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Date:   Wed, 10 Jul 2019 14:12:27 -0400
From:   Kris Van Hees <kris.van.hees@oracle.com>
To:     Kris Van Hees <kris.van.hees@oracle.com>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
        dtrace-devel@oss.oracle.com, linux-kernel@vger.kernel.org,
        rostedt@goodmis.org, mhiramat@kernel.org, acme@kernel.org,
        ast@kernel.org, daniel@iogearbox.net,
        Peter Zijlstra <peterz@infradead.org>, Chris Mason <clm@fb.com>
Subject: Re: [PATCH V2 1/1 (was 0/1 by accident)] tools/dtrace: initial
 implementation of DTrace
Message-ID: <20190710181227.GA9925@oracle.com>
References: <201907101537.x6AFboMR015946@aserv0122.oracle.com>
 <201907101542.x6AFgOO9012232@userv0121.oracle.com>
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This patch's subject should of course be [PATCH V2 1/1] rather than 0/1.
Sorry about that.

On Wed, Jul 10, 2019 at 08:42:24AM -0700, Kris Van Hees wrote:
> This initial implementation of a tiny subset of DTrace functionality
> provides the following options:
> 
> 	dtrace [-lvV] [-b bufsz] -s script
> 	    -b  set trace buffer size
> 	    -l  list probes (only works with '-s script' for now)
> 	    -s  enable or list probes for the specified BPF program
> 	    -V  report DTrace API version
> 
> The patch comprises quite a bit of code due to DTrace requiring a few
> crucial components, even in its most basic form.
> 
> The code is structured around the command line interface implemented in
> dtrace.c.  It provides option parsing and drives the three modes of
> operation that are currently implemented:
> 
> 1. Report DTrace API version information.
> 	Report the version information and terminate.
> 
> 2. List probes in BPF programs.
> 	Initialize the list of probes that DTrace recognizes, load BPF
> 	programs, parse all BPF ELF section names, resolve them into
> 	known probes, and emit the probe names.  Then terminate.
> 
> 3. Load BPF programs and collect tracing data.
> 	Initialize the list of probes that DTrace recognizes, load BPF
> 	programs and attach them to their corresponding probes, set up
> 	perf event output buffers, and start processing tracing data.
> 
> This implementation makes extensive use of BPF (handled by dt_bpf.c) and
> the perf event output ring buffer (handled by dt_buffer.c).  DTrace-style
> probe handling (dt_probe.c) offers an interface to probes that hides the
> implementation details of the individual probe types by provider (dt_fbt.c
> and dt_syscall.c).  Probe lookup by name uses a hashtable implementation
> (dt_hash.c).  The dt_utils.c code populates a list of online CPU ids, so
> we know what CPUs we can obtain tracing data from.
> 
> Building the tool is trivial because its only dependency (libbpf) is in
> the kernel tree under tools/lib/bpf.  A simple 'make' in the tools/dtrace
> directory suffices.
> 
> The 'dtrace' executable needs to run as root because BPF programs cannot
> be loaded by non-root users.
> 
> Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
> Reviewed-by: David Mc Lean <david.mclean@oracle.com>
> Reviewed-by: Eugene Loh <eugene.loh@oracle.com>
> ---
> Changes in v2:
>         - Use ring_buffer_read_head() and ring_buffer_write_tail() to
>           avoid use of volatile.
>         - Handle perf events that wrap around the ring buffer boundary.
>         - Remove unnecessary PERF_EVENT_IOC_ENABLE.
>         - Remove -I$(srctree)/tools/perf from KBUILD_HOSTCFLAGS since it
>           is not actually used.
>         - Use PT_REGS_PARM1(x), etc instead of my own macros.  Adding 
>           PT_REGS_PARM6(x) in bpf_sample.c because we need to be able to
>           support up to 6 arguments passed by registers.
> ---
>  MAINTAINERS                |   6 +
>  tools/dtrace/Makefile      |  87 ++++++++++
>  tools/dtrace/bpf_sample.c  | 146 ++++++++++++++++
>  tools/dtrace/dt_bpf.c      | 185 ++++++++++++++++++++
>  tools/dtrace/dt_buffer.c   | 338 +++++++++++++++++++++++++++++++++++++
>  tools/dtrace/dt_fbt.c      | 201 ++++++++++++++++++++++
>  tools/dtrace/dt_hash.c     | 211 +++++++++++++++++++++++
>  tools/dtrace/dt_probe.c    | 230 +++++++++++++++++++++++++
>  tools/dtrace/dt_syscall.c  | 179 ++++++++++++++++++++
>  tools/dtrace/dt_utils.c    | 132 +++++++++++++++
>  tools/dtrace/dtrace.c      | 249 +++++++++++++++++++++++++++
>  tools/dtrace/dtrace.h      |  13 ++
>  tools/dtrace/dtrace_impl.h | 101 +++++++++++
>  13 files changed, 2078 insertions(+)
>  create mode 100644 tools/dtrace/Makefile
>  create mode 100644 tools/dtrace/bpf_sample.c
>  create mode 100644 tools/dtrace/dt_bpf.c
>  create mode 100644 tools/dtrace/dt_buffer.c
>  create mode 100644 tools/dtrace/dt_fbt.c
>  create mode 100644 tools/dtrace/dt_hash.c
>  create mode 100644 tools/dtrace/dt_probe.c
>  create mode 100644 tools/dtrace/dt_syscall.c
>  create mode 100644 tools/dtrace/dt_utils.c
>  create mode 100644 tools/dtrace/dtrace.c
>  create mode 100644 tools/dtrace/dtrace.h
>  create mode 100644 tools/dtrace/dtrace_impl.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cfa9ed89c031..410240732d55 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5485,6 +5485,12 @@ W:	https://linuxtv.org
>  S:	Odd Fixes
>  F:	drivers/media/pci/dt3155/
>  
> +DTRACE
> +M:	Kris Van Hees <kris.van.hees@oracle.com>
> +L:	dtrace-devel@oss.oracle.com
> +S:	Maintained
> +F:	tools/dtrace/
> +
>  DVB_USB_AF9015 MEDIA DRIVER
>  M:	Antti Palosaari <crope@iki.fi>
>  L:	linux-media@vger.kernel.org
> diff --git a/tools/dtrace/Makefile b/tools/dtrace/Makefile
> new file mode 100644
> index 000000000000..03ae498d1429
> --- /dev/null
> +++ b/tools/dtrace/Makefile
> @@ -0,0 +1,87 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# This Makefile is based on samples/bpf.
> +#
> +# Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> +
> +DT_VERSION		:= 2.0.0
> +DT_GIT_VERSION		:= $(shell git rev-parse HEAD 2>/dev/null || \
> +				   echo Unknown)
> +
> +DTRACE_PATH		?= $(abspath $(srctree)/$(src))
> +TOOLS_PATH		:= $(DTRACE_PATH)/..
> +SAMPLES_PATH		:= $(DTRACE_PATH)/../../samples
> +
> +hostprogs-y		:= dtrace
> +
> +LIBBPF			:= $(TOOLS_PATH)/lib/bpf/libbpf.a
> +OBJS			:= dt_bpf.o dt_buffer.o dt_utils.o dt_probe.o \
> +			   dt_hash.o \
> +			   dt_fbt.o dt_syscall.o
> +
> +dtrace-objs		:= $(OBJS) dtrace.o
> +
> +always			:= $(hostprogs-y)
> +always			+= bpf_sample.o
> +
> +KBUILD_HOSTCFLAGS	+= -DDT_VERSION=\"$(DT_VERSION)\"
> +KBUILD_HOSTCFLAGS	+= -DDT_GIT_VERSION=\"$(DT_GIT_VERSION)\"
> +KBUILD_HOSTCFLAGS	+= -I$(srctree)/tools/lib
> +KBUILD_HOSTCFLAGS	+= -I$(srctree)/tools/include/uapi
> +KBUILD_HOSTCFLAGS	+= -I$(srctree)/tools/include/
> +KBUILD_HOSTCFLAGS	+= -I$(srctree)/usr/include
> +
> +KBUILD_HOSTLDLIBS	:= $(LIBBPF) -lelf
> +
> +LLC			?= llc
> +CLANG			?= clang
> +LLVM_OBJCOPY		?= llvm-objcopy
> +
> +ifdef CROSS_COMPILE
> +HOSTCC			= $(CROSS_COMPILE)gcc
> +CLANG_ARCH_ARGS		= -target $(ARCH)
> +endif
> +
> +all:
> +	$(MAKE) -C ../../ $(CURDIR)/ DTRACE_PATH=$(CURDIR)
> +
> +clean:
> +	$(MAKE) -C ../../ M=$(CURDIR) clean
> +	@rm -f *~
> +
> +$(LIBBPF): FORCE
> +	$(MAKE) -C $(dir $@) RM='rm -rf' LDFLAGS= srctree=$(DTRACE_PATH)/../../ O=
> +
> +FORCE:
> +
> +.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
> +
> +$(DTRACE_PATH)/*.c: verify_target_bpf $(LIBBPF)
> +$(src)/*.c: verify_target_bpf $(LIBBPF)
> +
> +$(obj)/%.o: $(src)/%.c
> +	@echo "  CLANG-bpf " $@
> +	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) -I$(obj) \
> +		-I$(srctree)/tools/testing/selftests/bpf/ \
> +		-D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign \
> +		-D__TARGET_ARCH_$(ARCH) -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 $(CLANG_ARCH_ARGS) \
> +		-I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \
> +		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@
> diff --git a/tools/dtrace/bpf_sample.c b/tools/dtrace/bpf_sample.c
> new file mode 100644
> index 000000000000..9862f75f92d3
> --- /dev/null
> +++ b/tools/dtrace/bpf_sample.c
> @@ -0,0 +1,146 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This sample DTrace BPF tracing program demonstrates how actions can be
> + * associated with different probe types.
