13 files changed, 250 insertions, 70 deletions

diff --git a/tools/hv/hv_fcopy_uio_daemon.c b/tools/hv/hv_fcopy_uio_daemon.c
index 0198321d14a2..92e8307b2a46 100644
--- a/tools/hv/hv_fcopy_uio_daemon.c
+++ b/tools/hv/hv_fcopy_uio_daemon.c
@@ -35,7 +35,10 @@
 #define WIN8_SRV_MINOR		1
 #define WIN8_SRV_VERSION	(WIN8_SRV_MAJOR << 16 | WIN8_SRV_MINOR)
 
-#define FCOPY_UIO		"/sys/bus/vmbus/devices/eb765408-105f-49b6-b4aa-c123b64d17d4/uio"
+#define FCOPY_DEVICE_PATH(subdir) \
+	"/sys/bus/vmbus/devices/eb765408-105f-49b6-b4aa-c123b64d17d4/" #subdir
+#define FCOPY_UIO_PATH          FCOPY_DEVICE_PATH(uio)
+#define FCOPY_CHANNELS_PATH     FCOPY_DEVICE_PATH(channels)
 
 #define FCOPY_VER_COUNT		1
 static const int fcopy_versions[] = {
@@ -47,9 +50,62 @@ static const int fw_versions[] = {
 	UTIL_FW_VERSION
 };
 
-#define HV_RING_SIZE		0x4000 /* 16KB ring buffer size */
+static uint32_t get_ring_buffer_size(void)
+{
+	char ring_path[PATH_MAX];
+	DIR *dir;
+	struct dirent *entry;
+	struct stat st;
+	uint32_t ring_size = 0;
+	int retry_count = 0;
+
+	/* Find the channel directory */
+	dir = opendir(FCOPY_CHANNELS_PATH);
+	if (!dir) {
+		usleep(100 * 1000); /* Avoid race with kernel, wait 100ms and retry once */
+		dir = opendir(FCOPY_CHANNELS_PATH);
+		if (!dir) {
+			syslog(LOG_ERR, "Failed to open channels directory: %s", strerror(errno));
+			return 0;
+		}
+	}
+
+retry_once:
+	while ((entry = readdir(dir)) != NULL) {
+		if (entry->d_type == DT_DIR && strcmp(entry->d_name, ".") != 0 &&
+		    strcmp(entry->d_name, "..") != 0) {
+			snprintf(ring_path, sizeof(ring_path), "%s/%s/ring",
+				 FCOPY_CHANNELS_PATH, entry->d_name);
+
+			if (stat(ring_path, &st) == 0) {
+				/*
+				 * stat returns size of Tx, Rx rings combined,
+				 * so take half of it for individual ring size.
+				 */
+				ring_size = (uint32_t)st.st_size / 2;
+				syslog(LOG_INFO, "Ring buffer size from %s: %u bytes",
+				       ring_path, ring_size);
+				break;
+			}
+		}
+	}
+
+	if (!ring_size && retry_count == 0) {
+		retry_count = 1;
+		rewinddir(dir);
+		usleep(100 * 1000); /* Wait 100ms and retry once */
+		goto retry_once;
+	}
+
+	closedir(dir);
 
-static unsigned char desc[HV_RING_SIZE];
+	if (!ring_size)
+		syslog(LOG_ERR, "Could not determine ring size");
+
+	return ring_size;
+}
+
+static unsigned char *desc;
 
 static int target_fd;
 static char target_fname[PATH_MAX];
@@ -62,8 +118,11 @@ static int hv_fcopy_create_file(char *file_name, char *path_name, __u32 flags)
 
 	filesize = 0;
 	p = path_name;
-	snprintf(target_fname, sizeof(target_fname), "%s/%s",
-		 path_name, file_name);
+	if (snprintf(target_fname, sizeof(target_fname), "%s/%s",
+		     path_name, file_name) >= sizeof(target_fname)) {
+		syslog(LOG_ERR, "target file name is too long: %s/%s", path_name, file_name);
+		goto done;
+	}
 
 	/*
 	 * Check to see if the path is already in place; if not,
@@ -270,7 +329,7 @@ static void wcstoutf8(char *dest, const __u16 *src, size_t dest_size)
 {
 	size_t len = 0;
 
