bpf/verifier: per-register parent pointers
By giving each register its own liveness chain, we elide the skip_callee()
logic. Instead, each register's parent is the state it inherits from;
both check_func_call() and prepare_func_exit() automatically connect
reg states to the correct chain since when they copy the reg state across
(r1-r5 into the callee as args, and r0 out as the return value) they also
copy the parent pointer.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 38b04f5..b42b60a 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -41,6 +41,7 @@
};
struct bpf_reg_state {
+ /* Ordering of fields matters. See states_equal() */
enum bpf_reg_type type;
union {
/* valid when type == PTR_TO_PACKET */
@@ -59,7 +60,6 @@
* came from, when one is tested for != NULL.
*/
u32 id;
- /* Ordering of fields matters. See states_equal() */
/* For scalar types (SCALAR_VALUE), this represents our knowledge of
* the actual value.
* For pointer types, this represents the variable part of the offset
@@ -76,15 +76,15 @@
s64 smax_value; /* maximum possible (s64)value */
u64 umin_value; /* minimum possible (u64)value */
u64 umax_value; /* maximum possible (u64)value */
+ /* parentage chain for liveness checking */
+ struct bpf_reg_state *parent;
/* Inside the callee two registers can be both PTR_TO_STACK like
* R1=fp-8 and R2=fp-8, but one of them points to this function stack
* while another to the caller's stack. To differentiate them 'frameno'
* is used which is an index in bpf_verifier_state->frame[] array
* pointing to bpf_func_state.
- * This field must be second to last, for states_equal() reasons.
*/
u32 frameno;
- /* This field must be last, for states_equal() reasons. */
enum bpf_reg_liveness live;
};
@@ -107,7 +107,6 @@
*/
struct bpf_func_state {
struct bpf_reg_state regs[MAX_BPF_REG];
- struct bpf_verifier_state *parent;
/* index of call instruction that called into this func */
int callsite;
/* stack frame number of this function state from pov of
@@ -129,7 +128,6 @@
struct bpf_verifier_state {
/* call stack tracking */
struct bpf_func_state *frame[MAX_CALL_FRAMES];
- struct bpf_verifier_state *parent;
u32 curframe;
};