> + *
> + * The kprobe/ksys_write probe is a Function Boundary Tracing (FBT) entry probe
> + * on the ksys_write(fd, buf, count) function in the kernel.  Arguments to the
> + * function can be retrieved from the CPU registers (struct pt_regs).
> + *
> + * The tracepoint/syscalls/sys_enter_write probe is a System Call entry probe
> + * for the write(d, buf, count) system call.  Arguments to the system call can
> + * be retrieved from the tracepoint data passed to the BPF program as context
> + * struct syscall_data) when the probe fires.
> + *
> + * The BPF program associated with each probe prepares a DTrace BPF context
> + * (struct dt_bpf_context) that stores the probe ID and up to 10 arguments.
> + * Only 3 arguments are used in this sample.  Then the prorgams call a shared
> + * BPF function (bpf_action) that implements the actual action to be taken when
> + * a probe fires.  It prepares a data record to be stored in the tracing buffer
> + * and submits it to the buffer.  The data in the data record is obtained from
> + * the DTrace BPF context.
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <uapi/linux/bpf.h>
> +#include <linux/ptrace.h>
> +#include <linux/version.h>
> +#include <uapi/linux/unistd.h>
> +#include "bpf_helpers.h"
> +
> +#include "dtrace.h"
> +
> +struct syscall_data {
> +	struct pt_regs *regs;
> +	long syscall_nr;
> +	long arg[6];
> +};
> +
> +struct bpf_map_def SEC("maps") buffers = {
> +	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
> +	.key_size = sizeof(u32),
> +	.value_size = sizeof(u32),
> +	.max_entries = NR_CPUS,
> +};
> +
> +#if defined(bpf_target_x86)
> +# define PT_REGS_PARM6(x)	((x)->r9)
> +#elif defined(bpf_target_s390x)
> +# define PT_REGS_PARM6(x)	((x)->gprs[7])
> +#elif defined(bpf_target_arm)
> +# define PT_REGS_PARM6(x)	((x)->uregs[5])
> +#elif defined(bpf_target_arm64)
> +# define PT_REGS_PARM6(x)	((x)->regs[5])
> +#elif defined(bpf_target_mips)
> +# define PT_REGS_PARM6(x)	((x)->regs[9])
> +#elif defined(bpf_target_powerpc)
> +# define PT_REGS_PARM6(x)	((x)->gpr[8])
> +#elif defined(bpf_target_sparc)
> +# define PT_REGS_PARM6(x)	((x)->u_regs[UREG_I5])
> +#else
> +# error Argument retrieval from pt_regs is not supported yet on this arch.
> +#endif
> +
> +/*
> + * We must pass a valid BPF context pointer because the bpf_perf_event_output()
> + * helper requires a BPF context pointer as first argument (and the verifier is
> + * validating that we pass a value that is known to be a context pointer).
> + *
> + * This BPF function implements the following D action:
> + * {
> + *	trace(curthread);
> + *	trace(arg0);
> + *	trace(arg1);
> + *	trace(arg2);
> + * }
> + *
> + * Expected output will look like:
> + *   CPU     ID
> + *    15  70423 0xffff8c0968bf8ec0 0x00000000000001 0x0055e019eb3f60 0x0000000000002c
> + *    15  18876 0xffff8c0968bf8ec0 0x00000000000001 0x0055e019eb3f60 0x0000000000002c
> + *    |   |     +-- curthread      +--> arg0 (fd)   +--> arg1 (buf)  +-- arg2 (count)
> + *    |   |
> + *    |   +--> probe ID
> + *    |
> + *    +--> CPU the probe fired on
> + */
> +static noinline int bpf_action(void *bpf_ctx, struct dt_bpf_context *ctx)
> +{
> +	int			cpu = bpf_get_smp_processor_id();
> +	struct data {
> +		u32	probe_id;	/* mandatory */
> +
> +		u64	task;		/* first data item (current task) */
> +		u64	arg0;		/* 2nd data item (arg0, fd) */
> +		u64	arg1;		/* 3rd data item (arg1, buf) */
> +		u64	arg2;		/* 4th data item (arg2, count) */
> +	}			rec;
> +
> +	memset(&rec, 0, sizeof(rec));
> +
> +	rec.probe_id = ctx->probe_id;
> +	rec.task = bpf_get_current_task();
> +	rec.arg0 = ctx->argv[0];
> +	rec.arg1 = ctx->argv[1];
> +	rec.arg2 = ctx->argv[2];
> +
> +	bpf_perf_event_output(bpf_ctx, &buffers, cpu, &rec, sizeof(rec));
> +
> +	return 0;
> +}
> +
> +SEC("kprobe/ksys_write")
> +int bpf_kprobe(struct pt_regs *regs)
> +{
> +	struct dt_bpf_context	ctx;
> +
> +	memset(&ctx, 0, sizeof(ctx));
> +
> +	ctx.probe_id = 18876;
> +	ctx.argv[0] = PT_REGS_PARM1(regs);
> +	ctx.argv[1] = PT_REGS_PARM2(regs);
> +	ctx.argv[2] = PT_REGS_PARM3(regs);
> +	ctx.argv[3] = PT_REGS_PARM4(regs);
> +	ctx.argv[4] = PT_REGS_PARM5(regs);
> +	ctx.argv[5] = PT_REGS_PARM6(regs);
> +
> +	return bpf_action(regs, &ctx);
> +}
> +
> +SEC("tracepoint/syscalls/sys_enter_write")
> +int bpf_tp(struct syscall_data *scd)
> +{
> +	struct dt_bpf_context	ctx;
> +
> +	memset(&ctx, 0, sizeof(ctx));
> +
> +	ctx.probe_id = 70423;
> +	ctx.argv[0] = scd->arg[0];
> +	ctx.argv[1] = scd->arg[1];
> +	ctx.argv[2] = scd->arg[2];
> +
> +	return bpf_action(scd, &ctx);
> +}
> +
> +char _license[] SEC("license") = "GPL";
> +u32 _version SEC("version") = LINUX_VERSION_CODE;
> diff --git a/tools/dtrace/dt_bpf.c b/tools/dtrace/dt_bpf.c
> new file mode 100644
> index 000000000000..78c90de016c6
> --- /dev/null
> +++ b/tools/dtrace/dt_bpf.c
> @@ -0,0 +1,185 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file provides the interface for handling BPF.  It uses the bpf library
> + * to interact with BPF ELF object files.
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <errno.h>
> +#include <stdarg.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <bpf/libbpf.h>
> +#include <linux/kernel.h>
> +#include <linux/perf_event.h>
> +#include <sys/ioctl.h>
> +
> +#include "dtrace_impl.h"
> +
> +/*
> + * Validate the output buffer map that is specified in the BPF ELF object.  It
> + * must match the following definition to be valid:
> + *
> + * struct bpf_map_def SEC("maps") buffers = {
> + *	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
> + *	.key_size = sizeof(u32),
> + *	.value_size = sizeof(u32),
> + *	.max_entries = num,
> + * };
> + * where num is greater than dt_maxcpuid.
> + */
> +static int is_valid_buffers(const struct bpf_map_def *mdef)
> +{
> +	return mdef->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY &&
> +	       mdef->key_size == sizeof(u32) &&
> +	       mdef->value_size == sizeof(u32) &&
> +	       mdef->max_entries > dt_maxcpuid;
> +}
> +
> +/*
> + * List the probes specified in the given BPF ELF object file.
> + */
> +int dt_bpf_list_probes(const char *fn)
> +{
> +	struct bpf_object	*obj;
> +	struct bpf_program	*prog;
> +	int			rc, fd;
> +
> +	libbpf_set_print(NULL);
> +
> +	/*
> +	 * Listing probes is done before the DTrace command line utility loads
> +	 * the supplied programs.  We load them here without attaching them to
> +	 * probes so that we can retrieve the ELF section names for each BPF
> +	 * program.  The section name indicates the probe that the program is
> +	 * associated with.
> +	 */
> +	rc = bpf_prog_load(fn, BPF_PROG_TYPE_UNSPEC, &obj, &fd);
> +	if (rc)
> +		return rc;
> +
> +	/*
> +	 * Loop through the programs in the BPF ELF object, and try to resolve
> +	 * the section names into probes.  Use the supplied callback function
> +	 * to emit the probe description.
> +	 */
> +	for (prog = bpf_program__next(NULL, obj); prog != NULL;
> +	     prog = bpf_program__next(prog, obj)) {
> +		struct dt_probe	*probe;
> +
> +		probe = dt_probe_resolve_event(bpf_program__title(prog, false));
> +
> +		printf("%5d %10s %17s %33s %s\n", probe->id,
> +		       probe->prv_name ? probe->prv_name : "",
> +		       probe->mod_name ? probe->mod_name : "",
> +		       probe->fun_name ? probe->fun_name : "",
> +		       probe->prb_name ? probe->prb_name : "");
> +	}
> +
> +
> +	/* Done with the BPF ELF object.  */
> +	bpf_object__close(obj);
> +
> +	return 0;
> +}
> +
> +/*
> + * Load the given BPF ELF object file.