-	while (len < dest_size) {
+	while (len < dest_size && *src) {
 		if (src[len] < 0x80)
 			dest[len++] = (char)(*src++);
 		else
@@ -282,27 +341,15 @@ static void wcstoutf8(char *dest, const __u16 *src, size_t dest_size)
 
 static int hv_fcopy_start(struct hv_start_fcopy *smsg_in)
 {
-	setlocale(LC_ALL, "en_US.utf8");
-	size_t file_size, path_size;
-	char *file_name, *path_name;
-	char *in_file_name = (char *)smsg_in->file_name;
-	char *in_path_name = (char *)smsg_in->path_name;
-
-	file_size = wcstombs(NULL, (const wchar_t *restrict)in_file_name, 0) + 1;
-	path_size = wcstombs(NULL, (const wchar_t *restrict)in_path_name, 0) + 1;
-
-	file_name = (char *)malloc(file_size * sizeof(char));
-	path_name = (char *)malloc(path_size * sizeof(char));
-
-	if (!file_name || !path_name) {
-		free(file_name);
-		free(path_name);
-		syslog(LOG_ERR, "Can't allocate memory for file name and/or path name");
-		return HV_E_FAIL;
-	}
+	/*
+	 * file_name and path_name should have same length with appropriate
+	 * member of hv_start_fcopy.
+	 */
+	char file_name[W_MAX_PATH], path_name[W_MAX_PATH];
 
-	wcstoutf8(file_name, (__u16 *)in_file_name, file_size);
-	wcstoutf8(path_name, (__u16 *)in_path_name, path_size);
+	setlocale(LC_ALL, "en_US.utf8");
+	wcstoutf8(file_name, smsg_in->file_name, W_MAX_PATH - 1);
+	wcstoutf8(path_name, smsg_in->path_name, W_MAX_PATH - 1);
 
 	return hv_fcopy_create_file(file_name, path_name, smsg_in->copy_flags);
 }
@@ -406,7 +453,7 @@ int main(int argc, char *argv[])
 	int daemonize = 1, long_index = 0, opt, ret = -EINVAL;
 	struct vmbus_br txbr, rxbr;
 	void *ring;
-	uint32_t len = HV_RING_SIZE;
+	uint32_t ring_size, len;
 	char uio_name[NAME_MAX] = {0};
 	char uio_dev_path[PATH_MAX] = {0};
 
@@ -437,7 +484,20 @@ int main(int argc, char *argv[])
 	openlog("HV_UIO_FCOPY", 0, LOG_USER);
 	syslog(LOG_INFO, "starting; pid is:%d", getpid());
 
-	fcopy_get_first_folder(FCOPY_UIO, uio_name);
+	ring_size = get_ring_buffer_size();
+	if (!ring_size) {
+		ret = -ENODEV;
+		goto exit;
+	}
+
+	desc = malloc(ring_size * sizeof(unsigned char));
+	if (!desc) {
+		syslog(LOG_ERR, "malloc failed for desc buffer");
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	fcopy_get_first_folder(FCOPY_UIO_PATH, uio_name);
 	snprintf(uio_dev_path, sizeof(uio_dev_path), "/dev/%s", uio_name);
 	fcopy_fd = open(uio_dev_path, O_RDWR);
 
@@ -445,17 +505,17 @@ int main(int argc, char *argv[])
 		syslog(LOG_ERR, "open %s failed; error: %d %s",
 		       uio_dev_path, errno, strerror(errno));
 		ret = fcopy_fd;
-		goto exit;
+		goto free_desc;
 	}
 
-	ring = vmbus_uio_map(&fcopy_fd, HV_RING_SIZE);
+	ring = vmbus_uio_map(&fcopy_fd, ring_size);
 	if (!ring) {
 		ret = errno;
 		syslog(LOG_ERR, "mmap ringbuffer failed; error: %d %s", ret, strerror(ret));
 		goto close;
 	}
-	vmbus_br_setup(&txbr, ring, HV_RING_SIZE);
-	vmbus_br_setup(&rxbr, (char *)ring + HV_RING_SIZE, HV_RING_SIZE);
+	vmbus_br_setup(&txbr, ring, ring_size);
+	vmbus_br_setup(&rxbr, (char *)ring + ring_size, ring_size);
 
 	rxbr.vbr->imask = 0;
 
@@ -472,7 +532,7 @@ int main(int argc, char *argv[])
 			goto close;
 		}
 
-		len = HV_RING_SIZE;
+		len = ring_size;
 		ret = rte_vmbus_chan_recv_raw(&rxbr, desc, &len);
 		if (unlikely(ret <= 0)) {
 			/* This indicates a failure to communicate (or worse) */
@@ -492,6 +552,8 @@ int main(int argc, char *argv[])
 	}
 close:
 	close(fcopy_fd);
+free_desc:
+	free(desc);
 exit:
 	return ret;
 }
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 52e353368f58..d41ee26b9443 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -735,7 +735,7 @@ struct bpf_object {
 
 	struct usdt_manager *usdt_man;
 
