[PATCH v3 1/2] bpf/btf: Fix is_int_ptr()

[Feng zhou]

From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>

When tracing a kernel function with arg type is u32*, btf_ctx_access()
would report error: arg2 type INT is not a struct.

The commit bb6728d75611 ("bpf: Allow access to int pointer arguments
in tracing programs") added support for int pointer, but don't skip
modifiers before checking it's type. This patch fixes it.

Fixes: bb6728d75611 ("bpf: Allow access to int pointer arguments in tracing programs")
Co-developed-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
---
 kernel/bpf/btf.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 593c45a294d0..5abd8dfa6b70 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5910,12 +5910,8 @@ struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
 
 static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
 {
-	/* t comes in already as a pointer */
-	t = btf_type_by_id(btf, t->type);
-
-	/* allow const */
-	if (BTF_INFO_KIND(t->info) == BTF_KIND_CONST)
-		t = btf_type_by_id(btf, t->type);
+	/* skip modifiers */
+	t = btf_type_skip_modifiers(btf, t->type, NULL);
 
 	return btf_type_is_int(t);
 }
-- 
2.20.1