> + */
> +int dt_bpf_load_file(const char *fn)
> +{
> +	struct bpf_object	*obj;
> +	struct bpf_map		*map;
> +	struct bpf_program	*prog;
> +	int			rc, fd;
> +
> +	libbpf_set_print(NULL);
> +
> +	/* Load the BPF ELF object file. */
> +	rc = bpf_prog_load(fn, BPF_PROG_TYPE_UNSPEC, &obj, &fd);
> +	if (rc)
> +		return rc;
> +
> +	/* Validate buffers map. */
> +	map = bpf_object__find_map_by_name(obj, "buffers");
> +	if (map && is_valid_buffers(bpf_map__def(map)))
> +		dt_bufmap_fd = bpf_map__fd(map);
> +	else
> +		goto fail;
> +
> +	/*
> +	 * Loop through the programs and resolve each into the matching probe.
> +	 * Attach the program to the probe.
> +	 */
> +	for (prog = bpf_program__next(NULL, obj); prog != NULL;
> +	     prog = bpf_program__next(prog, obj)) {
> +		struct dt_probe	*probe;
> +
> +		probe = dt_probe_resolve_event(bpf_program__title(prog, false));
> +		if (!probe)
> +			return -ENOENT;
> +		if (probe->prov && probe->prov->attach)
> +			probe->prov->attach(bpf_program__title(prog, false),
> +					    bpf_program__fd(prog));
> +	}
> +
> +	return 0;
> +
> +fail:
> +	bpf_object__close(obj);
> +	return -EINVAL;
> +}
> +
> +/*
> + * Store the (key, value) pair in the map referenced by the given fd.
> + */
> +int dt_bpf_map_update(int fd, const void *key, const void *val)
> +{
> +	union bpf_attr	attr;
> +
> +	memset(&attr, 0, sizeof(attr));
> +
> +	attr.map_fd = fd;
> +	attr.key = (u64)(unsigned long)key;
> +	attr.value = (u64)(unsigned long)val;
> +	attr.flags = 0;
> +
> +	return bpf(BPF_MAP_UPDATE_ELEM, &attr);
> +}
> +
> +/*
> + * Attach a trace event and associate a BPF program with it.
> + */
> +int dt_bpf_attach(int event_id, int bpf_fd)
> +{
> +	int			event_fd;
> +	int			rc;
> +	struct perf_event_attr	attr = {};
> +
> +	attr.type = PERF_TYPE_TRACEPOINT;
> +	attr.sample_type = PERF_SAMPLE_RAW;
> +	attr.sample_period = 1;
> +	attr.wakeup_events = 1;
> +	attr.config = event_id;
> +
> +	/*
> +	 * Register the event (based on its id), and obtain a fd.  It gets
> +	 * created as an enabled probe, so we don't have to explicitly enable
> +	 * it.
> +	 */
> +	event_fd = perf_event_open(&attr, -1, 0, -1, 0);
> +	if (event_fd < 0) {
> +		perror("sys_perf_event_open");
> +		return -1;
> +	}
> +
> +	/* Associate the BPF program with the event. */
> +	rc = ioctl(event_fd, PERF_EVENT_IOC_SET_BPF, bpf_fd);
> +	if (rc < 0) {
> +		perror("PERF_EVENT_IOC_SET_BPF");
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> diff --git a/tools/dtrace/dt_buffer.c b/tools/dtrace/dt_buffer.c
> new file mode 100644
> index 000000000000..19bb7e4cfc92
> --- /dev/null
> +++ b/tools/dtrace/dt_buffer.c
> @@ -0,0 +1,338 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file provides the tracing buffer handling for DTrace.  It makes use of
> + * the perf event output ring buffers that can be written to from BPF programs.
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <syscall.h>
> +#include <unistd.h>
> +#include <sys/epoll.h>
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +#include <linux/bpf.h>
> +#include <linux/perf_event.h>
> +#include <linux/ring_buffer.h>
> +
> +#include "dtrace_impl.h"
> +
> +/*
> + * Probe data is recorded in per-CPU perf ring buffers.
> + */
> +struct dtrace_buffer {
> +	int	cpu;			/* ID of CPU that uses this buffer */
> +	int	fd;			/* fd of perf output buffer */
> +	size_t	page_size;		/* size of each page in buffer */
> +	size_t	data_size;		/* total buffer size */
> +	u8	*base;			/* address of buffer */
> +	u8	*endp;			/* address of end of buffer */
> +	u8	*tmp;			/* temporary event buffer */
> +	u32	tmp_len;		/* length of temporary event buffer */
> +};
> +
> +static struct dtrace_buffer	*dt_buffers;
> +
> +/*
> + * File descriptor for the BPF map that holds the buffers for the online CPUs.
> + * The map is a bpf_array indexed by CPU id, and it stores a file descriptor as
> + * value (the fd for the perf_event that represents the CPU buffer).
> + */
> +int				dt_bufmap_fd = -1;
> +
> +/*
> + * Create a perf_event buffer for the given DTrace buffer.  This will create
> + * a perf_event ring_buffer, mmap it, and enable the perf_event that owns the
> + * buffer.
> + */
> +static int perf_buffer_open(struct dtrace_buffer *buf)
> +{
> +	int			pefd;
> +	struct perf_event_attr	attr = {};
> +
> +	/*
> +	 * Event configuration for BPF-generated output in perf_event ring
> +	 * buffers.  The event is created in enabled state.
> +	 */
> +	attr.config = PERF_COUNT_SW_BPF_OUTPUT;
> +	attr.type = PERF_TYPE_SOFTWARE;
> +	attr.sample_type = PERF_SAMPLE_RAW;
> +	attr.sample_period = 1;
> +	attr.wakeup_events = 1;
> +	pefd = perf_event_open(&attr, -1, buf->cpu, -1, PERF_FLAG_FD_CLOEXEC);
> +	if (pefd < 0) {
> +		fprintf(stderr, "perf_event_open(cpu %d): %s\n", buf->cpu,
> +			strerror(errno));
> +		goto fail;
> +	}
> +
> +	/*
> +	 * We add buf->page_size to the buf->data_size, because perf maintains
> +	 * a meta-data page at the beginning of the memory region.  That page
> +	 * is used for reader/writer symchronization.
> +	 */
> +	buf->fd = pefd;
> +	buf->base = mmap(NULL, buf->page_size + buf->data_size,
> +			 PROT_READ | PROT_WRITE, MAP_SHARED, buf->fd, 0);
> +	buf->endp = buf->base + buf->page_size + buf->data_size - 1;
> +	if (!buf->base)
> +		goto fail;
> +
> +	return 0;
> +
> +fail:
> +	if (buf->base) {
> +		munmap(buf->base, buf->page_size + buf->data_size);
> +		buf->base = NULL;
> +		buf->endp = NULL;
> +	}
> +	if (buf->fd) {
> +		close(buf->fd);
> +		buf->fd = -1;
> +	}
> +
> +	return -1;
> +}
> +
> +/*
> + * Close the given DTrace buffer.  This function disables the perf_event that
> + * owns the buffer, munmaps the memory space, and closes the perf buffer fd.
> + */
> +static void perf_buffer_close(struct dtrace_buffer *buf)
> +{
> +	/*
> +	 * If the perf buffer failed to open, there is no need to close it.
> +	 */
> +	if (buf->fd < 0)
> +		return;
> +
> +	if (ioctl(buf->fd, PERF_EVENT_IOC_DISABLE, 0) < 0)
> +		fprintf(stderr, "PERF_EVENT_IOC_DISABLE(cpu %d): %s\n",
> +			buf->cpu, strerror(errno));
> +
> +	munmap(buf->base, buf->page_size + buf->data_size);
> +
> +	if (close(buf->fd))
> +		fprintf(stderr, "perf buffer close(cpu %d): %s\n",
> +			buf->cpu, strerror(errno));
> +
> +	buf->base = NULL;
> +	buf->fd = -1;
> +}
> +
> +/*
> + * Initialize the probe data buffers (one per online CPU).  Each buffer will
> + * contain the given number of pages (i.e. total size of each buffer will be
> + * num_pages * getpagesize()).  This function also sets up an event polling
> + * descriptor that monitors all CPU buffers at once.
> + */
> +int dt_buffer_init(int num_pages)
> +{
> +	int	i;
> +	int	epoll_fd;
> +
> +	if (dt_bufmap_fd < 0)
> +		return -EINVAL;
> +
> +	/* Allocate the per-CPU buffer structs. */
> +	dt_buffers = calloc(dt_numcpus, sizeof(struct dtrace_buffer));
> +	if (dt_buffers == NULL)
> +		return -ENOMEM;
> +
> +	/* Set up the event polling file descriptor. */
> +	epoll_fd = epoll_create1(EPOLL_CLOEXEC);
> +	if (epoll_fd < 0) {
> +		free(dt_buffers);
> +		return -errno;
> +	}
> +
> +	for (i = 0; i < dt_numcpus; i++) {
> +		int			cpu = dt_cpuids[i];
> +		struct epoll_event	ev;
> +		struct dtrace_buffer	*buf = &dt_buffers[i];
> +
> +		buf->cpu = cpu;
> +		buf->page_size = getpagesize();
> +		buf->data_size = num_pages * buf->page_size;
> +		buf->tmp = NULL;
> +		buf->tmp_len = 0;
> +
> +		/* Try to create the perf buffer for this DTrace buffer. */
> +		if (perf_buffer_open(buf) == -1)
> +			continue;
> +
> +		/* Store the perf buffer fd in the buffer map. */
> +		dt_bpf_map_update(dt_bufmap_fd, &cpu, &buf->fd);
> +
> +		/* Add the buffer to the event polling descriptor. */
> +		ev.events = EPOLLIN;
> +		ev.data.ptr = buf;
> +		if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, buf->fd, &ev) == -1) {
> +			fprintf(stderr, "EPOLL_CTL_ADD(cpu %d): %s\n",
> +				buf->cpu, strerror(errno));
> +			continue;
> +		}
> +	}
> +
> +	return epoll_fd;
> +}
> +
> +/*
> + * Clean up the buffers.
