On Fri, Feb 21, 2025 at 2:14 PM Mykyta Yatsenko
<mykyta.yatsenko5@xxxxxxxxx> wrote:
>
> From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
>
> Add XDP setup type for dynptr tests, enabling testing for
> non-contiguous buffer.
> Add 2 tests:
> - test_dynptr_copy - verify correctness for the fast (contiguous
> buffer) code path.
> - test_dynptr_copy_xdp - verifies code paths that handle
> non-contiguous buffer.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> ---
> .../testing/selftests/bpf/prog_tests/dynptr.c | 21 ++++
> .../selftests/bpf/progs/dynptr_success.c | 112 +++++++++++++++++-
> 2 files changed, 128 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
> index b614a5272dfd..e29cc16124c2 100644
> --- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
> +++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
> @@ -10,6 +10,7 @@ enum test_setup_type {
> SETUP_SYSCALL_SLEEP,
> SETUP_SKB_PROG,
> SETUP_SKB_PROG_TP,
> + SETUP_XDP_PROG,
> };
>
> static struct {
> @@ -18,6 +19,8 @@ static struct {
> } success_tests[] = {
> {"test_read_write", SETUP_SYSCALL_SLEEP},
> {"test_dynptr_data", SETUP_SYSCALL_SLEEP},
> + {"test_dynptr_copy", SETUP_SYSCALL_SLEEP},
> + {"test_dynptr_copy_xdp", SETUP_XDP_PROG},
> {"test_ringbuf", SETUP_SYSCALL_SLEEP},
> {"test_skb_readonly", SETUP_SKB_PROG},
> {"test_dynptr_skb_data", SETUP_SKB_PROG},
> @@ -120,6 +123,24 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
>
> break;
> }
> + case SETUP_XDP_PROG:
> + {
> + char data[5000];
> + int err, prog_fd;
> + LIBBPF_OPTS(bpf_test_run_opts, opts,
> + .data_in = &data,
> + .data_size_in = sizeof(data),
> + .repeat = 1,
> + );
> +
> + prog_fd = bpf_program__fd(prog);
> + err = bpf_prog_test_run_opts(prog_fd, &opts);
> +
> + if (!ASSERT_OK(err, "test_run"))
> + goto cleanup;
> +
> + break;
> + }
> }
>
> ASSERT_EQ(skel->bss->err, 0, "err");
> diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
> index bfcc85686cf0..dd10411d1c02 100644
> --- a/tools/testing/selftests/bpf/progs/dynptr_success.c
> +++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
> @@ -1,20 +1,19 @@
> // SPDX-License-Identifier: GPL-2.0
> /* Copyright (c) 2022 Facebook */
>
> +#include <vmlinux.h>
> #include <string.h>
> #include <stdbool.h>
> -#include <linux/bpf.h>
> #include <bpf/bpf_helpers.h>
> #include <bpf/bpf_tracing.h>
> #include "bpf_misc.h"
> -#include "bpf_kfuncs.h"
> #include "errno.h"
>
> char _license[] SEC("license") = "GPL";
>
> int pid, err, val;
>
> -struct sample {
> +struct ringbuf_sample {
> int pid;
> int seq;
> long value;
> @@ -121,7 +120,7 @@ int test_dynptr_data(void *ctx)
>
> static int ringbuf_callback(__u32 index, void *data)
> {
> - struct sample *sample;
> + struct ringbuf_sample *sample;
>
> struct bpf_dynptr *ptr = (struct bpf_dynptr *)data;
>
> @@ -138,7 +137,7 @@ SEC("?tp/syscalls/sys_enter_nanosleep")
> int test_ringbuf(void *ctx)
> {
> struct bpf_dynptr ptr;
> - struct sample *sample;
> + struct ringbuf_sample *sample;
>
> if (bpf_get_current_pid_tgid() >> 32 != pid)
> return 0;
> @@ -567,3 +566,106 @@ int BPF_PROG(test_dynptr_skb_tp_btf, void *skb, void *location)
>
> return 1;
> }
> +
> +SEC("?tp/syscalls/sys_enter_nanosleep")
> +int test_dynptr_copy(void *ctx)
> +{
> + char data[] = "hello there, world!!";
> + char buf[32] = {'\0'};
> + __u32 sz = sizeof(data);
> + struct bpf_dynptr src, dst;
