selftests/bpf: convert lirc_mode2 to prog_tests and extend coverage

While porting, extend coverage of the BPF_LIRC_MODE2 attach/detach/
query API:

 - bpf_prog_attach() with invalid flags is rejected with -EINVAL
   and does not attach the program
 - bpf_prog_query() with invalid flags is rejected with -EINVAL
   without disturbing existing attachments
 - bpf_prog_query() reports the correct program id, not just count,
   at each step, via bpf_prog_get_info_by_fd()
 - a lirc chardev can hold more than one attached program: load a
   second, independent instance, attach it alongside the first,
   confirm both are reported by bpf_prog_query(), then detach it
   without disturbing the first program's attachment
 - detaching an already-detached program consistently fails with
   -ENOENT, for both the first and second program

Signed-off-by: Sean Young <sean@mess.org>
Assisted-by: Claude:claude-sonnet-5

Author: seanyoung

tools/testing/selftests/bpf/.gitignore

@@ -17,7 +17,6 @@ test_verifier_log
 feature
 urandom_read
 test_sockmap
-test_lirc_mode2_user
 flow_dissector_load
 test_tcpnotify_user
 test_libbpf

tools/testing/selftests/bpf/Makefile

@@ -123,7 +123,6 @@ TEST_FILES = xsk_prereqs.sh $(wildcard progs/btf_dump_test_case_*.c)
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \
-	test_lirc_mode2.sh \
 	test_bpftool_build.sh \
 	test_doc_build.sh \
 	test_xsk.sh \
@@ -141,7 +140,6 @@ TEST_GEN_PROGS_EXTENDED = \
 	bench \
 	flow_dissector_load \
 	test_cpp \
-	test_lirc_mode2_user \
 	veristat \
 	xdp_features \
 	xdp_hw_metadata \
@@ -338,7 +336,6 @@ $(OUTPUT)/test_sockmap: $(CGROUP_HELPERS) $(TESTING_HELPERS)
 $(OUTPUT)/test_tcpnotify_user: $(CGROUP_HELPERS) $(TESTING_HELPERS) $(TRACE_HELPERS)
 $(OUTPUT)/test_sock_fields: $(CGROUP_HELPERS) $(TESTING_HELPERS)
 $(OUTPUT)/test_tag: $(TESTING_HELPERS)
-$(OUTPUT)/test_lirc_mode2_user: $(TESTING_HELPERS)
 $(OUTPUT)/flow_dissector_load: $(TESTING_HELPERS)
 $(OUTPUT)/test_maps: $(TESTING_HELPERS)
 $(OUTPUT)/test_verifier: $(TESTING_HELPERS) $(CAP_HELPERS) $(UNPRIV_HELPERS)

