_u64(mask, stack_mask); + for_each_set_bit(i, mask, 64) { + n = snprintf(buf, buf_sz, "%s%d", first ? "" : ",", -(i + 1) * 8); + first = false; + buf += n; + buf_sz -= n; + if (buf_sz < 0) + break; + } +} + /* For given verifier state backtrack_insn() is called from the last insn to * the first insn. Its purpose is to compute a bitmask of registers and * stack slots that needs precision in the parent verifier state. @@ -3289,7 +3328,11 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, if (insn->code == 0) return 0; if (env->log.level & BPF_LOG_LEVEL2) { - verbose(env, "regs=%x stack=%llx before ", bt_reg_mask(bt), bt_stack_mask(bt)); + fmt_reg_mask(env->tmp_str_buf, TMP_STR_BUF_LEN, bt_reg_mask(bt)); + verbose(env, "mark_precise: frame%d: regs=%s ", + bt->frame, env->tmp_str_buf); + fmt_stack_mask(env->tmp_str_buf, TMP_STR_BUF_LEN, bt_stack_mask(bt)); + verbose(env, "stack=%s before ", env->tmp_str_buf); verbose(env, "%d: ", idx); print_bpf_insn(&cbs, insn, env->allow_ptr_leaks); } @@ -3489,6 +3532,11 @@ static void mark_all_scalars_precise(struct bpf_verifier_env *env, struct bpf_reg_state *reg; int i, j;
+ if (env->log.level & BPF_LOG_LEVEL2) { + verbose(env, "mark_precise: frame%d: falling back to forcing all scalars precise\n", + st->curframe); + } + /* big hammer: mark all scalars precise in this path. * pop_stack may still get !precise scalars. * We also skip current state and go straight to first parent state, @@ -3500,17 +3548,25 @@ static void mark_all_scalars_precise(struct bpf_verifier_env *env, func = st->frame[i]; for (j = 0; j < BPF_REG_FP; j++) { reg = &func->regs[j]; - if (reg->type != SCALAR_VALUE) + if (reg->type != SCALAR_VALUE || reg->precise) continue; reg->precise = true; + if (env->log.level & BPF_LOG_LEVEL2) { + verbose(env, "force_precise: frame%d: forcing r%d to be precise\n", + i, j); + } } for (j = 0; j < func->allocated_stack / BPF_REG_SIZE; j++) { if (!is_spilled_reg(&func->stack[j])) continue; reg = &func->stack[j].spilled_ptr; - if (reg->type != SCALAR_VALUE) + if (reg->type != SCALAR_VALUE || reg->precise) continue; reg->precise = true; + if (env->log.level & BPF_LOG_LEVEL2) { + verbose(env, "force_precise: frame%d: forcing fp%d to be precise\n", + i, -(j + 1) * 8); + } } } } @@ -3674,8 +3730,10 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r DECLARE_BITMAP(mask, 64); u32 history = st->jmp_history_cnt;
- if (env->log.level & BPF_LOG_LEVEL2) - verbose(env, "last_idx %d first_idx %d\n", last_idx, first_idx); + if (env->log.level & BPF_LOG_LEVEL2) { + verbose(env, "mark_precise: frame%d: last_idx %d first_idx %d\n", + bt->frame, last_idx, first_idx); + }
if (last_idx < 0) { /* we are at the entry into subprog, which diff --git a/tools/testing/selftests/bpf/verifier/precise.c b/tools/testing/selftests/bpf/verifier/precise.c index 6c03a7d805f9d..86cb0722792f0 100644 --- a/tools/testing/selftests/bpf/verifier/precise.c +++ b/tools/testing/selftests/bpf/verifier/precise.c @@ -38,25 +38,24 @@ .fixup_map_array_48b = { 1 }, .result = VERBOSE_ACCEPT, .errstr = - "26: (85) call bpf_probe_read_kernel#113\ - last_idx 26 first_idx 20\ - regs=4 stack=0 before 25\ - regs=4 stack=0 before 24\ - regs=4 stack=0 before 23\ - regs=4 stack=0 before 22\ - regs=4 stack=0 before 20\ - parent didn't have regs=4 stack=0 marks\ - last_idx 19 first_idx 10\ - regs=4 stack=0 before 19\ - regs=200 stack=0 before 18\ - regs=300 stack=0 before 17\ - regs=201 stack=0 before 15\ - regs=201 stack=0 before 14\ - regs=200 stack=0 before 13\ - regs=200 stack=0 before 12\ - regs=200 stack=0 before 11\ - regs=200 stack=0 before 10\ - parent already had regs=0 stack=0 marks", + "mark_precise: