When using GCC on x86-64 to compile an usdt prog with -O1 or higher optimization, the compiler will generate SIB addressing mode for global array and PC-relative addressing mode for global variable, e.g. "1@-96(%rbp,%rax,8)" and "-1@4+t1(%rip)".
In this patch: - enrich subtest_basic_usdt test case to cover SIB addressing usdt argument spec handling logic
Signed-off-by: Jiawei Zhao phoenix500526@163.com --- tools/testing/selftests/bpf/prog_tests/usdt.c | 62 ++++++++++++++++++- tools/testing/selftests/bpf/progs/test_usdt.c | 32 ++++++++++ 2 files changed, 92 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c index 9057e983cc54..0d5e40eca0d4 100644 --- a/tools/testing/selftests/bpf/prog_tests/usdt.c +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c @@ -10,6 +10,26 @@
int lets_test_this(int);
+#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)" + */ +static volatile short array[] = {-1, -2, -3, -4}; +#define USDT_SIB_ARG_SPEC -2@(%%rdx,%%rax,2) +#endif + static volatile int idx = 2; static volatile __u64 bla = 0xFEDCBA9876543210ULL; static volatile short nums[] = {-1, -2, -3, -4}; @@ -25,6 +45,10 @@ unsigned short test_usdt0_semaphore SEC(".probes"); unsigned short test_usdt3_semaphore SEC(".probes"); unsigned short test_usdt12_semaphore SEC(".probes");
+#if defined(__x86_64__) || defined(__i386__) +unsigned short test_usdt_sib_semaphore SEC(".probes"); +#endif + static void __always_inline trigger_func(int x) { long y = 42;
@@ -40,12 +64,27 @@ static void __always_inline trigger_func(int x) { } }
+#if defined(__x86_64__) || defined(__i386__) +static void trigger_sib_spec(void) +{ + /* Base address + offset + (index * scale) */ + /* Force SIB addressing with inline assembly */ + asm volatile( + STAP_PROBE_ASM(test, usdt_sib, USDT_SIB_ARG_SPEC) + : + : "d"(array), "a"(0) + : "memory" + ); +} +#endif + static void subtest_basic_usdt(void) { LIBBPF_OPTS(bpf_usdt_opts, opts); struct test_usdt *skel; struct test_usdt__bss *bss; int err, i; + const __u64 expected_cookie = 0xcafedeadbeeffeed;
skel = test_usdt__open_and_load(); if (!ASSERT_OK_PTR(skel, "skel_open")) @@ -59,20 +98,29 @@ static void subtest_basic_usdt(void) 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;
+#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 + trigger_func(1);
ASSERT_EQ(bss->usdt0_called, 1, "usdt0_called"); ASSERT_EQ(bss->usdt3_called, 1, "usdt3_called"); ASSERT_EQ(bss->usdt12_called, 1, "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"); @@ -156,6 +204,16 @@ static void subtest_basic_usdt(void) 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); } diff --git a/tools/testing/selftests/bpf/progs/test_usdt.c b/tools/testing/selftests/bpf/progs/test_usdt.c index 096488f47fbc..63db72253316 100644 --- a/tools/testing/selftests/bpf/progs/test_usdt.c +++ b/tools/testing/selftests/bpf/progs/test_usdt.c @@ -107,4 +107,36 @@ int BPF_USDT(usdt12, int a1, int a2, long a3, long a4, unsigned a5, return 0; }
+ +int usdt_sib_called; +u64 usdt_sib_cookie; +int usdt_sib_arg_cnt; +int usdt_sib_arg_ret; +u64 usdt_sib_arg; +int usdt_sib_arg_size; + +/* + * usdt_sib is only tested on x86-related architectures, so it requires + * manual attach since auto-attach will panic tests under other architectures + */ +SEC("usdt") +int usdt_sib(struct pt_regs *ctx) +{ + long tmp; + + if (my_pid != (bpf_get_current_pid_tgid() >> 32)) + return 0; + + __sync_fetch_and_add(&usdt_sib_called, 1); + + usdt_sib_cookie = bpf_usdt_cookie(ctx); + usdt_sib_arg_cnt = bpf_usdt_arg_cnt(ctx); + + usdt_sib_arg_ret = bpf_usdt_arg(ctx, 0, &tmp); + usdt_sib_arg = (short)tmp; + usdt_sib_arg_size = bpf_usdt_arg_size(ctx, 0); + + return 0; +} + char _license[] SEC("license") = "GPL";