-	struct bpf_map *arena_map;
+	int arena_map_idx;
 	void *arena_data;
 	size_t arena_data_sz;
 
@@ -1517,6 +1517,7 @@ static struct bpf_object *bpf_object__new(const char *path,
 	obj->efile.obj_buf_sz = obj_buf_sz;
 	obj->efile.btf_maps_shndx = -1;
 	obj->kconfig_map_idx = -1;
+	obj->arena_map_idx = -1;
 
 	obj->kern_version = get_kernel_version();
 	obj->state  = OBJ_OPEN;
@@ -2964,7 +2965,7 @@ static int init_arena_map_data(struct bpf_object *obj, struct bpf_map *map,
 	const long page_sz = sysconf(_SC_PAGE_SIZE);
 	size_t mmap_sz;
 
-	mmap_sz = bpf_map_mmap_sz(obj->arena_map);
+	mmap_sz = bpf_map_mmap_sz(map);
 	if (roundup(data_sz, page_sz) > mmap_sz) {
 		pr_warn("elf: sec '%s': declared ARENA map size (%zu) is too small to hold global __arena variables of size %zu\n",
 			sec_name, mmap_sz, data_sz);
@@ -3038,12 +3039,12 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
 		if (map->def.type != BPF_MAP_TYPE_ARENA)
 			continue;
 
-		if (obj->arena_map) {
+		if (obj->arena_map_idx >= 0) {
 			pr_warn("map '%s': only single ARENA map is supported (map '%s' is also ARENA)\n",
-				map->name, obj->arena_map->name);
+				map->name, obj->maps[obj->arena_map_idx].name);
 			return -EINVAL;
 		}
-		obj->arena_map = map;
+		obj->arena_map_idx = i;
 
 		if (obj->efile.arena_data) {
 			err = init_arena_map_data(obj, map, ARENA_SEC, obj->efile.arena_data_shndx,
@@ -3053,7 +3054,7 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
 				return err;
 		}
 	}
-	if (obj->efile.arena_data && !obj->arena_map) {
+	if (obj->efile.arena_data && obj->arena_map_idx < 0) {
 		pr_warn("elf: sec '%s': to use global __arena variables the ARENA map should be explicitly declared in SEC(\".maps\")\n",
 			ARENA_SEC);
 		return -ENOENT;
@@ -4583,8 +4584,13 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 	if (shdr_idx == obj->efile.arena_data_shndx) {
 		reloc_desc->type = RELO_DATA;
 		reloc_desc->insn_idx = insn_idx;
-		reloc_desc->map_idx = obj->arena_map - obj->maps;
+		reloc_desc->map_idx = obj->arena_map_idx;
 		reloc_desc->sym_off = sym->st_value;
+
+		map = &obj->maps[obj->arena_map_idx];
+		pr_debug("prog '%s': found arena map %d (%s, sec %d, off %zu) for insn %u\n",
+			 prog->name, obj->arena_map_idx, map->name, map->sec_idx,
+			 map->sec_offset, insn_idx);
 		return 0;
 	}
 
