Commit 6aed15e3 authored by David Vernet's avatar David Vernet Committed by Daniel Borkmann
Browse files

selftests/bpf: Add testcase for static kfunc with unused arg 



kfuncs are allowed to be static, or not use one or more of their
arguments. For example, bpf_xdp_metadata_rx_hash() in net/core/xdp.c is
meant to be implemented by drivers, with the default implementation just
returning -EOPNOTSUPP. As described in [0], such kfuncs can have their
arguments elided, which can cause BTF encoding to be skipped. The new
__bpf_kfunc macro should address this, and this patch adds a selftest
which verifies that a static kfunc with at least one unused argument can
still be encoded and invoked by a BPF program.

Signed-off-by: default avatarDavid Vernet <void@manifault.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230201173016.342758-5-void@manifault.com
parent 400031e0

net/bpf/test_run.c

+6 −0
Original line number Diff line number Diff line
@@ -741,6 +741,11 @@ __bpf_kfunc void bpf_kfunc_call_test_destructive(void) 
{

}



__bpf_kfunc static u32 bpf_kfunc_call_test_static_unused_arg(u32 arg, u32 unused)

{

	return arg;

}



__diag_pop();



BTF_SET8_START(bpf_test_modify_return_ids)
@@ -779,6 +784,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail1) 
BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail2)

BTF_ID_FLAGS(func, bpf_kfunc_call_test_ref, KF_TRUSTED_ARGS)

BTF_ID_FLAGS(func, bpf_kfunc_call_test_destructive, KF_DESTRUCTIVE)

BTF_ID_FLAGS(func, bpf_kfunc_call_test_static_unused_arg)

BTF_SET8_END(test_sk_check_kfunc_ids)



static void *bpf_test_init(const union bpf_attr *kattr, u32 user_size,

tools/testing/selftests/bpf/prog_tests/kfunc_call.c

+1 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ static struct kfunc_test_params kfunc_tests[] = { 
	TC_TEST(kfunc_call_test_get_mem, 42),

	SYSCALL_TEST(kfunc_syscall_test, 0),

	SYSCALL_NULL_CTX_TEST(kfunc_syscall_test_null, 0),

	TC_TEST(kfunc_call_test_static_unused_arg, 0),

};



struct syscall_test_args {

tools/testing/selftests/bpf/progs/kfunc_call_test.c

+11 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ extern void bpf_kfunc_call_test_mem_len_pass1(void *mem, int len) __ksym; 
extern void bpf_kfunc_call_test_mem_len_fail2(__u64 *mem, int len) __ksym;

extern int *bpf_kfunc_call_test_get_rdwr_mem(struct prog_test_ref_kfunc *p, const int rdwr_buf_size) __ksym;

extern int *bpf_kfunc_call_test_get_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size) __ksym;

extern u32 bpf_kfunc_call_test_static_unused_arg(u32 arg, u32 unused) __ksym;



SEC("tc")

int kfunc_call_test4(struct __sk_buff *skb)
@@ -181,4 +182,14 @@ int kfunc_call_test_get_mem(struct __sk_buff *skb) 
	return ret;

}



SEC("tc")

int kfunc_call_test_static_unused_arg(struct __sk_buff *skb)

{



	u32 expected = 5, actual;



	actual = bpf_kfunc_call_test_static_unused_arg(expected, 0xdeadbeef);

	return actual != expected ? -1 : 0;

}



char _license[] SEC("license") = "GPL";