Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

8 files changed, 963 insertions, 0 deletions

diff --git a/samples/hid/.gitignore b/samples/hid/.gitignore
new file mode 100644
index 000000000..3ea0fed3b
--- /dev/null
+++ b/samples/hid/.gitignore
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+hid_mouse
+hid_surface_dial
+*.out
+*.skel.h
+/vmlinux.h
+/bpftool/
+/libbpf/
diff --git a/samples/hid/Makefile b/samples/hid/Makefile
new file mode 100644
index 000000000..db5a077c7
--- /dev/null
+++ b/samples/hid/Makefile
@@ -0,0 +1,250 @@
+# SPDX-License-Identifier: GPL-2.0
+
+HID_SAMPLES_PATH ?= $(abspath $(src))
+TOOLS_PATH := $(HID_SAMPLES_PATH)/../../tools
+
+pound := \#
+
+# List of programs to build
+tprogs-y += hid_mouse
+tprogs-y += hid_surface_dial
+
+# Libbpf dependencies
+LIBBPF_SRC = $(TOOLS_PATH)/lib/bpf
+LIBBPF_OUTPUT = $(abspath $(HID_SAMPLES_PATH))/libbpf
+LIBBPF_DESTDIR = $(LIBBPF_OUTPUT)
+LIBBPF_INCLUDE = $(LIBBPF_DESTDIR)/include
+LIBBPF = $(LIBBPF_OUTPUT)/libbpf.a
+
+EXTRA_BPF_HEADERS := hid_bpf_helpers.h
+
+hid_mouse-objs := hid_mouse.o
+hid_surface_dial-objs := hid_surface_dial.o
+
+# Tell kbuild to always build the programs
+always-y := $(tprogs-y)
+
+ifeq ($(ARCH), arm)
+# Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
+# headers when arm instruction set identification is requested.
+ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS))
+BPF_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR)
+TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
+endif
+
+ifeq ($(ARCH), mips)
+TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
+ifdef CONFIG_MACH_LOONGSON64
+BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-loongson64
+BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-generic
+endif
+endif
+
+COMMON_CFLAGS += -Wall -O2
+COMMON_CFLAGS += -Wmissing-prototypes
+COMMON_CFLAGS += -Wstrict-prototypes
+
+TPROGS_CFLAGS += $(COMMON_CFLAGS)
+TPROGS_CFLAGS += -I$(objtree)/usr/include
+TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
+TPROGS_CFLAGS += -I$(srctree)/tools/include
+
+ifdef SYSROOT
+COMMON_CFLAGS += --sysroot=$(SYSROOT)
+TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
+endif
+
+TPROGS_LDLIBS			+= $(LIBBPF) -lelf -lz
+
+# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
+# make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang
+LLC ?= llc
+CLANG ?= clang
+OPT ?= opt
+LLVM_DIS ?= llvm-dis
+LLVM_OBJCOPY ?= llvm-objcopy
+LLVM_READELF ?= llvm-readelf
+BTF_PAHOLE ?= pahole
+
+# Detect that we're cross compiling and use the cross compiler
+ifdef CROSS_COMPILE
+CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%))
+endif
+
+# Don't evaluate probes and warnings if we need to run make recursively
+ifneq ($(src),)
+HDR_PROBE := $(shell printf "$(pound)include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
+	$(CC) $(TPROGS_CFLAGS) $(TPROGS_LDFLAGS) -x c - \
+	-o /dev/null 2>/dev/null && echo okay)
+
+ifeq ($(HDR_PROBE),)
+$(warning WARNING: Detected possible issues with include path.)
+$(warning WARNING: Please install kernel headers locally (make headers_install).)