tools/testing/selftests/bpf/prog_tests/lirc_mode2.c

@@ -0,0 +1,334 @@
+// SPDX-License-Identifier: GPL-2.0
+// test ir decoder
+//
+// Copyright (C) 2018 Sean Young <sean@mess.org>
+
+// A lirc chardev is a device representing a consumer IR (cir) device which
+// can receive infrared signals from remote control and/or transmit IR.
+//
+// IR is sent as a series of pulses and space somewhat like morse code. The
+// BPF program can decode this into scancodes so that rc-core can translate
+// this into input key codes using the rc keymap.
+//
+// This test works by sending IR over rc-loopback, so the IR is processed by
+// BPF and then decoded into scancodes. The lirc chardev must be the one
+// associated with rc-loopback, see the output of ir-keytable(1).
+//
+// The following CONFIG options must be enabled for the test to succeed:
+// CONFIG_RC_CORE=y
+// CONFIG_BPF_LIRC_MODE2=y
+// CONFIG_RC_LOOPBACK=y
+// CONFIG_LIRC=y
+
+#include <linux/input.h>
+#include <linux/lirc.h>
+#include <glob.h>
+#include <limits.h>
+#include <poll.h>
+#include <test_progs.h>
+#include "lirc_mode2.skel.h"
+
+/*
+ * Read the DEVNAME= line out of the first uevent file that matches
+ * pattern, and turn it into a /dev/<name> path.
+ */
+static bool find_devname(const char *pattern, char *path, size_t path_sz)
+{
+	glob_t gl = {};
+	bool found = false;
+	FILE *f;
+
+	if (glob(pattern, 0, NULL, &gl) || gl.gl_pathc == 0)
+		goto out;
+
+	f = fopen(gl.gl_pathv[0], "r");
+	if (!f)
+		goto out;
+
+	char line[256];
+
+	while (fgets(line, sizeof(line), f)) {
+		char *val;
+
+		if (strncmp(line, "DEVNAME=", 8))
+			continue;
+
+		val = line + 8;
+		val[strcspn(val, "\n")] = '\0';
+		snprintf(path, path_sz, "/dev/%s", val);
+		found = true;
+		break;
+	}
+
+	fclose(f);
+out:
+	globfree(&gl);
+	return found;
+}
+
+/* Load rc-loopback and find the lirc and input chardevs it created. */
+static bool find_loopback_devices(char *lirc_path, char *input_path,
+				  size_t path_sz)
+{
+	glob_t gl = {};
+	bool found = false;
+
+	/* Ignore failure, we check for the resulting devices below. */
+	SYS_NOFAIL("modprobe rc-loopback > /dev/null 2>&1");
+
+	if (glob("/sys/class/rc/rc*", 0, NULL, &gl))
+		goto out;
+
+	for (size_t i = 0; i < gl.gl_pathc; i++) {
+		const char *rcdir = gl.gl_pathv[i];
+		char uevent_path[PATH_MAX];
+		char uevent[4096];
+		char pattern[PATH_MAX];
+		FILE *f;
+		size_t n;
+
+		snprintf(uevent_path, sizeof(uevent_path), "%s/uevent", rcdir);
+		f = fopen(uevent_path, "r");
+		if (!f)
+			continue;
+		n = fread(uevent, 1, sizeof(uevent) - 1, f);
+		fclose(f);
+		uevent[n] = '\0';
+
+		if (!strstr(uevent, "DRV_NAME=rc-loopback"))
+			continue;
+
+		snprintf(pattern, sizeof(pattern), "%s/lirc*/uevent", rcdir);
+		if (!find_devname(pattern, lirc_path, path_sz))
+			continue;
+
+		snprintf(pattern, sizeof(pattern), "%s/input*/event*/uevent", rcdir);
+		if (!find_devname(pattern, input_path, path_sz))
+			continue;
+
+		found = true;
+		break;
+	}
+
+out:
+	if (!found) {
+		fprintf(stderr, "No rc devices found\n");
+		fprintf(stderr, "Enable CONFIG_RC_LOOPBACK and CONFIG_BPF_LIRC_MODE2\n");
+	}
+
+	globfree(&gl);
+	return found;
+}
+
+void test_lirc_mode2(void)
+{
+	char lirc_path[PATH_MAX], input_path[PATH_MAX];
+	int lircfd = -1, inputfd = -1, progfd, progfd2 = -1;
+	struct lirc_mode2 *skel = NULL, *skel2 = NULL;
+	__u32 prog_ids[10], prog_flags[10], prog_cnt;
+	struct bpf_prog_info info;
+	__u32 info_len, prog_id, prog_id2;
+	int testir1 = 0x8ead;	/* keydown flag (0x8000) | scancode 0xead */
+	int testir2 = 0x4081;	/* pointer_rel flag (0x4000) | rel_x=1 | rel_y=1 */
+	struct input_event event;
