Adding test to verify that when called from outside of the
trampoline provided by kernel, the uretprobe syscall will cause
calling process to receive SIGILL signal and the attached bpf
program is not executed.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../selftests/bpf/prog_tests/uprobe_syscall.c | 95 +++++++++++++++++++
 .../bpf/progs/uprobe_syscall_executed.c       | 17 ++++
 2 files changed, 112 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall_executed.c

diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
index 1a50cd35205d..c6fdb8c59ea3 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c

@@ -7,7 +7,10 @@
 #include <unistd.h>
 #include <asm/ptrace.h>
 #include <linux/compiler.h>
+#include <linux/stringify.h>
+#include <sys/wait.h>
 #include "uprobe_syscall.skel.h"
+#include "uprobe_syscall_executed.skel.h"

 __naked unsigned long uretprobe_regs_trigger(void)
 {

@@ -209,6 +212,91 @@ static void test_uretprobe_regs_change(void)
        }
 }

+#ifndef __NR_uretprobe
+#define __NR_uretprobe 462
+#endif
+
+__naked unsigned long uretprobe_syscall_call_1(void)
+{
+       /*
+        * Pretend we are uretprobe trampoline to trigger the return
+        * probe invocation in order to verify we get SIGILL.
+        */
+       asm volatile (
+               "pushq %rax\n"
+               "pushq %rcx\n"
+               "pushq %r11\n"
+               "movq $" __stringify(__NR_uretprobe) ", %rax\n"
+               "syscall\n"
+               "popq %r11\n"
+               "popq %rcx\n"
+               "retq\n"
+       );
+}
+
+__naked unsigned long uretprobe_syscall_call(void)
+{
+       asm volatile (
+               "call uretprobe_syscall_call_1\n"
+               "retq\n"
+       );
+}
+
+static void test_uretprobe_syscall_call(void)
+{
+       LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
+               .retprobe = true,
+       );
+       struct uprobe_syscall_executed *skel;
+       int pid, status, err, go[2], c;
+
+       if (pipe(go))
+               return;