Re: [PATCH bpf-next v9 21/23] samples/bpf: add new hid_mouse example
From: Benjamin Tissoires
Date: Wed Aug 24 2022 - 15:30:45 EST
On Wed, Aug 24, 2022 at 3:42 PM Benjamin Tissoires
<benjamin.tissoires@xxxxxxxxxx> wrote:
>
> 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.
>
> This example will probably ever only work on the Etekcity Scroll 6E
> because we need to adapt the various raw values to the actual device.
>
> On that device, the X and Y axis will be swapped and inverted, and on
> any other device, chances are high that the device will not work until
> Ctrl-C is hit.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
>
> ---
Sorry, I realized that there are two 21/23 and 22/23...
This one should be disregarded, as there are minor improvements in the
other 21/23 :(
The good ones are the 2 starting with "samples/bpf: HID:"
Cheers,
Benjamin
>
>
> changes in v9:
> - amended the usage part
>
> no changes in v8
>
> changes in v7:
> - remove unnecessary __must_check definition
>
> changes in v6:
> - clean up code by removing old comments
>
> changes in v5:
> - bring back same features than v3, with the new API
>
> changes in v4:
> - dropped the not-yet-implemented rdesc_fixup
> - use the new API
>
> 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
>
> fix hid_mouse
> ---
> samples/bpf/.gitignore | 1 +
> samples/bpf/Makefile | 23 ++++++
> samples/bpf/hid_mouse.bpf.c | 134 ++++++++++++++++++++++++++++++
> samples/bpf/hid_mouse.c | 161 ++++++++++++++++++++++++++++++++++++
> 4 files changed, 319 insertions(+)
> create mode 100644 samples/bpf/hid_mouse.bpf.c
> create mode 100644 samples/bpf/hid_mouse.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 727da3c5879b..a965bbfaca47 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -57,6 +57,8 @@ 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
> @@ -119,6 +121,8 @@ xdp_redirect-objs := xdp_redirect_user.o $(XDP_SAMPLE)
> xdp_monitor-objs := xdp_monitor_user.o $(XDP_SAMPLE)
> xdp_router_ipv4-objs := xdp_router_ipv4_user.o $(XDP_SAMPLE)
>
> +hid_mouse-objs := hid_mouse.o
> +
> # Tell kbuild to always build the programs
> always-y := $(tprogs-y)
> always-y += sockex1_kern.o
> @@ -338,6 +342,8 @@ $(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
> $(obj)/hbm.o: $(src)/hbm.h
> $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
>
> +$(obj)/hid_mouse.o: $(obj)/hid_mouse.skel.h
> +
> # Override includes for xdp_sample_user.o because $(srctree)/usr/include in
> # TPROGS_CFLAGS causes conflicts
> XDP_SAMPLE_CFLAGS += -Wall -O2 \
> @@ -422,6 +428,23 @@ $(BPF_SKELS_LINKED): $(BPF_OBJS_LINKED) $(BPFTOOL)
> @echo " BPF GEN-SKEL" $(@:.skel.h=)
> $(Q)$(BPFTOOL) gen skeleton $(@:.skel.h=.lbpf.o) name $(notdir $(@:.skel.h=)) > $@
>
> +# Generate BPF skeletons for non XDP progs
> +OTHER_BPF_SKELS := hid_mouse.skel.h
> +
> +hid_mouse.skel.h-deps := hid_mouse.bpf.o
> +
> +OTHER_BPF_SRCS_LINKED := $(patsubst %.skel.h,%.bpf.c, $(OTHER_BPF_SKELS))
> +OTHER_BPF_OBJS_LINKED := $(patsubst %.bpf.c,$(obj)/%.bpf.o, $(OTHER_BPF_SRCS_LINKED))
> +OTHER_BPF_SKELS_LINKED := $(addprefix $(obj)/,$(OTHER_BPF_SKELS))
> +
> +$(OTHER_BPF_SKELS_LINKED): $(OTHER_BPF_OBJS_LINKED) $(BPFTOOL)
> + @echo " BPF GEN-OBJ " $(@:.skel.h=)
> + $(Q)$(BPFTOOL) gen object $(@:.skel.h=.lbpf.o) $(addprefix $(obj)/,$($(@F)-deps))
> + @echo " BPF GEN-SKEL" $(@:.skel.h=)
> + $(Q)$(BPFTOOL) gen skeleton $(@:.skel.h=.lbpf.o) name $(notdir $(@:.skel.h=_lskel)) > $@
> +# $(call msg,GEN-SKEL,$@)
> +# $(Q)$(BPFTOOL) gen skeleton $< > $@
> +
> # asm/sysreg.h - inline assembly used by it is incompatible with llvm.
> # But, there is no easy way to fix it, so just exclude it since it is
> # useless for BPF samples.
