Re: [PATCH bpf-next 2/2] selftests/bpf: Add testcase for updating attached freplace prog to PROG_ARRAY map

[leon.hwang@linux.dev]

Hi Yonghong,

Thank you for your review.

26 July 2024 at 05:11, "Yonghong Song" <yonghong.song@linux.dev> wrote:



> 
> On 7/24/24 5:32 PM, Leon Hwang wrote:
> 
> > 
> > Add a selftest to confirm the issue, which gets -EINVAL when update
> > 
> >  attached freplace prog to PROG_ARRAY map, has been fixed.
> > 
> >  cd tools/testing/selftests/bpf; ./test_progs -t tailcalls
> > 
> >  327/25 tailcalls/tailcall_freplace:OK
> > 
> >  327 tailcalls:OK
> > 
> >  Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED
> > 
> >  Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> > 
> >  ---
> > 
> >  .../selftests/bpf/prog_tests/tailcalls.c | 76 ++++++++++++++++++-
> > 
> >  .../selftests/bpf/progs/tailcall_freplace.c | 33 ++++++++
> > 
> >  .../testing/selftests/bpf/progs/tc_bpf2bpf.c | 23 ++++++
> > 
> >  3 files changed, 131 insertions(+), 1 deletion(-)
> > 
> >  create mode 100644 tools/testing/selftests/bpf/progs/tailcall_freplace.c
> > 
> >  create mode 100644 tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
> > 
> >  diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> > 
> >  index e01fabb8cc415..f1145601c0005 100644
> > 
> >  --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> > 
> >  +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> > 
> >  @@ -5,7 +5,8 @@
> > 
> >  #include "tailcall_poke.skel.h"
> > 
> >  #include "tailcall_bpf2bpf_hierarchy2.skel.h"
> > 
> >  #include "tailcall_bpf2bpf_hierarchy3.skel.h"
> > 
> >  -
> > 
> >  +#include "tailcall_freplace.skel.h"
> > 
> >  +#include "tc_bpf2bpf.skel.h"
> > 
> >  > /* test_tailcall_1 checks basic functionality by patching multiple locations
> > 
> >  * in a single program for a single tail call slot with nop->jmp, jmp->nop
> > 
> >  @@ -1495,6 +1496,77 @@ static void test_tailcall_bpf2bpf_hierarchy_3(void)
> > 
> >  RUN_TESTS(tailcall_bpf2bpf_hierarchy3);
> > 
> >  }
> > 
> >  > +/* test_tailcall_freplace checks that the attached freplace prog is OK to
> > 
> >  + * update to PROG_ARRAY map.
> > 
> 
> update the prog_array map.

Ack.

> 
> > 
> > + */
> > 
> >  +static void test_tailcall_freplace(void)
> > 
> >  +{
> > 
> >  + struct tailcall_freplace *fr_skel = NULL;
> > 
> >  + struct tc_bpf2bpf *tc_skel = NULL;
> > 
> >  + struct bpf_link *fr_link = NULL;
> > 
> >  + int prog_fd, map_fd;
> > 
> >  + char buff[128] = {};
> > 
> >  + int err, key;
> > 
> >  +
> > 
> >  + LIBBPF_OPTS(bpf_test_run_opts, topts,
> > 
> >  + .data_in = buff,
> > 
> >  + .data_size_in = sizeof(buff),
> > 
> >  + .repeat = 1,
> > 
> >  + );
> > 
> >  +
> > 
> >  + fr_skel = tailcall_freplace__open();
> > 
> >  + if (!ASSERT_OK_PTR(fr_skel, "open fr_skel"))
> > 
> 
> if (!ASSERT_OK_PTR(fr_skel, "open fr_skel"))
> 
> ==>
> 
> if (!ASSERT_OK_PTR(fr_skel, "tailcall_freplace__open"))
> 
> Similar for below other ASSERT_* macros.

Ack.

> 
> > 
> > + goto out;
> > 
> 
> Let us just do 'return' here.

Ack.

> 
> > 
> > +
> > 
> >  + tc_skel = tc_bpf2bpf__open_and_load();
> > 
> >  + if (!ASSERT_OK_PTR(tc_skel, "open tc_skel"))
> > 
> >  + goto out;
> > 
> >  +
> > 
> >  + prog_fd = bpf_program__fd(tc_skel->progs.entry);
> > 
> >  + if (!ASSERT_GE(prog_fd, 0, "tc_skel entry prog_id"))
> > 
> >  + goto out;
> > 
> 
> ASSERT_GE is not necessary, prog_fd should already be valid.

Ack.

I should read bpf_program__fd() source code before using it.

> 
> > 
> > +
> > 
> >  + err = bpf_program__set_attach_target(fr_skel->progs.entry,
> > 
> >  + prog_fd, "subprog");
> > 
> >  + if (!ASSERT_OK(err, "set_attach_target"))
> > 
> >  + goto out;
> > 
> >  +
> > 
> >  + err = tailcall_freplace__load(fr_skel);
> > 
> >  + if (!ASSERT_OK(err, "load fr_skel"))
> > 
> >  + goto out;
> > 
> >  +
> > 
> >  + fr_link = bpf_program__attach_freplace(fr_skel->progs.entry,
> > 
> >  + prog_fd, "subprog");
> > 
> >  + if (!ASSERT_OK_PTR(fr_link, "attach_freplace"))
> > 
> >  + goto out;
> > 
> >  +
> > 
> >  + prog_fd = bpf_program__fd(fr_skel->progs.entry);
> > 
> >  + if (!ASSERT_GE(prog_fd, 0, "fr_skel entry prog_fd"))
> > 
> >  + goto out;
> > 
> 
> prog_fd is valid here. No need ASSERT_GE.

