[PATCH bpf-next 1/2] bpf: Resolve modifiers when walking structs

[PATCH bpf-next 1/2] bpf: Resolve modifiers when walking structs

[Stanislav Fomichev]

It is impossible to use skb_frag_t in the tracing program.
Resolve typedefs when walking structs.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 kernel/bpf/btf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 29fe21099298..3dd47451f097 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6135,6 +6135,8 @@ static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf,
 
 	*flag = 0;
 again:
+	if (btf_type_is_modifier(t))
+		t = btf_type_skip_modifiers(btf, t->type, NULL);
 	tname = __btf_name_by_offset(btf, t->name_off);
 	if (!btf_type_is_struct(t)) {
 		bpf_log(log, "Type '%s' is not a struct\n", tname);
-- 
2.41.0.162.gfafddb0af9-goog

[PATCH bpf-next 2/2] selftests/bpf: Add test to exercise typedef walking

[Stanislav Fomichev]

Add new bpf_fentry_test_sinfo with skb_shared_info argument
and try to access frags.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 net/bpf/test_run.c                            |  4 ++++
 .../selftests/bpf/prog_tests/verifier.c       |  2 ++
 .../selftests/bpf/progs/verifier_typedef.c    | 23 +++++++++++++++++++
 3 files changed, 29 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_typedef.c

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 2321bd2f9964..63b11f7a5392 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -555,6 +555,10 @@ __bpf_kfunc u32 bpf_fentry_test9(u32 *a)
 	return *a;
 }
 
+void noinline bpf_fentry_test_sinfo(struct skb_shared_info *sinfo)
+{
+}
+
 __bpf_kfunc int bpf_modify_return_test(int a, int *b)
 {
 	*b += 1;
diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 070a13833c3f..c375e59ff28d 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -58,6 +58,7 @@
 #include "verifier_stack_ptr.skel.h"
 #include "verifier_subprog_precision.skel.h"
 #include "verifier_subreg.skel.h"
+#include "verifier_typedef.skel.h"
 #include "verifier_uninit.skel.h"
 #include "verifier_unpriv.skel.h"
 #include "verifier_unpriv_perf.skel.h"
@@ -159,6 +160,7 @@ void test_verifier_spin_lock(void)            { RUN(verifier_spin_lock); }
 void test_verifier_stack_ptr(void)            { RUN(verifier_stack_ptr); }
 void test_verifier_subprog_precision(void)    { RUN(verifier_subprog_precision); }
 void test_verifier_subreg(void)               { RUN(verifier_subreg); }
+void test_verifier_typedef(void)              { RUN(verifier_typedef); }
 void test_verifier_uninit(void)               { RUN(verifier_uninit); }
 void test_verifier_unpriv(void)               { RUN(verifier_unpriv); }
 void test_verifier_unpriv_perf(void)          { RUN(verifier_unpriv_perf); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_typedef.c b/tools/testing/selftests/bpf/progs/verifier_typedef.c
new file mode 100644
index 000000000000..08481cfaac4b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_typedef.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+SEC("fentry/bpf_fentry_test_sinfo")
+__description("typedef: resolve")
+__success __retval(0)
+__naked void resolve_typedef(void)
+{
+	asm volatile ("					\
+	r1 = *(u64 *)(r1 +0);				\
+	r2 = *(u64 *)(r1 +%[frags_offs]);		\
+	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm_const(frags_offs,
+		      offsetof(struct skb_shared_info, frags))
+	: __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.41.0.162.gfafddb0af9-goog

Re: [PATCH bpf-next 1/2] bpf: Resolve modifiers when walking structs

[Yonghong Song]

On 6/26/23 2:25 PM, Stanislav Fomichev wrote:
> It is impossible to use skb_frag_t in the tracing program.
> Resolve typedefs when walking structs.
> 
> Signed-off-by: Stanislav Fomichev <sdf@google.com>

Acked-by: Yonghong Song <yhs@fb.com>

Re: [PATCH bpf-next 2/2] selftests/bpf: Add test to exercise typedef walking

[Yonghong Song]

On 6/26/23 2:25 PM, Stanislav Fomichev wrote:
> Add new bpf_fentry_test_sinfo with skb_shared_info argument
> and try to access frags.
> 
> Signed-off-by: Stanislav Fomichev <sdf@google.com>

Acked-by: Yonghong Song <yhs@fb.com>

Re: [PATCH bpf-next 1/2] bpf: Resolve modifiers when walking structs

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Mon, 26 Jun 2023 14:25:21 -0700 you wrote:
> It is impossible to use skb_frag_t in the tracing program.
> Resolve typedefs when walking structs.
> 
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---
>  kernel/bpf/btf.c | 2 ++
>  1 file changed, 2 insertions(+)

Here is the summary with links:
  - [bpf-next,1/2] bpf: Resolve modifiers when walking structs
    https://git.kernel.org/bpf/bpf-next/c/819d43428a86
  - [bpf-next,2/2] selftests/bpf: Add test to exercise typedef walking
    https://git.kernel.org/bpf/bpf-next/c/2597a25cb865

You are awesome, thank you!
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