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linux/tools/testing/selftests/bpf/prog_tests/arena_atomics.c
Peilin Ye ff3afe5da9 selftests/bpf: Add selftests for load-acquire and store-release instructions 
Add several ./test_progs tests:

  - arena_atomics/load_acquire
  - arena_atomics/store_release
  - verifier_load_acquire/*
  - verifier_store_release/*
  - verifier_precision/bpf_load_acquire
  - verifier_precision/bpf_store_release

The last two tests are added to check if backtrack_insn() handles the
new instructions correctly.

Additionally, the last test also makes sure that the verifier
"remembers" the value (in src_reg) we store-release into e.g. a stack
slot.  For example, if we take a look at the test program:

    #0:  r1 = 8;
      /* store_release((u64 *)(r10 - 8), r1); */
    #1:  .8byte %[store_release];
    #2:  r1 = *(u64 *)(r10 - 8);
    #3:  r2 = r10;
    #4:  r2 += r1;
    #5:  r0 = 0;
    #6:  exit;

At #1, if the verifier doesn't remember that we wrote 8 to the stack,
then later at #4 we would be adding an unbounded scalar value to the
stack pointer, which would cause the program to be rejected:

  VERIFIER LOG:
  =============
...
  math between fp pointer and register with unbounded min value is not allowed

For easier CI integration, instead of using built-ins like
__atomic_{load,store}_n() which depend on the new
__BPF_FEATURE_LOAD_ACQ_STORE_REL pre-defined macro, manually craft
load-acquire/store-release instructions using __imm_insn(), as suggested
by Eduard.

All new tests depend on:

  (1) Clang major version >= 18, and
  (2) ENABLE_ATOMICS_TESTS is defined (currently implies -mcpu=v3 or
      v4), and
  (3) JIT supports load-acquire/store-release (currently arm64 and
      x86-64)

In .../progs/arena_atomics.c:

  /* 8-byte-aligned */
  __u8 __arena_global load_acquire8_value = 0x12;
  /* 1-byte hole */
  __u16 __arena_global load_acquire16_value = 0x1234;

That 1-byte hole in the .addr_space.1 ELF section caused clang-17 to
crash:

  fatal error: error in backend: unable to write nop sequence of 1 bytes

To work around such llvm-17 CI job failures, conditionally define
__arena_global variables as 64-bit if __clang_major__ < 18, to make sure
.addr_space.1 has no holes.  Ideally we should avoid compiling this file
using clang-17 at all (arena tests depend on
__BPF_FEATURE_ADDR_SPACE_CAST, and are skipped for llvm-17 anyway), but
that is a separate topic.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Peilin Ye <yepeilin@google.com>
Link: https://lore.kernel.org/r/1b46c6feaf0f1b6984d9ec80e500cc7383e9da1a.1741049567.git.yepeilin@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-03-15 11:48:29 -07:00

