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authorJakub Kicinski <jakub.kicinski@netronome.com>2018-12-19 22:13:04 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-12-20 17:28:28 +0100
commit960ea056561a08e2b837b2f02d22c53226414a84 (patch)
tree3359d4a96bb494e1a92c16f0ec44f86cc796a257 /kernel
parent5a8d5209ac0228c9cf8f335dfdfffa71c54b3201 (diff)
downloadlinux-960ea056561a08e2b837b2f02d22c53226414a84.tar.bz2
bpf: verifier: teach the verifier to reason about the BPF_JSET instruction
Some JITs (nfp) try to optimize code on their own. It could make sense in case of BPF_JSET instruction which is currently not interpreted by the verifier, meaning for instance that dead could would not be detected if it was under BPF_JSET branch. Teach the verifier basics of BPF_JSET, JIT optimizations will be removed shortly. Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Jiong Wang <jiong.wang@netronome.com> Acked-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5c64281d566e..98ed27bbd045 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3859,6 +3859,12 @@ static int is_branch_taken(struct bpf_reg_state *reg, u64 val, u8 opcode)
if (tnum_is_const(reg->var_off))
return !tnum_equals_const(reg->var_off, val);
break;
+ case BPF_JSET:
+ if ((~reg->var_off.mask & reg->var_off.value) & val)
+ return 1;
+ if (!((reg->var_off.mask | reg->var_off.value) & val))
+ return 0;
+ break;
case BPF_JGT:
if (reg->umin_value > val)
return 1;
@@ -3943,6 +3949,13 @@ static void reg_set_min_max(struct bpf_reg_state *true_reg,
*/
__mark_reg_known(false_reg, val);
break;
+ case BPF_JSET:
+ false_reg->var_off = tnum_and(false_reg->var_off,
+ tnum_const(~val));
+ if (is_power_of_2(val))
+ true_reg->var_off = tnum_or(true_reg->var_off,
+ tnum_const(val));
+ break;
case BPF_JGT:
false_reg->umax_value = min(false_reg->umax_value, val);
true_reg->umin_value = max(true_reg->umin_value, val + 1);
@@ -4015,6 +4028,13 @@ static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
*/
__mark_reg_known(false_reg, val);
break;
+ case BPF_JSET:
+ false_reg->var_off = tnum_and(false_reg->var_off,
+ tnum_const(~val));
+ if (is_power_of_2(val))
+ true_reg->var_off = tnum_or(true_reg->var_off,
+ tnum_const(val));
+ break;
case BPF_JGT:
true_reg->umax_value = min(true_reg->umax_value, val - 1);
false_reg->umin_value = max(false_reg->umin_value, val);