+endif
+
+BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
+BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
+BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
+BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
+			  $(CLANG) --target=bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
+			  $(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
+			  /bin/rm -f ./llvm_btf_verify.o)
+
+BPF_EXTRA_CFLAGS += -fno-stack-protector
+ifneq ($(BTF_LLVM_PROBE),)
+	BPF_EXTRA_CFLAGS += -g
+else
+ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
+	BPF_EXTRA_CFLAGS += -g
+	LLC_FLAGS += -mattr=dwarfris
+	DWARF2BTF = y
+endif
+endif
+endif
+
+# Trick to allow make to be run from this directory
+all:
+	$(MAKE) -C ../../ M=$(CURDIR) HID_SAMPLES_PATH=$(CURDIR)
+
+clean:
+	$(MAKE) -C ../../ M=$(CURDIR) clean
+	@find $(CURDIR) -type f -name '*~' -delete
+	@$(RM) -r $(CURDIR)/libbpf $(CURDIR)/bpftool
+
+$(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)
+# Fix up variables inherited from Kbuild that tools/ build system won't like
+	$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(COMMON_CFLAGS)" \
+		LDFLAGS=$(TPROGS_LDFLAGS) srctree=$(HID_SAMPLES_PATH)/../../ \
+		O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
+		$@ install_headers
+
+BPFTOOLDIR := $(TOOLS_PATH)/bpf/bpftool
+BPFTOOL_OUTPUT := $(abspath $(HID_SAMPLES_PATH))/bpftool
+BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool
+$(BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT)
+	$(MAKE) -C $(BPFTOOLDIR) srctree=$(HID_SAMPLES_PATH)/../../ 		\
+		OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap
+
+$(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
+	$(call msg,MKDIR,$@)
+	$(Q)mkdir -p $@
+
+FORCE:
+
+
+# Verify LLVM compiler tools are available and bpf target is supported by llc
+.PHONY: verify_cmds verify_target_bpf $(CLANG) $(LLC)
+
+verify_cmds: $(CLANG) $(LLC)
+	@for TOOL in $^ ; do \
+		if ! (which -- "$${TOOL}" > /dev/null 2>&1); then \
+			echo "*** ERROR: Cannot find LLVM tool $${TOOL}" ;\
+			exit 1; \
+		else true; fi; \
+	done
+
+verify_target_bpf: verify_cmds
+	@if ! (${LLC} -march=bpf -mattr=help > /dev/null 2>&1); then \
+		echo "*** ERROR: LLVM (${LLC}) does not support 'bpf' target" ;\
+		echo "   NOTICE: LLVM version >= 3.7.1 required" ;\
+		exit 2; \
+	else true; fi
+
+$(HID_SAMPLES_PATH)/*.c: verify_target_bpf $(LIBBPF)
+$(src)/*.c: verify_target_bpf $(LIBBPF)
+
+libbpf_hdrs: $(LIBBPF)
+
+.PHONY: libbpf_hdrs
+
+$(obj)/hid_mouse.o: $(obj)/hid_mouse.skel.h
+$(obj)/hid_surface_dial.o: $(obj)/hid_surface_dial.skel.h
+
+-include $(HID_SAMPLES_PATH)/Makefile.target
+
+VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))				\
+		     $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux))	\
+		     $(abspath $(objtree)/vmlinux)
+VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+
+$(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
+ifeq ($(VMLINUX_H),)
+ifeq ($(VMLINUX_BTF),)
+	$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\
+		build the kernel or set VMLINUX_BTF or VMLINUX_H variable)
+endif
+	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+else
+	$(Q)cp "$(VMLINUX_H)" $@
+endif
+
+clean-files += vmlinux.h
+
+# Get Clang's default includes on this system, as opposed to those seen by
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
+# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
+#
+# Use '-idirafter': Don't interfere with include mechanics except where the
+# build would have failed anyways.
+define get_sys_includes
+$(shell $(1) -v -E - </dev/null 2>&1 \
+        | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
+$(shell $(1) -dM -E - </dev/null | grep '#define __riscv_xlen ' | sed 's/#define /-D/' | sed 's/ /=/')
+endef
+
+CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
+
+EXTRA_BPF_HEADERS_SRC := $(addprefix $(src)/,$(EXTRA_BPF_HEADERS))
+
+$(obj)/%.bpf.o: $(src)/%.bpf.c $(EXTRA_BPF_HEADERS_SRC) $(obj)/vmlinux.h
+	@echo "  CLANG-BPF " $@
+	$(Q)$(CLANG) -g -O2 --target=bpf -D__TARGET_ARCH_$(SRCARCH) \
+		-Wno-compare-distinct-pointer-types -I$(srctree)/include \
+		-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
+		-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
+		-c $(filter %.bpf.c,$^) -o $@
+
+LINKED_SKELS := hid_mouse.skel.h hid_surface_dial.skel.h
+clean-files += $(LINKED_SKELS)
+
+hid_mouse.skel.h-deps := hid_mouse.bpf.o
+hid_surface_dial.skel.h-deps := hid_surface_dial.bpf.o
+
+LINKED_BPF_SRCS := $(patsubst %.bpf.o,%.bpf.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))
+
+BPF_SRCS_LINKED := $(notdir $(wildcard $(src)/*.bpf.c))
+BPF_OBJS_LINKED := $(patsubst %.bpf.c,$(obj)/%.bpf.o, $(BPF_SRCS_LINKED))
+BPF_SKELS_LINKED := $(addprefix $(obj)/,$(LINKED_SKELS))
+
+$(BPF_SKELS_LINKED): $(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=)) > $@
+
+# asm/sysreg.h - inline assembly used by it is incompatible with llvm.
