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Message-ID: <20250912124059.0428127b@canb.auug.org.au>
Date: Fri, 12 Sep 2025 12:40:59 +1000
From: Stephen Rothwell <sfr@...b.auug.org.au>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>,
Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov
<ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>
Cc: Jiawei Zhao <phoenix500526@....com>, Jiri Olsa <jolsa@...nel.org>, bpf
<bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>, Linux Kernel
Mailing List <linux-kernel@...r.kernel.org>, Linux Next Mailing List
<linux-next@...r.kernel.org>
Subject: linux-next: manual merge of the tip tree with the bpf-next tree
Hi all,
Today's linux-next merge of the tip tree got a conflict in:
tools/testing/selftests/bpf/prog_tests/usdt.c
between commit:
69424097ee10 ("selftests/bpf: Enrich subtest_basic_usdt case in selftests to cover SIB handling logic")
from the bpf-next tree and commit:
875e1705ad99 ("selftests/bpf: Add optimized usdt variant for basic usdt test")
from the tip tree.
I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging. You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.
--
Cheers,
Stephen Rothwell
diff --cc tools/testing/selftests/bpf/prog_tests/usdt.c
index 615e9c3e93bf,833eb87483a1..000000000000
--- a/tools/testing/selftests/bpf/prog_tests/usdt.c
+++ b/tools/testing/selftests/bpf/prog_tests/usdt.c
@@@ -40,73 -40,20 +40,80 @@@ static void __always_inline trigger_fun
}
}
+#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(void)
+ 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;
+ int err, i, called;
+ const __u64 expected_cookie = 0xcafedeadbeeffeed;
+ #define TRIGGER(x) ({ \
+ trigger_func(x); \
+ if (optimized) \
+ trigger_func(x); \
+ optimized ? 2 : 1; \
+ })
+
skel = test_usdt__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_open"))
return;
@@@ -126,22 -73,13 +133,22 @@@
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);
+ called = TRIGGER(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_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");
@@@ -225,18 -163,9 +232,19 @@@
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
}
unsigned short test_usdt_100_semaphore SEC(".probes");
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