diff options
Diffstat (limited to 'tools/testing/selftests/bpf/prog_tests/usdt.c')
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/usdt.c | 85 |
1 files changed, 82 insertions, 3 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c index 833eb87483a1..4f7f45e69315 100644 --- a/tools/testing/selftests/bpf/prog_tests/usdt.c +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c @@ -40,12 +40,72 @@ static void __always_inline trigger_func(int x) { } } +#if defined(__x86_64__) || defined(__i386__) +/* + * SIB (Scale-Index-Base) addressing format: "size@(base_reg, index_reg, scale)" + * - 'size' is the size in bytes of the array element, and its sign indicates + * whether the type is signed (negative) or unsigned (positive). + * - 'base_reg' is the register holding the base address, normally rdx or edx + * - 'index_reg' is the register holding the index, normally rax or eax + * - 'scale' is the scaling factor (typically 1, 2, 4, or 8), which matches the + * size of the element type. + * + * For example, for an array of 'short' (signed 2-byte elements), the SIB spec would be: + * - size: -2 (negative because 'short' is signed) + * - scale: 2 (since sizeof(short) == 2) + * + * The resulting SIB format: "-2@(%%rdx,%%rax,2)" for x86_64, "-2@(%%edx,%%eax,2)" for i386 + */ +static volatile short array[] = {-1, -2, -3, -4}; + +#if defined(__x86_64__) +#define USDT_SIB_ARG_SPEC -2@(%%rdx,%%rax,2) +#else +#define USDT_SIB_ARG_SPEC -2@(%%edx,%%eax,2) +#endif + +unsigned short test_usdt_sib_semaphore SEC(".probes"); + +static void trigger_sib_spec(void) +{ + /* + * Force SIB addressing with inline assembly. + * + * You must compile with -std=gnu99 or -std=c99 to use the + * STAP_PROBE_ASM macro. + * + * The STAP_PROBE_ASM macro generates a quoted string that gets + * inserted between the surrounding assembly instructions. In this + * case, USDT_SIB_ARG_SPEC is embedded directly into the instruction + * stream, creating a probe point between the asm statement boundaries. + * It works fine with gcc/clang. + * + * Register constraints: + * - "d"(array): Binds the 'array' variable to %rdx or %edx register + * - "a"(0): Binds the constant 0 to %rax or %eax register + * These ensure that when USDT_SIB_ARG_SPEC references %%rdx(%edx) and + * %%rax(%eax), they contain the expected values for SIB addressing. + * + * The "memory" clobber prevents the compiler from reordering memory + * accesses around the probe point, ensuring that the probe behavior + * is predictable and consistent. + */ + asm volatile( + STAP_PROBE_ASM(test, usdt_sib, USDT_SIB_ARG_SPEC) + : + : "d"(array), "a"(0) + : "memory" + ); +} +#endif + static void subtest_basic_usdt(bool optimized) { LIBBPF_OPTS(bpf_usdt_opts, opts); struct test_usdt *skel; struct test_usdt__bss *bss; int err, i, called; + const __u64 expected_cookie = 0xcafedeadbeeffeed; #define TRIGGER(x) ({ \ trigger_func(x); \ @@ -66,20 +126,29 @@ static void subtest_basic_usdt(bool optimized) goto cleanup; /* usdt0 won't be auto-attached */ - opts.usdt_cookie = 0xcafedeadbeeffeed; + opts.usdt_cookie = expected_cookie; skel->links.usdt0 = bpf_program__attach_usdt(skel->progs.usdt0, 0 /*self*/, "/proc/self/exe", "test", "usdt0", &opts); if (!ASSERT_OK_PTR(skel->links.usdt0, "usdt0_link")) goto cleanup; - called = TRIGGER(1); +#if defined(__x86_64__) || defined(__i386__) + opts.usdt_cookie = expected_cookie; + skel->links.usdt_sib = bpf_program__attach_usdt(skel->progs.usdt_sib, + 0 /*self*/, "/proc/self/exe", + "test", "usdt_sib", &opts); + if (!ASSERT_OK_PTR(skel->links.usdt_sib, "usdt_sib_link")) + goto cleanup; +#endif + + alled = TRIGGER(1); ASSERT_EQ(bss->usdt0_called, called, "usdt0_called"); ASSERT_EQ(bss->usdt3_called, called, "usdt3_called"); ASSERT_EQ(bss->usdt12_called, called, "usdt12_called"); - ASSERT_EQ(bss->usdt0_cookie, 0xcafedeadbeeffeed, "usdt0_cookie"); + ASSERT_EQ(bss->usdt0_cookie, expected_cookie, "usdt0_cookie"); ASSERT_EQ(bss->usdt0_arg_cnt, 0, "usdt0_arg_cnt"); ASSERT_EQ(bss->usdt0_arg_ret, -ENOENT, "usdt0_arg_ret"); ASSERT_EQ(bss->usdt0_arg_size, -ENOENT, "usdt0_arg_size"); @@ -163,6 +232,16 @@ static void subtest_basic_usdt(bool optimized) ASSERT_EQ(bss->usdt3_args[1], 42, "usdt3_arg2"); ASSERT_EQ(bss->usdt3_args[2], (uintptr_t)&bla, "usdt3_arg3"); +#if defined(__x86_64__) || defined(__i386__) + trigger_sib_spec(); + ASSERT_EQ(bss->usdt_sib_called, 1, "usdt_sib_called"); + ASSERT_EQ(bss->usdt_sib_cookie, expected_cookie, "usdt_sib_cookie"); + ASSERT_EQ(bss->usdt_sib_arg_cnt, 1, "usdt_sib_arg_cnt"); + ASSERT_EQ(bss->usdt_sib_arg, nums[0], "usdt_sib_arg"); + ASSERT_EQ(bss->usdt_sib_arg_ret, 0, "usdt_sib_arg_ret"); + ASSERT_EQ(bss->usdt_sib_arg_size, sizeof(nums[0]), "usdt_sib_arg_size"); +#endif + cleanup: test_usdt__destroy(skel); #undef TRIGGER |