[PATCH/RFC bpf-next 01/16] bpf: turn "enum bpf_reg_liveness" into bit representation

[Jiong Wang]

"enum bpf_reg_liveness" is actually used as bit instead of integer. For
example:

        if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN | REG_LIVE_DONE))

Using enum to represent bit is error prone, better to use explicit bit
macros.

Signed-off-by: Jiong Wang <jiong.w...@netronome.com>
---
 include/linux/bpf_verifier.h | 16 +++++++++-------
 kernel/bpf/verifier.c        |  5 ++---
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 7d8228d..f03c86a 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -34,12 +34,14 @@
  * but of the link between it and its parent.  See mark_reg_read() and
  * mark_stack_slot_read() in kernel/bpf/verifier.c.
  */
-enum bpf_reg_liveness {
-       REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
-       REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
-       REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
-       REG_LIVE_DONE = 4, /* liveness won't be updating this register anymore 
*/
-};
+/* Reg hasn't been read or written this branch. */
+#define REG_LIVE_NONE          0x0
+/* Reg was read, so we're sensitive to initial value. */
+#define REG_LIVE_READ          0x1
+/* Reg was written first, screening off later reads. */
+#define REG_LIVE_WRITTEN       0x2
+/* Liveness won't be updating this register anymore. */
+#define REG_LIVE_DONE          0x4
 
 struct bpf_reg_state {
        /* Ordering of fields matters.  See states_equal() */
@@ -131,7 +133,7 @@ struct bpf_reg_state {
         * pointing to bpf_func_state.
         */
        u32 frameno;
-       enum bpf_reg_liveness live;
+       u8 live;
 };
 
 enum bpf_stack_slot_type {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index dffeec3..6cc8c38 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -407,8 +407,7 @@ static char slot_type_char[] = {
        [STACK_ZERO]    = '0',
 };
 
-static void print_liveness(struct bpf_verifier_env *env,
-                          enum bpf_reg_liveness live)
+static void print_liveness(struct bpf_verifier_env *env, u8 live)
 {
        if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN | REG_LIVE_DONE))
            verbose(env, "_");
@@ -5687,8 +5686,8 @@ static bool check_ids(u32 old_id, u32 cur_id, struct 
idpair *idmap)
 static void clean_func_state(struct bpf_verifier_env *env,
                             struct bpf_func_state *st)
 {
-       enum bpf_reg_liveness live;
        int i, j;
+       u8 live;
 
        for (i = 0; i < BPF_REG_FP; i++) {
                live = st->regs[i].live;
-- 
2.7.4