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| author |   Jakub Kicinski <jakub.kicinski@netronome.com> | 2018-12-19 22:13:04 -0800 |
|---|---|---|
| committer |   Daniel Borkmann <daniel@iogearbox.net> | 2018-12-20 17:28:28 +0100 |
| commit | 960ea056561a08e2b837b2f02d22c53226414a84 (patch) | |
| tree | 3359d4a96bb494e1a92c16f0ec44f86cc796a257 /kernel/bpf/verifier.c | |
| parent | selftests: bpf: add trivial JSET tests (diff) | |
| download | linux-dev-960ea056561a08e2b837b2f02d22c53226414a84.tar.xz linux-dev-960ea056561a08e2b837b2f02d22c53226414a84.zip | |
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/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 20 |
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); |