> + */
> +void dt_buffer_exit(int epoll_fd)
> +{
> +	int	i;
> +
> +	for (i = 0; i < dt_numcpus; i++)
> +		perf_buffer_close(&dt_buffers[i]);
> +
> +	free(dt_buffers);
> +	close(epoll_fd);
> +}
> +
> +/*
> + * Process and output the probe data at the supplied address.
> + */
> +static void output_event(int cpu, u64 *buf)
> +{
> +	u8				*data = (u8 *)buf;
> +	struct perf_event_header	*hdr;
> +
> +	hdr = (struct perf_event_header *)data;
> +	data += sizeof(struct perf_event_header);
> +
> +	if (hdr->type == PERF_RECORD_SAMPLE) {
> +		u8		*ptr = data;
> +		u32		i, size, probe_id;
> +
> +		/*
> +		 * struct {
> +		 *	struct perf_event_header	header;
> +		 *	u32				size;
> +		 *	u32				probe_id;
> +		 *	u32				gap;
> +		 *	u64				data[n];
> +		 * }
> +		 * and data points to the 'size' member at this point.
> +		 */
> +		if (ptr > (u8 *)buf + hdr->size) {
> +			fprintf(stderr, "BAD: corrupted sample header\n");
> +			return;
> +		}
> +
> +		size = *(u32 *)data;
> +		data += sizeof(size);
> +		ptr += sizeof(size) + size;
> +		if (ptr != (u8 *)buf + hdr->size) {
> +			fprintf(stderr, "BAD: invalid sample size\n");
> +			return;
> +		}
> +
> +		probe_id = *(u32 *)data;
> +		data += sizeof(probe_id);
> +		size -= sizeof(probe_id);
> +		data += sizeof(u32);		/* skip 32-bit gap */
> +		size -= sizeof(u32);
> +		buf = (u64 *)data;
> +
> +		printf("%3d %6d ", cpu, probe_id);
> +		for (i = 0, size /= sizeof(u64); i < size; i++)
> +			printf("%#016lx ", buf[i]);
> +		printf("\n");
> +	} else if (hdr->type == PERF_RECORD_LOST) {
> +		u64	lost;
> +
> +		/*
> +		 * struct {
> +		 *	struct perf_event_header	header;
> +		 *	u64				id;
> +		 *	u64				lost;
> +		 * }
> +		 * and data points to the 'id' member at this point.
> +		 */
> +		lost = *(u64 *)(data + sizeof(u64));
> +
> +		printf("[%ld probes dropped]\n", lost);
> +	} else
> +		fprintf(stderr, "UNKNOWN: record type %d\n", hdr->type);
> +}
> +
> +/*
> + * Process the available probe data in the given buffer.
> + */
> +static void process_data(struct dtrace_buffer *buf)
> +{
> +	struct perf_event_mmap_page	*rb_page = (void *)buf->base;
> +	struct perf_event_header	*hdr;
> +	u8				*base;
> +	u64				head, tail;
> +
> +	/* Set base to be the start of the buffer data. */
> +	base = buf->base + buf->page_size;
> +
> +	for (;;) {
> +		head = ring_buffer_read_head(rb_page);
> +		tail = rb_page->data_tail;
> +
> +		if (tail == head)
> +			break;
> +
> +		do {
> +			u8	*event = base + tail % buf->data_size;
> +			u32	len;
> +
> +			hdr = (struct perf_event_header *)event;
> +			len = hdr->size;
> +
> +			/*
> +			 * If the perf event data wraps around the boundary of
> +			 * the buffer, we make a copy in contiguous memory.
> +			 */
> +			if (event + len > buf->endp) {
> +				u8	*dst;
> +				u32	num;
> +
> +				/* Increase buffer as needed. */
> +				if (buf->tmp_len < len) {
> +					buf->tmp = realloc(buf->tmp, len);
> +					buf->tmp_len = len;
> +				}
> +
> +				dst = buf->tmp;
> +				num = buf->endp - event + 1;
> +				memcpy(dst, event, num);
> +				memcpy(dst + num, base, len - num);
> +
> +				event = dst;
> +			}
> +
> +			output_event(buf->cpu, (u64 *)event);
> +
> +			tail += hdr->size;
> +		} while (tail != head);
> +
> +		ring_buffer_write_tail(rb_page, tail);
> +	}
> +}
> +
> +/*
> + * Wait for data to become available in any of the buffers.
> + */
> +int dt_buffer_poll(int epoll_fd, int timeout)
> +{
> +	struct epoll_event	events[dt_numcpus];
> +	int			i, cnt;
> +
> +	cnt = epoll_wait(epoll_fd, events, dt_numcpus, timeout);
> +	if (cnt < 0)
> +		return -errno;
> +
> +	for (i = 0; i < cnt; i++)
> +		process_data((struct dtrace_buffer *)events[i].data.ptr);
> +
> +	return cnt;
> +}
> diff --git a/tools/dtrace/dt_fbt.c b/tools/dtrace/dt_fbt.c
> new file mode 100644
> index 000000000000..fcf95243bf97
> --- /dev/null
> +++ b/tools/dtrace/dt_fbt.c
> @@ -0,0 +1,201 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The Function Boundary Tracing (FBT) provider for DTrace.
> + *
> + * FBT probes are exposed by the kernel as kprobes.  They are listed in the
> + * TRACEFS/available_filter_functions file.  Some kprobes are associated with
> + * a specific kernel module, while most are in the core kernel.
> + *
> + * Mapping from event name to DTrace probe name:
> + *
> + *      <name>					fbt:vmlinux:<name>:entry
> + *						fbt:vmlinux:<name>:return
> + *   or
> + *      <name> [<modname>]			fbt:<modname>:<name>:entry
> + *						fbt:<modname>:<name>:return
> + *
> + * Mapping from BPF section name to DTrace probe name:
> + *
> + *      kprobe/<name>				fbt:vmlinux:<name>:entry
> + *      kretprobe/<name>			fbt:vmlinux:<name>:return
> + *
> + * (Note that the BPF section does not carry information about the module that
> + *  the function is found in.  This means that BPF section name cannot be used
> + *  to distinguish between functions with the same name occurring in different
> + *  modules.)
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <linux/bpf.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +
> +#include "dtrace_impl.h"
> +
> +#define KPROBE_EVENTS	TRACEFS "kprobe_events"
> +#define PROBE_LIST	TRACEFS "available_filter_functions"
> +
> +static const char	provname[] = "fbt";
> +static const char	modname[] = "vmlinux";
> +
> +/*
> + * Scan the PROBE_LIST file and add entry and return probes for every function
> + * that is listed.
> + */
> +static int fbt_populate(void)
> +{
> +	FILE			*f;
> +	char			buf[256];
> +	char			*p;
> +
> +	f = fopen(PROBE_LIST, "r");
> +	if (f == NULL)
> +		return -1;
> +
> +	while (fgets(buf, sizeof(buf), f)) {
> +		/*
> +		 * Here buf is either "funcname\n" or "funcname [modname]\n".
> +		 */
> +		p = strchr(buf, '\n');
> +		if (p) {
> +			*p = '\0';
> +			if (p > buf && *(--p) == ']')
> +				*p = '\0';
> +		} else {
> +			/* If we didn't see a newline, the line was too long.
> +			 * Report it, and continue until the end of the line.
> +			 */
> +			fprintf(stderr, "%s: Line too long: %s\n",
> +				PROBE_LIST, buf);
> +			do
> +				fgets(buf, sizeof(buf), f);
> +			while (strchr(buf, '\n') == NULL);
> +			continue;
> +		}
> +
> +		/*
> +		 * Now buf is either "funcname" or "funcname [modname".  If
> +		 * there is no module name provided, we will use the default.
> +		 */
> +		p = strchr(buf, ' ');
> +		if (p) {
> +			*p++ = '\0';
> +			if (*p == '[')
> +				p++;
> +		}
> +
> +		dt_probe_new(&dt_fbt, provname, p ? p : modname, buf, "entry");
> +		dt_probe_new(&dt_fbt, provname, p ? p : modname, buf, "return");
> +	}
> +
> +	fclose(f);
> +
> +	return 0;
> +}
> +
> +#define ENTRY_PREFIX	"kprobe/"
> +#define EXIT_PREFIX	"kretprobe/"
> +
> +/*
> + * Perform a probe lookup based on an event name (BPF ELF section name).
> + */
> +static struct dt_probe *fbt_resolve_event(const char *name)
> +{
> +	const char	*prbname;
> +	struct dt_probe	tmpl;
> +	struct dt_probe	*probe;
> +
> +	if (!name)
> +		return NULL;
> +
> +	if (strncmp(name, ENTRY_PREFIX, sizeof(ENTRY_PREFIX) - 1) == 0) {
> +		name += sizeof(ENTRY_PREFIX) - 1;
> +		prbname = "entry";
> +	} else if (strncmp(name, EXIT_PREFIX, sizeof(EXIT_PREFIX) - 1) == 0) {
> +		name += sizeof(EXIT_PREFIX) - 1;
> +		prbname = "return";
> +	} else
> +		return NULL;
> +
> +	memset(&tmpl, 0, sizeof(tmpl));
> +	tmpl.prv_name = provname;
> +	tmpl.mod_name = modname;
> +	tmpl.fun_name = name;
> +	tmpl.prb_name = prbname;
> +
> +	probe = dt_probe_by_name(&tmpl);
> +
> +	return probe;
> +}
> +
> +/*
> + * Attach the given BPF program (identified by its file descriptor) to the
> + * kprobe identified by the given section name.