+	struct pollfd pfd = {};
+	int ret;
+
+	if (getuid() != 0) {
+		test__skip();
+		return;
+	}
+
+	if (!find_loopback_devices(lirc_path, input_path, sizeof(lirc_path))) {
+		test__skip();
+		return;
+	}
+
+	skel = lirc_mode2__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "lirc_mode2__open_and_load"))
+		return;
+
+	progfd = bpf_program__fd(skel->progs.bpf_decoder);
+
+	memset(&info, 0, sizeof(info));
+	info_len = sizeof(info);
+	ret = bpf_prog_get_info_by_fd(progfd, &info, &info_len);
+	if (!ASSERT_OK(ret, "get first program's info"))
+		goto out;
+	prog_id = info.id;
+
+	lircfd = open(lirc_path, O_RDWR | O_NONBLOCK);
+	if (!ASSERT_GE(lircfd, 0, "open lirc device"))
+		goto out;
+
+	/* Try to detach it before it was ever attached, should fail. */
+	ret = bpf_prog_detach2(progfd, lircfd, BPF_LIRC_MODE2);
+	if (!ASSERT_EQ(ret, -ENOENT, "detach unattached program"))
+		goto out;
+
+	inputfd = open(input_path, O_RDONLY | O_NONBLOCK);
+	if (!ASSERT_GE(inputfd, 0, "open input device"))
+		goto out;
+
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 0, prog_flags, prog_ids,
+			     &prog_cnt);
+	if (!ASSERT_OK(ret, "query programs before attach"))
+		goto out;
+	if (!ASSERT_EQ(prog_cnt, 0, "no programs should be attached yet"))
+		goto out;
+
+	/* Invalid attach flags must be rejected, and must not attach. */
+	ret = bpf_prog_attach(progfd, lircfd, BPF_LIRC_MODE2, 1);
+	if (!ASSERT_EQ(ret, -EINVAL, "attach with invalid flags"))
+		goto out;
+
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 0, prog_flags, prog_ids,
+			     &prog_cnt);
+	if (!ASSERT_OK(ret, "query programs after rejected attach"))
+		goto out;
+	if (!ASSERT_EQ(prog_cnt, 0, "rejected attach should not attach"))
+		goto out;
+
+	ret = bpf_prog_attach(progfd, lircfd, BPF_LIRC_MODE2, 0);
+	if (!ASSERT_OK(ret, "attach program to lirc device"))
+		goto out;
+
+	/* Invalid query flags must be rejected too, without upsetting state. */
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 1, prog_flags, prog_ids,
+			     &prog_cnt);
+	ASSERT_EQ(ret, -EINVAL, "query with invalid flags");
+
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 0, prog_flags, prog_ids,
+			     &prog_cnt);
+	if (!ASSERT_OK(ret, "query programs after attach"))
+		goto out_detach;
+	if (!ASSERT_EQ(prog_cnt, 1, "one program should be attached"))
+		goto out_detach;
+	ASSERT_EQ(prog_ids[0], prog_id, "queried id should match attached program");
+
+	/* Write raw IR */
+	ret = write(lircfd, &testir1, sizeof(testir1));
+	if (!ASSERT_EQ(ret, sizeof(testir1), "send test IR message 1"))
+		goto out_detach;
+
+	pfd.fd = inputfd;
+	pfd.events = POLLIN;
+
+	for (;;) {
+		poll(&pfd, 1, 100);
+
+		/* Read decoded IR */
+		ret = read(inputfd, &event, sizeof(event));
+		if (!ASSERT_EQ(ret, sizeof(event), "read decoded IR 1"))
+			goto out_detach;
+
+		if (event.type == EV_MSC && event.code == MSC_SCAN &&
+		    event.value == 0xead)
+			break;
+	}
+
+	/* Write raw IR */
+	ret = write(lircfd, &testir2, sizeof(testir2));
+	if (!ASSERT_EQ(ret, sizeof(testir2), "send test IR message 2"))
+		goto out_detach;
+
+	for (;;) {
+		poll(&pfd, 1, 100);
+
+		/* Read decoded IR */
+		ret = read(inputfd, &event, sizeof(event));
+		if (!ASSERT_EQ(ret, sizeof(event), "read decoded IR 2"))
+			goto out_detach;
+
+		if (event.type == EV_REL && event.code == REL_Y &&
+		    event.value == 1)
+			break;
+	}
+
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 0, prog_flags, prog_ids,
+			     &prog_cnt);
+	if (!ASSERT_OK(ret, "query programs after IR was decoded"))
+		goto out_detach;
+	if (!ASSERT_EQ(prog_cnt, 1, "one program should still be attached"))
+		goto out_detach;
+
