@@ -5669,6 +5669,7 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
if (!ctx_struct)
/* should not happen */
return NULL;
+again:
ctx_tname = btf_name_by_offset(btf_vmlinux, ctx_struct->name_off);
if (!ctx_tname) {
/* should not happen */
@@ -5682,8 +5683,16 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
* int socket_filter_bpf_prog(struct __sk_buff *skb)
* { // no fields of skb are ever used }
*/
- if (strcmp(ctx_tname, tname))
- return NULL;
+ if (strcmp(ctx_tname, tname)) {
+ /* bpf_user_pt_regs_t is a typedef, so resolve it to
+ * underlying struct and check name again
+ */
+ if (!btf_type_is_modifier(ctx_struct))
+ return NULL;
+ while (btf_type_is_modifier(ctx_struct))
+ ctx_struct = btf_type_by_id(btf_vmlinux, ctx_struct->type);
+ goto again;
+ }
return ctx_type;
}
KPROBE program's user-facing context type is defined as typedef bpf_user_pt_regs_t. This leads to a problem when trying to passing kprobe/uprobe/usdt context argument into global subprog, as kernel always strip away mods and typedefs of user-supplied type, but takes expected type from bpf_ctx_convert as is, which causes mismatch. Current way to work around this is to define a fake struct with the same name as expected typedef: struct bpf_user_pt_regs_t {}; __noinline my_global_subprog(struct bpf_user_pt_regs_t *ctx) { ... } This patch fixes the issue by resolving expected type, if it's not a struct. It still leaves the above work-around working for backwards compatibility. Fixes: 91cc1a99740e ("bpf: Annotate context types") Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- kernel/bpf/btf.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)