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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
#include <test_progs.h>
#include "arena_atomics.skel.h"
static void test_add(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.add);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->add64_value, 3, "add64_value");
ASSERT_EQ(skel->arena->add64_result, 1, "add64_result");
ASSERT_EQ(skel->arena->add32_value, 3, "add32_value");
ASSERT_EQ(skel->arena->add32_result, 1, "add32_result");
ASSERT_EQ(skel->arena->add_stack_value_copy, 3, "add_stack_value");
ASSERT_EQ(skel->arena->add_stack_result, 1, "add_stack_result");
ASSERT_EQ(skel->arena->add_noreturn_value, 3, "add_noreturn_value");
}
static void test_sub(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.sub);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->sub64_value, -1, "sub64_value");
ASSERT_EQ(skel->arena->sub64_result, 1, "sub64_result");
ASSERT_EQ(skel->arena->sub32_value, -1, "sub32_value");
ASSERT_EQ(skel->arena->sub32_result, 1, "sub32_result");
ASSERT_EQ(skel->arena->sub_stack_value_copy, -1, "sub_stack_value");
ASSERT_EQ(skel->arena->sub_stack_result, 1, "sub_stack_result");
ASSERT_EQ(skel->arena->sub_noreturn_value, -1, "sub_noreturn_value");
}
static void test_and(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.and);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->and64_value, 0x010ull << 32, "and64_value");
ASSERT_EQ(skel->arena->and32_value, 0x010, "and32_value");
}
static void test_or(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.or);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->or64_value, 0x111ull << 32, "or64_value");
ASSERT_EQ(skel->arena->or32_value, 0x111, "or32_value");
}
static void test_xor(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.xor);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->xor64_value, 0x101ull << 32, "xor64_value");
ASSERT_EQ(skel->arena->xor32_value, 0x101, "xor32_value");
}
static void test_cmpxchg(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.cmpxchg);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->cmpxchg64_value, 2, "cmpxchg64_value");
ASSERT_EQ(skel->arena->cmpxchg64_result_fail, 1, "cmpxchg_result_fail");
ASSERT_EQ(skel->arena->cmpxchg64_result_succeed, 1, "cmpxchg_result_succeed");
ASSERT_EQ(skel->arena->cmpxchg32_value, 2, "lcmpxchg32_value");
ASSERT_EQ(skel->arena->cmpxchg32_result_fail, 1, "cmpxchg_result_fail");
ASSERT_EQ(skel->arena->cmpxchg32_result_succeed, 1, "cmpxchg_result_succeed");
}
static void test_xchg(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.xchg);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->xchg64_value, 2, "xchg64_value");
ASSERT_EQ(skel->arena->xchg64_result, 1, "xchg64_result");
ASSERT_EQ(skel->arena->xchg32_value, 2, "xchg32_value");
ASSERT_EQ(skel->arena->xchg32_result, 1, "xchg32_result");
}
static void test_uaf(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.uaf);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->uaf_recovery_fails, 0, "uaf_recovery_fails");
}
static void test_load_acquire(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
if (skel->data->skip_lacq_srel_tests) {
printf("%s:SKIP: ENABLE_ATOMICS_TESTS not defined, Clang doesn't support addr_space_cast, and/or JIT doesn't support load-acquire\n",
__func__);
test__skip();
return;
}
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.load_acquire);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->load_acquire8_result, 0x12,
"load_acquire8_result");
ASSERT_EQ(skel->arena->load_acquire16_result, 0x1234,
"load_acquire16_result");
ASSERT_EQ(skel->arena->load_acquire32_result, 0x12345678,
"load_acquire32_result");
ASSERT_EQ(skel->arena->load_acquire64_result, 0x1234567890abcdef,
"load_acquire64_result");
}
static void test_store_release(struct arena_atomics *skel)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
int err, prog_fd;
if (skel->data->skip_lacq_srel_tests) {
printf("%s:SKIP: ENABLE_ATOMICS_TESTS not defined, Clang doesn't support addr_space_cast, and/or JIT doesn't support store-release\n",
__func__);
test__skip();
return;
}
/* No need to attach it, just run it directly */
prog_fd = bpf_program__fd(skel->progs.store_release);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_OK(err, "test_run_opts err"))
return;
if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
return;
ASSERT_EQ(skel->arena->store_release8_result, 0x12,
"store_release8_result");
ASSERT_EQ(skel->arena->store_release16_result, 0x1234,
"store_release16_result");
ASSERT_EQ(skel->arena->store_release32_result, 0x12345678,
"store_release32_result");
ASSERT_EQ(skel->arena->store_release64_result, 0x1234567890abcdef,
"store_release64_result");
}
void test_arena_atomics(void)
{
struct arena_atomics *skel;
int err;
skel = arena_atomics__open();
if (!ASSERT_OK_PTR(skel, "arena atomics skeleton open"))
return;
if (skel->data->skip_all_tests) {
printf("%s:SKIP:no ENABLE_ATOMICS_TESTS or no addr_space_cast support in clang",
__func__);
test__skip();
goto cleanup;
}
err = arena_atomics__load(skel);
if (!ASSERT_OK(err, "arena atomics skeleton load"))
return;
skel->bss->pid = getpid();
if (test__start_subtest("add"))
test_add(skel);
if (test__start_subtest("sub"))
test_sub(skel);
if (test__start_subtest("and"))
test_and(skel);
if (test__start_subtest("or"))
test_or(skel);
if (test__start_subtest("xor"))
test_xor(skel);
if (test__start_subtest("cmpxchg"))
test_cmpxchg(skel);
if (test__start_subtest("xchg"))
test_xchg(skel);
if (test__start_subtest("uaf"))
test_uaf(skel);
if (test__start_subtest("load_acquire"))
test_load_acquire(skel);
if (test__start_subtest("store_release"))
test_store_release(skel);
cleanup:
arena_atomics__destroy(skel);
}
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