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index d967ac001498..67d76f3a1dce 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -224,6 +224,7 @@ static bool is_rust_noreturn(const struct symbol *func)
 	       str_ends_with(func->name, "_4core9panicking14panic_explicit")				||
 	       str_ends_with(func->name, "_4core9panicking14panic_nounwind")				||
 	       str_ends_with(func->name, "_4core9panicking18panic_bounds_check")			||
+	       str_ends_with(func->name, "_4core9panicking18panic_nounwind_fmt")			||
 	       str_ends_with(func->name, "_4core9panicking19assert_failed_inner")			||
 	       str_ends_with(func->name, "_4core9panicking30panic_null_pointer_dereference")		||
 	       str_ends_with(func->name, "_4core9panicking36panic_misaligned_pointer_dereference")	||
diff --git a/tools/testing/selftests/bpf/prog_tests/recursive_attach.c b/tools/testing/selftests/bpf/prog_tests/recursive_attach.c
index 8100509e561b..0ffa01d54ce2 100644
--- a/tools/testing/selftests/bpf/prog_tests/recursive_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/recursive_attach.c
@@ -149,3 +149,70 @@ close_prog:
 	fentry_recursive_target__destroy(target_skel);
 	fentry_recursive__destroy(tracing_skel);
 }
+
+static void *fentry_target_test_run(void *arg)
+{
+	for (;;) {
+		int prog_fd = __atomic_load_n((int *)arg, __ATOMIC_SEQ_CST);
+		LIBBPF_OPTS(bpf_test_run_opts, topts);
+		int err;
+
+		if (prog_fd == -1)
+			break;
+		err = bpf_prog_test_run_opts(prog_fd, &topts);
+		if (!ASSERT_OK(err, "fentry_target test_run"))
+			break;
+	}
+
+	return NULL;
+}
+
+void test_fentry_attach_stress(void)
+{
+	struct fentry_recursive_target *target_skel = NULL;
+	struct fentry_recursive *tracing_skel = NULL;
+	struct bpf_program *prog;
+	int err, i, tgt_prog_fd;
+	pthread_t thread;
+
+	target_skel = fentry_recursive_target__open_and_load();
+	if (!ASSERT_OK_PTR(target_skel,
+			   "fentry_recursive_target__open_and_load"))
+		goto close_prog;
+	tgt_prog_fd = bpf_program__fd(target_skel->progs.fentry_target);
+	err = pthread_create(&thread, NULL,
+			     fentry_target_test_run, &tgt_prog_fd);
+	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+		goto close_prog;
+
+	for (i = 0; i < 1000; i++) {
+		tracing_skel = fentry_recursive__open();
+		if (!ASSERT_OK_PTR(tracing_skel, "fentry_recursive__open"))
+			goto stop_thread;
+
+		prog = tracing_skel->progs.recursive_attach;
+		err = bpf_program__set_attach_target(prog, tgt_prog_fd,
+						     "fentry_target");
+		if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+			goto stop_thread;
+
+		err = fentry_recursive__load(tracing_skel);
+		if (!ASSERT_OK(err, "fentry_recursive__load"))
+			goto stop_thread;
+
+		err = fentry_recursive__attach(tracing_skel);
+		if (!ASSERT_OK(err, "fentry_recursive__attach"))
+			goto stop_thread;
+
+		fentry_recursive__destroy(tracing_skel);
+		tracing_skel = NULL;
+	}
+
+stop_thread:
+	__atomic_store_n(&tgt_prog_fd, -1, __ATOMIC_SEQ_CST);
+	err = pthread_join(thread, NULL);
+	ASSERT_OK(err, "pthread_join");
+close_prog:
+	fentry_recursive__destroy(tracing_skel);
+	fentry_recursive_target__destroy(target_skel);
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/snprintf.c b/tools/testing/selftests/bpf/prog_tests/snprintf.c
index 4be6fdb78c6a..594441acb707 100644
--- a/tools/testing/selftests/bpf/prog_tests/snprintf.c
+++ b/tools/testing/selftests/bpf/prog_tests/snprintf.c
@@ -116,6 +116,8 @@ static void test_snprintf_negative(void)
 	ASSERT_ERR(load_single_snprintf("%llc"), "invalid specifier 7");
 	ASSERT_ERR(load_single_snprintf("\x80"), "non ascii character");
 	ASSERT_ERR(load_single_snprintf("\x1"), "non printable character");
+	ASSERT_ERR(load_single_snprintf("%p%"), "invalid specifier 8");
+	ASSERT_ERR(load_single_snprintf("%s%"), "invalid specifier 9");
 }
 
 void test_snprintf(void)
diff --git a/tools/testing/selftests/drivers/net/lib/py/load.py b/tools/testing/selftests/drivers/net/lib/py/load.py
index d9c10613ae67..44151b7b1a24 100644
--- a/tools/testing/selftests/drivers/net/lib/py/load.py
+++ b/tools/testing/selftests/drivers/net/lib/py/load.py
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
+import re
 import time
 
 from lib.py import ksft_pr, cmd, ip, rand_port, wait_port_listen
@@ -10,12 +11,11 @@ class GenerateTraffic:
 
         self.env = env
 
-        if port is None:
-            port = rand_port()
-        self._iperf_server = cmd(f"iperf3 -s -1 -p {port}", background=True)
-        wait_port_listen(port)
+        self.port = rand_port() if port is None else port
+        self._iperf_server = cmd(f"iperf3 -s -1 -p {self.port}", background=True)
+        wait_port_listen(self.port)
         time.sleep(0.1)
-        self._iperf_client = cmd(f"iperf3 -c {env.addr} -P 16 -p {port} -t 86400",
+        self._iperf_client = cmd(f"iperf3 -c {env.addr} -P 16 -p {self.port} -t 86400",
                                  background=True, host=env.remote)
 