+# But, there is no easy way to fix it, so just exclude it since it is
+# useless for BPF samples.
+# below we use long chain of commands, clang | opt | llvm-dis | llc,
+# to generate final object file. 'clang' compiles the source into IR
+# with native target, e.g., x64, arm64, etc. 'opt' does bpf CORE IR builtin
+# processing (llvm12) and IR optimizations. 'llvm-dis' converts
+# 'opt' output to IR, and finally 'llc' generates bpf byte code.
+$(obj)/%.o: $(src)/%.c
+	@echo "  CLANG-bpf " $@
+	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(BPF_EXTRA_CFLAGS) \
+		-I$(obj) -I$(srctree)/tools/testing/selftests/bpf/ \
+		-I$(LIBBPF_INCLUDE) \
+		-D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign \
+		-D__TARGET_ARCH_$(SRCARCH) -Wno-compare-distinct-pointer-types \
+		-Wno-gnu-variable-sized-type-not-at-end \
+		-Wno-address-of-packed-member -Wno-tautological-compare \
+		-Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \
+		-fno-asynchronous-unwind-tables \
+		-I$(srctree)/samples/hid/ \
+		-O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \
+		$(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \
+		$(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@
+ifeq ($(DWARF2BTF),y)
+	$(BTF_PAHOLE) -J $@
+endif
diff --git a/samples/hid/Makefile.target b/samples/hid/Makefile.target
new file mode 100644
index 000000000..7621f55e2
--- /dev/null
+++ b/samples/hid/Makefile.target
@@ -0,0 +1,75 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Building binaries on the host system
+# Binaries are not used during the compilation of the kernel, and intended
+# to be build for target board, target board can be host of course. Added to
+# build binaries to run not on host system.
+#
+# Sample syntax
+# tprogs-y := xsk_example
+# Will compile xsk_example.c and create an executable named xsk_example
+#
+# tprogs-y    := xdpsock
+# xdpsock-objs := xdpsock_1.o xdpsock_2.o
+# Will compile xdpsock_1.c and xdpsock_2.c, and then link the executable
+# xdpsock, based on xdpsock_1.o and xdpsock_2.o
+#
+# Derived from scripts/Makefile.host
+#
+__tprogs := $(sort $(tprogs-y))
+
+# C code
+# Executables compiled from a single .c file
+tprog-csingle	:= $(foreach m,$(__tprogs), \
+			$(if $($(m)-objs),,$(m)))
+
+# C executables linked based on several .o files
+tprog-cmulti	:= $(foreach m,$(__tprogs),\
+			$(if $($(m)-objs),$(m)))
+
+# Object (.o) files compiled from .c files
+tprog-cobjs	:= $(sort $(foreach m,$(__tprogs),$($(m)-objs)))
+
+tprog-csingle	:= $(addprefix $(obj)/,$(tprog-csingle))
+tprog-cmulti	:= $(addprefix $(obj)/,$(tprog-cmulti))
+tprog-cobjs	:= $(addprefix $(obj)/,$(tprog-cobjs))
+
+#####
+# Handle options to gcc. Support building with separate output directory
+
+_tprogc_flags   = $(TPROGS_CFLAGS) \
+                 $(TPROGCFLAGS_$(basetarget).o)
+
+# $(objtree)/$(obj) for including generated headers from checkin source files
+ifeq ($(KBUILD_EXTMOD),)
+ifdef building_out_of_srctree
+_tprogc_flags   += -I $(objtree)/$(obj)
+endif
+endif
+
+tprogc_flags    = -Wp,-MD,$(depfile) $(_tprogc_flags)
+
+# Create executable from a single .c file
+# tprog-csingle -> Executable
+quiet_cmd_tprog-csingle 	= CC  $@
+      cmd_tprog-csingle	= $(CC) $(tprogc_flags) $(TPROGS_LDFLAGS) -o $@ $< \
+		$(TPROGS_LDLIBS) $(TPROGLDLIBS_$(@F))
+$(tprog-csingle): $(obj)/%: $(src)/%.c FORCE
+	$(call if_changed_dep,tprog-csingle)
+
+# Link an executable based on list of .o files, all plain c
+# tprog-cmulti -> executable
+quiet_cmd_tprog-cmulti	= LD  $@
+      cmd_tprog-cmulti	= $(CC) $(tprogc_flags) $(TPROGS_LDFLAGS) -o $@ \
+			  $(addprefix $(obj)/,$($(@F)-objs)) \
+			  $(TPROGS_LDLIBS) $(TPROGLDLIBS_$(@F))
