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@redhat.com
---
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; +}