Add comments to the datastructure tracking the stack state, as the
mapping between each stack slot and where its state is stored is not
entirely obvious.
Signed-off-by: Andrei Matei <andreimatei1@xxxxxxxxx>
---
include/linux/bpf_verifier.h | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index bada59812e00..314b679fb494 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -321,7 +321,17 @@ struct bpf_func_state {
/* The following fields should be last. See copy_func_state() */
int acquired_refs;
struct bpf_reference_state *refs;
+ /* The state of the stack. Each element of the array describes BPF_REG_SIZE
+ * (i.e. 8) bytes worth of stack memory.
+ * stack[0] represents bytes [*(r10-8)..*(r10-1)]
+ * stack[1] represents bytes [*(r10-16)..*(r10-9)]
+ * ...
+ * stack[allocated_stack/8 - 1] represents [*(r10-allocated_stack)..*(r10-allocated_stack+7)]
+ */
struct bpf_stack_state *stack;
+ /* Size of the current stack, in bytes. The stack state is tracked below, in
+ * `stack`. allocated_stack is always a multiple of BPF_REG_SIZE.
+ */
int allocated_stack;
};
@@ -658,6 +668,10 @@ struct bpf_verifier_env {
int exception_callback_subprog;
bool explore_alu_limits;
bool allow_ptr_leaks;
+ /* Allow access to uninitialized stack memory. Writes with fixed offset are
+ * always allowed, so this refers to reads (with fixed or variable offset),
+ * to writes with variable offset and to indirect (helper) accesses.
+ */
bool allow_uninit_stack;
bool bpf_capable;
bool bypass_spec_v1;
--
2.40.1