+$(tprog-cmulti): $(tprog-cobjs) FORCE
+	$(call if_changed,tprog-cmulti)
+$(call multi_depend, $(tprog-cmulti), , -objs)
+
+# Create .o file from a single .c file
+# tprog-cobjs -> .o
+quiet_cmd_tprog-cobjs	= CC  $@
+      cmd_tprog-cobjs	= $(CC) $(tprogc_flags) -c -o $@ $<
+$(tprog-cobjs): $(obj)/%.o: $(src)/%.c FORCE
+	$(call if_changed_dep,tprog-cobjs)
diff --git a/samples/hid/hid_bpf_helpers.h b/samples/hid/hid_bpf_helpers.h
new file mode 100644
index 000000000..4fff31dbe
--- /dev/null
+++ b/samples/hid/hid_bpf_helpers.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+
+#ifndef __HID_BPF_HELPERS_H
+#define __HID_BPF_HELPERS_H
+
+/* following are kfuncs exported by HID for HID-BPF */
+extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
+			      unsigned int offset,
+			      const size_t __sz) __ksym;
+extern int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, u32 flags) __ksym;
+extern struct hid_bpf_ctx *hid_bpf_allocate_context(unsigned int hid_id) __ksym;
+extern void hid_bpf_release_context(struct hid_bpf_ctx *ctx) __ksym;
+extern int hid_bpf_hw_request(struct hid_bpf_ctx *ctx,
+			      __u8 *data,
+			      size_t buf__sz,
+			      enum hid_report_type type,
+			      enum hid_class_request reqtype) __ksym;
+
+#endif /* __HID_BPF_HELPERS_H */
diff --git a/samples/hid/hid_mouse.bpf.c b/samples/hid/hid_mouse.bpf.c
new file mode 100644
index 000000000..f7f722dcf
--- /dev/null
+++ b/samples/hid/hid_mouse.bpf.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "hid_bpf_helpers.h"
+
+static int 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;
+}
+
+static int 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("struct_ops/hid_device_event")
+int BPF_PROG(hid_event, struct hid_bpf_ctx *hctx, enum hid_report_type type)
+{
+	int ret = hid_y_event(hctx);
+
+	if (ret)
+		return ret;
+
+	return hid_x_event(hctx);
+}
+
+
+SEC("struct_ops/hid_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;
+}
+
+SEC(".struct_ops.link")
+struct hid_bpf_ops mouse_invert = {
+	.hid_rdesc_fixup = (void *)hid_rdesc_fixup,
+	.hid_device_event = (void *)hid_event,
+};
+
+char _license[] SEC("license") = "GPL";
diff --git a/samples/hid/hid_mouse.c b/samples/hid/hid_mouse.c
new file mode 100644
index 000000000..4b80d4e4c
--- /dev/null
+++ b/samples/hid/hid_mouse.c
@@ -0,0 +1,138 @@
+// 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/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "hid_mouse.skel.h"
+
+static bool running = true;
+
+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 *skel;
+	struct bpf_link *link;
+	int err;
+	const char *optstr = "";
+	const char *sysfs_path;
+	int opt, hid_id;
+
+	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__open();
+	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;
+	}
+	skel->struct_ops.mouse_invert->hid_id = hid_id;
+
+	err = hid_mouse__load(skel);
+	if (err < 0) {
+		fprintf(stderr, "can not load HID-BPF program: %m\n");
+		return 1;
+	}
+
+	link = bpf_map__attach_struct_ops(skel->maps.mouse_invert);
+	if (!link) {
+		fprintf(stderr, "can not attach HID-BPF program: %m\n");
+		return 1;
+	}
+
+	signal(SIGINT, int_exit);
+	signal(SIGTERM, int_exit);
+
+	while (running)
+		sleep(1);
+
+	hid_mouse__destroy(skel);
+
+	return 0;
+}
diff --git a/samples/hid/hid_surface_dial.bpf.c b/samples/hid/hid_surface_dial.bpf.c
new file mode 100644
index 000000000..527d58481
--- /dev/null
+++ b/samples/hid/hid_surface_dial.bpf.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "hid_bpf_helpers.h"
+
+#define HID_UP_BUTTON		0x0009
+#define HID_GD_WHEEL		0x0038
+
+SEC("struct_ops/hid_device_event")
+int BPF_PROG(hid_event, struct hid_bpf_ctx *hctx)