> + */
> +static int fbt_attach(const char *name, int bpf_fd)
> +{
> +	char    efn[256];
> +	char    buf[256];
> +	int	event_id, fd, rc;
> +
> +	name += 7;				/* skip "kprobe/" */
> +	snprintf(buf, sizeof(buf), "p:%s %s\n", name, name);
> +
> +	/*
> +	 * Register the kprobe with the tracing subsystem.  This will create
> +	 * a tracepoint event.
> +	 */
> +	fd = open(KPROBE_EVENTS, O_WRONLY | O_APPEND);
> +	if (fd < 0) {
> +		perror(KPROBE_EVENTS);
> +		return -1;
> +	}
> +	rc = write(fd, buf, strlen(buf));
> +	if (rc < 0) {
> +		perror(KPROBE_EVENTS);
> +		close(fd);
> +		return -1;
> +	}
> +	close(fd);
> +
> +	/*
> +	 * Read the tracepoint event id for the kprobe we just registered.
> +	 */
> +	strcpy(efn, EVENTSFS);
> +	strcat(efn, "kprobes/");
> +	strcat(efn, name);
> +	strcat(efn, "/id");
> +
> +	fd = open(efn, O_RDONLY);
> +	if (fd < 0) {
> +		perror(efn);
> +		return -1;
> +	}
> +	rc = read(fd, buf, sizeof(buf));
> +	if (rc < 0 || rc >= sizeof(buf)) {
> +		perror(efn);
> +		close(fd);
> +		return -1;
> +	}
> +	close(fd);
> +	buf[rc] = '\0';
> +	event_id = atoi(buf);
> +
> +	/*
> +	 * Attaching a BPF program (by file descriptor) to an event (by ID) is
> +	 * a generic operation provided by the BPF interface code.
> +	 */
> +	return dt_bpf_attach(event_id, bpf_fd);
> +}
> +
> +struct dt_provider	dt_fbt = {
> +	.name		= "fbt",
> +	.populate	= &fbt_populate,
> +	.resolve_event	= &fbt_resolve_event,
> +	.attach		= &fbt_attach,
> +};
> diff --git a/tools/dtrace/dt_hash.c b/tools/dtrace/dt_hash.c
> new file mode 100644
> index 000000000000..b1f563bc0773
> --- /dev/null
> +++ b/tools/dtrace/dt_hash.c
> @@ -0,0 +1,211 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file provides a generic hashtable implementation for probes.
> + *
> + * The hashtable is created with 4 user-provided functions:
> + *	hval(probe)		- calculate a hash value for the given probe
> + *	cmp(probe1, probe2)	- compare two probes
> + *	add(head, probe)	- add a probe to a list of probes
> + *	del(head, probe)	- delete a probe from a list of probes
> + *
> + * Probes are hashed into a hashtable slot based on the return value of
> + * hval(probe).  Each hashtable slot holds a list of buckets, with each
> + * bucket storing probes that are equal under the cmp(probe1, probe2)
> + * function. Probes are added to the list of probes in a bucket using the
> + * add(head, probe) function, and they are deleted using a call to the
> + * del(head, probe) function.
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <errno.h>
> +#include <stdint.h>
> +#include <stdlib.h>
> +
> +#include "dtrace_impl.h"
> +
> +/*
> + * Hashtable implementation for probes.
> + */
> +struct dt_hbucket {
> +	u32			hval;
> +	struct dt_hbucket	*next;
> +	struct dt_probe		*head;
> +	int			nprobes;
> +};
> +
> +struct dt_htab {
> +	struct dt_hbucket	**tab;
> +	int			size;
> +	int			mask;
> +	int			nbuckets;
> +	dt_hval_fn		hval;		/* calculate hash value */
> +	dt_cmp_fn		cmp;		/* compare 2 probes */
> +	dt_add_fn		add;		/* add probe to list */
> +	dt_del_fn		del;		/* delete probe from list */
> +};
> +
> +/*
> + * Create a new (empty) hashtable.
> + */
> +struct dt_htab *dt_htab_new(dt_hval_fn hval, dt_cmp_fn cmp, dt_add_fn add,
> +			    dt_del_fn del)
> +{
> +	struct dt_htab	*htab = malloc(sizeof(struct dt_htab));
> +
> +	if (!htab)
> +		return NULL;
> +
> +	htab->size = 1;
> +	htab->mask = htab->size - 1;
> +	htab->nbuckets = 0;
> +	htab->hval = hval;
> +	htab->cmp = cmp;
> +	htab->add = add;
> +	htab->del = del;
> +
> +	htab->tab = calloc(htab->size, sizeof(struct dt_hbucket *));
> +	if (!htab->tab) {
> +		free(htab);
> +		return NULL;
> +	}
> +
> +	return htab;
> +}
> +
> +/*
> + * Resize the hashtable by doubling the number of slots.
> + */
> +static int resize(struct dt_htab *htab)
> +{
> +	int			i;
> +	int			osize = htab->size;
> +	int			nsize = osize << 1;
> +	int			nmask = nsize - 1;
> +	struct dt_hbucket	**ntab;
> +
> +	ntab = calloc(nsize, sizeof(struct dt_hbucket *));
> +	if (!ntab)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < osize; i++) {
> +		struct dt_hbucket	*bucket, *next;
> +
> +		for (bucket = htab->tab[i]; bucket; bucket = next) {
> +			int	idx	= bucket->hval & nmask;
> +
> +			next = bucket->next;
> +			bucket->next = ntab[idx];
> +			ntab[idx] = bucket;
> +		}
> +	}
> +
> +	free(htab->tab);
> +	htab->tab = ntab;
> +	htab->size = nsize;
> +	htab->mask = nmask;
> +
> +	return 0;
> +}
> +
> +/*
> + * Add a probe to the hashtable.  Resize if necessary, and allocate a new
> + * bucket if necessary.
> + */
> +int dt_htab_add(struct dt_htab *htab, struct dt_probe *probe)
> +{
> +	u32			hval = htab->hval(probe);
> +	int			idx;
> +	struct dt_hbucket	*bucket;
> +
> +retry:
> +	idx = hval & htab->mask;
> +	for (bucket = htab->tab[idx]; bucket; bucket = bucket->next) {
> +		if (htab->cmp(bucket->head, probe) == 0)
> +			goto add;
> +	}
> +
> +	if ((htab->nbuckets >> 1) > htab->size) {
> +		int	err;
> +
> +		err = resize(htab);
> +		if (err)
> +			return err;
> +
> +		goto retry;
> +	}
> +
> +	bucket = malloc(sizeof(struct dt_hbucket));
> +	if (!bucket)
> +		return -ENOMEM;
> +
> +	bucket->hval = hval;
> +	bucket->next = htab->tab[idx];
> +	bucket->head = NULL;
> +	bucket->nprobes = 0;
> +	htab->tab[idx] = bucket;
> +	htab->nbuckets++;
> +
> +add:
> +	bucket->head = htab->add(bucket->head, probe);
> +	bucket->nprobes++;
> +
> +	return 0;
> +}
> +
> +/*
> + * Find a probe in the hashtable.
> + */
> +struct dt_probe *dt_htab_lookup(const struct dt_htab *htab,
> +				const struct dt_probe *probe)
> +{
> +	u32			hval = htab->hval(probe);
> +	int			idx = hval & htab->mask;
> +	struct dt_hbucket	*bucket;
> +
> +	for (bucket = htab->tab[idx]; bucket; bucket = bucket->next) {
> +		if (htab->cmp(bucket->head, probe) == 0)
> +			return bucket->head;
> +	}
> +
> +	return NULL;
> +}
> +
> +/*
> + * Remove a probe from the hashtable.  If we are deleting the last probe in a
> + * bucket, get rid of the bucket.
> + */
> +int dt_htab_del(struct dt_htab *htab, struct dt_probe *probe)
> +{
> +	u32			hval = htab->hval(probe);
> +	int			idx = hval & htab->mask;
> +	struct dt_hbucket	*bucket;
> +	struct dt_probe		*head;
> +
> +	for (bucket = htab->tab[idx]; bucket; bucket = bucket->next) {
> +		if (htab->cmp(bucket->head, probe) == 0)
> +			break;
> +	}
> +
> +	if (bucket == NULL)
> +		return -ENOENT;
> +
> +	head = htab->del(bucket->head, probe);
> +	if (!head) {
> +		struct dt_hbucket	*b = htab->tab[idx];
> +
> +		if (bucket == b)
> +			htab->tab[idx] = bucket->next;
> +		else {
> +			while (b->next != bucket)
> +				b = b->next;
> +
> +			b->next = bucket->next;
> +		}
> +
> +		htab->nbuckets--;
> +		free(bucket);
> +	} else
> +		bucket->head = head;
> +
> +	return 0;
> +}
> diff --git a/tools/dtrace/dt_probe.c b/tools/dtrace/dt_probe.c
> new file mode 100644
> index 000000000000..0b6228eaff29
> --- /dev/null
> +++ b/tools/dtrace/dt_probe.c
> @@ -0,0 +1,230 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file implements the interface to probes grouped by provider.
> + *
> + * Probes are named by a set of 4 identifiers:
> + *	- provider name
> + *	- module name
> + *	- function name
> + *	- probe name
> + *
> + * The Fully Qualified Name (FQN) is "provider:module:function:name".
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <linux/bpf.h>
> +#include <linux/kernel.h>
> +
> +#include "dtrace_impl.h"
> +
> +static struct dt_provider      *dt_providers[] = {
> +							&dt_fbt,
> +							&dt_syscall,
> +						 };
> +
> +static struct dt_htab	*ht_byfqn;
> +
> +static u32		next_probe_id;
> +
> +/*
> + * Calculate a hash value based on a given string and an initial value.  The
> + * initial value is used to calculate compound hash values, e.g.
