Re: [PATCH v4 bpf-next 5/7] selftests/bpf: Add tests for fd_array_cnt

[Anton Protopopov <aspsk@isovalent.com>]

On 24/12/03 01:27PM, Andrii Nakryiko wrote:
> On Tue, Dec 3, 2024 at 6:13 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)
> 
> nit: should be removed, there is no such test anymore
> 
> >
> >   * 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       | 340 ++++++++++++++++++
> >  1 file changed, 340 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..1d4bff4a1269
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/fd_array.c
> > @@ -0,0 +1,340 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <test_progs.h>
> > +
> > +#include <linux/btf.h>
> > +#include <bpf/bpf.h>
> > +
> > +#include "../test_btf.h"
> > +
> > +static inline int new_map(void)
> > +{
> > +       LIBBPF_OPTS(bpf_map_create_opts, opts);
> > +       const char *name = NULL;
> > +       __u32 max_entries = 1;
> > +       __u32 value_size = 8;
> > +       __u32 key_size = 4;
> > +
> > +       return bpf_map_create(BPF_MAP_TYPE_ARRAY, name,
> > +                             key_size, value_size,
> > +                             max_entries, &opts);
> 
> nit: you don't really need to pass empty opts, passing NULL is always
> ok if no options are specified
> 
> > +}
> > +
> > +static int new_btf(void)
> > +{
> > +       LIBBPF_OPTS(bpf_btf_load_opts, opts);
> > +       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] */
> > +               },
> > +       };
> > +
> > +       return bpf_btf_load(&raw_btf, sizeof(raw_btf), &opts);
> 
> same, you don't seem to actually use opts
> 
> > +}
> > +
> > +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),
> > +       };
> 
> nit: bpf_prog_info should be explicitly memset(0), and only then
> fields should be filled out. It might be ok right now because we don't
> have any padding (or compiler does zero that padding out, even though
> it's not required to do that), but this might pop up later, so best to
> avoid that.
> 
> > +       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, const 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(),
> > +       };
> > +       LIBBPF_OPTS(bpf_prog_load_opts, opts);
> > +
> > +       opts.fd_array = fd_array;
> > +       opts.fd_array_cnt = fd_array_cnt;
> > +
> > +       return bpf_prog_load(BPF_PROG_TYPE_XDP, NULL, "GPL", insns, ARRAY_SIZE(insns), &opts);
> > +}
> > +
> > +static int load_test_prog(const int *fd_array, int fd_array_cnt)
> > +{
> > +       int map_fd;
> > +       int ret;
> > +
> > +       map_fd = new_map();
> > +       if (!ASSERT_GE(map_fd, 0, "new_map"))
> > +               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;
> 
> this errno might have been modified by close(), but you actually don't
> need errno, libbpf will return errno directly from bpf_prog_load(), so
> you can just do:
> 
> ret = __load_test_prog(...);
> close(map_fd);
> return ret;
> 
> > +       return ret;
> > +}
> > +
> > +static bool check_expected_map_ids(int prog_fd, int expected, __u32 *map_ids, __u32 *nr_map_ids)
> > +{
> > +       int err;
> > +
> > +       err = bpf_prog_get_map_ids(prog_fd, nr_map_ids, map_ids);
> > +       if (!ASSERT_OK(err, "bpf_prog_get_map_ids"))
> > +               return false;
> > +       if (!ASSERT_EQ(*nr_map_ids, expected, "unexpected nr_map_ids"))
> > +               return false;
> > +
> > +       return true;
> > +}
> > +
> > +/*
> > + * Load a program, which uses one map. No fd_array maps are present.
> > + * On return only one map is expected to be bound to prog.
> > + */
> > +static void check_fd_array_cnt__no_fd_array(void)
> > +{
> > +       __u32 map_ids[16];
> > +       __u32 nr_map_ids;
> > +       int prog_fd = -1;
> > +
> > +       prog_fd = load_test_prog(NULL, 0);
> > +       if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
> > +               return;
> > +       nr_map_ids = ARRAY_SIZE(map_ids);
> > +       check_expected_map_ids(prog_fd, 1, map_ids, &nr_map_ids);
> > +       close(prog_fd);
> > +}
> > +
> > +/*
> > + * Load a program, which uses one map, and pass two extra, non-equal, maps in
> > + * fd_array with fd_array_cnt=2. On return three maps are expected to be bound
> > + * to the program.
> > + */
> > +static void check_fd_array_cnt__fd_array_ok(void)
> > +{
> > +       int extra_fds[2] = { -1, -1 };
> > +       __u32 map_ids[16];
> > +       __u32 nr_map_ids;
> > +       int prog_fd = -1;
> > +
> > +       extra_fds[0] = new_map();
> > +       if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
> > +               goto cleanup;
> > +       extra_fds[1] = new_map();
> > +       if (!ASSERT_GE(extra_fds[1], 0, "new_map"))
> > +               goto cleanup;
> > +       prog_fd = load_test_prog(extra_fds, 2);
> > +       if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
> > +               goto cleanup;
> > +       nr_map_ids = ARRAY_SIZE(map_ids);
> > +       if (!check_expected_map_ids(prog_fd, 3, map_ids, &nr_map_ids))
> > +               goto cleanup;
> > +
> > +       /* maps should still exist when original file descriptors are closed */
> > +       close(extra_fds[0]);
> > +       close(extra_fds[1]);
> > +       if (!ASSERT_EQ(map_exists(map_ids[0]), true, "map_ids[0] should exist"))
> > +               goto cleanup;
> > +       if (!ASSERT_EQ(map_exists(map_ids[1]), true, "map_ids[1] should exist"))
