bpf: Reuse MAX_BPF_FUNC_ARGS for maximum number of arguments

Currently, MAX_BPF_FUNC_ARGS is used for tracepoint related progs where
the number of parameters cannot exceed MAX_BPF_FUNC_ARGS.

Here, MAX_BPF_FUNC_ARGS is reused to set a limit of the number of arguments
for bpf functions and kfuncs. The current value for MAX_BPF_FUNC_ARGS
is 12 which should be sufficient for majority of bpf functions and
kfuncs.

Acked-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260423033511.2542870-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d3aea3931b85d16f78de7836cace34c8fc055065..715b6df9c4035e7a41907995fd984ad025302513 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1151,6 +1151,11 @@ struct bpf_prog_offload {
 
 /* The longest tracepoint has 12 args.
  * See include/trace/bpf_probe.h
+ *
+ * Also reuse this macro for maximum number of arguments a BPF function
+ * or a kfunc can have. Args 1-5 are passed in registers, args 6-12 via
+ * stack arg slots. The JIT may map some stack arg slots to registers based
+ * on the native calling convention (e.g., arg 6 to R9 on x86-64).
  */
 #define MAX_BPF_FUNC_ARGS 12