Add testcases to test bpf_send_signal_pid/tgid(). In these new test cases,
the main process triggers the BPF program and the forked process
receives the signals.

Signed-off-by: Puranjay Mohan <puran...@kernel.org>
---
 .../selftests/bpf/prog_tests/send_signal.c    | 110 +++++++++++++-----
 .../bpf/progs/test_send_signal_kern.c         |  17 ++-
 2 files changed, 95 insertions(+), 32 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c 
b/tools/testing/selftests/bpf/prog_tests/send_signal.c
index 6cc69900b310..a8392dfc69e2 100644
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -12,13 +12,15 @@ static void sigusr1_handler(int signum)
 }
 
 static void test_send_signal_common(struct perf_event_attr *attr,
-                                   bool signal_thread)
+                                   bool signal_thread, bool remote)
 {
        struct test_send_signal_kern *skel;
        int pipe_c2p[2], pipe_p2c[2];
        int err = -1, pmu_fd = -1;
+       volatile int j = 0;
        char buf[256];
        pid_t pid;
+       int old_prio;
 
        if (!ASSERT_OK(pipe(pipe_c2p), "pipe_c2p"))
                return;
@@ -39,9 +41,6 @@ static void test_send_signal_common(struct perf_event_attr 
*attr,
        }
 
        if (pid == 0) {
-               int old_prio;
-               volatile int j = 0;
-
                /* install signal handler and notify parent */
                ASSERT_NEQ(signal(SIGUSR1, sigusr1_handler), SIG_ERR, "signal");
 
@@ -52,10 +51,12 @@ static void test_send_signal_common(struct perf_event_attr 
*attr,
                 * that if an interrupt happens, the underlying task
                 * is this process.
                 */
-               errno = 0;
-               old_prio = getpriority(PRIO_PROCESS, 0);
-               ASSERT_OK(errno, "getpriority");
-               ASSERT_OK(setpriority(PRIO_PROCESS, 0, -20), "setpriority");
+               if (!remote) {
+                       errno = 0;
+                       old_prio = getpriority(PRIO_PROCESS, 0);
+                       ASSERT_OK(errno, "getpriority");
+                       ASSERT_OK(setpriority(PRIO_PROCESS, 0, -20), 
"setpriority");
+               }
 
                /* notify parent signal handler is installed */
                ASSERT_EQ(write(pipe_c2p[1], buf, 1), 1, "pipe_write");
@@ -66,9 +67,12 @@ static void test_send_signal_common(struct perf_event_attr 
*attr,
                /* wait a little for signal handler */
                for (int i = 0; i < 1000000000 && !sigusr1_received; i++) {
                        j /= i + j + 1;
-                       if (!attr)
-                               /* trigger the nanosleep tracepoint program. */
-                               usleep(1);
+                       if (remote)
+                               sleep(1);
+                       else
+                               if (!attr)
+                                       /* trigger the nanosleep tracepoint 
program. */
+                                       usleep(1);
                }
 
                buf[0] = sigusr1_received ? '2' : '0';
@@ -79,7 +83,8 @@ static void test_send_signal_common(struct perf_event_attr 
*attr,
                ASSERT_EQ(read(pipe_p2c[0], buf, 1), 1, "pipe_read");
 
                /* restore the old priority */
-               ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), 
"setpriority");
+               if (!remote)
+                       ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), 
"setpriority");
 
                close(pipe_c2p[1]);
                close(pipe_p2c[0]);
@@ -93,6 +98,17 @@ static void test_send_signal_common(struct perf_event_attr 
*attr,
        if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
                goto skel_open_load_failure;
 
+       /* boost with a high priority so we got a higher chance
+        * that if an interrupt happens, the underlying task
+        * is this process.
+        */
+       if (remote) {
+               errno = 0;
+               old_prio = getpriority(PRIO_PROCESS, 0);
+               ASSERT_OK(errno, "getpriority");
+               ASSERT_OK(setpriority(PRIO_PROCESS, 0, -20), "setpriority");
+       }
+
        if (!attr) {
                err = test_send_signal_kern__attach(skel);
                if (!ASSERT_OK(err, "skel_attach")) {
@@ -100,8 +116,12 @@ static void test_send_signal_common(struct perf_event_attr 
*attr,
                        goto destroy_skel;
                }
        } else {
-               pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1 /* cpu */,
-                                -1 /* group id */, 0 /* flags */);
+               if (!remote)
+                       pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1 /* 
cpu */,
+                                        -1 /* group id */, 0 /* flags */);
+               else
+                       pmu_fd = syscall(__NR_perf_event_open, attr, getpid(), 
-1 /* cpu */,
+                                        -1 /* group id */, 0 /* flags */);
                if (!ASSERT_GE(pmu_fd, 0, "perf_event_open")) {
                        err = -1;
                        goto destroy_skel;
@@ -119,11 +139,30 @@ static void test_send_signal_common(struct 
perf_event_attr *attr,
        /* trigger the bpf send_signal */
        skel->bss->signal_thread = signal_thread;
        skel->bss->sig = SIGUSR1;
-       skel->bss->pid = pid;
+       if (!remote) {
+               skel->bss->target_pid = 0;
+               skel->bss->pid = pid;
+       } else {
+               skel->bss->target_pid = pid;
+               skel->bss->pid = getpid();
+       }
 