> > +               goto cleanup;
> > +
> > +       /* some fds might be invalid, so ignore return codes */
> > +cleanup:
> > +       close(extra_fds[1]);
> > +       close(extra_fds[0]);
> > +       close(prog_fd);
> 
> nit: technically, you should check each fd to be >= 0 before closing it
> 
> > +}
> > +
> > +/*
> > + * Load a program with a few extra maps duplicated in the fd_array.
> > + * After the load maps should only be referenced once.
> > + */
> > +static void check_fd_array_cnt__duplicated_maps(void)
> > +{
> > +       int extra_fds[4] = { -1, -1, -1, -1 };
> > +       __u32 map_ids[16];
> > +       __u32 nr_map_ids;
> > +       int prog_fd = -1;
> > +
> > +       extra_fds[0] = extra_fds[2] = new_map();
> > +       if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
> > +               goto cleanup;
> > +       extra_fds[1] = extra_fds[3] = new_map();
> > +       if (!ASSERT_GE(extra_fds[1], 0, "new_map"))
> > +               goto cleanup;
> > +       prog_fd = load_test_prog(extra_fds, 4);
> > +       if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
> > +               goto cleanup;
> > +       nr_map_ids = ARRAY_SIZE(map_ids);
> > +       if (!check_expected_map_ids(prog_fd, 3, map_ids, &nr_map_ids))
> > +               goto cleanup;
> > +
> > +       /* maps should still exist when original file descriptors are closed */
> > +       close(extra_fds[0]);
> > +       close(extra_fds[1]);
> > +       if (!ASSERT_EQ(map_exists(map_ids[0]), true, "map should exist"))
> > +               goto cleanup;
> > +       if (!ASSERT_EQ(map_exists(map_ids[1]), true, "map should exist"))
> > +               goto cleanup;
> > +
> > +       /* some fds might be invalid, so ignore return codes */
> > +cleanup:
> > +       close(extra_fds[1]);
> > +       close(extra_fds[0]);
> > +       close(prog_fd);
> 
> same about if (fd >=0) close(fd); pattern
> 
> > +}
> > +
> > +/*
> > + * Check that if maps which are referenced by a program are
> > + * passed in fd_array, then they will be referenced only once
> > + */
> > +static void check_fd_array_cnt__referenced_maps_in_fd_array(void)
> > +{
> > +       int extra_fds[1] = { -1 };
> > +       __u32 map_ids[16];
> > +       __u32 nr_map_ids;
> > +       int prog_fd = -1;
> > +
> > +       extra_fds[0] = new_map();
> > +       if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
> > +               goto cleanup;
> > +       prog_fd = __load_test_prog(extra_fds[0], extra_fds, 1);
> > +       if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
> > +               goto cleanup;
> > +       nr_map_ids = ARRAY_SIZE(map_ids);
> > +       if (!check_expected_map_ids(prog_fd, 1, map_ids, &nr_map_ids))
> > +               goto cleanup;
> > +
> > +       /* map should still exist when original file descriptor is closed */
> > +       close(extra_fds[0]);
> > +       if (!ASSERT_EQ(map_exists(map_ids[0]), true, "map should exist"))
> > +               goto cleanup;
> > +
> > +       /* some fds might be invalid, so ignore return codes */
> > +cleanup:
> > +       close(extra_fds[0]);
> > +       close(prog_fd);
> 
> ditto
> 
> > +}
> > +
> > +/*
> > + * Test that a program with trash in fd_array can't be loaded:
> > + * only map and BTF file descriptors should be accepted.
> > + */
> > +static void check_fd_array_cnt__fd_array_with_trash(void)
> > +{
> > +       int extra_fds[3] = { -1, -1, -1 };
> > +       int prog_fd = -1;
> > +
> > +       extra_fds[0] = new_map();
> > +       if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
> > +               goto cleanup;
> > +       extra_fds[1] = new_btf();
> > +       if (!ASSERT_GE(extra_fds[1], 0, "new_btf"))
> > +               goto cleanup;
> > +
> > +       /* trash 1: not a file descriptor */
> > +       extra_fds[2] = 0xbeef;
> > +       prog_fd = load_test_prog(extra_fds, 3);
> > +       if (!ASSERT_EQ(prog_fd, -EBADF, "prog should have been rejected with -EBADF"))
> > +               goto cleanup;
> > +
> > +       /* trash 2: not a map or btf */
> > +       extra_fds[2] = socket(AF_INET, SOCK_STREAM, 0);
> > +       if (!ASSERT_GE(extra_fds[2], 0, "socket"))
> > +               goto cleanup;
> > +
> > +       prog_fd = load_test_prog(extra_fds, 3);
> > +       if (!ASSERT_EQ(prog_fd, -EINVAL, "prog should have been rejected with -EINVAL"))
> > +               goto cleanup;
> > +
> > +       /* some fds might be invalid, so ignore return codes */
> > +cleanup:
> > +       close(extra_fds[2]);
> > +       close(extra_fds[1]);
> > +       close(extra_fds[0]);
> 
> ditto
> 
> > +}
> > +
> > +/*
> > + * Test that a program with too big fd_array can't be loaded.
> > + */
> > +static void check_fd_array_cnt__fd_array_too_big(void)
> > +{
> > +       int extra_fds[65];
> > +       int prog_fd = -1;
> > +       int i;
> > +
> > +       for (i = 0; i < 65; i++) {
> > +               extra_fds[i] = new_map();
> > +               if (!ASSERT_GE(extra_fds[i], 0, "new_map"))
> > +                       goto cleanup_fds;
> > +       }
> > +
> > +       prog_fd = load_test_prog(extra_fds, 65);
> 
> nit: hard-coding 65 as the limit seems iffy, when we change
> MAX_USED_MAPS this will need adjustment immediately. How about picking
> something significantly larger, like 4096, creating just one map with
> new_map(), but using that map FD in each entry, then doing
> load_test_prog() once and check for -E2BIG?

