package/linux-tools: add rtla

The RealTime Linux Analysis tool includes a set of commands that relies
on the osnoise and timerlat tracers from the ftrace kernel subsystem,
allowing to analyze the lantency sources coming from the hardware and
the kernel itself.

This tool was introduced in v5.17 but until v5.19 it relied on libprocps
that has been deprecated soon. So let's make it available for v5.19+.
Rtla relies on libtracefs and libtraceevent, although libtraceevent itself
is already a dependency for libtracefs.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
[Giulio: fix install on recent Linux versions]
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
[Andreas: deal with Linux Fixups, musl, SSP]
Signed-off-by: Andreas Ziegler <br015@umbiko.net>
[yann.morin.1998@free.fr: reword and extend help text]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

DEVELOPERS

@@ -1237,6 +1237,7 @@ F:	package/libnss/
 F:	package/libnvme/
 F:	package/libtraceevent/
 F:	package/libtracefs
+F:	package/linux-tools/linux-tool-rtla.mk.in
 F:	package/mali-driver/
 F:	package/minicom/
 F:	package/mongoose/
@@ -2136,6 +2137,7 @@ F:	package/timescaledb/
 N:	Maxime Chevallier <maxime.chevallier@bootlin.com>
 F:	package/libtraceevent/
 F:	package/libtracefs
+F:	package/linux-tools/linux-tool-rtla.mk.in
 
 N:	Michael Durrant <mdurrant@arcturusnetworks.com>
 F:	board/arcturus/

package/linux-tools/Config.in

@@ -102,6 +102,27 @@ config BR2_PACKAGE_LINUX_TOOLS_PERF_NEEDS_HOST_PYTHON3
 
 endif
 
+config BR2_PACKAGE_LINUX_TOOLS_RTLA
+	bool "rtla"
+	select BR2_PACKAGE_LINUX_TOOLS
+	select BR2_PACKAGE_LIBTRACEFS
+	help
+	  These tracers allow performing latency analysis, for which the
+	  rtla tool provides wrapper commands to visualize and extract
+	  latency traces and reports.
+
+	  rtla includes three tracers, which have been introduced in
+	  different kernel versions:
+	    - Linux 5.19 introduced the osnoise and timerlat tracers,
+	    - Linux 6.3 introduced the hwnoise tracer
+
+	  osnoise and timerlat are always installed, while hwnoise is
+	  installed if your kernel is recent enough.
+
+	  Note: rtla in kernels before 5.19 had additional dependencies,
+	  not available in Buildroot, so only rtla in kernels 5.19
+	  onwards is actually supported in Buildroot.
+
 config BR2_PACKAGE_LINUX_TOOLS_SELFTESTS
 	bool"selftests"
 	depends on BR2_PACKAGE_BUSYBOX_SHOW_OTHERS # bash

package/linux-tools/linux-tool-rtla.mk.in

@@ -0,0 +1,52 @@
+################################################################################
+#
+# rtla
+#
+################################################################################
+
+LINUX_TOOLS += rtla
+
+RTLA_DEPENDENCIES = host-pkgconf libtracefs
+RTLA_MAKE_OPTS = $(LINUX_MAKE_FLAGS) \
+	CC=$(TARGET_CC) \
+	EXTRA_CFLAGS="-D_GNU_SOURCE" \
+	LDFLAGS="$(TARGET_LDFLAGS)" \
+	PKG_CONFIG_PATH=$(STAGING_DIR)/usr/lib/pkgconfig
+
+ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
+define RTLA_DISABLE_STACK_PROTECTOR
+	$(SED) 's/-fstack-protector.* //' $(LINUX_DIR)/tools/tracing/rtla/Makefile
+endef
+endif
+
+define RTLA_LINUX_CONFIG_FIXUPS
+	$(call KCONFIG_ENABLE_OPT,CONFIG_FTRACE)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_TIMERLAT_TRACER)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_HIST_TRIGGERS)
+endef
+
+define RTLA_BUILD_CMDS
+	$(Q)if ! grep install $(LINUX_DIR)/tools/tracing/rtla/Makefile >/dev/null 2>&1 ; then \
+		echo "Your kernel version is too old and does not implement the rtla tool." ; \
+		echo "At least kernel 5.19 must be used." ; \
+		exit 1 ; \
+	fi
+	$(RTLA_DISABLE_STACK_PROTECTOR)
+	$(TARGET_MAKE_ENV) $(MAKE) $(RTLA_MAKE_OPTS) \
+		-C $(LINUX_DIR)/tools/tracing rtla
+endef
+
+# make rtla_install build and install by default documentation using rst2man
+# but it's not available in Buildroot and we don't want manual files in target
+# folder so let's simply install the resulting rtla binary and create symlinks
+# like Linux does in its tools/tracing/rtla/Makefile
+define RTLA_INSTALL_TARGET_CMDS
+	$(INSTALL) -m 0755 -D $(LINUX_DIR)/tools/tracing/rtla/rtla $(TARGET_DIR)/usr/bin
+	ln -sf rtla $(TARGET_DIR)/usr/bin/osnoise
+	ln -sf rtla $(TARGET_DIR)/usr/bin/timerlat
+
+	# Check if hwnoise is provided or not
+	if grep -q hwnoise $(LINUX_DIR)/tools/tracing/rtla/Makefile; then \
+		ln -sf rtla $(TARGET_DIR)/usr/bin/hwnoise ; \
+	fi
+endef