On 7/10/22 1:35 AM, Matthieu Baerts wrote:
Our CI[1] reported these warnings when using Sparse:
$ touch net/mptcp/bpf.c
$ make C=1 net/mptcp/bpf.o
net/mptcp/bpf.c: note: in included file:
include/linux/bpf_verifier.h:348:26: error: dubious one-bit signed bitfield
include/linux/bpf_verifier.h:349:29: error: dubious one-bit signed bitfield
These two fields from the new 'bpf_loop_inline_state' structure are used
as booleans. Instead of declaring two 'unsigned int', we can declare
them as 'bool'.
While at it, also set 'state->initialized' to 'true' instead of '1' to
make it clearer it is linked to a 'bool' type.
[1] https://github.com/multipath-tcp/mptcp_net-next/actions/runs/2643588487
Fixes: 1ade23711971 ("bpf: Inline calls to bpf_loop when callback is known")
Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
---
include/linux/bpf_verifier.h | 8 ++++----
kernel/bpf/verifier.c | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 81b19669efba..2ac424641cc3 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -345,10 +345,10 @@ struct bpf_verifier_state_list {
};
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
- */
+ bool initialized; /* set to true upon first entry */
+ bool fit_for_inline; /* true if callback function is the same
+ * at each call and flags are always zero
+ */
I think changing 'int' to 'unsigned' is a better alternative for
potentially adding more bitfields in the future. This is also a pattern
for many other kernel data structures.
u32 callback_subprogno; /* valid when fit_for_inline is true */
};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 328cfab3af60..4fa49d852a59 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7144,7 +7144,7 @@ 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->initialized = true;
state->fit_for_inline = loop_flag_is_zero(env);
state->callback_subprogno = subprogno;
return;
