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 <phoenix500...@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";
--
2.43.0
