Re: [PATCH v2 bpf-next 4/6] selftests/bpf: Add tests for fd_array_cnt

[Anton Protopopov <aspsk@isovalent.com>]

On 24/11/26 10:54AM, Andrii Nakryiko wrote:
> On Tue, Nov 19, 2024 at 2:13 AM Anton Protopopov <aspsk@isovalent.com> wrote:
> >
> > Add a new set of tests to test the new field in PROG_LOAD-related
> > part of bpf_attr: fd_array_cnt.
> >
> > Add the following test cases:
> >
> >   * fd_array_cnt/no-fd-array: program is loaded in a normal
> >     way, without any fd_array present
> >
> >   * fd_array_cnt/fd-array-ok: pass two extra non-used maps,
> >     check that they're bound to the program
> >
> >   * fd_array_cnt/fd-array-dup-input: pass a few extra maps,
> >     only two of which are unique
> >
> >   * fd_array_cnt/fd-array-ref-maps-in-array: pass a map in
> >     fd_array which is also referenced from within the program
> >
> >   * fd_array_cnt/fd-array-trash-input: pass array with some trash
> >
> >   * fd_array_cnt/fd-array-with-holes: pass an array with holes (fd=0)
> >
> >   * fd_array_cnt/fd-array-2big: pass too large array
> >
> > All the tests above are using the bpf(2) syscall directly,
> > no libbpf involved.
> >
> > Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> > ---
> >  .../selftests/bpf/prog_tests/fd_array.c       | 381 ++++++++++++++++++
> >  1 file changed, 381 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/fd_array.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/fd_array.c b/tools/testing/selftests/bpf/prog_tests/fd_array.c
> > new file mode 100644
> > index 000000000000..1b47386e66c3
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/fd_array.c
> > @@ -0,0 +1,381 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <test_progs.h>
> > +
> > +#include <linux/btf.h>
> > +#include <sys/syscall.h>
> > +#include <bpf/bpf.h>
> > +
> > +#include "../test_btf.h"
> > +
> > +static inline int _bpf_map_create(void)
> > +{
> > +       static union bpf_attr attr = {
> > +               .map_type = BPF_MAP_TYPE_ARRAY,
> > +               .key_size = 4,
> > +               .value_size = 8,
> > +               .max_entries = 1,
> > +       };
> > +
> > +       return syscall(__NR_bpf, BPF_MAP_CREATE, &attr, sizeof(attr));
> > +}
> 
> libbpf provides bpf_map_create() API. Please use that (and make sure
> it supports the new field as well), don't re-define your own wrappers.

Thanks, ack (for here and your comments below)

> 
> > +
> > +static int _btf_create(void)
> > +{
> > +       struct btf_blob {
> > +               struct btf_header btf_hdr;
> > +               __u32 types[8];
> > +               __u32 str;
> > +       } raw_btf = {
> > +               .btf_hdr = {
> > +                       .magic = BTF_MAGIC,
> > +                       .version = BTF_VERSION,
> > +                       .hdr_len = sizeof(struct btf_header),
> > +                       .type_len = sizeof(raw_btf.types),
> > +                       .str_off = offsetof(struct btf_blob, str) - offsetof(struct btf_blob, types),
> > +                       .str_len = sizeof(raw_btf.str),
> > +               },
> > +               .types = {
> > +                       /* long */
> > +                       BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 64, 8),  /* [1] */
> > +                       /* unsigned long */
> > +                       BTF_TYPE_INT_ENC(0, 0, 0, 64, 8),  /* [2] */
> > +               },
> > +       };
> > +       static union bpf_attr attr = {
> > +               .btf_size = sizeof(raw_btf),
> > +       };
> > +
> > +       attr.btf = (long)&raw_btf;
> > +
> > +       return syscall(__NR_bpf, BPF_BTF_LOAD, &attr, sizeof(attr));
> 
> ditto, libbpf provides low-level API wrappers for a reason, let's tick to them
> 
> > +}
> > +
> > +static bool map_exists(__u32 id)
> > +{
> > +       int fd;
> > +
> > +       fd = bpf_map_get_fd_by_id(id);
> > +       if (fd >= 0) {
> > +               close(fd);
> > +               return true;
> > +       }
> > +       return false;
> > +}
> > +
> > +static inline int bpf_prog_get_map_ids(int prog_fd, __u32 *nr_map_ids, __u32 *map_ids)
> > +{
> > +       __u32 len = sizeof(struct bpf_prog_info);
> > +       struct bpf_prog_info info = {
> > +               .nr_map_ids = *nr_map_ids,
> > +               .map_ids = ptr_to_u64(map_ids),
> > +       };
> > +       int err;
> > +
> > +       err = bpf_prog_get_info_by_fd(prog_fd, &info, &len);
> > +       if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd"))
> > +               return -1;
> > +
> > +       *nr_map_ids = info.nr_map_ids;
> > +
> > +       return 0;
> > +}
> > +
> > +static int __load_test_prog(int map_fd, int *fd_array, int fd_array_cnt)
> > +{
> > +       /* A trivial program which uses one map */
> > +       struct bpf_insn insns[] = {
> > +               BPF_LD_MAP_FD(BPF_REG_1, map_fd),
> > +               BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
> > +               BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
> > +               BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
> > +               BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
> > +               BPF_MOV64_IMM(BPF_REG_0, 0),
> > +               BPF_EXIT_INSN(),
> > +       };
> > +       union bpf_attr attr = {
> > +               .prog_type = BPF_PROG_TYPE_XDP, /* we don't care */
> > +               .insns     = ptr_to_u64(insns),
> > +               .insn_cnt  = ARRAY_SIZE(insns),
> > +               .license   = ptr_to_u64("GPL"),
> > +               .fd_array = ptr_to_u64(fd_array),
> > +               .fd_array_cnt = fd_array_cnt,
> > +       };
> > +
> > +       return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
> 
> bpf_prog_load() API
> 
> > +}
> > +
> > +static int load_test_prog(int *fd_array, int fd_array_cnt)
> > +{
> > +       int map_fd;
> > +       int ret;
> > +
> > +       map_fd = _bpf_map_create();
> > +       if (!ASSERT_GE(map_fd, 0, "_bpf_map_create"))
> > +               return map_fd;
> > +
> > +       ret = __load_test_prog(map_fd, fd_array, fd_array_cnt);
> > +       close(map_fd);
> > +
> > +       /* switch back to returning the actual value */
> > +       if (ret < 0)
> > +               return -errno;
> > +       return ret;
> > +}
> > +
> 
> [...]