Ack.

> 
> > 
> > +
> > 
> >  + map_fd = bpf_map__fd(fr_skel->maps.jmp_table);
> > 
> >  + if (!ASSERT_GE(map_fd, 0, "fr_skel jmp_table map_fd"))
> > 
> >  + goto out;
> > 
> 
> map_fd is valid. No need ASSERT_GE.

Ack.

> 
> > 
> > +
> > 
> >  + key = 0;
> > 
> >  + err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY);
> > 
> >  + if (!ASSERT_OK(err, "update jmp_table"))
> > 
> >  + goto out;
> > 
> >  +
> > 
> >  + prog_fd = bpf_program__fd(tc_skel->progs.entry);
> > 
> >  + if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
> > 
> >  + goto out;
> > 
> 
> prog_fd is valid here.

Ack.

> 
> > 
> > +
> > 
> >  + err = bpf_prog_test_run_opts(prog_fd, &topts);
> > 
> >  + ASSERT_OK(err, "test_run");
> > 
> >  + ASSERT_EQ(topts.retval, 34, "test_run retval");
> > 
> >  +
> > 
> >  +out:
> > 
> >  + bpf_link__destroy(fr_link);
> > 
> >  + tc_bpf2bpf__destroy(tc_skel);
> > 
> >  + tailcall_freplace__destroy(fr_skel);
> > 
> >  +}
> > 
> >  +
> > 
> >  void test_tailcalls(void)
> > 
> >  {
> > 
> >  if (test__start_subtest("tailcall_1"))
> > 
> >  @@ -1543,4 +1615,6 @@ void test_tailcalls(void)
> > 
> >  test_tailcall_bpf2bpf_hierarchy_fentry_entry();
> > 
> >  test_tailcall_bpf2bpf_hierarchy_2();
> > 
> >  test_tailcall_bpf2bpf_hierarchy_3();
> > 
> >  + if (test__start_subtest("tailcall_freplace"))
> > 
> >  + test_tailcall_freplace();
> > 
> >  }
> > 
> >  diff --git a/tools/testing/selftests/bpf/progs/tailcall_freplace.c b/tools/testing/selftests/bpf/progs/tailcall_freplace.c
> > 
> >  new file mode 100644
> > 
> >  index 0000000000000..80b5fa386ed9c
> > 
> >  --- /dev/null
> > 
> >  +++ b/tools/testing/selftests/bpf/progs/tailcall_freplace.c
> > 
> >  @@ -0,0 +1,33 @@
> > 
> >  +// SPDX-License-Identifier: GPL-2.0
> > 
> >  +
> > 
> >  +#include <linux/bpf.h>
> > 
> >  +#include <bpf/bpf_helpers.h>
> > 
> >  +#include "bpf_legacy.h"
> > 
> 
> bpf_legacy.h is not needed.

Ack.

> 
> > 
> > +
> > 
> >  +struct {
> > 
> >  + __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
> > 
> >  + __uint(max_entries, 1);
> > 
> >  + __uint(key_size, sizeof(__u32));
> > 
> >  + __uint(value_size, sizeof(__u32));
> > 
> >  +} jmp_table SEC(".maps");
> > 
> >  +
> > 
> >  +int count = 0;
> > 
> >  +
> > 
> >  +__noinline
> > 
> >  +int subprog(struct __sk_buff *skb)
> > 
> >  +{
> > 
> >  + count++;
> > 
> >  +
> > 
> >  + bpf_tail_call_static(skb, &jmp_table, 0);
> > 
> >  +
> > 
> >  + return count;
> > 
> >  +}
> > 
> 
> subprog() can be inlined into entry(). This
> 
> can avoid confusing vs. tc_bpf2bpf.c.
> 
> Better if you can differentiate two 'entry()' function
> 
> names, e.g., entry_freplace(), entry_tc(), it can make
> 
> it easy for people to understand your change in tailcalls.c.

Indeed. Thanks for your suggestion.

> 
> > 
> > +
> > 
> >  +SEC("freplace")
> > 
> >  +int entry(struct __sk_buff *skb)
> > 
> >  +{
> > 
> >  + return subprog(skb);
> > 
> >  +}
> > 
> >  +
> > 
> >  +char __license[] SEC("license") = "GPL";
> > 
> >  +
> > 
> >  diff --git a/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
> > 
> >  new file mode 100644
> > 
> >  index 0000000000000..4810961554585
> > 
> >  --- /dev/null
> > 
> >  +++ b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
> > 
> >  @@ -0,0 +1,23 @@
> > 
> >  +// SPDX-License-Identifier: GPL-2.0
> > 
> >  +
> > 
> >  +#include <linux/bpf.h>
> > 
> >  +#include <bpf/bpf_helpers.h>
> > 
> >  +#include "bpf_legacy.h"
> > 
> >  +
> > 
> >  +__noinline
> > 
> >  +int subprog(struct __sk_buff *skb)
> > 
> >  +{
> > 
> >  + volatile int ret = 1;
> > 
> >  +
> > 
> >  + asm volatile (""::"r+"(ret));
> > 
> >  + return ret;
> > 
> >  +}
> > 
> >  +
> > 
> >  +SEC("tc")
> > 
> >  +int entry(struct __sk_buff *skb)
> > 
> >  +{
> > 
> >  + return subprog(skb);
> > 
> >  +}
> > 
> >  +
> > 
> >  +char __license[] SEC("license") = "GPL";
> > 
> >  +
> >
>