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 <ec...@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;