frame0: last_idx 26 first_idx 20\ + mark_precise: frame0: regs=r2 stack= before 25\ + mark_precise: frame0: regs=r2 stack= before 24\ + mark_precise: frame0: regs=r2 stack= before 23\ + mark_precise: frame0: regs=r2 stack= before 22\ + mark_precise: frame0: regs=r2 stack= before 20\ + parent didn't have regs=4 stack=0 marks:\ + mark_precise: frame0: last_idx 19 first_idx 10\ + mark_precise: frame0: regs=r2 stack= before 19\ + mark_precise: frame0: regs=r9 stack= before 18\ + mark_precise: frame0: regs=r8,r9 stack= before 17\ + mark_precise: frame0: regs=r0,r9 stack= before 15\ + mark_precise: frame0: regs=r0,r9 stack= before 14\ + mark_precise: frame0: regs=r9 stack= before 13\ + mark_precise: frame0: regs=r9 stack= before 12\ + mark_precise: frame0: regs=r9 stack= before 11\ + mark_precise: frame0: regs=r9 stack= before 10\ + parent already had regs=0 stack=0 marks:", }, { "precise: test 2", @@ -100,20 +99,20 @@ .flags = BPF_F_TEST_STATE_FREQ, .errstr = "26: (85) call bpf_probe_read_kernel#113\ - last_idx 26 first_idx 22\ - regs=4 stack=0 before 25\ - regs=4 stack=0 before 24\ - regs=4 stack=0 before 23\ - regs=4 stack=0 before 22\ - parent didn't have regs=4 stack=0 marks\ - last_idx 20 first_idx 20\ - regs=4 stack=0 before 20\ - parent didn't have regs=4 stack=0 marks\ - last_idx 19 first_idx 17\ - regs=4 stack=0 before 19\ - regs=200 stack=0 before 18\ - regs=300 stack=0 before 17\ - parent already had regs=0 stack=0 marks", + mark_precise: frame0: last_idx 26 first_idx 22\ + mark_precise: frame0: regs=r2 stack= before 25\ + mark_precise: frame0: regs=r2 stack= before 24\ + mark_precise: frame0: regs=r2 stack= before 23\ + mark_precise: frame0: regs=r2 stack= before 22\ + parent didn't have regs=4 stack=0 marks:\ + mark_precise: frame0: last_idx 20 first_idx 20\ + mark_precise: frame0: regs=r2 stack= before 20\ + parent didn't have regs=4 stack=0 marks:\ + mark_precise: frame0: last_idx 19 first_idx 17\ + mark_precise: frame0: regs=r2 stack= before 19\ + mark_precise: frame0: regs=r9 stack= before 18\ + mark_precise: frame0: regs=r8,r9 stack= before 17\ + parent already had regs=0 stack=0 marks:", }, { "precise: cross frame pruning", @@ -153,15 +152,15 @@ }, .prog_type = BPF_PROG_TYPE_XDP, .flags = BPF_F_TEST_STATE_FREQ, - .errstr = "5: (2d) if r4 > r0 goto pc+0\ - last_idx 5 first_idx 5\ - parent didn't have regs=10 stack=0 marks\ - last_idx 4 first_idx 2\ - regs=10 stack=0 before 4\ - regs=10 stack=0 before 3\ - regs=0 stack=1 before 2\ - last_idx 5 first_idx 5\ - parent didn't have regs=1 stack=0 marks", + .errstr = "mark_precise: frame0: last_idx 5 first_idx 5\ + parent didn't have regs=10 stack=0 marks:\ + 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\ + mark_precise: frame0: last_idx 5 first_idx 5\ + parent didn't have regs=1 stack=0 marks:", .result = VERBOSE_ACCEPT, .retval = -1, }, @@ -179,16 +178,19 @@ }, .prog_type = BPF_PROG_TYPE_XDP, .flags = BPF_F_TEST_STATE_FREQ, - .errstr = "last_idx 6 first_idx 6\ - parent didn't have regs=10 stack=0 marks\ - last_idx 5 first_idx 3\ - regs=10 stack=0 before 5\ - regs=10 stack=0 before 4\ - regs=0 stack=1 before 3\ - last_idx 6 first_idx 6\ - parent didn't have regs=1 stack=0 marks\ - last_idx 5 first_idx 3\ - regs=1 stack=0 before 5", + .errstr = "mark_precise: frame0: last_idx 6 first_idx 6\ + parent didn't have regs=10 stack=0 marks:\ + 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\ + mark_precise: frame0: last_idx 6 first_idx 6\ + parent didn't have regs=1 stack=0 marks:\ + mark_precise: frame0: last_idx 5 first_idx 3\ + mark_precise: frame0: regs=r0 stack= before 5", .result = VERBOSE_ACCEPT, .retval = -1, },