> + *
> + *	u32	hval;
> + *
> + *	hval = str2hval(str1, 0);
> + *	hval = str2hval(str2, hval);
> + */
> +static u32 str2hval(const char *p, u32 hval)
> +{
> +	u32	g;
> +
> +	if (!p)
> +		return hval;
> +
> +	while (*p) {
> +		hval = (hval << 4) + *p++;
> +		g = hval & 0xf0000000;
> +		if (g != 0)
> +			hval ^= g >> 24;
> +
> +		hval &= ~g;
> +	}
> +
> +	return hval;
> +}
> +
> +/*
> + * String compare function that can handle either or both strings being NULL.
> + */
> +static int safe_strcmp(const char *p, const char *q)
> +{
> +	return (!p) ? (!q) ? 0
> +			   : -1
> +		    : (!q) ? 1
> +			   : strcmp(p, q);
> +}
> +
> +/*
> + * Calculate the hash value of a probe as the cummulative hash value of the
> + * FQN.
> + */
> +static u32 fqn_hval(const struct dt_probe *probe)
> +{
> +	u32	hval = 0;
> +
> +	hval = str2hval(probe->prv_name, hval);
> +	hval = str2hval(":", hval);
> +	hval = str2hval(probe->mod_name, hval);
> +	hval = str2hval(":", hval);
> +	hval = str2hval(probe->fun_name, hval);
> +	hval = str2hval(":", hval);
> +	hval = str2hval(probe->prb_name, hval);
> +
> +	return hval;
> +}
> +
> +/*
> + * Compare two probes based on the FQN.
> + */
> +static int fqn_cmp(const struct dt_probe *p, const struct dt_probe *q)
> +{
> +	int	rc;
> +
> +	rc = safe_strcmp(p->prv_name, q->prv_name);
> +	if (rc)
> +		return rc;
> +	rc = safe_strcmp(p->mod_name, q->mod_name);
> +	if (rc)
> +		return rc;
> +	rc = safe_strcmp(p->fun_name, q->fun_name);
> +	if (rc)
> +		return rc;
> +	rc = safe_strcmp(p->prb_name, q->prb_name);
> +	if (rc)
> +		return rc;
> +
> +	return 0;
> +}
> +
> +/*
> + * Add the given probe 'new' to the double-linked probe list 'head'.  Probe
> + * 'new' becomes the new list head.
> + */
> +static struct dt_probe *fqn_add(struct dt_probe *head, struct dt_probe *new)
> +{
> +	if (!head)
> +		return new;
> +
> +	new->he_fqn.next = head;
> +	head->he_fqn.prev = new;
> +
> +	return new;
> +}
> +
> +/*
> + * Remove the given probe 'probe' from the double-linked probe list 'head'.
> + * If we are deleting the current head, the next probe in the list is returned
> + * as the new head.  If that value is NULL, the list is now empty.
> + */
> +static struct dt_probe *fqn_del(struct dt_probe *head, struct dt_probe *probe)
> +{
> +	if (head == probe) {
> +		if (!probe->he_fqn.next)
> +			return NULL;
> +
> +		head = probe->he_fqn.next;
> +		head->he_fqn.prev = NULL;
> +		probe->he_fqn.next = NULL;
> +
> +		return head;
> +	}
> +
> +	if (!probe->he_fqn.next) {
> +		probe->he_fqn.prev->he_fqn.next = NULL;
> +		probe->he_fqn.prev = NULL;
> +
> +		return head;
> +	}
> +
> +	probe->he_fqn.prev->he_fqn.next = probe->he_fqn.next;
> +	probe->he_fqn.next->he_fqn.prev = probe->he_fqn.prev;
> +	probe->he_fqn.prev = probe->he_fqn.next = NULL;
> +
> +	return head;
> +}
> +
> +/*
> + * Initialize the probe handling by populating the FQN hashtable with probes
> + * from all providers.
> + */
> +int dt_probe_init(void)
> +{
> +	int	i;
> +
> +	ht_byfqn = dt_htab_new(fqn_hval, fqn_cmp, fqn_add, fqn_del);
> +
> +	for (i = 0; i < ARRAY_SIZE(dt_providers); i++) {
> +		if (dt_providers[i]->populate() < 0)
> +			return -1;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Allocate a new probe and add it to the FQN hashtable.
> + */
> +int dt_probe_new(const struct dt_provider *prov, const char *pname,
> +		 const char *mname, const char *fname, const char *name)
> +{
> +	struct dt_probe	*probe;
> +
> +	probe = malloc(sizeof(struct dt_probe));
> +	if (!probe)
> +		return -ENOMEM;
> +
> +	memset(probe, 0, sizeof(struct dt_probe));
> +	probe->id = next_probe_id++;
> +	probe->prov = prov;
> +	probe->prv_name = pname ? strdup(pname) : NULL;
> +	probe->mod_name = mname ? strdup(mname) : NULL;
> +	probe->fun_name = fname ? strdup(fname) : NULL;
> +	probe->prb_name = name ? strdup(name) : NULL;
> +
> +	dt_htab_add(ht_byfqn, probe);
> +
> +	return 0;
> +}
> +
> +/*
> + * Perform a probe lookup based on FQN.
> + */
> +struct dt_probe *dt_probe_by_name(const struct dt_probe *tmpl)
> +{
> +	return dt_htab_lookup(ht_byfqn, tmpl);
> +}
> +
> +/*
> + * Resolve an event name (BPF ELF section name) into a probe.  We query each
> + * provider, and as soon as we get a hit, we return the result.
> + */
> +struct dt_probe *dt_probe_resolve_event(const char *name)
> +{
> +	int		i;
> +	struct dt_probe	*probe;
> +
> +	for (i = 0; i < ARRAY_SIZE(dt_providers); i++) {
> +		if (!dt_providers[i]->resolve_event)
> +			continue;
> +		probe = dt_providers[i]->resolve_event(name);
> +		if (probe)
> +			return probe;
> +	}
> +
> +	return NULL;
> +}
> diff --git a/tools/dtrace/dt_syscall.c b/tools/dtrace/dt_syscall.c
> new file mode 100644
> index 000000000000..6695a4a1c701
> --- /dev/null
> +++ b/tools/dtrace/dt_syscall.c
> @@ -0,0 +1,179 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The syscall provider for DTrace.
> + *
> + * System call probes are exposed by the kernel as tracepoint events in the
> + * "syscalls" group.  Entry probe names start with "sys_enter_" and exit probes
> + * start with "sys_exit_".
> + *
> + * Mapping from event name to DTrace probe name:
> + *
> + *	syscalls:sys_enter_<name>		syscall:vmlinux:<name>:entry
> + *	syscalls:sys_exit_<name>		syscall:vmlinux:<name>:return
> + *
> + * Mapping from BPF section name to DTrace probe name:
> + *
> + *	tracepoint/syscalls/sys_enter_<name>	syscall:vmlinux:<name>:entry
> + *	tracepoint/syscalls/sys_exit_<name>	syscall:vmlinux:<name>:return
> + *
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <ctype.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <linux/bpf.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +
> +#include "dtrace_impl.h"
> +
> +static const char	provname[] = "syscall";
> +static const char	modname[] = "vmlinux";
> +
> +#define PROBE_LIST	TRACEFS "available_events"
> +
> +#define PROV_PREFIX	"syscalls:"
> +#define ENTRY_PREFIX	"sys_enter_"
> +#define EXIT_PREFIX	"sys_exit_"
> +
> +/*
> + * Scan the PROBE_LIST file and add probes for any syscalls events.
> + */
> +static int syscall_populate(void)
> +{
> +	FILE			*f;
> +	char			buf[256];
> +
> +	f = fopen(PROBE_LIST, "r");
> +	if (f == NULL)
> +		return -1;
> +
> +	while (fgets(buf, sizeof(buf), f)) {
> +		char	*p;
> +
> +		/* * Here buf is "group:event".  */
> +		p = strchr(buf, '\n');
> +		if (p)
> +			*p = '\0';
> +		else {
> +			/*
> +			 * If we didn't see a newline, the line was too long.
> +			 * Report it, and continue until the end of the line.
> +			 */
> +			fprintf(stderr, "%s: Line too long: %s\n",
> +				PROBE_LIST, buf);
> +			do
> +				fgets(buf, sizeof(buf), f);
> +			while (strchr(buf, '\n') == NULL);
> +			continue;
> +		}
> +
> +		/* We need "group:" to match "syscalls:". */
> +		p = buf;
> +		if (memcmp(p, PROV_PREFIX, sizeof(PROV_PREFIX) - 1) != 0)
> +			continue;
> +
> +		p += sizeof(PROV_PREFIX) - 1;
> +		/*
> +		 * Now p will be just "event", and we are only interested in
> +		 * events that match "sys_enter_*" or "sys_exit_*".
> +		 */
> +		if (!memcmp(p, ENTRY_PREFIX, sizeof(ENTRY_PREFIX) - 1)) {
> +			p += sizeof(ENTRY_PREFIX) - 1;
> +			dt_probe_new(&dt_syscall, provname, modname, p,
> +				     "entry");
> +		} else if (!memcmp(p, EXIT_PREFIX, sizeof(EXIT_PREFIX) - 1)) {
> +			p += sizeof(EXIT_PREFIX) - 1;
> +			dt_probe_new(&dt_syscall, provname, modname, p,
> +				     "return");
> +		}
> +	}
> +
> +	fclose(f);
> +
> +	return 0;
> +}
> +
> +#define EVENT_PREFIX	"tracepoint/syscalls/"
> +
> +/*
> + * Perform a probe lookup based on an event name (BPF ELF section name).
