[PATCH bpf-next v2 2/2] selftests/bpf: add selftest to check rdtsc jit

[Vadim Fedorenko <vadfed@xxxxxxxx>]

get_hw_counter() is replaced with rdtsc instruction on x86_64. Add
tests to check it.

Signed-off-by: Vadim Fedorenko <vadfed@xxxxxxxx>
---
 .../selftests/bpf/prog_tests/verifier.c       |  2 +
 .../selftests/bpf/progs/verifier_rdtsc.c      | 58 +++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_rdtsc.c

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index e26b5150fc43..cf7417465010 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -95,6 +95,7 @@
 #include "verifier_xdp_direct_packet_access.skel.h"
 #include "verifier_bits_iter.skel.h"
 #include "verifier_lsm.skel.h"
+#include "verifier_rdtsc.skel.h"
 
 #define MAX_ENTRIES 11
 
@@ -220,6 +221,7 @@ void test_verifier_xdp(void)                  { RUN(verifier_xdp); }
 void test_verifier_xdp_direct_packet_access(void) { RUN(verifier_xdp_direct_packet_access); }
 void test_verifier_bits_iter(void) { RUN(verifier_bits_iter); }
 void test_verifier_lsm(void)                  { RUN(verifier_lsm); }
+void test_verifier_rdtsc(void)                { RUN(verifier_rdtsc); }
 
 static int init_test_val_map(struct bpf_object *obj, char *map_name)
 {
diff --git a/tools/testing/selftests/bpf/progs/verifier_rdtsc.c b/tools/testing/selftests/bpf/progs/verifier_rdtsc.c
new file mode 100644
index 000000000000..cfce4172c9ab
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_rdtsc.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Inc. */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+
+SEC("syscall")
+__arch_x86_64
+__xlated("0: call kernel-function")
+__naked int bpf_rdtsc(void)
+{
+	asm volatile(
+	"call %[bpf_get_hw_counter];"
+	"exit"
+	:
+	: __imm(bpf_get_hw_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_hw_counter];"
+	"exit"
+	:
+	: __imm(bpf_get_hw_counter)
+	: __clobber_all
+	);
+}
+
+void rdtsc(void)
+{
+	bpf_get_hw_counter();
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.43.5