bpf: make liveness.c track stack with 4-byte granularity

Convert liveness bitmask type from u64 to spis_t, doubling the number
of trackable stack slots from 64 to 128 to support 4-byte granularity.

Each 8-byte SPI now maps to two consecutive 4-byte sub-slots in the
bitmask: spi*2 half and spi*2+1 half. In verifier.c,
check_stack_write_fixed_off() now reports 4-byte aligned writes of
4-byte writes as half-slot marks and 8-byte aligned 8-byte writes as
two slots. Similar logic applied in check_stack_read_fixed_off().

Queries (is_live_before) are not yet migrated to half-slot
granularity.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-4-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index f34e7a074a20..7b31d8024c61 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -1217,8 +1217,8 @@ s64 bpf_kfunc_stack_access_bytes(struct bpf_verifier_env *env,
 int bpf_stack_liveness_init(struct bpf_verifier_env *env);
 void bpf_stack_liveness_free(struct bpf_verifier_env *env);
 int bpf_update_live_stack(struct bpf_verifier_env *env);
-int bpf_mark_stack_read(struct bpf_verifier_env *env, u32 frameno, u32 insn_idx, u64 mask);
-void bpf_mark_stack_write(struct bpf_verifier_env *env, u32 frameno, u64 mask);
+int bpf_mark_stack_read(struct bpf_verifier_env *env, u32 frameno, u32 insn_idx, spis_t mask);
+void bpf_mark_stack_write(struct bpf_verifier_env *env, u32 frameno, spis_t mask);
 int bpf_reset_stack_write_marks(struct bpf_verifier_env *env, u32 insn_idx);
 int bpf_commit_stack_write_marks(struct bpf_verifier_env *env);
 int bpf_live_stack_query_init(struct bpf_verifier_env *env, struct bpf_verifier_state *st);