Messages in this thread | | | Date | Tue, 15 Aug 2017 18:33:46 +0200 | From | Daniel Borkmann <> | Subject | Re: [PATCH v2 net-next] bpf/verifier: track liveness for pruning |
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On 08/15/2017 03:53 PM, Edward Cree wrote: > State of a register doesn't matter if it wasn't read in reaching an exit; > a write screens off all reads downstream of it from all explored_states > upstream of it. > This allows us to prune many more branches; here are some processed insn > counts for some Cilium programs: > Program before after > bpf_lb_opt_-DLB_L3.o 6515 3361 > bpf_lb_opt_-DLB_L4.o 8976 5176 > bpf_lb_opt_-DUNKNOWN.o 2960 1137 > bpf_lxc_opt_-DDROP_ALL.o 95412 48537 > bpf_lxc_opt_-DUNKNOWN.o 141706 78718 > bpf_netdev.o 24251 17995 > bpf_overlay.o 10999 9385 > > The runtime is also improved; here are 'time' results in ms: > Program before after > bpf_lb_opt_-DLB_L3.o 24 6 > bpf_lb_opt_-DLB_L4.o 26 11 > bpf_lb_opt_-DUNKNOWN.o 11 2 > bpf_lxc_opt_-DDROP_ALL.o 1288 139 > bpf_lxc_opt_-DUNKNOWN.o 1768 234 > bpf_netdev.o 62 31 > bpf_overlay.o 15 13 > > Signed-off-by: Edward Cree <ecree@solarflare.com> [...] > @@ -1639,10 +1675,13 @@ static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx) > } > > /* reset caller saved regs */ > - for (i = 0; i < CALLER_SAVED_REGS; i++) > + for (i = 0; i < CALLER_SAVED_REGS; i++) { > mark_reg_not_init(regs, caller_saved[i]); > + check_reg_arg(env, i, DST_OP_NO_MARK);
Ah, I oversaw that earlier, this needs to be: s/i/caller_saved[i]/
> + } > > /* update return register */ > + check_reg_arg(env, BPF_REG_0, DST_OP_NO_MARK);
We could leave this for clarity, but ...
> if (fn->ret_type == RET_INTEGER) { > /* sets type to SCALAR_VALUE */ > mark_reg_unknown(regs, BPF_REG_0); [...] > > /* reset caller saved regs to unreadable */ > - for (i = 0; i < CALLER_SAVED_REGS; i++) > + for (i = 0; i < CALLER_SAVED_REGS; i++) { > mark_reg_not_init(regs, caller_saved[i]); > + check_reg_arg(env, i, DST_OP_NO_MARK);
caller_saved[i]
> + } > > /* mark destination R0 register as readable, since it contains > - * the value fetched from the packet > + * the value fetched from the packet. > + * Already marked as written above.
... then it should be here as well. Other option is to leave out both BPF_REG_0 since covered by caller_saved[] already.
> */ > mark_reg_unknown(regs, BPF_REG_0); > return 0; > @@ -3194,7 +3236,11 @@ static bool regsafe(struct bpf_reg_state *rold, > struct bpf_reg_state *rcur, > bool varlen_map_access, struct idpair *idmap) > { > - if (memcmp(rold, rcur, sizeof(*rold)) == 0) > + if (!(rold->live & REG_LIVE_READ)) > + /* explored state didn't use this */ > + return true;
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