2022-02-03 08:47:32

by Matteo Croce

Subject: [PATCH bpf-next v2 2/2] selftests/bpf: test maximum recursion depth for bpf_core_types_are_compat()

From: Matteo Croce <[email protected]>

bpf_core_types_are_compat() was limited to 2 recursion levels, which are
enough to parse a function prototype.
Add a test which checks the existence of a function prototype, so to
test the bpf_core_types_are_compat() code path.

Signed-off-by: Matteo Croce <[email protected]>
---
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 3 +++
tools/testing/selftests/bpf/progs/core_kern.c | 14 ++++++++++++++
2 files changed, 17 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 595d32ab285a..a457071a7751 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -13,6 +13,9 @@
#define CREATE_TRACE_POINTS
#include "bpf_testmod-events.h"

+typedef int (*func_proto_typedef)(long);
+func_proto_typedef funcp = NULL;
+
DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123;

noinline void
diff --git a/tools/testing/selftests/bpf/progs/core_kern.c b/tools/testing/selftests/bpf/progs/core_kern.c
index 13499cc15c7d..bfea86b42563 100644
--- a/tools/testing/selftests/bpf/progs/core_kern.c
+++ b/tools/testing/selftests/bpf/progs/core_kern.c
@@ -101,4 +101,18 @@ int balancer_ingress(struct __sk_buff *ctx)
return 0;
}

+typedef int (*func_proto_typedef___match)(long);
+typedef void (*func_proto_typedef___doesnt_match)(char*);
+
+int out[2];
+
+SEC("raw_tracepoint/sys_enter")
+int core_relo_recur_limit(void *ctx)
+{
+ out[0] = bpf_core_type_exists(func_proto_typedef___match);
+ out[1] = bpf_core_type_exists(func_proto_typedef___doesnt_match);
+
+ return 0;
+}
+
char LICENSE[] SEC("license") = "GPL";
--
2.34.1

2022-02-04 17:11:16

by Alexei Starovoitov

Subject: Re: [PATCH bpf-next v2 2/2] selftests/bpf: test maximum recursion depth for bpf_core_types_are_compat()

On Wed, Feb 2, 2022 at 1:13 PM Matteo Croce <[email protected]> wrote:
>
> From: Matteo Croce <[email protected]>
>
> bpf_core_types_are_compat() was limited to 2 recursion levels, which are
> enough to parse a function prototype.
> Add a test which checks the existence of a function prototype, so to
> test the bpf_core_types_are_compat() code path.
>
> Signed-off-by: Matteo Croce <[email protected]>
> ---
> .../selftests/bpf/bpf_testmod/bpf_testmod.c | 3 +++
> tools/testing/selftests/bpf/progs/core_kern.c | 14 ++++++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> index 595d32ab285a..a457071a7751 100644
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> @@ -13,6 +13,9 @@
> #define CREATE_TRACE_POINTS
> #include "bpf_testmod-events.h"
>
> +typedef int (*func_proto_typedef)(long);
> +func_proto_typedef funcp = NULL;
> +
> DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123;
>
> noinline void
> diff --git a/tools/testing/selftests/bpf/progs/core_kern.c b/tools/testing/selftests/bpf/progs/core_kern.c
> index 13499cc15c7d..bfea86b42563 100644
> --- a/tools/testing/selftests/bpf/progs/core_kern.c
> +++ b/tools/testing/selftests/bpf/progs/core_kern.c
> @@ -101,4 +101,18 @@ int balancer_ingress(struct __sk_buff *ctx)
> return 0;
> }
>
> +typedef int (*func_proto_typedef___match)(long);
> +typedef void (*func_proto_typedef___doesnt_match)(char*);
> +
> +int out[2];
> +
> +SEC("raw_tracepoint/sys_enter")
> +int core_relo_recur_limit(void *ctx)
> +{
> + out[0] = bpf_core_type_exists(func_proto_typedef___match);
> + out[1] = bpf_core_type_exists(func_proto_typedef___doesnt_match);

How does it test it?
The kernel code could be a nop and there will be no failure in this "test".
Please make it real.
Also add tests that exercise the limit of recursion.
One that goes over and fails and another that is right at the limit
and passes.