On 3/22/24 7:08 AM, Daniel Hodges wrote:
This patch adds a led trigger that interfaces with the bpf subsystem. It
allows for BPF programs to control LED activity through calling bpf
kfuncs. This functionality is useful in giving users a physical
indication that a BPF program has performed an operation such as
handling a packet or probe point.
Signed-off-by: Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>
---
drivers/leds/trigger/Kconfig | 10 +++++
drivers/leds/trigger/Makefile | 1 +
drivers/leds/trigger/ledtrig-bpf.c | 72 ++++++++++++++++++++++++++++++
3 files changed, 83 insertions(+)
create mode 100644 drivers/leds/trigger/ledtrig-bpf.c
diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index d11d80176fc0..30b0fd3847be 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -152,4 +152,14 @@ config LEDS_TRIGGER_TTY
When build as a module this driver will be called ledtrig-tty.
+config LEDS_TRIGGER_BPF
+ tristate "LED BPF Trigger"
+ depends on BPF
+ depends on BPF_SYSCALL
+ help
+ This allows LEDs to be controlled by the BPF subsystem. This trigger
+ must be used with a loaded BPF program in order to control LED state.
+ BPF programs can control LED state with kfuncs.
+ If unsure, say N.
+
endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index 25c4db97cdd4..ac47128d406c 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -16,3 +16,4 @@ obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
obj-$(CONFIG_LEDS_TRIGGER_PATTERN) += ledtrig-pattern.o
obj-$(CONFIG_LEDS_TRIGGER_AUDIO) += ledtrig-audio.o
obj-$(CONFIG_LEDS_TRIGGER_TTY) += ledtrig-tty.o
+obj-$(CONFIG_LEDS_TRIGGER_BPF) += ledtrig-bpf.o
diff --git a/drivers/leds/trigger/ledtrig-bpf.c b/drivers/leds/trigger/ledtrig-bpf.c
new file mode 100644
index 000000000000..e3b0b8281b70
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-bpf.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LED BPF Trigger
+ *
+ * Author: Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/btf_ids.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+
+
+DEFINE_LED_TRIGGER(ledtrig_bpf);
+
+__bpf_hook_start()
+
+__bpf_kfunc void bpf_ledtrig_blink(unsigned long delay_on, unsigned long delay_off, int invert)
+{
+ led_trigger_blink_oneshot(ledtrig_bpf, delay_on, delay_off, invert);
+}
+__bpf_hook_end();
+
+BTF_SET8_START(ledtrig_bpf_kfunc_ids)
+BTF_ID_FLAGS(func, bpf_ledtrig_blink)
+BTF_SET8_END(ledtrig_bpf_kfunc_ids)
+
+static const struct btf_kfunc_id_set ledtrig_bpf_kfunc_set = {
+ .owner = THIS_MODULE,
+ .set = &ledtrig_bpf_kfunc_ids,
+};
+
+static int init_bpf(void)
+{
+ int ret;
+
+ ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
+ &ledtrig_bpf_kfunc_set);
If you add the kfunc to BPF_PROG_TYPE_UNSPEC, then
you do not need to add to the following prog types
since the kernel will search BPF_PROG_TYPE_UNSPEC
for all prog types.
But if the kfunc only intends to be used for the following
program types, I suggest removing the above BPF_PROG_TYPE_UNSPEC
registration.
+ ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
+ &ledtrig_bpf_kfunc_set);
+ ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL,
+ &ledtrig_bpf_kfunc_set);
+ ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SK_SKB,
+ &ledtrig_bpf_kfunc_set);
+ ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
+ &ledtrig_bpf_kfunc_set);
+ ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_ACT,
+ &ledtrig_bpf_kfunc_set);
+ return ret;
+}
+
+static int ledtrig_bpf_init(void)
+{
+ led_trigger_register_simple("bpf", &ledtrig_bpf);
+
+ return init_bpf();
+}
+
+static void __exit ledtrig_bpf_exit(void)
+{
+ led_trigger_unregister_simple(ledtrig_bpf);
+}
+
+module_init(ledtrig_bpf_init);
+module_exit(ledtrig_bpf_exit);
+
+MODULE_AUTHOR("Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>");
+MODULE_DESCRIPTION("BPF LED trigger");
+MODULE_LICENSE("GPL v2");