+	/*
+	 * The lirc chardev can hold more than one attached program at once.
+	 * Load a second, independent instance and check it can be attached
+	 * alongside the first, queried, and then detached on its own
+	 * without disturbing the first program's attachment.
+	 */
+	skel2 = lirc_mode2__open_and_load();
+	if (!ASSERT_OK_PTR(skel2, "lirc_mode2__open_and_load (2nd)"))
+		goto out_detach;
+
+	progfd2 = bpf_program__fd(skel2->progs.bpf_decoder);
+
+	memset(&info, 0, sizeof(info));
+	info_len = sizeof(info);
+	ret = bpf_prog_get_info_by_fd(progfd2, &info, &info_len);
+	if (!ASSERT_OK(ret, "get second program's info"))
+		goto out_detach;
+	prog_id2 = info.id;
+
+	ret = bpf_prog_attach(progfd2, lircfd, BPF_LIRC_MODE2, 0);
+	if (!ASSERT_OK(ret, "attach second program to lirc device"))
+		goto out_detach;
+
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 0, prog_flags, prog_ids,
+			     &prog_cnt);
+	if (!ASSERT_OK(ret, "query programs after second attach"))
+		goto out_detach2;
+	if (!ASSERT_EQ(prog_cnt, 2, "two programs should be attached"))
+		goto out_detach2;
+	ASSERT_TRUE((prog_ids[0] == prog_id && prog_ids[1] == prog_id2) ||
+		    (prog_ids[0] == prog_id2 && prog_ids[1] == prog_id),
+		    "queried ids should be the two attached programs");
+
+	/* Detach the second program; the first should remain attached. */
+	ret = bpf_prog_detach2(progfd2, lircfd, BPF_LIRC_MODE2);
+	if (!ASSERT_OK(ret, "detach second program"))
+		goto out_detach2;
+
+	/* Detaching an already-detached program should now fail. */
+	ret = bpf_prog_detach2(progfd2, lircfd, BPF_LIRC_MODE2);
+	ASSERT_EQ(ret, -ENOENT, "detach second program again");
+
+	prog_cnt = ARRAY_SIZE(prog_ids);
+	ret = bpf_prog_query(lircfd, BPF_LIRC_MODE2, 0, prog_flags, prog_ids,
+			     &prog_cnt);
+	if (!ASSERT_OK(ret, "query programs after second detach"))
+		goto out_detach;
+	if (!ASSERT_EQ(prog_cnt, 1, "one program should remain attached"))
+		goto out_detach;
+	ASSERT_EQ(prog_ids[0], prog_id, "remaining program should be the first one");
+
+out_detach:
+	/* Let's try detaching it now it is actually attached. */
+	ret = bpf_prog_detach2(progfd, lircfd, BPF_LIRC_MODE2);
+	ASSERT_OK(ret, "detach program from lirc device");
+
+	/* Detaching it again should now fail the same way. */
+	ret = bpf_prog_detach2(progfd, lircfd, BPF_LIRC_MODE2);
+	ASSERT_EQ(ret, -ENOENT, "detach program from lirc device again");
+	goto out;
+
+out_detach2:
+	/* Best-effort cleanup of the second program before bailing out. */
+	bpf_prog_detach2(progfd2, lircfd, BPF_LIRC_MODE2);
+	goto out_detach;
+
+out:
+	if (inputfd >= 0)
+		close(inputfd);
+	if (lircfd >= 0)
+		close(lircfd);
+	lirc_mode2__destroy(skel2);
+	lirc_mode2__destroy(skel);
+}

tools/testing/selftests/bpf/progs/lirc_mode2.c

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+// test ir decoder
+//
+// Copyright (C) 2018 Sean Young <sean@mess.org>
+
+#include <linux/bpf.h>
+#include <linux/lirc.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("lirc_mode2")
+int bpf_decoder(unsigned int *sample)
+{
+	if (LIRC_IS_PULSE(*sample)) {
+		unsigned int duration = LIRC_VALUE(*sample);
+
+		/*
+		 * Flag bits picked deliberately low: rc-loopback simulates
+		 * a receiver overflow for any pulse over MS_TO_US(50) (see
+		 * loop_tx_ir() in rc-loopback.c), which would silently
+		 * swallow the sample before it ever reaches this decoder.
+		 */
+		if (duration & 0x8000)
+			bpf_rc_keydown(sample, 0x40, duration & 0x3fff, 0);
+		if (duration & 0x4000)
+			bpf_rc_pointer_rel(sample, (duration >> 7) & 0x7f,
+					   duration & 0x7f);
+	}
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";