> + */
> +static struct dt_probe *systrace_resolve_event(const char *name)
> +{
> +	const char	*prbname;
> +	struct dt_probe	tmpl;
> +	struct dt_probe	*probe;
> +
> +	if (!name)
> +		return NULL;
> +
> +	/* Exclude anything that is not a syscalls tracepoint */
> +	if (strncmp(name, EVENT_PREFIX, sizeof(EVENT_PREFIX) - 1) != 0)
> +		return NULL;
> +	name += sizeof(EVENT_PREFIX) - 1;
> +
> +	if (strncmp(name, ENTRY_PREFIX, sizeof(ENTRY_PREFIX) - 1) == 0) {
> +		name += sizeof(ENTRY_PREFIX) - 1;
> +		prbname = "entry";
> +	} else if (strncmp(name, EXIT_PREFIX, sizeof(EXIT_PREFIX) - 1) == 0) {
> +		name += sizeof(EXIT_PREFIX) - 1;
> +		prbname = "return";
> +	} else
> +		return NULL;
> +
> +	memset(&tmpl, 0, sizeof(tmpl));
> +	tmpl.prv_name = provname;
> +	tmpl.mod_name = modname;
> +	tmpl.fun_name = name;
> +	tmpl.prb_name = prbname;
> +
> +	probe = dt_probe_by_name(&tmpl);
> +
> +	return probe;
> +}
> +
> +#define SYSCALLSFS	EVENTSFS "syscalls/"
> +
> +/*
> + * Attach the given BPF program (identified by its file descriptor) to the
> + * event identified by the given section name.
> + */
> +static int syscall_attach(const char *name, int bpf_fd)
> +{
> +	char    efn[256];
> +	char    buf[256];
> +	int	event_id, fd, rc;
> +
> +	name += sizeof(EVENT_PREFIX) - 1;
> +	strcpy(efn, SYSCALLSFS);
> +	strcat(efn, name);
> +	strcat(efn, "/id");
> +
> +	fd = open(efn, O_RDONLY);
> +	if (fd < 0) {
> +		perror(efn);
> +		return -1;
> +	}
> +	rc = read(fd, buf, sizeof(buf));
> +	if (rc < 0 || rc >= sizeof(buf)) {
> +		perror(efn);
> +		close(fd);
> +		return -1;
> +	}
> +	close(fd);
> +	buf[rc] = '\0';
> +	event_id = atoi(buf);
> +
> +	return dt_bpf_attach(event_id, bpf_fd);
> +}
> +
> +struct dt_provider	dt_syscall = {
> +	.name		= "syscall",
> +	.populate	= &syscall_populate,
> +	.resolve_event	= &systrace_resolve_event,
> +	.attach		= &syscall_attach,
> +};
> diff --git a/tools/dtrace/dt_utils.c b/tools/dtrace/dt_utils.c
> new file mode 100644
> index 000000000000..55d51bae1d97
> --- /dev/null
> +++ b/tools/dtrace/dt_utils.c
> @@ -0,0 +1,132 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +#include "dtrace_impl.h"
> +
> +#define BUF_SIZE	1024		/* max size for online cpu data */
> +
> +int	dt_numcpus;			/* number of online CPUs */
> +int	dt_maxcpuid;			/* highest CPU id */
> +int	*dt_cpuids;			/* list of CPU ids */
> +
> +/*
> + * Populate the online CPU id information from sysfs data.  We only do this
> + * once because we do not care about CPUs coming online after we started
> + * tracing.  If a CPU goes offline during tracing, we do not care either
> + * because that simply means that it won't be writing any new probe data into
> + * its buffer.
> + */
> +void cpu_list_populate(void)
> +{
> +	char buf[BUF_SIZE];
> +	int fd, cnt, start, end, i;
> +	int *cpu;
> +	char *p, *q;
> +
> +	fd = open("/sys/devices/system/cpu/online", O_RDONLY);
> +	if (fd < 0)
> +		goto fail;
> +	cnt = read(fd, buf, sizeof(buf));
> +	close(fd);
> +	if (cnt <= 0)
> +		goto fail;
> +
> +	/*
> +	 * The string should always end with a newline, but let's make sure.
> +	 */
> +	if (buf[cnt - 1] == '\n')
> +		buf[--cnt] = 0;
> +
> +	/*
> +	 * Count how many CPUs we have.
> +	 */
> +	dt_numcpus = 0;
> +	p = buf;
> +	do {
> +		start = (int)strtol(p, &q, 10);
> +		switch (*q) {
> +		case '-':		/* range */
> +			p = q + 1;
> +			end = (int)strtol(p, &q, 10);
> +			dt_numcpus += end - start + 1;
> +			if (*q == 0) {	/* end of string */
> +				p = q;
> +				break;
> +			}
> +			if (*q != ',')
> +				goto fail;
> +			p = q + 1;
> +			break;
> +		case 0:			/* end of string */
> +			dt_numcpus++;
> +			p = q;
> +			break;
> +		case ',':	/* gap  */
> +			dt_numcpus++;
> +			p = q + 1;
> +			break;
> +		}
> +	} while (*p != 0);
> +
> +	dt_cpuids = calloc(dt_numcpus,  sizeof(int));
> +	cpu = dt_cpuids;
> +
> +	/*
> +	 * Fill in the CPU ids.
> +	 */
> +	p = buf;
> +	do {
> +		start = (int)strtol(p, &q, 10);
> +		switch (*q) {
> +		case '-':		/* range */
> +			p = q + 1;
> +			end = (int)strtol(p, &q, 10);
> +			for (i = start; i <= end; i++)
> +				*cpu++ = i;
> +			if (*q == 0) {	/* end of string */
> +				p = q;
> +				break;
> +			}
> +			if (*q != ',')
> +				goto fail;
> +			p = q + 1;
> +			break;
> +		case 0:			/* end of string */
> +			*cpu = start;
> +			p = q;
> +			break;
> +		case ',':	/* gap  */
> +			*cpu++ = start;
> +			p = q + 1;
> +			break;
> +		}
> +	} while (*p != 0);
> +
> +	/* Record the highest CPU id of the set of online CPUs. */
> +	dt_maxcpuid = *(cpu - 1);
> +
> +	return;
> +fail:
> +	if (dt_cpuids)
> +		free(dt_cpuids);
> +
> +	dt_numcpus = 0;
> +	dt_maxcpuid = 0;
> +	dt_cpuids = NULL;
> +}
> +
> +void cpu_list_free(void)
> +{
> +	free(dt_cpuids);
> +	dt_numcpus = 0;
> +	dt_maxcpuid = 0;
> +	dt_cpuids = NULL;
> +}
> diff --git a/tools/dtrace/dtrace.c b/tools/dtrace/dtrace.c
> new file mode 100644
> index 000000000000..36ad526c1cd4
> --- /dev/null
> +++ b/tools/dtrace/dtrace.c
> @@ -0,0 +1,249 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#include <errno.h>
> +#include <libgen.h>
> +#include <stdarg.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <linux/log2.h>
> +
> +#include "dtrace_impl.h"
> +
> +#define DTRACE_BUFSIZE	32		/* default buffer size (in pages) */
> +
> +#define DMODE_VERS	0		/* display version information (-V) */
> +#define DMODE_LIST	1		/* list probes (-l) */
> +#define DMODE_EXEC	2		/* compile program and start tracing */
> +
> +#define E_SUCCESS	0
> +#define E_ERROR		1
> +#define E_USAGE		2
> +
> +#define NUM_PAGES(sz)	(((sz) + getpagesize() - 1) / getpagesize())
> +
> +static const char		*dtrace_options = "+b:ls:V";
> +
> +static char			*g_pname;
> +static int			g_mode = DMODE_EXEC;
> +
> +static int usage(void)
> +{
> +	fprintf(stderr, "Usage: %s [-lV] [-b bufsz] -s script\n", g_pname);
> +	fprintf(stderr,
> +	"\t-b  set trace buffer size\n"
> +	"\t-l  list probes matching specified criteria\n"
> +	"\t-s  enable or list probes for the specified BPF program\n"
> +	"\t-V  report DTrace API version\n");
> +
> +	return E_USAGE;
> +}
> +
> +static u64 parse_size(const char *arg)
> +{
> +	long long	mul = 1;
> +	long long	neg, val;
> +	size_t		len;
> +	char		*end;
> +
> +	if (!arg)
> +		return -1;
> +
> +	len = strlen(arg);
> +	if (!len)
> +		return -1;
> +
> +	switch (arg[len - 1]) {
> +	case 't':
> +	case 'T':
> +		mul *= 1024;
> +		/* fall-through */
> +	case 'g':
> +	case 'G':
> +		mul *= 1024;
> +		/* fall-through */
> +	case 'm':
> +	case 'M':
> +		mul *= 1024;
> +		/* fall-through */
> +	case 'k':
> +	case 'K':
> +		mul *= 1024;
> +		/* fall-through */
> +	default:
> +		break;
> +	}
> +
> +	neg = strtoll(arg, NULL, 0);
> +	errno = 0;
> +	val = strtoull(arg, &end, 0) * mul;
> +
> +	if ((mul > 1 && end != &arg[len - 1]) || (mul == 1 && *end != '\0') ||
> +	    val < 0 || neg < 0 || errno != 0)
> +		return -1;
> +
> +	return val;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	int	i;
> +	int	modec = 0;
> +	int	bufsize = DTRACE_BUFSIZE;
> +	int	epoll_fd;
> +	int	cnt;
> +	char	**prgv;
> +	int	prgc;
> +
> +	g_pname = basename(argv[0]);
> +
> +	if (argc == 1)
> +		return usage();
> +
> +	prgc = 0;
> +	prgv = calloc(argc, sizeof(char *));
> +	if (!prgv) {
> +		fprintf(stderr, "failed to allocate memory for arguments: %s\n",
> +			strerror(errno));
> +		return E_ERROR;
> +	}
> +
> +	argv[0] = g_pname;			/* argv[0] for getopt errors */
> +
> +	for (optind = 1; optind < argc; optind++) {
> +		int	opt;
> +
> +		while ((opt = getopt(argc, argv, dtrace_options)) != EOF) {
> +			u64			val;
> +
> +			switch (opt) {
> +			case 'b':
> +				val = parse_size(optarg);
> +				if (val < 0) {
> +					fprintf(stderr, "invalid: -b %s\n",
> +						optarg);
> +					return E_ERROR;
> +				}
> +
> +				/*
> +				 * Bufsize needs to be a number of pages, and
> +				 * must be a power of 2.  This is required by
> +				 * the perf event buffer code.
