usdt: daemon

This commit adds a daemon, "dtprobed", which usually runs at boot
(monitored by systemd, if possible), providing /dev/dtrace/helper using
CUSE, accepting DOF from processes doing the usual DTrace ioctl()s to
that device, and using infrastructure in prior commits in this series to
pass the DOF to a child jailed with seccomp() for parsing, and accepting
structures containing parsed results back, then emitting uprobes from
these results before allowing the ioctl()ing.  The uprobes created have
stereotyped names and argument lists that include an encoded
representation of the name of the corresponding DTrace USDT probe.  (The
name also contains the address and a number of other things, so that
probes that appear in multiple places in a process still work.)

(The CUSE device is an "unrestricted ioctl" device, which restricts
dtprobed to running only as root, because the ioctl has to pull data --
the DOF -- out of arbitrary places in the client memory according to the
passed-in structure. Since you need to be root to create uprobes at all
this is not any kind of restriction.)

Extra complexity is provided by changes to libfuse.  Recent (> 2018)
libfuse has a nice logging interface, which if available means that
libfuse will log FUSE-side problems into syslog or anywhere else of your
choosing: we emit into syslog if -d or -F (debug, foreground) are not
specified and systemd is not in use (if systemd is in use, we never
daemonize at all).  But older libfuse does not provide this, and
unfortunately OL8 (but not OL7!) has such an older libfuse.  So we add a
compatibility wrapper providing a minimal reimplementation of the
logging interface if built against such an old libfuse.  The wrapper is
named like the header and source file implementing the real thing in
FUSE itself, but prepended with rpl_ to avoid the possibility of
dependencies on header file ordering when the new FUSE code is present.

Testing-wise, in installed mode the running dtprobed daemon is used, but
in in-source-tree mode runtest.sh kicks off a new dtprobed emitting to a
local device file named /dev/dtrace/test-$pid, and uses a new
testing-only environment variable to force drti.c to emit its ioctl()s
to that temporary device.  So in-tree testing always tests the actual
dtprobed in the tree (with any bugfixes), not the system copy.

Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>

GNUmakefile

@@ -3,7 +3,7 @@
 # Build files in subdirectories are included by this file.
 #
 # Oracle Linux DTrace.
-# Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2011, 2022, Oracle and/or its affiliates. All rights reserved.
 # Licensed under the Universal Permissive License v 1.0 as shown at
 # http://oss.oracle.com/licenses/upl.
 
@@ -85,6 +85,10 @@ INCLUDEDIR := $(prefix)/include
 INSTINCLUDEDIR := $(DESTDIR)$(INCLUDEDIR)
 SBINDIR := $(prefix)/sbin
 INSTSBINDIR := $(DESTDIR)$(SBINDIR)
+UDEVDIR := $(prefix)/lib/udev/rules.d
+INSTUDEVDIR := $(DESTDIR)$(UDEVDIR)
+SYSTEMDUNITDIR := $(prefix)/lib/systemd/system
+INSTSYSTEMDUNITDIR := $(DESTDIR)$(SYSTEMDUNITDIR)
 DOCDIR := $(prefix)/share/doc/dtrace-$(VERSION)
 INSTDOCDIR := $(DESTDIR)$(DOCDIR)
 MANDIR := $(prefix)/share/man/man1

Makeconfig

@@ -72,4 +72,6 @@ $(eval $(call check-symbol-rule,ELF_GETSHDRSTRNDX,elf_getshdrstrndx,elf))
 $(eval $(call check-symbol-rule,LIBCTF,ctf_open,ctf))
 $(eval $(call check-symbol-rule,STRRSTR,strrstr,c))
 $(eval $(call check-symbol-rule,WAITFD,waitfd,c))
+$(eval $(call check-symbol-rule,LIBSYSTEMD,sd_notify,systemd))
+$(eval $(call check-symbol-rule,FUSE_LOG,fuse_set_log_func,fuse3))
 $(eval $(call check-header-symbol-rule,CLOSE_RANGE,close_range(3,~0U,0),c,unistd))

dtprobed/60-dtprobed.rules

@@ -0,0 +1,4 @@
+# Licensed under the Universal Permissive License v 1.0 as shown at
+# http://oss.oracle.com/licenses/upl.
+
+KERNEL=="dtrace/helper", MODE="0666"

dtprobed/Build

@@ -0,0 +1,41 @@
+# Oracle Linux DTrace.
+# Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+# Licensed under the Universal Permissive License v 1.0 as shown at
+# http://oss.oracle.com/licenses/upl.
+
+CMDS += dtprobed
+
+dtprobed_DIR := $(current-dir)
+dtprobed_TARGET = dtprobed
+dtprobed_CPPFLAGS := -I. -Idtprobed -Ilibproc -Ilibcommon -Ilibport
+dtprobed_CFLAGS := $(shell pkg-config --cflags fuse3)
+dtprobed_LIBS := -lcommon -lproc -lcommon -lport -lelf $(shell pkg-config --libs fuse3)
+dtprobed_DEPS := libproc.a libcommon.a libport.a
+dtprobed_SOURCES := dtprobed.c
+dtprobed_LIBSOURCES := libproc libcommon
+
+ifdef HAVE_LIBSYSTEMD
+dtprobed_CFLAGS += $(shell pkg-config --cflags libsystemd)
+dtprobed_LIBS += $(shell pkg-config --libs libsystemd)
+endif
+
+ifndef HAVE_FUSE_LOG
+dtprobed_SOURCES += rpl_fuse_log.c
+endif
+
+dtprobed.c_CFLAGS := -Wno-pedantic
+
+install::
+	mkdir -p $(INSTSBINDIR)
+	$(call describe-install-target,$(INSTSBINDIR),dtprobed)
+	install -m 755 $(objdir)/dtprobed $(INSTSBINDIR)
+	mkdir -p $(INSTUDEVDIR)
+	$(call describe-install-target,$(INSTUDEVDIR),60-dtprobed.rules)
+	install -m 644 $(dtprobed_DIR)60-dtprobed.rules $(INSTUDEVDIR)
+ifdef HAVE_LIBSYSTEMD
+	mkdir -p $(INSTSYSTEMDUNITDIR)
+	$(call describe-install-target,$(INSTSYSTEMDUNITDIR),dtprobed.service)
+	install -m 644 $(dtprobed_DIR)dtprobed.service $(INSTSYSTEMDUNITDIR)
+	$(call describe-install-target,$(INSTSYSTEMDUNITDIR),dtrace-usdt.target)
+	install -m 644 $(dtprobed_DIR)dtrace-usdt.target $(INSTSYSTEMDUNITDIR)
+endif

dtprobed/GNUmakefile

@@ -0,0 +1,5 @@
+%:
+	$(MAKE) -C .. $@
+
+all::
+	$(MAKE) -C .. all