Everything should be available in the selftest part of the tree, but
providing an example without uhid and hidraw will be more easy to
follow for users.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
---
changes in v3:
- use the new hid_get_data API
- add a comment for the report descriptor fixup to explain what is done
changes in v2:
- split the series by bpf/libbpf/hid/selftests and samples
---
samples/bpf/.gitignore | 1 +
samples/bpf/Makefile | 4 ++
samples/bpf/hid_mouse_kern.c | 117 +++++++++++++++++++++++++++++++
samples/bpf/hid_mouse_user.c | 129 +++++++++++++++++++++++++++++++++++
4 files changed, 251 insertions(+)
create mode 100644 samples/bpf/hid_mouse_kern.c
create mode 100644 samples/bpf/hid_mouse_user.c
diff --git a/samples/bpf/.gitignore b/samples/bpf/.gitignore
index 0e7bfdbff80a..65440bd618b2 100644
--- a/samples/bpf/.gitignore
+++ b/samples/bpf/.gitignore
@@ -2,6 +2,7 @@
cpustat
fds_example
hbm
+hid_mouse
ibumad
lathist
lwt_len_hist
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 38638845db9d..84ef458487df 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -60,6 +60,8 @@ tprogs-y += xdp_redirect_map
tprogs-y += xdp_redirect
tprogs-y += xdp_monitor
+tprogs-y += hid_mouse
+
# Libbpf dependencies
LIBBPF_SRC = $(TOOLS_PATH)/lib/bpf
LIBBPF_OUTPUT = $(abspath $(BPF_SAMPLES_PATH))/libbpf
@@ -124,6 +126,7 @@ xdp_redirect_cpu-objs := xdp_redirect_cpu_user.o $(XDP_SAMPLE)
xdp_redirect_map-objs := xdp_redirect_map_user.o $(XDP_SAMPLE)
xdp_redirect-objs := xdp_redirect_user.o $(XDP_SAMPLE)
xdp_monitor-objs := xdp_monitor_user.o $(XDP_SAMPLE)
+hid_mouse-objs := hid_mouse_user.o
# Tell kbuild to always build the programs
always-y := $(tprogs-y)
@@ -181,6 +184,7 @@ always-y += ibumad_kern.o
always-y += hbm_out_kern.o
always-y += hbm_edt_kern.o
always-y += xdpsock_kern.o
+always-y += hid_mouse_kern.o
ifeq ($(ARCH), arm)
# Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
diff --git a/samples/bpf/hid_mouse_kern.c b/samples/bpf/hid_mouse_kern.c
new file mode 100644
index 000000000000..32285b1920c0
--- /dev/null
+++ b/samples/bpf/hid_mouse_kern.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+#include <linux/version.h>
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/bpf_hid.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("hid/device_event")
+int hid_y_event(struct hid_bpf_ctx *ctx)
+{
+ s16 y;
+ __u8 *data = bpf_hid_get_data(ctx, 0 /* offset */, 9 /* size */);
+
+ if (!data)
+ return 0; /* EPERM check */
+
+ bpf_printk("event: %02x size: %d", ctx->type, ctx->size);
+ bpf_printk("incoming event: %02x %02x %02x",
+ data[0],
+ data[1],
+ data[2]);
+ bpf_printk(" %02x %02x %02x",
+ data[3],
+ data[4],
+ data[5]);
+ bpf_printk(" %02x %02x %02x",
+ data[6],
+ data[7],
+ data[8]);
+
+ y = data[3] | (data[4] << 8);
+
+ y = -y;
+
+ data[3] = y & 0xFF;
+ data[4] = (y >> 8) & 0xFF;
+
+ bpf_printk("modified event: %02x %02x %02x",
+ data[0],
+ data[1],
+ data[2]);
+ bpf_printk(" %02x %02x %02x",
+ data[3],
+ data[4],
+ data[5]);
+ bpf_printk(" %02x %02x %02x",
+ data[6],
+ data[7],
+ data[8]);
+
+ return 0;
+}
+
+SEC("hid/device_event")
+int hid_x_event(struct hid_bpf_ctx *ctx)
+{
+ s16 x;
+ __u8 *data = bpf_hid_get_data(ctx, 0 /* offset */, 9 /* size */);
+
+ if (!data)
+ return 0; /* EPERM check */
+
+ x = data[1] | (data[2] << 8);
+
+ x = -x;
+
+ data[1] = x & 0xFF;
+ data[2] = (x >> 8) & 0xFF;
+ return 0;
+}
+
+SEC("hid/rdesc_fixup")
+int hid_rdesc_fixup(struct hid_bpf_ctx *ctx)
+{
+ __u8 *data = bpf_hid_get_data(ctx, 0 /* offset */, 4096 /* size */);
+
+ if (!data)
+ return 0; /* EPERM check */
+
+ if (ctx->type != HID_BPF_RDESC_FIXUP)
+ return 0;
+
+ bpf_printk("rdesc: %02x %02x %02x",
+ data[0],
+ data[1],
+ data[2]);
+ bpf_printk(" %02x %02x %02x",
+ data[3],
+ data[4],
+ data[5]);
+ bpf_printk(" %02x %02x %02x ...",
+ data[6],
+ data[7],
+ data[8]);
+
+ /*
+ * The original report descriptor contains:
+ *
+ * 0x05, 0x01, // Usage Page (Generic Desktop) 30
+ * 0x16, 0x01, 0x80, // Logical Minimum (-32767) 32
+ * 0x26, 0xff, 0x7f, // Logical Maximum (32767) 35
+ * 0x09, 0x30, // Usage (X) 38
+ * 0x09, 0x31, // Usage (Y) 40
+ *
+ * So byte 39 contains Usage X and byte 41 Usage Y.