> +				 */
> +				bufsize = roundup_pow_of_two(NUM_PAGES(val));
> +				if ((u64)bufsize * getpagesize() > val)
> +					fprintf(stderr,
> +						"bufsize increased to %ld\n",
> +						(u64)bufsize * getpagesize());
> +
> +				break;
> +			case 'l':
> +				g_mode = DMODE_LIST;
> +				modec++;
> +				break;
> +			case 's':
> +				prgv[prgc++] = optarg;
> +				break;
> +			case 'V':
> +				g_mode = DMODE_VERS;
> +				modec++;
> +				break;
> +			default:
> +				if (strchr(dtrace_options, opt) == NULL)
> +					return usage();
> +			}
> +		}
> +
> +		if (optind < argc) {
> +			fprintf(stderr, "unknown option '%s'\n", argv[optind]);
> +			return E_ERROR;
> +		}
> +	}
> +
> +	if (modec > 1) {
> +		fprintf(stderr,
> +			"only one of [-lV] can be specified at a time\n");
> +		return E_USAGE;
> +	}
> +
> +	/*
> +	 * We handle requests for version information first because we do not
> +	 * need probe information for it.
> +	 */
> +	if (g_mode == DMODE_VERS) {
> +		printf("%s\n"
> +		       "This is DTrace %s\n"
> +		       "dtrace(1) version-control ID: %s\n",
> +		       DT_VERS_STRING, DT_VERSION, DT_GIT_VERSION);
> +
> +		return E_SUCCESS;
> +	}
> +
> +	/* Initialize probes. */
> +	if (dt_probe_init() < 0) {
> +		fprintf(stderr, "failed to initialize probes: %s\n",
> +			strerror(errno));
> +		return E_ERROR;
> +	}
> +
> +	/*
> +	 * We handle requests to list probes next.
> +	 */
> +	if (g_mode == DMODE_LIST) {
> +		int	rc = 0;
> +
> +		printf("%5s %10s %17s %33s %s\n",
> +		       "ID", "PROVIDER", "MODULE", "FUNCTION", "NAME");
> +		for (i = 0; i < prgc; i++) {
> +			rc = dt_bpf_list_probes(prgv[i]);
> +			if (rc < 0)
> +				fprintf(stderr, "failed to load %s: %s\n",
> +					prgv[i], strerror(errno));
> +		}
> +
> +		return rc ? E_ERROR : E_SUCCESS;
> +	}
> +
> +	if (!prgc) {
> +		fprintf(stderr, "missing BPF program(s)\n");
> +		return E_ERROR;
> +	}
> +
> +	/* Process the BPF program. */
> +	for (i = 0; i < prgc; i++) {
> +		int	err;
> +
> +		err = dt_bpf_load_file(prgv[i]);
> +		if (err) {
> +			errno = -err;
> +			fprintf(stderr, "failed to load %s: %s\n",
> +				prgv[i], strerror(errno));
> +			return E_ERROR;
> +		}
> +	}
> +
> +	/* Get the list of online CPUs. */
> +	cpu_list_populate();
> +
> +	/* Initialize buffers. */
> +	epoll_fd = dt_buffer_init(bufsize);
> +	if (epoll_fd < 0) {
> +		errno = -epoll_fd;
> +		fprintf(stderr, "failed to allocate buffers: %s\n",
> +			strerror(errno));
> +		return E_ERROR;
> +	}
> +
> +	/* Process probe data. */
> +	printf("%3s %6s\n", "CPU", "ID");
> +	do {
> +		cnt = dt_buffer_poll(epoll_fd, 100);
> +	} while (cnt >= 0);
> +
> +	dt_buffer_exit(epoll_fd);
> +
> +	return E_SUCCESS;
> +}
> diff --git a/tools/dtrace/dtrace.h b/tools/dtrace/dtrace.h
> new file mode 100644
> index 000000000000..c79398432d17
> --- /dev/null
> +++ b/tools/dtrace/dtrace.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#ifndef _UAPI_LINUX_DTRACE_H
> +#define _UAPI_LINUX_DTRACE_H
> +
> +struct dt_bpf_context {
> +	u32		probe_id;
> +	u64		argv[10];
> +};
> +
> +#endif /* _UAPI_LINUX_DTRACE_H */
> diff --git a/tools/dtrace/dtrace_impl.h b/tools/dtrace/dtrace_impl.h
> new file mode 100644
> index 000000000000..9aa51b4c4aee
> --- /dev/null
> +++ b/tools/dtrace/dtrace_impl.h
> @@ -0,0 +1,101 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> + */
> +#ifndef _DTRACE_H
> +#define _DTRACE_H
> +
> +#include <unistd.h>
> +#include <bpf/libbpf.h>
> +#include <linux/types.h>
> +#include <linux/ptrace.h>
> +#include <linux/perf_event.h>
> +#include <sys/syscall.h>
> +
> +#include "dtrace.h"
> +
> +#define DT_DEBUG
> +
> +#define DT_VERS_STRING	"Oracle D 2.0.0"
> +
> +#define TRACEFS		"/sys/kernel/debug/tracing/"
> +#define EVENTSFS	TRACEFS "events/"
> +
> +extern int	dt_numcpus;
> +extern int	dt_maxcpuid;
> +extern int	*dt_cpuids;
> +
> +extern void cpu_list_populate(void);
> +extern void cpu_list_free(void);
> +
> +struct dt_provider {
> +	char		*name;
> +	int		(*populate)(void);
> +	struct dt_probe *(*resolve_event)(const char *name);
> +	int		(*attach)(const char *name, int bpf_fd);
> +};
> +
> +extern struct dt_provider	dt_fbt;
> +extern struct dt_provider	dt_syscall;
> +
> +struct dt_hentry {
> +	struct dt_probe		*next;
> +	struct dt_probe		*prev;
> +};
> +
> +struct dt_htab;
> +
> +typedef u32 (*dt_hval_fn)(const struct dt_probe *);
> +typedef int (*dt_cmp_fn)(const struct dt_probe *, const struct dt_probe *);
> +typedef struct dt_probe *(*dt_add_fn)(struct dt_probe *, struct dt_probe *);
> +typedef struct dt_probe *(*dt_del_fn)(struct dt_probe *, struct dt_probe *);
> +
> +extern struct dt_htab *dt_htab_new(dt_hval_fn hval, dt_cmp_fn cmp,
> +				   dt_add_fn add, dt_del_fn del);
> +extern int dt_htab_add(struct dt_htab *htab, struct dt_probe *probe);
> +extern struct dt_probe *dt_htab_lookup(const struct dt_htab *htab,
> +				       const struct dt_probe *probe);
> +extern int dt_htab_del(struct dt_htab *htab, struct dt_probe *probe);
> +
> +struct dt_probe {
> +	u32				id;
> +	int				event_fd;
> +	const struct dt_provider	*prov;
> +	const char			*prv_name;	/* provider name */
> +	const char			*mod_name;	/* module name */
> +	const char			*fun_name;	/* function name */
> +	const char			*prb_name;	/* probe name */
> +	struct dt_hentry		he_fqn;
> +};
> +
> +typedef void (*dt_probe_fn)(const struct dt_probe *probe);
> +
> +extern int dt_probe_init(void);
> +extern int dt_probe_new(const struct dt_provider *prov, const char *pname,
> +			const char *mname, const char *fname, const char *name);
> +extern struct dt_probe *dt_probe_by_name(const struct dt_probe *tmpl);
> +extern struct dt_probe *dt_probe_resolve_event(const char *name);
> +
> +extern int dt_bpf_list_probes(const char *fn);
> +extern int dt_bpf_load_file(const char *fn);
> +extern int dt_bpf_map_update(int fd, const void *key, const void *val);
> +extern int dt_bpf_attach(int event_id, int bpf_fd);
> +
> +extern int dt_bufmap_fd;
> +
> +extern int dt_buffer_init(int num_pages);
> +extern int dt_buffer_poll(int epoll_fd, int timeout);
> +extern void dt_buffer_exit(int epoll_fd);
> +
> +static inline int perf_event_open(struct perf_event_attr *attr, pid_t pid,
> +				  int cpu, int group_fd, unsigned long flags)
> +{
> +	return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
> +}
> +
> +extern inline int bpf(enum bpf_cmd cmd, union bpf_attr *attr)
> +{
> +	return syscall(__NR_bpf, cmd, attr, sizeof(union bpf_attr));
> +}
> +
> +#endif /* _DTRACE_H */
> -- 
> 2.20.1