selftests/bpf: Check that JMP32 pointer vs zero jumps are not predictedgrafted

Add jmp32_ptr_vs_zero_jne: the fall-through of the 32-bit compare, which
the verifier used to skip, contains an out of bounds map value access,
hence w/o the previous patch the program is accepted. See previous patch
for detailed description.

Reported-by: Nicholas Carlini <npc@anthropic.com>
Suggested-by: Nicholas Carlini <npc@anthropic.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20260904083325.2083493-6-eddyz87@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/rust/macros/export.rs b/rust/macros/export.rs
new file mode 100644
index 000000000..6d53521f6
--- /dev/null
+++ b/rust/macros/export.rs
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro2::TokenStream;
+use quote::quote;
+
+/// Please see [`crate::export`] for documentation.
+pub(crate) fn export(f: syn::ItemFn) -> TokenStream {
+    let name = &f.sig.ident;
+
+    quote! {
+        // This verifies that the function has the same signature as the declaration generated by
+        // bindgen. It makes use of the fact that all branches of an if/else must have the same
+        // type.
+        const _: () = {
+            if true {
+                ::kernel::bindings::#name
+            } else {
+                #name
+            };
+        };
+
+        #[no_mangle]
+        #f
+    }
+}