> diff --git a/samples/bpf/hid_mouse.bpf.c b/samples/bpf/hid_mouse.bpf.c
> new file mode 100644
> index 000000000000..0113e603f7a7
> --- /dev/null
> +++ b/samples/bpf/hid_mouse.bpf.c
> @@ -0,0 +1,134 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +/* following are kfuncs exported by HID for HID-BPF */
> +extern int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, u32 flags) __ksym;
> +extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
> + unsigned int offset,
> + const size_t __sz) __ksym;
> +extern void hid_bpf_data_release(__u8 *data) __ksym;
> +extern int hid_bpf_hw_request(struct hid_bpf_ctx *ctx) __ksym;
> +
> +struct attach_prog_args {
> + int prog_fd;
> + unsigned int hid;
> + int retval;
> +};
> +
> +SEC("syscall")
> +int attach_prog(struct attach_prog_args *ctx)
> +{
> + ctx->retval = hid_bpf_attach_prog(ctx->hid,
> + ctx->prog_fd,
> + 0);
> + return 0;
> +}
> +
> +SEC("fmod_ret/hid_bpf_device_event")
> +int BPF_PROG(hid_y_event, struct hid_bpf_ctx *hctx)
> +{
> + s16 y;
> + __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 9 /* size */);
> +
> + if (!data)
> + return 0; /* EPERM check */
> +
> + bpf_printk("event: size: %d", hctx->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("fmod_ret/hid_bpf_device_event")
> +int BPF_PROG(hid_x_event, struct hid_bpf_ctx *hctx)
> +{
> + s16 x;
> + __u8 *data = hid_bpf_get_data(hctx, 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("fmod_ret/hid_bpf_rdesc_fixup")
> +int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hctx)
> +{
> + __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
> +
> + if (!data)
> + return 0; /* EPERM check */
> +
> + 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";
> diff --git a/samples/bpf/hid_mouse.c b/samples/bpf/hid_mouse.c
> new file mode 100644
> index 000000000000..bea3650787c5
> --- /dev/null
> +++ b/samples/bpf/hid_mouse.c
> @@ -0,0 +1,161 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2022 Benjamin Tissoires
> + *
> + * This is a pure HID-BPF example, and should be considered as such:
> + * on the Etekcity Scroll 6E, the X and Y axes will be swapped and
> + * inverted. On any other device... Not sure what this will do.
> + *
> + * This C main file is generic though. To adapt the code and test, users
> + * must amend only the .bpf.c file, which this program will load any
> + * eBPF program it finds.
> + */
> +
> +#include <assert.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <libgen.h>
> +#include <signal.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/resource.h>
> +#include <unistd.h>
> +
> +#include <linux/bpf.h>
> +#include <linux/errno.h>
> +
> +#include "bpf_util.h"
> +#include <bpf/bpf.h>
> +#include <bpf/libbpf.h>
> +
> +#include "hid_mouse.skel.h"
> +
> +static bool running = true;
> +
> +struct attach_prog_args {
> + int prog_fd;
> + unsigned int hid;
> + int retval;
> +};
> +
> +static void int_exit(int sig)
> +{
> + running = false;
> + exit(0);
> +}
> +
> +static void usage(const char *prog)
> +{
> + fprintf(stderr,
> + "%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n",
> + __func__, prog);
> + fprintf(stderr,
> + "This program will upload and attach a HID-BPF program to the given device.\n"
> + "On the Etekcity Scroll 6E, the X and Y axis will be inverted, but on any other\n"
> + "device, chances are high that the device will not be working anymore\n\n"
> + "consider this as a demo and adapt the eBPF program to your needs\n"
> + "Hit Ctrl-C to unbind the program and reset the device\n");
> +}
> +
> +static int get_hid_id(const char *path)
> +{
> + const char *str_id, *dir;
> + char uevent[1024];
> + int fd;
> +
> + memset(uevent, 0, sizeof(uevent));
> + snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
> +
> + fd = open(uevent, O_RDONLY | O_NONBLOCK);
> + if (fd < 0)
> + return -ENOENT;
> +
> + close(fd);
> +
> + dir = basename((char *)path);
> +
> + str_id = dir + sizeof("0003:0001:0A37.");
> + return (int)strtol(str_id, NULL, 16);
> +}
> +
> +int main(int argc, char **argv)
> +{
> + struct hid_mouse_lskel *skel;
> + struct bpf_program *prog;
> + int err;
> + const char *optstr = "";
> + const char *sysfs_path;
> + int opt, hid_id, attach_fd;
> + struct attach_prog_args args = {
> + .retval = -1,
> + };
> + DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
> + .ctx_in = &args,
> + .ctx_size_in = sizeof(args),
> + );
> +
> + 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;
> + }
> +
> + skel = hid_mouse_lskel__open_and_load();
> + if (!skel) {
> + fprintf(stderr, "%s %s:%d", __func__, __FILE__, __LINE__);
> + return -1;
> + }
> +
> + hid_id = get_hid_id(sysfs_path);
> +
> + if (hid_id < 0) {
> + fprintf(stderr, "can not open HID device: %m\n");
> + return 1;
> + }
> + args.hid = hid_id;
> +
> + attach_fd = bpf_program__fd(skel->progs.attach_prog);
> + if (attach_fd < 0) {
> + fprintf(stderr, "can't locate attach prog: %m\n");
> + return 1;
> + }
> +
> + bpf_object__for_each_program(prog, *skel->skeleton->obj) {
> + /* ignore syscalls */
> + if (bpf_program__get_type(prog) != BPF_PROG_TYPE_TRACING)
> + continue;
> +
> + args.retval = -1;
> + args.prog_fd = bpf_program__fd(prog);
> + err = bpf_prog_test_run_opts(attach_fd, &tattr);
> + if (err) {
> + fprintf(stderr, "can't attach prog to hid device %d: %m (err: %d)\n",
> + hid_id, err);
> + return 1;
> + }
> + }
> +
> + signal(SIGINT, int_exit);
> + signal(SIGTERM, int_exit);
> +
> + while (running)
> + sleep(1);
> +
> + hid_mouse_lskel__destroy(skel);
> +
> + return 0;
> +}
> --
> 2.36.1
>