        /* notify child that bpf program can send_signal now */
        ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");
 
+       /* For the remote test, the BPF program is triggered from this
+        * process but the other process/thread is signaled.
+        */
+       if (remote) {
+               if (!attr) {
+                       for (int i = 0; i < 10; i++)
+                               usleep(1);
+               } else {
+                       for (int i = 0; i < 100000000; i++)
+                               j /= i + 1;
+               }
+       }
+
        /* wait for result */
        err = read(pipe_c2p[0], buf, 1);
        if (!ASSERT_GE(err, 0, "reading pipe"))
@@ -142,18 +181,21 @@ static void test_send_signal_common(struct 
perf_event_attr *attr,
        close(pmu_fd);
 destroy_skel:
        test_send_signal_kern__destroy(skel);
+       /* restore the old priority */
+       if (remote)
+               ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), 
"setpriority");
 skel_open_load_failure:
        close(pipe_c2p[0]);
        close(pipe_p2c[1]);
        wait(NULL);
 }
 
-static void test_send_signal_tracepoint(bool signal_thread)
+static void test_send_signal_tracepoint(bool signal_thread, bool remote)
 {
-       test_send_signal_common(NULL, signal_thread);
+       test_send_signal_common(NULL, signal_thread, remote);
 }
 
-static void test_send_signal_perf(bool signal_thread)
+static void test_send_signal_perf(bool signal_thread, bool remote)
 {
        struct perf_event_attr attr = {
                .freq = 1,
@@ -162,10 +204,10 @@ static void test_send_signal_perf(bool signal_thread)
                .config = PERF_COUNT_SW_CPU_CLOCK,
        };
 
-       test_send_signal_common(&attr, signal_thread);
+       test_send_signal_common(&attr, signal_thread, remote);
 }
 
-static void test_send_signal_nmi(bool signal_thread)
+static void test_send_signal_nmi(bool signal_thread, bool remote)
 {
        struct perf_event_attr attr = {
                .sample_period = 1,
@@ -191,21 +233,35 @@ static void test_send_signal_nmi(bool signal_thread)
                close(pmu_fd);
        }
 
-       test_send_signal_common(&attr, signal_thread);
+       test_send_signal_common(&attr, signal_thread, remote);
 }
 
 void test_send_signal(void)
 {
        if (test__start_subtest("send_signal_tracepoint"))
-               test_send_signal_tracepoint(false);
+               test_send_signal_tracepoint(false, false);
        if (test__start_subtest("send_signal_perf"))
-               test_send_signal_perf(false);
+               test_send_signal_perf(false, false);
        if (test__start_subtest("send_signal_nmi"))
-               test_send_signal_nmi(false);
+               test_send_signal_nmi(false, false);
        if (test__start_subtest("send_signal_tracepoint_thread"))
-               test_send_signal_tracepoint(true);
+               test_send_signal_tracepoint(true, false);
        if (test__start_subtest("send_signal_perf_thread"))
-               test_send_signal_perf(true);
+               test_send_signal_perf(true, false);
        if (test__start_subtest("send_signal_nmi_thread"))
-               test_send_signal_nmi(true);
+               test_send_signal_nmi(true, false);
+
+       /* Signal remote thread and thread group */
+       if (test__start_subtest("send_signal_tracepoint_remote"))
+               test_send_signal_tracepoint(false, true);
+       if (test__start_subtest("send_signal_perf_remote"))
+               test_send_signal_perf(false, true);
+       if (test__start_subtest("send_signal_nmi_remote"))
+               test_send_signal_nmi(false, true);
+       if (test__start_subtest("send_signal_tracepoint_thread_remote"))
+               test_send_signal_tracepoint(true, true);
+       if (test__start_subtest("send_signal_perf_thread_remote"))
+               test_send_signal_perf(true, true);
+       if (test__start_subtest("send_signal_nmi_thread_remote"))
+               test_send_signal_nmi(true, true);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c 
b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
index 92354cd72044..fd6c055377ae 100644
--- a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
@@ -4,7 +4,7 @@
 #include <linux/version.h>
 #include <bpf/bpf_helpers.h>
 
-__u32 sig = 0, pid = 0, status = 0, signal_thread = 0;
+__u32 sig = 0, pid = 0, status = 0, signal_thread = 0, target_pid = 0;
 
 static __always_inline int bpf_send_signal_test(void *ctx)
 {
@@ -14,10 +14,17 @@ static __always_inline int bpf_send_signal_test(void *ctx)
                return 0;
 
        if ((bpf_get_current_pid_tgid() >> 32) == pid) {
-               if (signal_thread)
-                       ret = bpf_send_signal_thread(sig);
-               else
-                       ret = bpf_send_signal(sig);
+               if (signal_thread) {
+                       if (target_pid != 0)
+                               ret = bpf_send_signal_pid(sig, target_pid);
+                       else
+                               ret = bpf_send_signal_thread(sig);
+               } else {
+                       if (target_pid != 0)
+                               ret = bpf_send_signal_tgid(sig, target_pid);
+                       else
+                               ret = bpf_send_signal(sig);
+               }
                if (ret == 0)
                        status = 1;
        }
-- 
2.40.1


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