         # Wait for traffic to ramp up
@@ -56,3 +56,16 @@ class GenerateTraffic:
             ksft_pr(">> Server:")
             ksft_pr(self._iperf_server.stdout)
             ksft_pr(self._iperf_server.stderr)
+        self._wait_client_stopped()
+
+    def _wait_client_stopped(self, sleep=0.005, timeout=5):
+        end = time.monotonic() + timeout
+
+        live_port_pattern = re.compile(fr":{self.port:04X} 0[^6] ")
+
+        while time.monotonic() < end:
+            data = cmd("cat /proc/net/tcp*", host=self.env.remote).stdout
+            if not live_port_pattern.search(data):
+                return
+            time.sleep(sleep)
+        raise Exception(f"Waiting for client to stop timed out after {timeout}s")
diff --git a/tools/testing/selftests/futex/include/futex2test.h b/tools/testing/selftests/futex/include/futex2test.h
index ea79662405bc..1f625b39948a 100644
--- a/tools/testing/selftests/futex/include/futex2test.h
+++ b/tools/testing/selftests/futex/include/futex2test.h
@@ -4,6 +4,7 @@
  *
  * Copyright 2021 Collabora Ltd.
  */
+#include <linux/time_types.h>
 #include <stdint.h>
 
 #define u64_to_ptr(x) ((void *)(uintptr_t)(x))
@@ -65,7 +66,12 @@ struct futex32_numa {
 static inline int futex_waitv(volatile struct futex_waitv *waiters, unsigned long nr_waiters,
 			      unsigned long flags, struct timespec *timo, clockid_t clockid)
 {
-	return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, timo, clockid);
+		struct __kernel_timespec ts = {
+			.tv_sec = timo->tv_sec,
+			.tv_nsec = timo->tv_nsec,
+		};
+
+		return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, &ts, clockid);
 }
 
 /*
diff --git a/tools/testing/selftests/net/mptcp/Makefile b/tools/testing/selftests/net/mptcp/Makefile
index e47788bfa671..4c7e51336ab2 100644
--- a/tools/testing/selftests/net/mptcp/Makefile
+++ b/tools/testing/selftests/net/mptcp/Makefile
@@ -4,7 +4,8 @@ top_srcdir = ../../../../..
 
 CFLAGS += -Wall -Wl,--no-as-needed -O2 -g -I$(top_srcdir)/usr/include $(KHDR_INCLUDES)
 
-TEST_PROGS := mptcp_connect.sh pm_netlink.sh mptcp_join.sh diag.sh \
+TEST_PROGS := mptcp_connect.sh mptcp_connect_mmap.sh mptcp_connect_sendfile.sh \
+	      mptcp_connect_checksum.sh pm_netlink.sh mptcp_join.sh diag.sh \
 	      simult_flows.sh mptcp_sockopt.sh userspace_pm.sh
 
 TEST_GEN_FILES = mptcp_connect pm_nl_ctl mptcp_sockopt mptcp_inq mptcp_diag
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect_checksum.sh b/tools/testing/selftests/net/mptcp/mptcp_connect_checksum.sh
new file mode 100755
index 000000000000..ce93ec2f107f
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect_checksum.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+MPTCP_LIB_KSFT_TEST="$(basename "${0}" .sh)" \
+	"$(dirname "${0}")/mptcp_connect.sh" -C "${@}"
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect_mmap.sh b/tools/testing/selftests/net/mptcp/mptcp_connect_mmap.sh
new file mode 100755
index 000000000000..5dd30f9394af
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect_mmap.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+MPTCP_LIB_KSFT_TEST="$(basename "${0}" .sh)" \
+	"$(dirname "${0}")/mptcp_connect.sh" -m mmap "${@}"
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect_sendfile.sh b/tools/testing/selftests/net/mptcp/mptcp_connect_sendfile.sh
new file mode 100755
index 000000000000..1d16fb1cc9bb
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect_sendfile.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+MPTCP_LIB_KSFT_TEST="$(basename "${0}" .sh)" \
+	"$(dirname "${0}")/mptcp_connect.sh" -m sendfile "${@}"
diff --git a/tools/testing/selftests/net/netfilter/conntrack_clash.sh b/tools/testing/selftests/net/netfilter/conntrack_clash.sh
index 3712c1b9b38b..606a43a60f73 100755
--- a/tools/testing/selftests/net/netfilter/conntrack_clash.sh
+++ b/tools/testing/selftests/net/netfilter/conntrack_clash.sh
@@ -93,32 +93,28 @@ ping_test()
 run_one_clash_test()
 {
 	local ns="$1"
-	local daddr="$2"
-	local dport="$3"
+	local ctns="$2"
+	local daddr="$3"
+	local dport="$4"
 	local entries
 	local cre
 