+{
+	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 9 /* size */);
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	/* Touch */
+	data[1] &= 0xfd;
+
+	/* X */
+	data[4] = 0;
+	data[5] = 0;
+
+	/* Y */
+	data[6] = 0;
+	data[7] = 0;
+
+	return 0;
+}
+
+/* 72 == 360 / 5 -> 1 report every 5 degrees */
+int resolution = 72;
+int physical = 5;
+
+struct haptic_syscall_args {
+	unsigned int hid;
+	int retval;
+};
+
+static __u8 haptic_data[8];
+
+SEC("syscall")
+int set_haptic(struct haptic_syscall_args *args)
+{
+	struct hid_bpf_ctx *ctx;
+	const size_t size = sizeof(haptic_data);
+	u16 *res;
+	int ret;
+
+	if (size > sizeof(haptic_data))
+		return -7; /* -E2BIG */
+
+	ctx = hid_bpf_allocate_context(args->hid);
+	if (!ctx)
+		return -1; /* EPERM check */
+
+	haptic_data[0] = 1;  /* report ID */
+
+	ret = hid_bpf_hw_request(ctx, haptic_data, size, HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
+
+	bpf_printk("probed/remove event ret value: %d", ret);
+	bpf_printk("buf: %02x %02x %02x",
+		   haptic_data[0],
+		   haptic_data[1],
+		   haptic_data[2]);
+	bpf_printk("     %02x %02x %02x",
+		   haptic_data[3],
+		   haptic_data[4],
+		   haptic_data[5]);
+	bpf_printk("     %02x %02x",
+		   haptic_data[6],
+		   haptic_data[7]);
+
+	/* whenever resolution multiplier is not 3600, we have the fixed report descriptor */
+	res = (u16 *)&haptic_data[1];
+	if (*res != 3600) {
+//		haptic_data[1] = 72; /* resolution multiplier */
+//		haptic_data[2] = 0;  /* resolution multiplier */
+//		haptic_data[3] = 0;  /* Repeat Count */
+		haptic_data[4] = 3;  /* haptic Auto Trigger */
+//		haptic_data[5] = 5;  /* Waveform Cutoff Time */
+//		haptic_data[6] = 80; /* Retrigger Period */
+//		haptic_data[7] = 0;  /* Retrigger Period */
+	} else {
+		haptic_data[4] = 0;
+	}
+
+	ret = hid_bpf_hw_request(ctx, haptic_data, size, HID_FEATURE_REPORT, HID_REQ_SET_REPORT);
+
+	bpf_printk("set haptic ret value: %d -> %d", ret, haptic_data[4]);
+
+	args->retval = ret;
+
+	hid_bpf_release_context(ctx);
+
+	return 0;
+}
+
+/* Convert REL_DIAL into REL_WHEEL */
+SEC("struct_ops/hid_rdesc_fixup")
+int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hctx)
+{
+	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
+	__u16 *res, *phys;
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	/* Convert TOUCH into a button */
+	data[31] = HID_UP_BUTTON;
+	data[33] = 2;
+
+	/* Convert REL_DIAL into REL_WHEEL */
+	data[45] = HID_GD_WHEEL;
+
+	/* Change Resolution Multiplier */
+	phys = (__u16 *)&data[61];
+	*phys = physical;
+	res = (__u16 *)&data[66];
+	*res = resolution;
+
+	/* Convert X,Y from Abs to Rel */
+	data[88] = 0x06;
+	data[98] = 0x06;
+
+	return 0;
+}
+
+SEC(".struct_ops.link")
+struct hid_bpf_ops surface_dial = {
+	.hid_rdesc_fixup = (void *)hid_rdesc_fixup,
+	.hid_device_event = (void *)hid_event,
+};
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = 1;
diff --git a/samples/hid/hid_surface_dial.c b/samples/hid/hid_surface_dial.c
new file mode 100644
index 000000000..9dd363845
--- /dev/null
+++ b/samples/hid/hid_surface_dial.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2022 Benjamin Tissoires
+ *
+ * This program will morph the Microsoft Surface Dial into a mouse,
+ * and depending on the chosen resolution enable or not the haptic feedback:
+ * - a resolution (-r) of 3600 will report 3600 "ticks" in one full rotation
+ *   without haptic feedback
+ * - any other resolution will report N "ticks" in a full rotation with haptic
+ *   feedback
+ *
+ * A good default for low resolution haptic scrolling is 72 (1 "tick" every 5
+ * degrees), and set to 3600 for smooth scrolling.