> +
> + bpf_ringbuf_reserve_dynptr(&ringbuf, sz, 0, &src);
> + bpf_ringbuf_reserve_dynptr(&ringbuf, sz, 0, &dst);
> +
> + /* Test basic case of copying contiguous memory backed dynptrs */
> + err = bpf_dynptr_write(&src, 0, data, sz, 0);
> + err = err ?: bpf_dynptr_copy(&dst, 0, &src, 0, sz);
> + err = err ?: bpf_dynptr_read(buf, sz, &dst, 0, 0);
> + err = err ?: __builtin_memcmp(data, buf, sz);
> +
> + /* Test that offsets are handled correctly */
> + err = err ?: bpf_dynptr_copy(&dst, 3, &src, 5, sz - 5);
> + err = err ?: bpf_dynptr_read(buf, sz - 5, &dst, 3, 0);
> + err = err ?: __builtin_memcmp(data + 5, buf, sz - 5);
> +
> + bpf_ringbuf_discard_dynptr(&src, 0);
> + bpf_ringbuf_discard_dynptr(&dst, 0);
> + return 0;
> +}
> +
> +SEC("xdp")
> +int test_dynptr_copy_xdp(struct xdp_md *xdp)
> +{
> + struct bpf_dynptr ptr_buf, ptr_xdp;
> + char data[] = "qwertyuiopasdfghjkl";
> + char buf[32] = {'\0'};
> + __u32 len = sizeof(data);
> + int i, chunks = 200;
> +
> + /* ptr_xdp is backed by non-contiguous memory */
> + bpf_dynptr_from_xdp(xdp, 0, &ptr_xdp);
> + bpf_ringbuf_reserve_dynptr(&ringbuf, len * chunks, 0, &ptr_buf);
> +
> + /* Destination dynptr is backed by non-contiguous memory */
> + bpf_for(i, 0, chunks) {
> + err = bpf_dynptr_write(&ptr_buf, i * len, data, len, 0);
> + if (err)
> + goto out;
> + }
> +
> + err = bpf_dynptr_copy(&ptr_xdp, 0, &ptr_buf, 0, len * chunks);
> + if (err)
> + goto out;
> +
> + bpf_for(i, 0, chunks) {
> + __builtin_memset(buf, 0, sizeof(buf));
> + err = bpf_dynptr_read(&buf, len, &ptr_xdp, i * len, 0);
> + if (err)
> + goto out;
> + if (__builtin_memcmp(data, buf, len) != 0)
Ok, so with GCC-BPF (see [0]) there is something wrong, seems like GCC
doesn't "inline" __builtin_memcmp() and falls back to calling actual
memcmp(). This is strange, as your buffer is pretty small (32 bytes),
so it should have been inlined. Jose, can you please take a look from
GCC-BPF side?
Meanwhile, Mykyta, can you please implement __builtin_memcp() using
bpf_for() loop logic to unblock landing this? Thanks!
pw-bot: cr
[0] https://github.com/kernel-patches/bpf/actions/runs/13548082739/job/37865378205
> + goto out;
> + }
> +
> + /* Source dynptr is backed by non-contiguous memory */
> + __builtin_memset(buf, 0, sizeof(buf));
> + bpf_for(i, 0, chunks) {
> + err = bpf_dynptr_write(&ptr_buf, i * len, buf, len, 0);
> + if (err)
> + goto out;
> + }
> +
> + err = bpf_dynptr_copy(&ptr_buf, 0, &ptr_xdp, 0, len * chunks);
> + if (err)
> + goto out;
> +
> + bpf_for(i, 0, chunks) {
> + __builtin_memset(buf, 0, sizeof(buf));
> + err = bpf_dynptr_read(&buf, len, &ptr_buf, i * len, 0);
> + if (err)
> + goto out;
> + if (__builtin_memcmp(data, buf, len) != 0)
> + goto out;
> + }
> +
> + /* Both source and destination dynptrs are backed by non-contiguous memory */
> + err = bpf_dynptr_copy(&ptr_xdp, 2, &ptr_xdp, len, len * (chunks - 1));
> + if (err)
> + goto out;
> +
> + bpf_for(i, 0, chunks - 1) {
> + __builtin_memset(buf, 0, sizeof(buf));
> + err = bpf_dynptr_read(&buf, len, &ptr_xdp, 2 + i * len, 0);
> + if (err)
> + goto out;
> + if (__builtin_memcmp(data, buf, len) != 0)
> + goto out;
> + }
> +
> + if (bpf_dynptr_copy(&ptr_xdp, 2000, &ptr_xdp, 0, len * chunks) != -E2BIG)
> + err = 1;
> +
> +out:
> + bpf_ringbuf_discard_dynptr(&ptr_buf, 0);
> + return XDP_DROP;
> +}
> --
> 2.48.1
>