This will not work with -E2BIG, as when maps are the same,
they will not be added to used_maps multiple times. I still
can try to bump the number here, but not sure if this is
possible to track MAX_USED_MAPS from userspace?

(All your comments above make sense, will fix.)

> 
> > +       ASSERT_EQ(prog_fd, -E2BIG, "prog should have been rejected with -E2BIG");
> > +
> > +cleanup_fds:
> > +       while (i > 0)
> > +               close(extra_fds[--i]);
> > +}
> > +
> > +void test_fd_array_cnt(void)
> > +{
> > +       if (test__start_subtest("no-fd-array"))
> > +               check_fd_array_cnt__no_fd_array();
> > +
> > +       if (test__start_subtest("fd-array-ok"))
> > +               check_fd_array_cnt__fd_array_ok();
> > +
> > +       if (test__start_subtest("fd-array-dup-input"))
> > +               check_fd_array_cnt__duplicated_maps();
> > +
> > +       if (test__start_subtest("fd-array-ref-maps-in-array"))
> > +               check_fd_array_cnt__referenced_maps_in_fd_array();
> > +
> > +       if (test__start_subtest("fd-array-trash-input"))
> > +               check_fd_array_cnt__fd_array_with_trash();
> > +
> > +       if (test__start_subtest("fd-array-2big"))
> > +               check_fd_array_cnt__fd_array_too_big();
> > +}
> > --
> > 2.34.1
> >
> >