[PATCH bpf-next v12 4/5] selftests/bpf: add selftest to check bpf_get_cpu_time_counter jit

[Vadim Fedorenko <vadfed@meta.com>]

bpf_get_cpu_time_counter() is replaced with rdtsc instruction on x86_64.
Add tests to check that JIT works as expected. When JIT is not
supported, bpf_cpu_time_counter_to_ns() can be inlined by verifier.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
---
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../selftests/bpf/progs/verifier_cpu_cycles.c | 120 ++++++++++++++++++
 2 files changed, 122 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index e66a57970d28..d5e7e302a344 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -102,6 +102,7 @@
 #include "verifier_xdp_direct_packet_access.skel.h"
 #include "verifier_bits_iter.skel.h"
 #include "verifier_lsm.skel.h"
+#include "verifier_cpu_cycles.skel.h"
 #include "irq.skel.h"
 
 #define MAX_ENTRIES 11
@@ -236,6 +237,7 @@ void test_verifier_bits_iter(void) { RUN(verifier_bits_iter); }
 void test_verifier_lsm(void)                  { RUN(verifier_lsm); }
 void test_irq(void)			      { RUN(irq); }
 void test_verifier_mtu(void)		      { RUN(verifier_mtu); }
+void test_verifier_cpu_cycles(void)	      { RUN(verifier_cpu_cycles); }
 
 static int init_test_val_map(struct bpf_object *obj, char *map_name)
 {
diff --git a/tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c b/tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c
new file mode 100644
index 000000000000..26c02010ccf1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Inc. */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+
+extern u64 bpf_cpu_time_counter_to_ns(u64 cycles) __weak __ksym;
+extern u64 bpf_get_cpu_time_counter(void) __weak __ksym;
+
+SEC("syscall")
+__arch_x86_64
+__xlated("0: call kernel-function")
+__naked int bpf_rdtsc(void)
+{
+	asm volatile(
+	"call %[bpf_get_cpu_time_counter];"
+	"exit"
+	:
+	: __imm(bpf_get_cpu_time_counter)
+	: __clobber_all
+	);
+}
+
+SEC("syscall")
+__arch_x86_64
+/* program entry for bpf_rdtsc_jit_x86_64(), regular function prologue */
+__jited("	endbr64")
+__jited("	nopl	(%rax,%rax)")
+__jited("	nopl	(%rax)")
+__jited("	pushq	%rbp")
+__jited("	movq	%rsp, %rbp")
+__jited("	endbr64")
+/* save RDX in R11 as it will be overwritten */
+__jited("	movq	%rdx, %r11")
+/* lfence may not be executed depending on cpu features */
+__jited("	{{(lfence|)}}")
+__jited("	rdtsc")
+/* combine EDX:EAX into RAX */
+__jited("	shlq	${{(32|0x20)}}, %rdx")
+__jited("	orq	%rdx, %rax")
+/* restore RDX from R11 */
+__jited("	movq	%r11, %rdx")
+__jited("	leave")
+__naked int bpf_rdtsc_jit_x86_64(void)
+{
+	asm volatile(
+	"call %[bpf_get_cpu_time_counter];"
+	"exit"
+	:
+	: __imm(bpf_get_cpu_time_counter)
+	: __clobber_all
+	);
+}
+
+SEC("syscall")
+__arch_arm64
+__xlated("0: r1 = 42")
+__xlated("1: r0 = r1")
+__naked int bpf_cyc2ns_arm(void)
+{
+	asm volatile(
+	"r1=0x2a;"
+	"call %[bpf_cpu_time_counter_to_ns];"
+	"exit"
+	:
+	: __imm(bpf_cpu_time_counter_to_ns)
+	: __clobber_all
+	);
+}
+
+SEC("syscall")
+__arch_x86_64
+__xlated("0: r1 = 42")
+__xlated("1: call kernel-function")
+__naked int bpf_cyc2ns(void)
+{
+	asm volatile(
+	"r1=0x2a;"
+	"call %[bpf_cpu_time_counter_to_ns];"
+	"exit"
+	:
+	: __imm(bpf_cpu_time_counter_to_ns)
+	: __clobber_all
+	);
+}
+
+SEC("syscall")
+__arch_x86_64
+/* program entry for bpf_rdtsc_jit_x86_64(), regular function prologue */
+__jited("	endbr64")
+__jited("	nopl	(%rax,%rax)")
+__jited("	nopl	(%rax)")
+__jited("	pushq	%rbp")
+__jited("	movq	%rsp, %rbp")
+__jited("	endbr64")
+/* save RDX in R11 as it will be overwritten */
+__jited("	movabsq	$0x2a2a2a2a2a, %rdi")
+__jited("	imulq	${{.*}}, %rdi, %rax")
+__jited("	shrq	${{.*}}, %rax")
+__jited("	leave")
+__naked int bpf_cyc2ns_jit_x86(void)
+{
+	asm volatile(
+	"r1=0x2a2a2a2a2a ll;"
+	"call %[bpf_cpu_time_counter_to_ns];"
+	"exit"
+	:
+	: __imm(bpf_cpu_time_counter_to_ns)
+	: __clobber_all
+	);
+}
+
+void rdtsc(void)
+{
+	bpf_get_cpu_time_counter();
+	bpf_cpu_time_counter_to_ns(42);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.47.1