+ */
+
+#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/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "hid_surface_dial.skel.h"
+
+static bool running = true;
+
+struct haptic_syscall_args {
+	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 [OPTIONS] /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n"
+		"  OPTIONS:\n"
+		"    -r N\t set the given resolution to the device (number of ticks per 360°)\n\n",
+		__func__, prog);
+	fprintf(stderr,
+		"This program will morph the Microsoft Surface Dial into a mouse,\n"
+		"and depending on the chosen resolution enable or not the haptic feedback:\n"
+		"- a resolution (-r) of 3600 will report 3600 'ticks' in one full rotation\n"
+		"  without haptic feedback\n"
+		"- any other resolution will report N 'ticks' in a full rotation with haptic\n"
+		"  feedback\n"
+		"\n"
+		"A good default for low resolution haptic scrolling is 72 (1 'tick' every 5\n"
+		"degrees), and set to 3600 for smooth scrolling.\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);
+}
+
+static int set_haptic(struct hid_surface_dial *skel, int hid_id)
+{
+	struct haptic_syscall_args args = {
+		.hid = hid_id,
+		.retval = -1,
+	};
+	int haptic_fd, err;
+	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
+			    .ctx_in = &args,
+			    .ctx_size_in = sizeof(args),
+	);
+
+	haptic_fd = bpf_program__fd(skel->progs.set_haptic);
+	if (haptic_fd < 0) {
+		fprintf(stderr, "can't locate haptic prog: %m\n");
+		return 1;
+	}
+
+	err = bpf_prog_test_run_opts(haptic_fd, &tattr);
+	if (err) {
+		fprintf(stderr, "can't set haptic configuration to hid device %d: %m (err: %d)\n",
+			hid_id, err);
+		return 1;
+	}
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	struct hid_surface_dial *skel;
+	const char *optstr = "r:";
+	struct bpf_link *link;
+	const char *sysfs_path;
+	int err, opt, hid_id, resolution = 72;
+
+	while ((opt = getopt(argc, argv, optstr)) != -1) {
+		switch (opt) {
+		case 'r':
+			{
+				char *endp = NULL;
+				long l = -1;
+
+				if (optarg) {
+					l = strtol(optarg, &endp, 10);
+					if (endp && *endp)
+						l = -1;
+				}
+
+				if (l < 0) {
+					fprintf(stderr,
+						"invalid r option %s - expecting a number\n",
+						optarg ? optarg : "");
+					exit(EXIT_FAILURE);
+				};
+
+				resolution = (int) l;
+				break;
+			}
+		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_surface_dial__open();
+	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;
+	}
+
+	skel->struct_ops.surface_dial->hid_id = hid_id;
+
+	err = hid_surface_dial__load(skel);
+	if (err < 0) {
+		fprintf(stderr, "can not load HID-BPF program: %m\n");
+		return 1;
+	}
+
+	skel->data->resolution = resolution;
+	skel->data->physical = (int)(resolution / 72);
+
+	link = bpf_map__attach_struct_ops(skel->maps.surface_dial);
+	if (!link) {
+		fprintf(stderr, "can not attach HID-BPF program: %m\n");
+		return 1;
+	}
+
+	signal(SIGINT, int_exit);
+	signal(SIGTERM, int_exit);
+
+	set_haptic(skel, hid_id);
+
+	while (running)
+		sleep(1);
+
+	hid_surface_dial__destroy(skel);
+
+	return 0;
+}