libbpf: Handle unsupported mmap-based /sys/kernel/btf/vmlinux correctly

libbpf_err_ptr() helpers are meant to return NULL and set errno, if
there is an error. But btf_parse_raw_mmap() is meant to be used
internally and is expected to return ERR_PTR() values. Because of this
mismatch, when libbpf tries to mmap /sys/kernel/btf/vmlinux, we don't
detect the error correctly with IS_ERR() check, and never fallback to
old non-mmap-based way of loading vmlinux BTF.

Fix this by using proper ERR_PTR() returns internally.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Fixes: 3c0421c93ce4 ("libbpf: Use mmap to parse vmlinux BTF from sysfs")
Cc: Lorenz Bauer <lmb@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20250606202134.2738910-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index f1d495dc66bba234c7ff8abbb2027e9f6d7a8fd7..37682908cb0f3bd4703eb2ee811aa3da3673c33b 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1384,12 +1384,12 @@ static struct btf *btf_parse_raw_mmap(const char *path, struct btf *base_btf)
 
        fd = open(path, O_RDONLY);
        if (fd < 0)
-               return libbpf_err_ptr(-errno);
+               return ERR_PTR(-errno);
 
        if (fstat(fd, &st) < 0) {
                err = -errno;
                close(fd);
-               return libbpf_err_ptr(err);
+               return ERR_PTR(err);
        }
 
        data = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
@@ -1397,7 +1397,7 @@ static struct btf *btf_parse_raw_mmap(const char *path, struct btf *base_btf)
        close(fd);
 
        if (data == MAP_FAILED)
-               return libbpf_err_ptr(err);
+               return ERR_PTR(err);
 
        btf = btf_new(data, st.st_size, base_btf, true);
        if (IS_ERR(btf))