From: Yonghong Song <yonghong.song@linux.dev>
Date: Wed, 13 May 2026 04:50:54 +0000 (-0700)
Subject: bpf: Prepare architecture JIT support for stack arguments
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=848d624acf668ae0d71b128f163d1d18d2ac6b90;p=thirdparty%2Flinux.git

bpf: Prepare architecture JIT support for stack arguments

Add bpf_jit_supports_stack_args() as a weak function defaulting to
false. Architectures that implement JIT support for stack arguments
override it to return true.

Reject BPF functions with more than 5 parameters at verification
time if the architecture does not support stack arguments.

Acked-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045054.2390945-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 918d9b34eac6a..a515a9769078e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1184,6 +1184,7 @@ bool bpf_jit_inlines_helper_call(s32 imm);
 bool bpf_jit_supports_subprog_tailcalls(void);
 bool bpf_jit_supports_percpu_insn(void);
 bool bpf_jit_supports_kfunc_call(void);
+bool bpf_jit_supports_stack_args(void);
 bool bpf_jit_supports_far_kfunc_call(void);
 bool bpf_jit_supports_exceptions(void);
 bool bpf_jit_supports_ptr_xchg(void);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 4fb8641546b8d..17d4ab0a82068 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7870,8 +7870,14 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
 			MAX_BPF_FUNC_ARGS, tname, nargs);
 		return -EFAULT;
 	}
-	if (nargs > MAX_BPF_FUNC_REG_ARGS)
+	if (nargs > MAX_BPF_FUNC_REG_ARGS) {
+		if (!bpf_jit_supports_stack_args()) {
+			bpf_log(log, "JIT does not support function %s() with %d args\n",
+				tname, nargs);
+			return -EFAULT;
+		}
 		sub->stack_arg_cnt = nargs - MAX_BPF_FUNC_REG_ARGS;
+	}
 
 	if (is_global && nargs > MAX_BPF_FUNC_REG_ARGS) {
 		bpf_log(log, "global function %s has %d > %d args, stack args not supported\n",
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 958d86f0beac3..e6b836f846ebf 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -3217,6 +3217,11 @@ bool __weak bpf_jit_supports_kfunc_call(void)
 	return false;
 }
 
+bool __weak bpf_jit_supports_stack_args(void)
+{
+	return false;
+}
+
 bool __weak bpf_jit_supports_far_kfunc_call(void)
 {
 	return false;