[PATCH] kernel:bpf Remove structure passing and assignment to save stack and no coping structures

[Karim Eshapa]

Use pointers to structure as arguments to function instead of coping
structures and less stack size. Also transfer TNUM(_v, _m) to
tnum.h file to be used in differnet files for creating anonymous structures
statically.

Signed-off-by: Karim Eshapa <karim.eshapa@xxxxxxxxx>

Thanks,
Karim
---
 include/linux/tnum.h  |  4 +++-
 kernel/bpf/tnum.c     | 14 +++++++-------
 kernel/bpf/verifier.c | 11 ++++++-----
 3 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/include/linux/tnum.h b/include/linux/tnum.h
index 0d2d3da..72938a0 100644
--- a/include/linux/tnum.h
+++ b/include/linux/tnum.h
@@ -13,6 +13,8 @@ struct tnum {
 };
 
 /* Constructors */
+/* Statically tnum constant */
+#define TNUM(_v, _m)	(struct tnum){.value = _v, .mask = _m}
 /* Represent a known constant as a tnum. */
 struct tnum tnum_const(u64 value);
 /* A completely unknown value */
@@ -26,7 +28,7 @@ struct tnum tnum_lshift(struct tnum a, u8 shift);
 /* Shift a tnum right (by a fixed shift) */
 struct tnum tnum_rshift(struct tnum a, u8 shift);
 /* Add two tnums, return @a + @b */
-struct tnum tnum_add(struct tnum a, struct tnum b);
+void tnum_add(struct tnum *res, struct tnum *a, struct tnum *b);
 /* Subtract two tnums, return @a - @b */
 struct tnum tnum_sub(struct tnum a, struct tnum b);
 /* Bitwise-AND, return @a & @b */
diff --git a/kernel/bpf/tnum.c b/kernel/bpf/tnum.c
index 1f4bf68..89e3182 100644
--- a/kernel/bpf/tnum.c
+++ b/kernel/bpf/tnum.c
@@ -8,7 +8,6 @@
 #include <linux/kernel.h>
 #include <linux/tnum.h>
 
-#define TNUM(_v, _m)	(struct tnum){.value = _v, .mask = _m}
 /* A completely unknown value */
 const struct tnum tnum_unknown = { .value = 0, .mask = -1 };
 
@@ -43,16 +42,17 @@ struct tnum tnum_rshift(struct tnum a, u8 shift)
 	return TNUM(a.value >> shift, a.mask >> shift);
 }
 
-struct tnum tnum_add(struct tnum a, struct tnum b)
+void tnum_add(struct tnum *res, struct tnum *a, struct tnum *b)
 {
 	u64 sm, sv, sigma, chi, mu;
 
-	sm = a.mask + b.mask;
-	sv = a.value + b.value;
+	sm = a->mask + b->mask;
+	sv = a->value + b->value;
 	sigma = sm + sv;
 	chi = sigma ^ sv;
-	mu = chi | a.mask | b.mask;
-	return TNUM(sv & ~mu, mu);
+	mu = chi | a->mask | b->mask;
+	res->value = (sv & ~mu);
+	res->mask = mu;
 }
 
 struct tnum tnum_sub(struct tnum a, struct tnum b)
@@ -102,7 +102,7 @@ static struct tnum hma(struct tnum acc, u64 value, u64 mask)
 {
 	while (mask) {
 		if (mask & 1)
-			acc = tnum_add(acc, TNUM(0, value));
+			tnum_add(&acc, &acc, &TNUM(0, value));
 		mask >>= 1;
 		value <<= 1;
 	}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b414d6b..b31b1c4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -999,7 +999,7 @@ static int check_pkt_ptr_alignment(struct bpf_verifier_env *env,
 	 */
 	ip_align = 2;
 
-	reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off));
+	tnum_add(&reg_off, &reg->var_off, &TNUM(ip_align + reg->off + off, 0));
 	if (!tnum_is_aligned(reg_off, size)) {
 		char tn_buf[48];
 
@@ -1023,8 +1023,7 @@ static int check_generic_ptr_alignment(struct bpf_verifier_env *env,
 	/* Byte size accesses are always allowed. */
 	if (!strict || size == 1)
 		return 0;
-
-	reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));
+	tnum_add(&reg_off, &reg->var_off, &TNUM(reg->off + off, 0));
 	if (!tnum_is_aligned(reg_off, size)) {
 		char tn_buf[48];
 
@@ -1971,7 +1970,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 			dst_reg->umin_value = umin_ptr + umin_val;
 			dst_reg->umax_value = umax_ptr + umax_val;
 		}
-		dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
+		tnum_add(&dst_reg->var_off, &ptr_reg->var_off,
+			&off_reg->var_off);
 		dst_reg->off = ptr_reg->off;
 		if (reg_is_pkt_pointer(ptr_reg)) {
 			dst_reg->id = ++env->id_gen;
@@ -2108,7 +2108,8 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 			dst_reg->umin_value += umin_val;
 			dst_reg->umax_value += umax_val;
 		}
-		dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
+		tnum_add(&dst_reg->var_off, &dst_reg->var_off,
+			&src_reg.var_off);
 		break;
 	case BPF_SUB:
 		if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
-- 
2.7.4