 	if ! ip netns exec "$ns" ./udpclash $daddr $dport;then
-		echo "FAIL: did not receive expected number of replies for $daddr:$dport"
-		ret=1
-		return 1
+		echo "INFO: did not receive expected number of replies for $daddr:$dport"
+		ip netns exec "$ctns" conntrack -S
+		# don't fail: check if clash resolution triggered after all.
 	fi
 
-	entries=$(conntrack -S | wc -l)
-	cre=$(conntrack -S | grep -v "clash_resolve=0" | wc -l)
+	entries=$(ip netns exec "$ctns" conntrack -S | wc -l)
+	cre=$(ip netns exec "$ctns" conntrack -S | grep "clash_resolve=0" | wc -l)
 
-	if [ "$cre" -ne "$entries" ] ;then
+	if [ "$cre" -ne "$entries" ];then
 		clash_resolution_active=1
 		return 0
 	fi
 
-	# 1 cpu -> parallel insertion impossible
-	if [ "$entries" -eq 1 ]; then
-		return 0
-	fi
-
-	# not a failure: clash resolution logic did not trigger, but all replies
-	# were received.  With right timing, xmit completed sequentially and
+	# not a failure: clash resolution logic did not trigger.
+	# With right timing, xmit completed sequentially and
 	# no parallel insertion occurs.
 	return $ksft_skip
 }
@@ -126,20 +122,23 @@ run_one_clash_test()
 run_clash_test()
 {
 	local ns="$1"
-	local daddr="$2"
-	local dport="$3"
+	local ctns="$2"
+	local daddr="$3"
+	local dport="$4"
+	local softerr=0
 
 	for i in $(seq 1 10);do
-		run_one_clash_test "$ns" "$daddr" "$dport"
+		run_one_clash_test "$ns" "$ctns" "$daddr" "$dport"
 		local rv=$?
 		if [ $rv -eq 0 ];then
 			echo "PASS: clash resolution test for $daddr:$dport on attempt $i"
 			return 0
-		elif [ $rv -eq 1 ];then
-			echo "FAIL: clash resolution test for $daddr:$dport on attempt $i"
-			return 1
+		elif [ $rv -eq $ksft_skip ]; then
+			softerr=1
 		fi
 	done
+
+	[ $softerr -eq 1 ] && echo "SKIP: clash resolution for $daddr:$dport did not trigger"
 }
 
 ip link add veth0 netns "$nsclient1" type veth peer name veth0 netns "$nsrouter"
@@ -161,11 +160,11 @@ spawn_servers "$nsclient2"
 
 # exercise clash resolution with nat:
 # nsrouter is supposed to dnat to 10.0.2.1:900{0,1,2,3}.
-run_clash_test "$nsclient1" 10.0.1.99 "$dport"
+run_clash_test "$nsclient1" "$nsrouter" 10.0.1.99 "$dport"
 
 # exercise clash resolution without nat.
 load_simple_ruleset "$nsclient2"
-run_clash_test "$nsclient2" 127.0.0.1 9001
+run_clash_test "$nsclient2" "$nsclient2" 127.0.0.1 9001
 
 if [ $clash_resolution_active -eq 0 ];then
 	[ "$ret" -eq 0 ] && ret=$ksft_skip
diff --git a/tools/testing/selftests/sched_ext/exit.c b/tools/testing/selftests/sched_ext/exit.c
index 9451782689de..ee25824b1cbe 100644
--- a/tools/testing/selftests/sched_ext/exit.c
+++ b/tools/testing/selftests/sched_ext/exit.c
@@ -22,6 +22,14 @@ static enum scx_test_status run(void *ctx)
 		struct bpf_link *link;
 		char buf[16];
 
+		/*
+		 * On single-CPU systems, ops.select_cpu() is never
+		 * invoked, so skip this test to avoid getting stuck
+		 * indefinitely.
+		 */
+		if (tc == EXIT_SELECT_CPU && libbpf_num_possible_cpus() == 1)
+			continue;
+
 		skel = exit__open();
 		SCX_ENUM_INIT(skel);
 		skel->rodata->exit_point = tc;