[PATCH] Remove structure passing and assignment to save stack and no coping structures.

[Karim Eshapa]

Signed-off-by: Karim Eshapa <karim.esh...@gmail.com>

Thanks,
Karim
---
 include/linux/tnum.h  |  2 +-
 kernel/bpf/tnum.c     | 13 +++++++------
 kernel/bpf/verifier.c | 12 ++++++++----
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/include/linux/tnum.h b/include/linux/tnum.h
index 0d2d3da..ddb1250 100644
--- a/include/linux/tnum.h
+++ b/include/linux/tnum.h
@@ -26,7 +26,7 @@ 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..f7f8b10 100644
--- a/kernel/bpf/tnum.c
+++ b/kernel/bpf/tnum.c
@@ -43,16 +43,17 @@ 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 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 +103,7 @@ 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..4acc16c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -999,7 +999,8 @@ 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_const(ip_align + reg->off + off));
        if (!tnum_is_aligned(reg_off, size)) {
                char tn_buf[48];
 
@@ -1024,7 +1025,8 @@ static int check_generic_ptr_alignment(struct 
bpf_verifier_env *env,
        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_const(reg->off + off));
        if (!tnum_is_aligned(reg_off, size)) {
                char tn_buf[48];
 
@@ -1971,7 +1973,8 @@ 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 +2111,8 @@ 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