[PATCH bpf-next v4 3/4] selftests/bpf: add selftest to check rdtsc jit

Vadim Fedorenko
2024-11-07T21:17:52Z

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

Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
---
.../selftests/bpf/prog_tests/verifier.c | 2 +
.../selftests/bpf/progs/verifier_cpu_cycles.c | 104 ++++++++++++++++++
2 files changed, 106 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 75f7a2ce334b..d76cc90f4bfb 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -97,6 +97,7 @@
#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"

#define MAX_ENTRIES 11

@@ -223,6 +224,7 @@ 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_cpu_cycles(void) { RUN(verifier_cpu_cycles); }

void test_verifier_mtu(void)
{
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..88bfa7211858
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c
@@ -0,0 +1,104 @@
+// 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"
+
+extern u64 bpf_cpu_cycles_to_ns(u64 cycles) __weak __ksym;
+extern u64 bpf_get_cpu_cycles(void) __weak __ksym;
+
+SEC("syscall")
+__arch_x86_64
+__xlated("0: call kernel-function")
+__naked int bpf_rdtsc(void)
+{
+ asm volatile(
+ "call %[bpf_get_cpu_cycles];"
+ "exit"
+ :
+ : __imm(bpf_get_cpu_cycles)
+ : __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_cycles];"
+ "exit"
+ :
+ : __imm(bpf_get_cpu_cycles)
+ : __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_cycles_to_ns];"
+ "exit"
+ :
+ : __imm(bpf_cpu_cycles_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_cycles_to_ns];"
+ "exit"
+ :
+ : __imm(bpf_cpu_cycles_to_ns)
+ : __clobber_all
+ );
+}
+
+void rdtsc(void)
+{
+ bpf_get_cpu_cycles();
+ bpf_cpu_cycles_to_ns(42);
+}
+
+char _license[] SEC("license") = "GPL";
--
2.43.5