+ *
+ * We simply swap the axes here.
+ */
+ data[39] = 0x31;
+ data[41] = 0x30;
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/samples/bpf/hid_mouse_user.c b/samples/bpf/hid_mouse_user.c
new file mode 100644
index 000000000000..a8a9e7a99b14
--- /dev/null
+++ b/samples/bpf/hid_mouse_user.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+#include <linux/bpf.h>
+#include <linux/if_link.h>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <libgen.h>
+#include <sys/resource.h>
+
+#include "bpf_util.h"
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+static char *sysfs_path;
+static int sysfs_fd;
+static int prog_count;
+
+struct prog {
+ int fd;
+ struct bpf_link *link;
+ enum bpf_attach_type type;
+};
+
+static struct prog progs[10];
+
+static void int_exit(int sig)
+{
+ for (prog_count--; prog_count >= 0; prog_count--)
+ bpf_link__destroy(progs[prog_count].link);
+
+ close(sysfs_fd);
+ exit(0);
+}
+
+static void usage(const char *prog)
+{
+ fprintf(stderr,
+ "%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID/uevent\n\n",
+ __func__, prog);
+}
+
+int main(int argc, char **argv)
+{
+ struct bpf_prog_info info = {};
+ __u32 info_len = sizeof(info);
+ const char *optstr = "";
+ struct bpf_object *obj;
+ struct bpf_program *prog;
+ int opt;
+ char filename[256];
+ int err;
+
+ while ((opt = getopt(argc, argv, optstr)) != -1) {
+ switch (opt) {
+ default:
+ usage(basename(argv[0]));
+ return 1;
+ }
+ }
+
+ if (optind == argc) {
+ usage(basename(argv[0]));
+ return 1;
+ }
+
+ sysfs_path = argv[optind];
+ if (!sysfs_path) {
+ perror("sysfs");
+ return 1;
+ }
+
+ snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+ obj = bpf_object__open_file(filename, NULL);
+ err = libbpf_get_error(obj);
+ if (err) {
+ fprintf(stderr, "ERROR: opening BPF object file failed\n");
+ obj = NULL;
+ err = 1;
+ goto cleanup;
+ }
+
+ /* load BPF program */
+ err = bpf_object__load(obj);
+ if (err) {
+ fprintf(stderr, "ERROR: loading BPF object file failed\n");
+ goto cleanup;
+ }
+
+ sysfs_fd = open(sysfs_path, O_RDONLY);
+
+ bpf_object__for_each_program(prog, obj) {
+ progs[prog_count].fd = bpf_program__fd(prog);
+ progs[prog_count].type = bpf_program__get_expected_attach_type(prog);
+ progs[prog_count].link = bpf_program__attach_hid(prog, sysfs_fd, 0);
+ if (libbpf_get_error(progs[prog_count].link)) {
+ fprintf(stderr, "bpf_prog_attach: err=%m\n");
+ progs[prog_count].fd = 0;
+ progs[prog_count].link = NULL;
+ goto cleanup;
+ }
+ prog_count++;
+ }
+
+ signal(SIGINT, int_exit);
+ signal(SIGTERM, int_exit);
+
+ err = bpf_obj_get_info_by_fd(progs[0].fd, &info, &info_len);
+ if (err) {
+ printf("can't get prog info - %s\n", strerror(errno));
+ goto cleanup;
+ }
+
+ while (1)
+ ;
+
+ cleanup:
+ for (prog_count--; prog_count >= 0; prog_count--)
+ bpf_link__destroy(progs[prog_count].link);
+
+ bpf_object__close(obj);
+ return err;
+}
--
2.35.1
